Dr. DIAGBOYA PAUL N.
Publication Title Assessing global-warming induced soil organic matter and iron oxides depletion: Empirical insights into sorption and uptake of atrazine by plants
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Düring R-A
Year Published 2024-09-15
Abstract Recent pesticide use is alarmingly high and unregulated in several parts of the world. Pesticide fate in soil is controlled by sorption processes which affect the subsequent transport and chemical reactivity in the environment, as well as uptake by plants. Sorption processes are dependent on soil composition and properties, but these are beginning to be affected by global warming-linked factors leading to soil depletion. Thus, it is vital to decipher soils’ response, especially in the sub-Sahara (SS), to the depletion of some inherent components in the presence of pesticides. This was ascertained by monitoring a model pesticide (atrazine) sorption and desorption on whole SS soil (WS), and the same soil whose organic matter (OMR) and iron oxides (IOR) were substantially depleted, as well as studying atrazine uptake from these soils by fast-growing vegetables. Organic matter depletion enhanced equilibrium in OMR. Sorption was enhanced at lower ambient pH, higher initial atrazine concentration, and higher temperature. Hysteresis was low resulting in high desorption. Overall, atrazine desorption of ?65?% was observed; it was higher in OMR (?95?%) since SOM enhanced hysteresis. Though sub-Saharan soils are rich in iron oxides, SOM played a significantly higher role in sorption than iron oxides in this soil. This result suggests a high potential for atrazine to leach into the aquifer in the sub-Saharan. Atrazine uptake experiment by waterleaf and spinach showed that it could be detected in soil after 63 d, and its presence significantly affected the growth of both vegetables especially in soils with depleted SOM and iron oxides, and at high (100?µg/kg) atrazine spiking. Spinach may be a higher atrazine accumulator than waterleaf. It may be concluded that waterleaf and spinach grown on atrazine-contaminated soils, especially on SOM/iron oxide-depleted soils, are likely to accumulate atrazine.
Publication Title Adsorptive decolorization of dyes in aqueous solution using magnetic sweet potato (Ipomoea batatas L.) peel waste
Publication Type journal
Publisher Royal Society of Chemistry
Publication Authors Diagboya PN, Odagwe, A, Oyem, H, Omoruyi, C, Osabohien E.
Year Published 2024-01-01
Abstract Valorizing domestic biomass waste for contaminated water treatment may be an effective way to achieve the sustainable development goal of attaining clean water for all. Hence, sweet potato peel (SPP) waste was valorized by magnetizing the pretreated SPP adsorbent to prepare the magnetized adsorbent (MSP) which was employed for methylene blue (MB) sorption. The MSP exhibited enhanced cation exchange capacity (11%) and MB sorption greater than 100% of either of the starting pristine materials. Sorption equilibrium was fast (20 min), and the adsorbent was effective over a wide pH (3–9) and temperature range (15–35 °C). The observed sorption capacity of the MSP for MB was 14.3 mg g?1 and this is better than those of most biomass-based adsorbents reported in the literature. The composite exhibited good reusability with ?70% efficiency after 5 cycles. The MB sorption mechanism was a rather complex process involving electrostatic interaction, multi-layer adsorption, and pore-filling. Notwithstanding the enhanced sorption capacity, the ease of magnetic separation of the MSP adsorbent from water post-adsorption, its stability, and reusability are the major merits of this adsorbent. These facts make the MSP composite an appealing cost-effective choice for treating MB-contaminated water.
Publication Title Isolation of aqueous pesticides on surface-functionalized SBA-15: glyphosate kinetics and detailed empirical insights for atrazine
Publication Type journal
Publisher Royal Society of Chemistry
Publication Authors Diagboya PN, Junck, J, Akpotu, S.O, Düring R-A
Year Published 2024-01-02
Abstract Atrazine and glyphosate are two of the most used pesticides around the world causing serious water contamination. In this study, amine-functionalized Santa Barbara Amorphous-15 silica (SBA-15-NH2) was synthesized and employed for the aqueous adsorption of atrazine and glyphosate. The adsorbent was mesoporous post-functionalization with lower surface area, pore volume, size, and stability when compared to the SBA-15. The pesticides adsorption rates were high with over 85% of potential adsorption having occurred within the initial 180 min. The equilibria for atrazine and glyphosate adsorption were 60 and 360 min, respectively, and the rate data fit the fractal pseudo-second-order and pseudo-second-order models, respectively. Atrazine adsorption was higher at lower solution pH with reduced adsorption as the pH value increased. There was enhanced atrazine adsorption as temperature increased from 22 to 32 °C, but further temperature rise resulted in lower adsorption compared to that recorded at 22 °C. The processes comprise electrostatic interaction, trapping of atrazine within mesopores, and multi-layer adsorption of atrazine on surface-adsorbed atrazine. The equilibrium data fitted the Langmuir adsorption isotherm model better than the Freundlich. The SBA-15-NH2 adsorption capacity for atrazine and glyphosate was better than many adsorbents reported in literature, the adsorbent is reusable, and exhibited sustained efficiencies for atrazine that was ?82% even after 3-cycles, an indication of chemical stability and renewability.
Publication Title Adsorption investigation of a composite of metal-organic framework and polyethylene oxide hydrogel
Publication Type journal
Publisher SAGE Publications
Publication Authors AttahDaniel EB, Dikio ED, Ayawei N, Wankasi D, Mtunzi FM, Diagboya PN.
Year Published 2023-07-06
Abstract Though adsorption techniques are eco-environmentally friendly, most lack the effectiveness of complete contaminant elimination leading to increasing concerns about the presence of aqueous contaminants on humans. Thus, synergistic combination of low adsorption capacity adsorbents may be an effective method to enhance their aqueous contaminant uptake. Sol-gel synthesized lanthanum-1,4-benzene dicarboxylate metal organic framework (LaBDC MOF) and polyethylene oxide (PEO) hydrogel were combined to prepare a synergistic composite adsorbent (PEO-LaBDC) for aqueous methylene blue (MB) adsorption. Major properties of the pristine LaBDC MOF and PEO hydrogel were expressed in the characterized composite indicating successful preparation. PEO-LaBDC composite MB removal rate of MB was at least twice as fast (60?min) to those of the pristine LaBDC MOF (120?min) and PEO hydrogel (125?min). The fitting of kinetics model was fractal in nature, and optimum adsorption was on the alkaline end of the pH spectrum for all adsorbents (pH?=?12, 10, and 10, respectively). Comparatively, the composite exhibited a better adsorption performance of ?177% higher than the pristine LaBDC MOF; buttressing the idea that synergistic combination of adsorbents in composites could enhance adsorption processes. Therefore, the PEO-LaBDC composite is a promising adsorbent for the remediation of aqueous MB.
Publication Title Sorption of competing heavy metals on laterite
Publication Type journal
Publisher Federal Polytechnic Ilaro
Publication Authors Oderinde AA, Diagboya PN.
Year Published 2023-06-14
Abstract Heavy metal pollution is a major concern for environmentalists. Competing ions affect the sorption of heavy metals onto the surfaces of soils. This study evaluated competitive adsorption of Cd, Cr, Pb, Cu and Zn from two laterite samples – Emuhu Laterite, LAEM and Abeokuta Laterite, LAAB, obtained from Nigeria. The equilibrium concentrations of heavy metals following adsorption using mixed metal solutions were determined. Laterite affinities for heavy metal adsorption were determined by means of selectivity sequences. The adsorption sequences obtained were Cu > Pb > Cr > Zn > Cd and Cu > Cr > Pb ? Zn > Cd for LAEM and LAAB, respectively. Cr, Pb, Cu were strongly adsorbed by both soils. Adsorptions of the heavy metals on LAEM and LAAB fitted into the Freundlich and Langmuir isotherm model, respectively. The results suggested that Emuhu Laterite, LAEM and Abeokuta Laterite, LAAB, can receive and hold Cr, Pb and Cu pollutants in solution. They can thus be recommended for remediation of the three metals from industrial waste effluents.
Publication Title Mechanistic interpretation of the sorption of terbuthylazine pesticide onto aged microplastics
Publication Type journal
Publisher Elsevier
Publication Authors Junck J, Diagboya PN, Peqini A, Rohnke M, Düring R-A
Year Published 2024-03-15
Abstract Microplastics (MPs) pose a global concern due to their ubiquitous distribution. Once in the environment, they are subject to aging, which changes their chemical-physical properties and ability to interact with organic pollutants, such as pesticides. Therefore, this study investigated the interaction of the hydrophobic herbicide terbuthylazine (TBA), which is widely used in agriculture, with artificially aged polyethylene (PE) MP (PE-MP) to understand how aging affects its sorption. PE was aged by an accelerated weathering process including UV irradiation, hydrogen peroxide, and ultrasonic treatment, and aged particles were characterized in comparison to pristine particles. Sorption kinetics were performed for aged and pristine materials, while further sorption studies with aged PE-MP included determining environmental factors such as pH, temperature, and TBA concentration. Sorption of TBA was found to be significantly lower on aged PE-MP compared to pristine particles because aging led to the formation of oxygen-containing functional groups, resulting in a reduction in hydrophobicity and the formation of negatively charged sites on oxidized surfaces. For pristine PE-MP, sorption kinetics were best described by the pseudo-second-order model, while it was intra-particle diffusion for aged PE-MP as a result of crack and pore formation. Sorption followed a decreasing trend with increasing pH, while it became less favorable at higher temperatures. The isotherm data revealed a complex sorption process on altered, heterogeneous surfaces involving hydrophobic interactions, hydrogen bonding, and ?-? interactions, and the process was best described by the Sips adsorption isotherm model. Desorption was found to be low, confirming a strong interaction. However, thermodynamic results imply that increased temperatures, such as those resulting from climate change, could promote the re-release of TBA from aged PE-MP into the environment. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed TBA sorption onto PE.
Publication Title Efficient decontamination of aqueous glyphosate using Santa Barbara Amorphous-15 (SBA-15) and graphene oxide-SBA-15 poly-amidoamine functionalized composites
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Heyde, B. J., Düring R-A
Year Published 2023-06-15
Abstract There are serious concerns about the effects of aqueous glyphosate on humans especially after its re-classification as a probable carcinogen. Thus, poly-amidoamine functionalized mesoporous SBA-15 (PSBA) and graphene oxide-SBA-15 (PGOSBA) composites were synthesized and employed for aqueous glyphosate decontamination via adsorption. Glyphosate adsorption on the PSBA and PGOSBA was ? 265% enhanced than on SBA-NH2. There were fast equilibrium attainments for the composites at 30 and 60 min, respectively, and no significant differences in adsorption trend were observed as solution pH and temperature varied. The fractal pseudo-second-order kinetics model and fractal Brouers–Sotolongo adsorption isotherm model fitted the adsorption data better indicating complex glyphosate adsorption mechanisms involving electrostatic interactions, pore-filling processes, and multi-layer adsorption. The composites are reusable and stable after several cycles retaining ? 77% of their original adsorption potential after 3 consecutive cycles. The PGOSBA and PSBA composites could reduce low-concentration glyphosate solutions to 182.9 ± 105.7 and 235.9 ± 4.2 µg/L, respectively, which are below the maximum permissible limits for several countries (Canada/Argentina–280 µg/L; the United States/China–700 µg/L; and Australia–1000 µg/L). These adsorbents are efficient and could be applied over wide aqueous pH, temperature, and concentration ranges, and thus would be potentially viable economically for water treatment.
Publication Title Designer composite of montmorillonite-reduced graphene oxide-PEG polymer for water treatment: Enrofloxacin sequestration and cost analysis
Publication Type journal
Publisher Elsevier
Publication Authors Akpotu SO*, Diagboya PN, Lawal IA, Sanni SO, Pholosi A, Peleyeju MG, Mtunzi FM, Ofomaja AE.
Year Published 2023-02-01
Abstract Synergistically combining lower performing adsorbents may effectively enhance the composite’s aqueous contaminant uptake and reduce water treatment cost. Hence in this study, Montmorillonite (Mont) was coupled to graphene oxide (GO)/reduced GO (rGO), and covalently bonded to polyethylene glycol methyl ether (PEG) using a scalable facile amidation method to produce the designer composite. This was employed for the sequestration of an aqueous emerging contaminant (enrofloxacin). Characterization showed attachment of thin GO-PEG films on the surface of Mont, with marked differences in elemental constitution and functionalities post-preparation. Enrofloxacin adsorption equilibrium was fast and optimal at ?30 min and pH 6, respectively, while the data fitted the pseudo-second order and Langmuir models with maximum adsorption of 310.6 mg/g. Reuse and cost analysis of the composite showed effective optimal reuse (?72 %) in real/simulated water samples after 4 adsorption–desorption cycles, while the clay-polymer composite was significantly a cheaper adsorbent with higher adsorption efficiency than other conventional adsorbents.
Publication Title Engineered geomedia kaolin clay-reduced graphene oxide–polymer composite for the remediation of olaquindox from water
Publication Type journal
Publisher American Chemical Society
Publication Authors Akpotu SO, Lawal IA, Diagboya PN, Mtunzi FM, Ofomaja AE
Year Published 2022-09-15
Abstract Globally, there is an upsurge in the use of unregulated veterinary pharmaceuticals with enhanced release into the environment, resulting in water pollution, which is difficult to remediate. To address this issue, we synthesized and characterized highly hydrophobic three-dimensional ordered engineered geomedia with multiple channels. Kaolin clay (K) was functionalized with either graphene oxide (GO) synthesized via Tour’s method or reduced GO in situ with covalently linked methoxyether polyethylene glycol (GO-PEG) using a simple and easily scalable amidation reaction. This was done to enhance the adsorption of olaquindox, a veterinary antibiotic. The X-ray diffraction profile confirmed the grafting of GO and GO-PEG to kaolin. Morphological analysis revealed the architecture of thin films of GO/GO-PEG grafted on the kaolin surface with extensive porosity. Energy-dispersive X-ray mapping, infra-red spectra, and elemental analysis confirmed the successful synthesis of the engineered geomedia composite of K, GO/rGO, and PEG (KrGO-PEG). Due to multiple surface functional groups of polyamide and amido-carbonic groups on the KrGO-PEG composite, it was suitable for olaquindox adsorption. In batch sorption studies of 0.5XKrO-PEG, the effect of pH (2–10) was negligible but with fast equilibrium time (2–1440 min) at 30 min, while the kinetics and equilibrium data suited the pseudo-second order and Langmuir models, respectively. The maximum adsorption value obtained for the composite was 59.5 mg/g; the higher the GO content, the higher the adsorption. The sorption mechanism was majorly through hydrophobic and ?–? interactions. Regenerated/reused adsorbents after 4 cycles had the same efficacy in remediating olaquindox from simulated/real water.
Publication Title Relative empirical evaluation of the aqueous sequestration of methylene blue using benzene-1, 4-dicarboxylic acid-linked lanthanum and zinc metal organic frameworks
Publication Type journal
Publisher Springer International Publishing
Publication Authors AttahDaniel EB, Mtunzi FM, Wankasi D, Ayawei N, Dikio ED, Diagboya PN
Year Published 2022-11-10
Abstract Two metal–organic frameworks (MOFs), lanthanum-1,4-benzene dicarboxylate (LaBDC) and zinc-1,4-benzene dicarboxylate (ZnBDC) were synthesized via the reflux-controlled solvothermal process. The characterization of both adsorbents confirmed the physicochemical properties of well-defined surface morphology with high porosity and thermal stability greater than 450 °C. Adsorption of methylene blue (MB) using both MOFs showed that the rate of MB removal reached equilibrium at 120 and 30 min for LaBDC and ZnBDC, respectively. The MB adsorption was pH dependent with optimum adsorption at pH 12, and the adsorption data trend fitted the fractal pseudo-second-order model (FPSOM), Langmuir and Freundlich adsorption isotherm models, and MB adsorption capacities of LaBDC and ZnBDC are 35.0 and 55.0 mg/g, respectively. The process is physisorption, spontaneous, and feasible. The ZnBDC MOF had a better potential for the removal of MB from an aqueous solution than LaBDC. Both MOFs have the potential to sequester MB from aqueous phases but can be enhanced for better performance.
Publication Title Empirical aspects of an emerging agricultural pesticide contaminant retention on two sub-Saharan soils
Publication Type journal
Publisher Elsevier
Publication Authors Olu-Owolabi BI, Diagboya, PN*, Mtunzi FM, Adebowale KO, Düring RA
Year Published 2022-05-01
Abstract Soils are highly heterogeneous dynamic mixtures with unique properties. The general properties of each type of soil affect its contaminants sorption; thus, obtaining sorption information about any regional soil may require actual sorption experiments. Hence, two soil types (alfisol–AFL and oxisol–OXL) were sampled and used for ivermectin sorption in order to obtain data on sub-Saharan soils for this new emerging contaminant from agriculture. Environmental parameters such as sorption time, ambient solution pH, ivermectin concentration, temperature and desorption were studied, while data were evaluated using two adsorption isotherm models, four kinetic models and the thermodynamics. The soils were neutral, typical of neutral West African soils and having slightly acidic pHpzc with similar particle size description and medium-to-low CECeff and SOM. Ivermectin sorption equilibrium was fast at 180 min for both soils. The rate constant k for sorption on AFL soil was slightly faster than for the OXL. Solution pH has some degree of influence on the sorption process which exhibited two sorption optimum peaks; one around pH 3 and the other around pH 9.5. Ivermectin sorption was concentration dependent; there was higher sorption as initial concentration increased, while sorption increased significantly with ambient temperature from 19.5 to 29.5 °C (?55%) but there was slight reduction on further temperature increase to 39.5 °C compared to sorption at 29.5 °C (?1%). The magnitude of the estimated energetics signaled a non-spontaneous and increasingly random process, with small size of the ?H° values which were compatible with low energy interactive sorption forces and the overall process was exothermic. The ivermectin sorption process was controlled by external mass transfer (which was concentration dependent), with approximately 81.6% of sorption occurring on the soil surfaces, while 18.4% was within the pores or soil phases. The better fits of the sorption data to both the Freundlich adsorption isotherm model and the homogeneous fractal pseudo-second order model are complementary, and confirms that ivermectin sorption process on both soils involves complex interactions on heterogeneous sorption surfaces which include electrostatic interactions, multi–layer adsorption probably facilitated by ?-? interactions between surface sorbed ivermectin molecules and those in solution, possibly trapping of ivermectin molecules within the soil pores, and various van der Waals attractive forces. Though ivermectin was rapidly dissipated on these soils, the hysteresis was high; irrespective of the soil, the amount of ivermectin leached per soil was small, in fact less than 6% of the initial amount sorbed. Our study has vital implications in predicting the fate of specific contaminants in the environment.
Publication Title Comparative empirical evaluation of the aqueous adsorptive sequestration potential of low-cost feldspar-biochar composites for ivermectin
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya, PN, Mtunzi FM, Adebowale KO, Düring R-A, Olu-Owolabi BI
Year Published 2022-02-05
Abstract Several recent studies are shedding light on the potential of synergistically combined low-cost adsorbents for organic and inorganic contaminants removal in water treatment. However, there exists a dearth of data for their potential for removal of emerging contaminants. In this study, low-cost feldspar (FLC) was combined with blended Carica papaya or pine cone seeds (ratio of 1:1), and calcined to obtain FLC-Carica papaya seeds (FPA) or FLC-pine cone seeds (FPC) composites which were characterized. The composites were evaluated for ivermectin sorption by varying experimental pH, time, concentration and temperature, as well as their potential for reusability. The FLC structural lattice was not significantly affected by the modification process but the composites exhibited physicochemical features which were markedly different, having new FTIR spectra bands, well reduced surface area, and enhanced cation exchange capacity. The composites ivermectin sorption rates and equilibrium were faster (60 min) than the FLC (360 min). Ivermectin sorption was pH and concentration dependent. The sorption data fitted better to the homogeneous fractal pseudo-second order (FPSO) kinetics and Freundlich adsorption isotherm model; implying that the process involves complex sorption mechanism. The process was exothermic and increase in solution temperature up to 39.5 ºC did not enhance sorption. Ivermectin sorption capacity and rate trends were similar: FPA (110.9 µg/g) >FLC (84.6 µg/g) >FPC (62.7 µg/g). The FPA exhibited the best sorption capacity as well as the best reusability with over 64% of its initial sorption capacity retained on first reuse. The FPA also exhibited high potential to reduce ivermectin in low concentration solution (?75 µg/L) to zero, with the trend of FPA ?FLC (5.0 ± 1.5 µg/L) >FPC (?27.5 µg/L). Though this kind of composite possesses economic potential in water treatment applications, not every biochar modification may result in enhanced sorption process.
Publication Title Potential of valourized Moringa oleifera seed waste modified with activated carbon for toxic metals decontamination in conventional water treatment
Publication Type journal
Publisher Elsevier
Publication Authors Sera PR, Diagboya, PN*, Akpotu SO, Mtunzi FM, Chokwe TB
Year Published 2021-12-01
Abstract Reducing the cost of adsorbents employed in contaminant removal during water treatment is vital to achieving sustainable clean water. Hence, two composites of commercial activated carbon (AC) and defatted Moringa oleifera (MS) seedcake biomass waste were prepared in ratio of 1:1 and 1:2, and named ACMS-1 and ACMS-2, respectively. Cursory adsorption experiments showed that the composites exhibited better average maximum sorption efficiencies of ?135, 1990 and 169% for As(III), Cd(II) and Pb(II), respectively, than the pristine AC and MS. The adsorption rates of all contaminants on both composites were high within the initial 60 min of commencing the experiment with almost 50% of the total adsorption occurring. The composites were reusable and lost ?25% of their initial adsorption capacity after the three cycles. The composites exhibited enhanced properties and better durability than several low-cost biomasses, cheaper than commercial AC, and easier to handle than raw biomass.
Publication Title Metals and Antibiotics as Aqueous Sequestration Targets for Magnetic Polyamidoamine-Grafted SBA-15
Publication Type journal
Publisher American Chemical Society
Publication Authors Zanele ZP, Mtunzi FM, Nelana SM, Ebelegi AN, Ayawei N, Dikio ED, Wankasi D, Diagboya PN
Year Published 2021-07-06
Abstract In this study, a magnetic generation-5 polyamidoamine (G-5 PAMAM) dendrimer-functionalized SBA-15 (mPSBA) composite was synthesized by coupling amine-functionalized silica (SBA-15-NH2) and amine-functionalized magnetic nanoparticles (MNP-NH2) with the G-5 PAMAM, before characterization and aqueous sorption of As(III), Cd(II), tetracycline, and ciprofloxacin using the composite. The mPSBA characterization data exhibited the typical Si–O–Si infrared peaks from the SBA-15 backbone in addition to the acquired characteristic infrared Fe–O and amide-I/II peaks from the MNP and G-5 PAMAM dendrimers, respectively. Postsorption infrared spectra showing shifts for the amide-linked groups indicated the likely points of contaminant attachment on the composite. Its thermal stability was lower than that of SBA-15 but higher than that of SBA-15-NH, while the XRD diffractograms of the backbone SBA-15-NH and MNP were unchanged in the final composite. The mPSBA composite was a better As(III) and Cd(II) adsorbent than SBA-15 by ?400 and 140%, respectively, with rapid uptake in the first 60 min and equilibrium achieved at 120 min. Sorption was enhanced with increasing pH (until pHpzc) and initial contaminant concentration. The process was spontaneous and endothermic; thus, increasing ambient temperature enhanced Cd(II) sorption. The sorption data fitted better to the homogeneous fractal pseudo-second-order (FPSO) kinetics model and the Brouers–Sotolongo fractal adsorption isotherm models, indicating complex sorption interactions and pore-filling/contaminant trapping within mPSBA. Further experiments using mPSBA for the uptake of tetracycline and ciprofloxacin showed 679% and 325% higher sorption, respectively, compared with that for SBA-15-NH. In addition to the added advantage of easy removal from solution/treated water after the adsorption process, mPSBA sorption capacities for these studied contaminants [As(III): 23.3 mg/g; Cd(II): 74.5 mg/g; tetracycline: 38.4 mg/g; ciprofloxacin: 23.0 mg/g] are better than those of several advanced adsorbents reported in the literature.
Publication Title Mesoporous SBA-15 Functionalized with G-5 Poly(amidoamine): A Sustainable Adsorbent for Effective Sequestration of an Emerging Aqueous Contaminant
Publication Type journal
Publisher American Chemical Society
Publication Authors Mtunzi FM, Diagboya, PN*, Düring RA, Olu-Owolabi BI
Year Published 2021-03-10
Abstract Emerging water contaminants such as avermectins occur at low concentrations but cause several eco-toxicological effects and are very difficult to remove using conventional water treatment methods. As their presence in water becomes increasingly common due to progressively enhanced usage, there is a need for effective removal technologies. Thus, succinic acid-terminated generation-5 poly(amidoamine) (G-5 PAMAM) was coupled to amine-functionalized Santa Barbara Amorphous-15 (SBA-15-NH2) silica to obtain G-5 PAMAM-functionalized SBA-15-NH2 (or PSBA). This was characterized and employed for low-concentration-solution ivermectin adsorption by investigating the adsorption rate r (15 ? r ? 1440 min), effects of pH (3 ? pH ? 11), concentration Co (100 ? Co ? 600 ?g/L), the temperature T (19.5 ? T ? 39.5 °C), and reusability at varying temperatures. Adsorption data were described using kinetics and adsorption isotherm models and thermodynamics. The PSBA Fourier transform infrared (FTIR) spectra exhibited typical silanol bands but lost the characteristic silanol hydroxyl group, while gaining ?CH and amide-linked bands. The thermal stability was less than that of SBA-15 but more than that of SBA-15-NH2, while both low- and wide-angle X-ray diffraction (XRD) spectra presented typically well-defined structural pore postfunctionalization with the primary SBA-15 structural lattice unchanged in PSBA. The PSBA Brunauer–Emmett–Teller (BET) surface area, pore volume, and size are of intermediate values compared to those of pristine SBA-15 and SBA-15-NH2. The ivermectin adsorption equilibrium was fast (60 min), accompanied by a very fast rate, and ?81% adsorption occurred within this time. The process is somewhat pH-dependent with dual adsorption peaks at pH values ?3 and ?11. Adsorption was concentration-dependent, increasing accordingly. Adsorption increased with temperature but subsequently decreased with further increase in temperature. The process was spontaneous and overall exothermic with increased disorderliness of ivermectin molecules in solution as the temperature increased. The adsorption models suggested that the process occurred by the transfer of surface electrons, which resulted in electrostatic interactions between the adsorption sites and ivermectin molecules. Adsorption likely occurred at heterogeneous adsorption sites that were energetically distinct, and the process was accompanied by multilayer adsorption on the initial layer of adsorbed ivermectin. Overall, the process was majorly influenced by a concentration-dependent external ivermectin mass transfer. PSBA could reduce ivermectin in low-concentration solutions to ?3.2 ?g/L from a <75 ?g/L solution at any of the studied temperatures. The PSBA adsorption capacity (479.4 ?g/g) is comparatively better than those of most adsorbents currently reported in the literature. The reusability of PSBA is promising for water treatment even after three consecutive reuse cycles with over 84% adsorption capacity retained.
Publication Title Assessment of the effects of soil organic matter and iron oxides on the individual sorption of two polycyclic aromatic hydrocarbons
Publication Type journal
Publisher Springer Berlin Heidelberg
Publication Authors Diagboya, PN, Mtunzi FM, Adebowale KO, Olu-Owolabi BI
Year Published 2021-03-23
Abstract Soils are the ultimate sink for environmental pollutants like polycyclic aromatic hydrocarbons (PAHs), but the roles of major soil constituents in this process are still unclear. The fate of PAHs is governed by sorption processes which in turn affect transport, chemical and biological reactivity of these PAHs. Thus, the effects and contributions of two major soil constituents (organic matter-OM and iron oxides-IOs) on pyrene and fluorene sorption on soils were assessed by removal of both constituents. The whole soils had higher sorption than the treated OM/IOs soils. Pyrene sorption on OM-rich soils was high and nearly instantaneous, while on the IOs-rich soils, it was lower with delayed equilibrium. The IOs contributed??IOR?>?OMR soils. Though, removal of any of these soil constituents usually reduced sorption and enhanced sorbed PAHs desorption, the presence of IOs masked some PAHs sorption sites, thus its removal resulted in higher sorption. In general, this study highlights the contributions of soil OM and IOs on the sorption of pyrene and fluorene.
Publication Title Empirical Assessment and Reusability of an Eco-Friendly Amine-Functionalized SBA-15 Adsorbent for Aqueous Ivermectin
Publication Type journal
Publisher American Chemical Society
Publication Authors Diagboya PN, Mtunzi FM, Düring RA, Olu-Owolabi BI
Year Published 2021-02-05
Abstract Ivermectin has efficacious broad-spectrum action against several human and veterinary endo-/ectoparasites. However, it is an emerging contaminant in water, causing serious concern to environmental health experts because of its toxicity/adverse ecological effects and increasing input. Currently, conventional water treatment methods are not designed to effectively eliminate it. Hence, amine moiety-grafted SBA-15 (SBA-15-NH2) was prepared, characterized, and evaluated for ivermectin adsorption from water as well as its reusability. Ivermectin adsorption data were analyzed with pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models, in addition to Langmuir and Freundlich adsorption isotherm models and the thermodynamics parameters evaluated. Characterization data revealed that the SBA-15 mesoporous structure was intact in SBA-15–NH2 with reduced surface areas and pore sizes. The SBA–15 characteristic hydroxyl group infrared broad band disappeared with the appearance of stronger amide–I band upon functionalization. In addition, SBA–15-NH2 has ?22% less thermal stability than the SBA–15, while both materials exhibited intense X-ray diffraction peaks typical of well-organized pore structures with no significant distortion after functionalization. Ivermectin adsorption was rapid, and equilibrium was reached within 180 min. The pseudo-second order kinetic model fit the data better than the pseudo-first order one, suggesting electrostatic interaction as a removal mechanism, while the intraparticle diffusion model indicated that ?80% ivermectin uptake occurred on the external surfaces. The process was pH- and concentration-dependent and exhibited higher adsorption at extreme pH conditions (pH values ?3 and 11) and higher concentrations. The SBA–15-NH2 adsorption capacity is 536.2 ?g/g at 30 °C, while the concentration left in solution could be as low as 1 ?g/L. Adsorption isotherm models revealed that the process involves multiple reaction phenomena including monolayer, heterogeneous, and multilayer adsorption simultaneously. Adsorption was spontaneous but exothermic, and thus, it decreased at high ambient temperature. The SBA-15-NH2 adsorbent exhibited potential for reusability with about 15% loss in efficiency after 3 cycles of adsorption and desorption.
Publication Title Utilizing eco-friendly kaolinite-biochar composite adsorbent for removal of ivermectin in aqueous media
Publication Type journal
Publisher Elsevier
Publication Authors Olu-Owolabi BI, Diagboya PN, Mtunzi FM, Düring R-A
Year Published 2021-02-01
Abstract Several emerging contaminants are currently used in an unregulated manner worldwide, resulting in their increasing stringent limits in water by regulatory bodies. Thus, more viable and cheap treatment technologies are required. Recently, synergistic combinations of low-cost adsorbents have shown huge potential for aqueous toxic metals adsorption in water treatment processes. However, there is dearth of data on their potential for emerging contaminant removal. Here, low-cost kaolinite (KAC) clay was synergistically combined with blended Carica papaya or pine cone seeds, and calcined to obtain composites of KAC-Carica papaya seeds (KPA) and KAC-pine cone seeds (KPC). These adsorbents were characterized and evaluated for ivermectin adsorption at varying operating times (15–1440 min), pH (3–11), concentration (100–600 ?g/L), and temperature (19.5–39.5 °C), as well as testing adsorbents’ reusability. The composites exhibited marked property differences including over 250% cation exchange capacity increases and ?50% surface area decreases, but unchanged KAC clay primary lattice structure. Ivermectin adsorption data were explained using kinetics and adsorption isotherm models. The rate of adsorption on KAC decreased over time, while rates for KPA and KPC increased until equilibrium at 180 min; the presence of biomaterials in the composites conferred better ivermectin adsorption and retention under continuous agitation. The adsorbents exhibited dual adsorption peaks one each at the acidic and alkaline pH regions as solution pH changed from 3 to 11. The rate data fitted (?0.9232) the homogeneous fractal Pseudo-Second Order (FPSO) better than any other kinetics model, as well as the Freundlich adsorption isotherm model (?0.9887); these indicate complex interactions between ivermectin and the adsorption sites of both composites. Ambient temperature increase up to ?30 °C caused higher ivermectin adsorption but beyond this temperature there was drastic drop in adsorption. The KPA and KPC adsorption capacities are 105.3 and 115.8 ?g/g, respectively. The KPC was better at reducing ivermecitn in low-concentration solution (?75 ?g/L) to less than 5.0 ?g/L compared with KPA with ?20.0 ?g/L. Though KPC showed better efficiency in adsorption capacity and lowering concentration in low-concentration solutions, KPA exhibited better reusability with 83.5 and 67.5% initial adsorption strengths remaining in the second and third adsorption cycles, respectively, compared to the 73.8 and 58.8% for the KPC. These results indicate that KPA and KPC composites have the economic potential for application in water treatment processes.
Publication Title Polyamidoamine-Functionalized Graphene Oxide–SBA-15 Mesoporous Composite: Adsorbent for Aqueous Arsenite, Cadmium, Ciprofloxacin, Ivermectin, and Tetracycline
Publication Type journal
Publisher American Chemical Society
Publication Authors RV Xikhongelo, FM Mtunzi, Diagboya, PN, BI Olu-Owolabi, RA Düring
Year Published 2021-01-20
Abstract Polyamidoamine functionalized graphene oxide–SBA-15 mesoporous composite (PGOSBA) was synthesized, characterized, and examined for aqueous adsorption of metals (As(III) and Cd(II)) and emerging pollutants (ciprofloxacin, ivermectin, and tetracycline). The adsorption data were explained with kinetics and adsorption isotherm models. PGOSBA is mesoporous, but has lower Brunauer–Emmett–Teller (BET) surface area and pore dimensions in comparison to the amine-functionalized SBA-15 (SBA-15-NH2). Infrared spectra peaks peculiar to the individual constituents were observed in the PGOSBA, which exhibited thermal stability in-between those of its SBA-15-NH2 and graphene oxide (GO) constituents. The basic structural lattices of individual constituents were unaffected in the PGOSBA morphology, which was covered by GO sheet-like structures. The adsorption of Cd(II), As(III), ciprofloxacin, and ivermectin attained equilibrium at 240, 20, 180, and 720 min, respectively. The adsorption rate data for Cd(II) fitted the pseudo-second-order kinetics model, while As(III), ciprofloxacin, and ivermectin adsorption fitted the fractal pseudo-second-order kinetics model better. PGOSBA exhibited one optimum adsorption pH for Cd(II) (pH 5), while two pH points were recorded for ivermectin (a lower peak at pH 3 and a higher one at pH 9). The Cd(II) and ivermectin adsorption processes were spontaneous and endothermic; an increase in temperature up to ?30 °C slightly enhanced Cd(II) adsorption (?5%), as well as ivermectin (?15%), but to an extent; a higher temperature increase (?40 °C) may result in lower adsorption (?2%) than at ?30 °C. Multiple sorption phenomena including electrostatic interactions, multilayer adsorption due to ?–? interactions, as well as pore filling were involved in the pollutants removal processes. The PGOSBA adsorption capacities for Cd(II), As(III), tetracycline, and ciprofloxacin are 92.4, 22.3, 29.2, and 24.6 mg/g, respectively, while it is 291.8 ?g/g for ivermectin. The adsorbent could lower ivermectin in low-concentration ivermectin solutions (<80 ?g/L) to less than 8.5 ?g/L. The PGOSBA reusability for ivermectin adsorption over three consecutive cycles of adsorption, desorption, and reuse was ?95%. These results imply that the PGOSBA adsorbent would be economically viable for potential use in water treatment processes.
Publication Title Application of eco-friendly multifunctional porous graphene oxide for adsorptive sequestration of chromium in aqueous solution
Publication Type journal
Publisher Wiley
Publication Authors Nkutha CS, Diagboya PN, Mtunzi FM, Dikio ED
Year Published 2020-07-09
Abstract Graphene oxide (GO) was functionalized using two silanes ((3-aminopropyl)-triethoxysilane and (3-mercaptopropyl)-triethoxysilane) to obtain, separately, the eco-friendly amine-functionalized GO (GONH) and thiol-functionalized GO (GOSH). Both silanes were also used together to obtain the amine–thiol dual-functionalized GO (GOSN). Various physicochemical characterizations were obtained including spectra from using Fourier-transform infrared (FTIR) spectrometer, thermogravimetric analyzer, and X-ray diffractometer. The adsorbents were used for a comparative study of Cr adsorption from aqueous solution. The obtained data were fitted to pseudo-first order (PFO) and pseudo-second order (PSO) models, the homogeneous fractal pseudo-second order (FPSO), and the Weber–Morris intraparticle diffusion (IPD) kinetics models. Model parameters of the Langmuir and Freundlich adsorption isotherm models, as well as the thermodynamics, were calculated. Characterization results showed successful functionalizations. The GONH, GOSH, and GOSN exhibited alkaline, acidic, and neutral pH, respectively, in water. Amine and thiol functional groups were observed in the new adsorbents, as well as reduced orderliness. The adsorbents had higher density per unit weight and better thermal stability than pristine GO. Equilibrium Cr adsorption was attained within 60 min for all adsorbents. The PSO and FPSO described the rate data better. The Cr adsorption decreased as solution pH increased; optimum adsorption was recorded at pH 2. Equilibrium adsorption data fitted the Langmuir adsorption isotherm model for the GONH, while it fitted the Freundlich for both GOSH and GOSN. The adsorption process was theoretically exothermic process that was spontaneous processes. The Cr adsorption capacities of these adsorbents are 114, 89.6, and 173 mg/g for GONH, GOSH, and GOSN, respectively, and these were better than several reported graphene-based adsorbents and suggest the potential of these adsorbents for water treatment.
Publication Title Clay-carbonaceous material composites: Towards a new class of functional adsorbents for water treatment
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Olu-Owolabi BI, Adebowale KO, Mtunzi FM
Year Published 2020-06-01
Abstract Contamination of water by toxic chemical substances and microbes are ubiquitous and has caused an enormous environmental challenge. In fact, it has been reported that over 3 billion people of the global population live in water-stressed areas. Most current water treatment techniques are inaccessible, expensive or lack the effectiveness for complete toxins removal; thus, the search for more efficient techniques. Adsorption-based techniques are usually preferred due to techno-economic and environmental considerations but the effectiveness of accessible and inexpensive low-cost adsorbents is another cause for concern. Clays and biomasses are low-cost adsorbents which have generated exciting interests because synergistically combined clay–biomass composite hybrid is a recent successful approach for achieving more efficient and specific goals in adsorbent properties. These include adding new structural and functional properties superior to those of the individual low-cost adsorbents. In this review, the focus is on the basic preparation of clay–biomass composite hybrid adsorbents, their physicochemical characterizations and possible applications for the removal of inorganic, organic, and microbial contaminants from water. Literature results have shown that clay-biomass composite hybrids have better adsorbent properties than the starting individual low-cost adsorbents. These composite hybrids are not only fascinating from an academic perspective but excitingly promising for industrial applications, especially for developing countries.
Publication Title Comparative study of the photocatalytic degradation of 2–chlorophenol under UV irradiation using pristine and Ag-doped species of TiO2, ZnO and ZnS photocatalysts
Publication Type journal
Publisher Elsevier
Publication Authors Onkani SP, Diagboya PN, Mtunzi FM, Klink MJ, Olu-Owolabi BI, Pakade V
Year Published 2020-04-15
Abstract A comparative photocatalytic degradation of 2-chlorophenol (2CP) in aqueous solution was investigated using pristine and Ag-doped semiconductor photocatalysts obtained from TiO2, ZnO and ZnS. Varying percentages (1, 3 and 5%) of Ag nanoparticles were doped on the semiconductor photocatalysts via the sol-gel method. The pristine and Ag-doped photocatalysts were characterized using UV–Vis diffuse reflectance spectroscopy, photo-luminescence spectroscopy, X-Ray diffractometry, Fourier transform infrared spectroscopy and transmission electron microscopy; and these techniques confirmed the successful syntheses of the pristine and Ag-doped species. The photocatalytic activities of all species for the degradation of 2CP were carried in photo-reactor using UV irradiation intensity of 1.4 mW/cm2 for 150 min; and the effects of various operating parameters (such as catalyst loading, pH and 2CP initial concentrations) were studied. The results showed enhanced 2CP degradation in the Ag-doped species in comparison to the pristine species while alkaline pH region was most suitable for 2CP degradation especially at low concentration. Lower loadings of the photocatalysts were usually more effective for the 2CP degradation and the degradation trend in the TiO2 and ZnS species was 5% Ag-doped >3% Ag-doped >1% Ag-doped > Pristine, while it was 1% Ag-doped >3% Ag-doped >5% Ag-doped > Pristine in the ZnO. Thus, although the Ag doping enhanced 2CP by all semiconductor photocatalysts, the Ag-doped TiO2 was more effective than the ZnO and ZnS species.
Publication Title Synthesis of amine and thiol dual functionalized graphene oxide for aqueous sequestration of lead
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Mmako HK, Dikio ED, Mtunzi FM
Year Published 2019-12-01
Abstract Recent advances in graphene chemistry indicate that it may play vital role in water treatment processes, especially when synergistically coupled with other functional moieties. Thus, graphene oxide (GO) was mono/dual-functionalized with amino and thiol groups to obtain amino–GO (GONH), thiol–GO (GOSH) and amino/thiol–GO (GOSN). These were characterized and used for Pb(II) adsorption. The Fourier transform infrared spectroscopy (FTIR), X-ray diffraction and thermogravimetric analysis confirmed the success of these syntheses. The adsorption process was spontaneous and endothermic, while the rate was high with up to 80% of total adsorption occurring within the initial 30?min of starting the experiment. Adsorption mechanism involved electrostatic interactions between active functional groups and the Pb(II) cations, but the data fits to models (either Langmuir, Freundlich or Brouers–Sotolongo–fractal adsorption isotherm model) were dependent on the specific functional groups involved on the adsorbent involved in the process. For instance, adsorption on the highly electrostatic functional groups having oxygen and nitrogen followed Langmuir model, while a combination of the weak and strong functional groups (involving the above as well as sulphur groups) followed the Freundlich or the more complex Brouers–Sotolongo–fractal adsorption isotherm model. The adsorption capacity of GONH (138.0?mg/g) was higher than for the GOSH (101.5?mg/g) and GOSN (97.8?mg/g), but relative to other adsorbents reported in literature, these values point to their potential for treatment of Pb(II) in real wastewater.
Publication Title Covalently bonded polyamidoamine functionalized silica used as a Pb(II) scavenger from aqueous solution
Publication Type journal
Publisher Elsevier
Publication Authors Ebelegi AN, Ayawei N, Wankasi D, Dikio ED, Diagboya PN, Mtunzi FM
Year Published 2019-08-01
Abstract Silica was successfully functionalized with generation-3 and 5 polyamidoamine (PAMAM) dendrimers via (3-aminopropyl)triethoxysilane (APTES) linkages to obtain the G3-PAMAM and G5-PAMAM functionalized silica adsorbents designated SG3 and SG5, respectively. The SG3 and SG5 were characterized and explored for Pb(II) removal from aqueous solution. The characterization highlighted successful PAMAM silica synthesis. Preliminary Pb(II) adsorption experiments showed that the SG3 had adsorption efficiency of over 93% compared to pristine silica, silica modified with PAMAM in the absence of the APTES linkage and silica modified with APTES only, each exhibiting ?1, ?1 and ?16% efficiency, respectively. The Pb(II) adsorption equilibria for both adsorbents was 90;min. with optimum adsorption pH of 6 and an experimental adsorption capacities of 121.3 and 132.8;mg/g, respectively. The adsorption process was spontaneous, feasible and endothermic. The adsorption isotherm models suggested Pb(II) ions removal mechanism involving monolayer electrostatic interactions with similar affinity occurring majorly on the SG3 and SG5 surfaces (?90%) and within the pores (?10%). The SG3 and SG5 adsorbents exhibited very good reusability even after three adsorption cycles maintaining ?80% of its adsorption capacity. These fact points to the potential of the SG3 and SG5 adsorbents for removal of Pb(II) from real wastewater.
Publication Title GC-MS fragmentation patterns of sprayed endosulfan and its sulphate metabolite in samples of Theobroma cacao L from a field kinetic study
Publication Type journal
Publisher SAGE Publications
Publication Authors Vaikosen EN, Gibson L, Davidson C, Olu-Owolabi BI, Adebowale KO, Ebeshi BU, Diagboya PN
Year Published 2019-08-02
Abstract Most environmental analytical methods for the determination of organochlorine pesticides (OCPs) are multi-residual with other organic compounds co-extracted and co-eluted. This has been observed in GC spectra using classical detectors like electron-capture detector (ECD) even after appropriate clean-up. This limitation could be resolved by using GC-MS methods which are more specific and selective. Thus, a commercial-grade endosulfan treated Theobroma cacao plantation was sampled. Representative samples comprising leaves, stem bark and pulp were obtained between 0.5?h and 60 days after treatment. Samples were analyzed for residual parent endosulfan (?- and ?-isomers) as well as the metabolite endosulfan sulphate using an ion trap GC-MS. The retention times and chromatogram peaks obtained for various endosulfan were identified and compared with reference standards, and confirmed with National Institute of Standards and Technology library. Results showed that the molecular ion at m/z 407 was exhibited by ?- and ?-endosulfan, representing the parent molecular ion M+• ([C9H6Cl6SO3]+•). The ?-isomer was more thermally stable, hence exhibited more relative abundance. Other predominant peaks were 339, 307, 277, 265, 243, 241, 207, 195, 160, 159, 99 and 75?m/z. The peak at m/z 159 was the base molecular ion. For endosulfan sulphate, the peak at m/z 422 corresponded to parent molecular ion (M+•), while m/z 424 was due to isotopic pattern characteristic of the chlorine atom. The peaks at 387, 357, 289, 272, 229, 206, 170, and 120?m/z were characteristic for the sulphate metabolite. The m/z peak at 272 was the base molecular ion, while m/z 143 may be due to metabolite diol and lactone. These results showed that the various endosulfan species can be identified and confirmed simultaneously using a GC-MS.
Publication Title Layered double hydroxide of cobalt-zinc-aluminium intercalated with carbonate ion: preparation and Pb(II) ion removal capacity
Publication Type journal
Publisher Routledge-Taylor and Francis
Paper Link https://www.tandfonline.com/doi/full/10.1080/00207233.2018.1517935?scroll=top&needAccess=true
Publication Authors Abasi CY, Diagboya PNE, Dikio ED
Year Published 2019-03-01
Abstract ernary layered double hydroxide (Co–Zn–Al LDH) intercalated with carbonate was synthesised via a simple co-precipitation method at pH ?10. It was characterised using the Fourier transform infrared (FTIR) spectrometer, X-ray diffractometer (XRD), surface area and porosity analyser, Thermo-gravimetric/differential thermal analysis (TGA–DTA), and Scanning Electron Microscope (SEM). The Pb(II) adsorption properties, mechanism, and possible reuse of the LDH were also investigated by the batch technique. The characterisation results showed the presence of hydroxyl group as well as the intercalated carbonate anions within the well-defined LDH crystal structure. The TGA-DTA results confirmed the presence of these anionic groups which were liberated from the structure at ?200 and 300°C, respectively. The LDH-specific surface area, pore diameter and width are 54.0 m2/g, 41.3 and 25.1 nm, respectively. Adsorption results showed that Pb(II) equilibrium could be achieved in 120 min, and adsorption increased with concentration and temperature. A Pb(II) adsorption capacity of 130.34 mg/g was reached for this LDH, and the adsorption process was spontaneous, endothermic and mainly electrostatic with most of the adsorption occurring within the pores. Desorption test suggested that approximately 90% of the adsorbed Pb(II) could be desorbed; hence, the Co–Zn–Al–CO3 LDH may be reused.
Publication Title Magnetic valorization of biomass and biochar of a typical plant nuisance for toxic metals contaminated water treatment
Publication Type journal
Publisher Elsevier
Publication Authors Mohubedu RP, Diagboya PN, Abasi CY, Dikio ED, Mtunzi, FM
Year Published 2019-02-01
Abstract Low-cost materials are promising aqueous pollutant adsorbents but when batch adsorption method is employed, separation of pollutant-loaded-adsorbents from water is a major challenge especially when dealing with a large volume of wastewater. Thus, biomass and biochar from Quercus robur fruits were valorized via magnetization (for easy post-adsorption separation) to prepare optimized biomass-magnetic hybrid (BMM 0.5:1) and biochar-magnetic hybrid (BCM 1:1). The BMM 0.5:1 and BCM 1:1 were employed for Pb(II) and Cd(II) removal from simulated contaminated water. The hybrids exhibited higher values of cation exchange capacity (CEC), BET surface area and pore sizes, as well as better thermal stability and the presence of pure spinal structures of Fe3O4, along with the characteristic functional groups of biomaterials (such as the hydroxyls, amides and carboxyls). The adsorption equilibria for both cations were attained within 180?min. Adsorption mechanism involved electrostatic interactions on both external and pore surfaces, with Pb(II) data fitting the Langmuir adsorption isotherm model while Cd(II) data fitted the Freundlich. The adsorption process was spontaneous and exothermic as solution temperature was increased from 292 to 310 and 328?K. The adsorption of Cd(II) initially increased with temperature but decreased on further temperature rise by similar percentages for both adsorbents. In contrast, adsorption of Pb(II) decreased continuously but the decrease was higher for BMM 0.5:1 than BCM 1:1 implying BCM is a more promising adsorbent. Adsorption capacities for BMM 0.5:1 are 63.6 and 21.0?mg/g, while BCM 1:1 has 58.2?mg/g and 21.3?mg/g for Pb(II) and Cd(II), respectively. These adsorption capacities were better than many low-cost adsorbents in literature. Thus magnetic valorization, apart from easing separation, enhances the adsorption capacity of low-cost adsorbents.
Publication Title Synthesis and characterization of undoped and Ag doped TiO2, ZnO and ZnS nanoparticles for the photocatalytic degradation of 2-chlorophenol under UV irradiation
Publication Type Disertations
Publisher PQDT-Global
Publication Authors Onkani SP; Diagboya PN
Year Published 2019-02-01
Abstract Phenol, 2-chlorophenol (2-CP) is used in the manufacture of several chemical compounds including other chlorophenols, dyes, dentifrice and pesticides. The usage of these chemicals results in the discharge of 2-CP that is harmful to most biota in the environment. Therefore there
is need to remove or degrade 2-CP from the environment, especially in water. This research focused on the synthesis, characterization and application of Ag doped semiconductor (TiO2, ZnO, and ZnS) nanoparticles for the removal of 2-CP from water. Sol-gel and co-precipitation
methods were used to synthesize the nanoparticles with different Ag contents (1%, 3% and 5%). Silver metal was used as a doping agent due to its antibacterial activity and ability to improve the photocatalytic activity of the semiconductors for 2-CPdegradation under UV irradiation.
Characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), Ultra-violet visible spectroscopy (UV-Vis) and photoluminescence spectra (PL) were used to characterize the structural, optical and physical properties of the nanoparticles, while
Transmission electron microscopy (TEM) was used to characterize the surface of the nanoparticles. The XRD results confirmed the formation of anatase, wurtzite and blend phases of TiO2, ZnO and ZnS nanoparticles, respectively. The band gaps of the synthesized nanoparticles
were 3.42 eV, 3.23 eV and 3.12 eV for TiO2, ZnO and ZnS nanoparticles respectively. The TEM images showed that all synthesized nanoparticles were uniform in shape. Photocatalytic degradation of 2-CP under UV irradiation confirmed that the semiconductor’s photocatalytic
activities improved with the addition of Ag ions. The best removal percentage was obtained at doped Ag percentages of 5, 1 and 5 % using TiO2, ZnO and ZnS, respectively. In addition, the effects of various parameters affecting the photocatalytic degradation such as pH, initial
concentrations of 2-CP and amount of catalyst (Ag doped TiO2, ZnO and ZnS, respectively) loading were examined and optimized. At the different initial concentrations of 2-CP, namely, 8, 20 and 50 ppm, the highest degradation efficiency was obtained at pH of 10.5 and 5 mg of
catalyst dosage. However a decrease in initial concentration of 2-CP showed an increase in the photocatalytic efficiency. The degradation percentage of 2-CP obtained with Ag doped TiO2; ZnO and ZnS nanoparticles were 74.74, 57.8 and 45.49 %, respectively. Doping of these
materials with Ag enhanced their photocatalytic activity; thus, they have the potential of degrading phenolic compounds, especially 2-chlorophenol, in water
Publication Title Silica-based mesoporous materials; emerging designer adsorbents for aqueous pollutants removal and water treatment
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Dikio ED
Year Published 2018-08-16
Abstract This is a review of recent literature on pristine and specifically functionalized mesoporous silica-based materials or ‘designer silicates’ used as adsorbents for aqueous pollutants removal and water treatment. Ordered mesoporous silicates, their synthesis, surfactants removal, and preparation of the designer silicates were briefly introduced before discussing their applications in the removal of inorganic and organic pollutants. Designer silicates, such as the nitrogen/thiol-containing, the magnetics, and the composites, are highlighted with their various applications for the removal of toxic metal cations, anionic species, dyes, pesticides, industrial organics, pharmaceuticals and other emerging pollutants. These applications were briefly discussed indicating salient features and using illustrating figures where possible.
Publication Title Scavenging of aqueous toxic organic and inorganic cations using novel facile magneto-carbon black-clay composite adsorbent
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Dikio ED
Year Published 2018-04-10
Abstract New magneto-carbon black-clay composite adsorbents derived from feldspar clay, acorn (Quercus robur) fruit pericarp have been developed for efficient removal of both organic (methylene blue- MB) and inorganic (Cd(II)) pollutants from aqueous solutions. The facile composite adsorbents prepared in a one-pot process using two varying mass ratios of clay to carbon black of 0.5:1 (BMF-0.5) and 1:1 (BMF-1) exhibited higher cation exchange capacity (CEC) than any of the starting adsorbents. The rates of removal of MB were faster than for Cd(II) ions in both composites, and consequently, faster equilibrium (30 and 120?min, respectively). The pseudo-second order kinetic model described the adsorption data better suggesting that the removal mechanism involved electrostatic interactions. Surface adsorption (?56%) accounted for the bulk of cations removal on the BMF-0.5 composite, while adsorption on pores or within various partitions was dominant (?54%) on the BMF-1 adsorbent for both cations. The equilibrium data for both cations adsorption onto BMF-0.5 and BMF-1 fit the Langmuir-type adsorption isotherm implying that adsorption of both cations occurred on adsorption sites having equal affinity for these cations and with the formation of only monolayer cations on adsorbent surfaces at equilibrium. Cd(II) was more adsorbed than MB on the adsorbents while increase in temperature enhanced adsorption to an extent: 298?>?288>308?K. The adsorption capacities of BMF-0.5 and BMF-1 for both cations were approximately 14 and 16?mg/g, respectively. Pre- and post-adsorptive IR spectra study suggested that the positions of active interactions between the cations and the adsorbents involved surface functional groups such as the single bondOH, single bondCOO–, and single bondCsingle bondN groups. The composite adsorbents could be reused more than three times without significantly losing the cation adsorption efficiency. Thus, magneto-carbon black-clay composite is a promising adsorbent for removal of organic and inorganic pollutants from water.
Publication Title Concentration-dependent and simultaneous sorption and desorption of pyrene and fluorene on major soil minerals in sub-Saharan Africa
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Olu-Owolabi BI, Dikio ED, Adebowale KO
Year Published 2018-03-01
Abstract Polycyclic aromatic hydrocarbons (PAHs) sorption-desorption in soils, as influenced by soils' physicochemical conditions, control the extent of PAHs translocation, persistence and bioavailability. Though mono-PAHs sorption on soils reports abound, co-occurrence of PAHs in the environment is common and affects individual PAHs sorption characteristics competitively or cooperatively. Besides, most reports were not on sub-Saharan soils. Hence, the batch experiments to study simultaneous sorption–desorption of pyrene and fluorene on five soils, with varying minerals contents, from different sub-Saharan agro-ecological zones. Sorption was concentration dependent and increased as concentration. There was higher preference for pyrene, though lower sorption than in mono-PAHs solutions. Irrespective of competition, soil organic matter (? 4.5%) caused high pyrene sorption similar to mono-PAHs sorption. At 25 °C, pyrene had lower hysteresis in simultaneous desorption compared to mono-PAHs, while higher hysteresis was observed in fluorene for all soils. Simultaneous sorption was higher at 40 than 25 °C and higher hysteresis exhibited as temperature increased in contrast to desorption at 25 °C. Isotherm model studies showed that simultaneous sorption of both PAHs were on heterogeneous surfaces and are composites of several linear and non-linear isotherms. Ultimately, soil constituents, PAHs concentration, competition for sorption sites, size and structural relationship play vital roles in simultaneous sorption on these soils. Risk of environmental contamination is higher for fluorene than pyrene during co-occurrence and likely so in the warmer and low organic matter soils of northern sub-Sahara.
Publication Title Dynamics of mercury solid phase extraction using Barbula lambarenensis
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Dikio ED
Year Published 2018-02-02
Abstract Water pollution and the attendant difficulty in developing viable local treatment techniques are major challenges in most countries. To address this, recent studies have focused on utilization of available low-cost adsorbents. However, a major limitation is their low adsorption capacities. Hence, we evaluated the effectiveness of naturally ubiquitous Barbula lambarenensis (RBL) for removal of aqueous Hg(II) ions via batch biosorption process. Biosorption was carried out at different temperatures (293–313 K), time (5–180 min), pH (3–7) and concentrations (20–60 mg/L), and data generated were explained using various kinetic and adsorption isotherm models. Results showed that equilibrium was attained in 120 min at 313 K and lower temperatures but faster at higher temperatures. However increase in temperature does not correspondingly lead to higher biosorption: 303
293
313 K. Optimum pH of adsorption was observed at 5.5. Modeling of the experimental data suggested that the biosorption process was majorly a monolayer surface phenomenon which occurred via sharing or exchange of valance electrons, and the RBL maximum adsorption capacity is 4.5 mg/g. The process was exothermic and spontaneous. Hydroxyl, carboxyl, thioesters and amide functional groups were implicated in the biosorption process. Overall, the study suggest that RBL may be useful for Hg(II) biosorption from aqueous solutions.
Publication Title Fractal-like concepts for evaluation of toxic metals adsorption efficiency of feldspar-biomass composites
Publication Type journal
Publisher Elsevier
Publication Authors Olu-Owolabi BI, Diagboya PN, Unuabonah EI, Alabi AH, Düring RA, Adebowale KO
Year Published 2018-01-10
Abstract Effective treatment of metals polluted water may be achieved using low-cost materials synergistically modified to obtain composite adsorbents. Thus, feldspar–biomass composites have been prepared via calcination of feldspar (FLC) and Carica papaya seeds or pine cone seeds to yield Carica papaya-FLC (CPF) and pine-cone-FLC (PCF) composite adsorbents, respectively. The composites physicochemical properties and effectiveness for Pb(II), Cd(II) and Cu(II) removal in aqueous solutions were examined. Results showed that calcination did not promote any structural modification in the basic FLC lattice. Though CPF and PCF exhibited lower specific surface area when compared with the FLC, their cation exchange capacities were enhanced. Unlike on the FLC, the metals adsorption on CPF and PCF were higher (>40%) for Cu(II) and Cd(II), pH independent and faster. The study showed that adsorption process on a system with varying types of surface sites and with varying affinity for an adsorbent can best be described by the fractal-like kinetic and equilibrium adsorption isotherm models (fractal pseudo-second order kinetic model and fractal Brouers–Sotolongo adsorption model) compared with the classical models (pseudo-first order and pseudo-second order kinetic models, Langmuir and Freundlich adsorption isotherm models). These adsorption processes were thermodynamically spontaneous, feasible and endothermic; however the modification significantly reduced their energy requirements. The Brouers–Sotolongo model showed that modification of FLC increased the width of the sorption energy distribution on the composites indicating the heterogeneity of the surface adsorption sites. Though no single classical theory of sorption can presently be put forward to explain the overall adsorptive process, metals adsorption on these feldspar-biomass composites are heterogeneous and complex processes with fractal architecture.
Publication Title Spatiotemporal distributions of polycyclic aromatic hydrocarbons close to a typical medical waste incinerator
Publication Type journal
Publisher Springer Berlin Heidelberg
Publication Authors Adesina OA, Sonibare JA, Diagboya PN, Adeniran J, Yusuf R
Year Published 2018-01-11
Abstract Environmental contaminations by polycyclic aromatic hydrocarbons (PAHs) especially from incinerators occur subtly, and PAH contribution from this source is underestimated. However, as environmental PAH concentrations build up, this may be a serious concern around the incinerator vicinity due to the potential consequences of PAHs on ecosystems and human health. Thus, the contribution of selected (12) PAHs from the Obafemi Awolowo University Teaching Hospital medical waste incinerator (or source, HWI_0) was determined by sampling stack gas and ambient air around incinerator vicinity from June 2014 to May 2015. Results showed that the 12 PAH source (HWI_0) concentrations were in the range of NA (for phenanthrene, pyrene, anthracene, benz[e]acephenanthrylene, and indeno[2,1-b]chromene) to 10.9 ng/m3 (pyrelene) and generally higher than the receptor points (hospital waste incinerators (HWIs)). The average total PAH concentrations per month at HWI_0 and the receptors—HWI_1, HWI_2, HWI_3, HWI_4 and HWI_5—were 73.0 ± 27.9, 60.4 ± 30.8, 42.5 ± 23.6, 38.7 ± 21.9, 35.0 ± 27.2, and 39.2 ± 22.9 ng/m3, respectively. These results and multivariate receptor model analysis indicated high correlations between source PAH contributions and the receptor points. The PAH concentrations in the dry season were higher than the wet season suggesting that hydrological condition affects ambient PAH concentrations. The average PAH concentrations in the HWIs as well as the cumulative exposure concentrations observed throughout the period are of major health concern because PAH concentrations detected are several times higher than both the European Union standard and the WHO guideline level.
Publication Title Periodic characterization of alkyl-naphthalenes in stack gas and ambient air around a medical waste incinerator
Publication Type journal
Publisher Springer Berlin Heidelberg
Publication Authors Adesina OA, Sonibare JA, Diagboya PN, Adejuwon A, Famubode T, Bello JO
Year Published 2017-09-24
Abstract Due to the subtle occurrence of environmental polycyclic aromatic hydrocarbon (PAHs) pollution from incinerators, it is seldom considered a significant source of PAH pollution. However, considering the recent build-up of toxics in urban air, this may be a serious concern around the incinerator vicinity due to the potential consequences of PAHs on human health. Hence, this study determined 11 alkyl-naphthalene contributions from a hospital waste incinerator (HWI_0) into ambient air receptor points (HWI_1 to HWI_5) for a 1-year period: June 2014–May 2015. The HWI_0 and ambient gases were sampled using filter-sorbent sampling system and polyurethane foam (PUF) passive samplers, respectively, and all alkyl-naphthalenes were determined using GC-MS. Results showed that the source concentrations were in the range of 0–14.0 ng/m3 and generally higher than the receptor points. The receptor point concentration trends were mainly HWI_1 > HWI_2 ? HWI_3 ? HWI_5 ? HWI_4. Multivariate receptor model analysis suggested high correlations between source and the receptor points though there might be some significant contributions from other emission sources. The average monthly concentrations (?alkyl-naphthalene) at HWI_0 and the receptors HWI_1, HWI_2, HWI_3, HWI_4 and HWI_5 were 67.4 ± 24.3, 57.9 ± 20.1, 42.8 ± 16.9, 39.7 ± 12.2, 36.5 ± 22.2 and 37.8 ± 15.4 ng/m3, respectively. Though these concentrations were lower than the estimated minimal risk level (MRL) for chronic inhalation exposure to naphthalene and its derivatives 0.003 mg/m3, continuous exposure to these pollutants might result in chronic effects. Finally, this study may be used to evaluate the environmental contribution of alkyl-naphthalenes from typical medical waste incinerator in Nigeria.
Publication Title Adsorptive removal of 2,4,6-trichlorophenol in aqueous solution using calcined kaolinite-biomass composites
Publication Type journal
Publisher Elsevier
Publication Authors Olu-Owolabi BI, Alabi AH, Diagboya PN, Unuabonah EI, Düring RA
Year Published 2017-05-01
Abstract Synergistically combined low-cost composites may be effective for the potential treatment of effluents containing organic pollutants. Hence, preparation of Carica-papaya-modified-kaolinite (CPK) and pine-cone-modified-kaolinite (PCK) composites via calcination of pure kaolinite (KAC), Carica-papaya and pine-cone seeds is demonstrated. The composites' specific surface areas were reduced by more than 57% but no structural modification in KAC lattice d-spacing, indicating impregnation of calcined biomass on clay surfaces and pores. However, composites' cation exchange capacities were enhanced over 4-fold, indicating higher potential for adsorption. Adsorption of 2,4,6-trichlorophenol on composites and KAC showed that CPK and PCK attained equilibrium relatively faster (30 min) compared to KAC (60 min). Modeling studies showed that 2,4,6-trichlorophenol removal mechanisms involved electrostatic interactions on sites of similar energy. Modification enhanced adsorption by 52 and 250% in PCK and CPK, respectively, and adsorption increased with temperature.
Publication Title Competitive biosorption of Pb(II) and Cd(II) ions from aqueous solutions using chemically modified moss biomass (Barbula lambarenensis)
Publication Type journal
Publisher Springer Berlin Heidelberg
Publication Authors Okoli PC, Diagboya PN, Anigbogu IO, Olu-Owolabi BI, Adebowale KO
Year Published 2017-01-12
Abstract Treatment of biosorbents to add functional groups that increase toxic metal biosorption is an important way to improve its effective application. Hence, different portions of pristine Barbula lambarenensis (RBL) were treated separately with sodium tripolyphosphate (TPP) and ethylene glycol. The pristine and treated RBL biomasses were used to evaluate the simultaneous removal of Pb(II) and Cd(II) from aqueous solutions. Equilibrium, kinetics and adsorption isotherms were studied. Results revealed that biosorption of Pb(II) and Cd(II) metal ions were spontaneous and described by the pseudo-second-order kinetics. TPP-treated RBL showed higher biosorption capacity for Pb(II), while the ethylene glycol-treated adsorbent was more efficient for Cd(II) biosorption. The simultaneous presence of Pb(II) and Cd(II) in solution did not affect Pb(II) biosorption. However, Cd(II) biosorption dropped 44, 42 and 19% for the pristine, ethylene glycol and TPP-treated adsorbents, respectively, in the competitive adsorption. Both treatments enhanced Pb(II) and Cd(II) biosorption by RBL.
Publication Title Sorption behaviour of pentachlorophenol in sub-Saharan tropical soils: soil types sorption dynamics
Publication Type journal
Publisher Springer Berlin Heidelberg
Publication Authors Diagboya PN, Olu-Owolabi BI, Adebowale KO
Year Published 2016-12-15
Abstract In order to predict exposure risks as well as appropriate remediation strategies for pesticides in soils, knowledge of pesticides sorption processes onto various representative soils is vital. Hence, laboratory batch experiments were carried out to study sorption of a pesticide, pentachlorophenol (PCP), on five soils obtained from different sub-Saharan agro-ecological zones (AEZs) in order to understand sorption equilibrium, kinetics, and thermodynamics. Experimental data showed that sorption equilibrium was attained within 24 h. The fitting of kinetic results and equilibrium data to different models suggested partly surface adsorption and partly partitioning of PCP within voids of the various soil components. Sorption was mainly attributed to sharing or exchange of valence electrons between negatively charged PCP molecules and positively charged soil sorption sites. The sorption process was spontaneous and accompanied by decreased entropy, but was pH and temperature dependent, reducing with increase in pH and temperature. The various soils’ PCP sorption capacities were directly proportional to their cation exchange capacities. The low PCP sorption observed in these soils suggested high risk of PCP being present in soil water solution, especially at higher temperatures, which can lead to contamination of the aquifer. This risk may be higher for soils obtained from AEZs with warmer natural temperatures.
Publication Title Immobilization of toxic metal cations on goethite-amended soils: a remediation strategy
Publication Type journal
Publisher University of Port Harcourt
Publication Authors Mokwenye II, Diagboya PN, Olu-Owolabi BI, Anigbogu IO, Owamah HI
Year Published 2016-06-25
Abstract The study investigates a simple and viable option to reduce toxic metals mobility and availability in four surface (0–30cm) soils with varying physicochemical properties amended by different percentages of goethite. Batch sorption experiments carried out to study the effectiveness of immobilizing Pb2+, Cu2+, Zn2+ and Cd2+ ions on these soils showed that goethite played vital role in the metals adsorption (?10% increase in adsorption). Removal of soil iron oxides caused reduced Pb2+ adsorption on soils with high organic matter (? 10% decrease in adsorption) with no significant increase in adsorption upon amendment, while soils having low organic matter had enhanced adsorption with amendment. Cu2+ and Cd2+ adsorptions were not enhanced even at 10% goethite amendment. However, Zn2+ adsorption was interestingly different: the soils showed ?55 % increases upon removal of inherent soil iron oxides without goethite amendment. Goethite amendments further enhanced Zn2+ adsorption on these soils. Generally, both whole and amended soils showed higher preference for Pb2+; the sorption trend is – Pb2+ >Cu2+ >Zn2+ >Cd2+. Goethite amendment of these soils improved Pb2+ and Zn2+ adsorption. Hence, goethite amendment may be an effective method for immobilizing Pb2+ and Zn2+ on these soils and thus reducing their availability to biota. The quantity of goethite required by a soil to attain maximum immobilization varies depending on the metal and the soil’s physicochemical properties; however, Cu2+ and Cd2+ may not be effectively immobilized using goethite amendment.
Publication Title Calcined biomass-modified bentonite clay for removal of aqueous metal ions
Publication Type journal
Publisher Elsevier
Publication Authors Olu-Owolabi BI, Alabi AH, Unuabonah EI, Diagboya PN, Böhm L, Düring RA
Year Published 2016-03-03
Abstract Recent studies have shown that kaolinite clay modified with biosorbents are promising low cost adsorbents for the removal of metals from aqueous solution because the resultant composites have higher adsorption capacities, and hence a better aqueous metal ions removal efficiencies. However, some clay properties suggest that not all such modifications enhance adsorption capacity. In this study, bentonite (BEN) clay was calcined after modification with Carica papaya seeds or pine cone to obtain C. papaya-modified bentonite (CPB) and pine cone-modified bentonite (PCB). The efficiencies of these adsorbents for the removal of Pb(II), Cu(II) and Cd(II) ions from aqueous solutions were studied as a function of pH, time, sorbate concentration and temperature. X-ray diffraction results showed that CPB and PCB had lattice structure as BEN, but reductions in the surface areas of CPB and PCB were observed. Adsorption results showed that pH did not significantly affect removal of aqueous metal ions between pH 3 and 7. The adsorption fitted pseudo-second order (r2 ? 0.966) and intra-particle diffusion models and indicated mainly surface phenomena involving sharing of electrons between the adsorbent surfaces and the metal ion species. Unlike Cu(II) and Cd(II), Pb(II) adsorption reduced in CPB and PCB indicating that not all calcined biomass-clay composites have enhanced aqueous metal adsorption efficiency. However, undesired properties such as adsorbent bleeding were removed and mechanical strength enhanced while easier separation of the adsorbents from solution as compared to the raw bentonite was observed.
Publication Title Effects of time, soil organic matter, and iron oxides on the relative retention and redistribution of lead, cadmium, and copper on soils
Publication Type journal
Publisher Springer Berlin Heidelberg
Publication Authors Diagboya PN, Olu-Owolabi BI, Adebowale KO
Year Published 2015-07-08
Abstract In order to predict the bioavailability of toxic metals in soils undergoing degradation of organic matter (OM) and iron oxides (IOs), it is vital to understand the roles of these soil components in relation to metal retention and redistribution with time. In this present work, batch competitive sorptions of Pb(II), Cu(II), and Cd(II) were investigated between 1 and 90 days. Results showed that competition affected Cd(II) sorption more than Cu(II) and Pb(II). The sorption followed the trend Pb(II) >?>?Cu(II)?>?Cd(II), irrespective of aging, and this high preference for Pb(II) ions in soils reduced with time. Removal of OM led to reduction in distribution coefficient (K d) values of ?33 % for all cations within the first day. However, K d increased nearly 100 % after 7 days and over 1000 % after 90-day period. The enhanced K d values indicated that sorptions occurred on the long run on surfaces which were masked by OM. Removal of IO caused selective increases in the K d values, but this was dependent on the dominant soil constituent(s) in the absence of IO. The K d values of the IO-degraded samples nearly remained constant irrespective of aging indicating that sorptions on soil components other than the IO are nearly instantaneous while iron oxides played greater role than other constituents with time. Hence, in the soils studied, organic matter content determines the immediate relative metal retention while iron oxides determine the redistribution of metals with time.
Publication Title Sorption and desorption of fluorene on five tropical soils from different climes
Publication Type journal
Publisher Elsevier
Publication Authors Olu-Owolabi BI, Diagboya PN, Adebowale KO
Year Published 2015-02-01
Abstract The main processes controlling soil–polycyclic aromatic hydrocarbon interaction is sorption–desorption as influenced by the soil physicochemical conditions. Sorption–desorption phenomena can influence translocation, persistence and bioavailability. Hence, laboratory batch experiments were undertaken to investigate the sorption characteristics of fluorene on five tropical soils from varying tropical agro-ecological zones having different physicochemical properties. Fluorene concentrations used for the study ranged from 20 to 100 ?g/L, and results showed that fluorene sorption equilibria were attained usually within 24 h. Increase in pH had a negative effect on fluorene sorption. Fluorene sorption was concentration dependent and exothermic. The sorbed fluorene molecules were distributed between surface adsorption sites and phases in soil. Sorption was controlled by weak hydrophobic forces, such as the ?–? interactions and Van der Waal's forces. Desorption hysteresis were most pronounced in soils with high organic matter contents than lower ones. The sorption was characterized as multiple reaction phenomena composed of several linear and non-linear isotherms. The physicochemical conditions of the soil must be understood in order to predict the fate and bioavailability of fluorene in soil.
Publication Title Sorption and desorption of selected organic and inorganic pollutants in soils collected from different agro-ecological zones of Nigeria
Publication Type Published Research
Publisher University of Ibadan
Publication Authors Diagboya PN
Year Published 2015-02-10
Abstract Environmental pollution caused by persistent and bioaccumulative toxic chemicals is a global issue in view of its effects on biota. Researches abound on the sources and concentration of soil pollutants but there is paucity of information on their sorption/desorption in Nigerian soils. This is necessary for accurate prediction of toxicity and effective remediation strategy. Therefore, this study was aimed at assessing the sorption/desorption of selected organic and inorganic pollutants in soils from different Agro-Ecological Zones (AEZs) of Nigeria. Representative composite soil samples (0-30 cm depth) were collected from the eight
AEZs (15 each) and their physicochemical characteristics determined using standard methods. Soil treatments were carried out by removing Organic Matter (OM) and iron oxides to give Organic-Matter-Removed (OMR) and Iron-Oxides-Removed (IOR) samples, respectively. Batch sorptions/desorptions of pyrene and fluorene [Polycyclic Aromatic Hydrocarbons (PAHs)], Pentachlorophenol [PCP; Pesticide], and Pb(II), Cu(II),
and Cd(II) [Heavy Metals (HM)] were investigated at varying times (0-4320 min.), solution pH (3-9), sorbate concentrations (20-100 ?g/L PAHs; 10-40 mg/L PCP; 50-300 mg/L HM), and temperatures (25 and 40 ?C) for untreated, OMR and IOR soil samples. Competitive sorptions/desorptions were investigated using batch method. Data were fitted to four kinetics models [Pseudo-First-Order (PFO), Pseudo-Second-Order (PSO), Elovich,
and Intra-Particle-Diffusion (IPD)] and three adsorption isotherm models [Langmuir, Freundlich, and Distributed Reactivity Model (DRM)]. Thermodynamic parameters (Gibb’s free energy-?G?, entropy-?S?, and enthalpy-?H?) were determined and the regression analyses were carried out. Soil pH values ranged from 6.2 to 7.4, while their Cation Exchange Capacity (CEC) ranged from 2.4 to 8.3 meq/100g. The OMR soils exhibited acidic pH (4.1-6.1) and reduced CEC (2.1-3.9 meq/100g), while IOR soils were alkaline (pH of 7.8-8.1) with increased CEC (17.9-37.9 meq/100g). Equilibrium sorptions were attained within 1440 minutes for all sorbates. Increasing pH decreased organics sorption (16.0-42.0%) but increased metals sorption (?75.0%). Competition decreased the sorptions of organic pollutants while higher temperature increased sorptions. Metal distribution coefficients (Kd) values were directly proportional to OM content, and single and competitive sorptions followed the same trend: Pb(II)>Cu(II)>Cd(II). Desorptions hystereses were related to OM content: the higher the OM, the higher the hysteresis. Sorptions data fitted PSO (R2=0.99-1.00), Elovich (R2=0.90-1.00) and IPD (R2=0.71-0.96) models which suggested some degree of boundary-layer-control. Sorptions data were better described by
DRM and Freundlich adsorption isotherms for PAHs and PCP, respectively; while both Langmuir and Freundlich isotherms described the metals confirming the heterogeneous nature of the soils. Sorptions of selected pollutants were spontaneous and feasible (?G? <–15.5kJmol-1), accompanied by low ?S? values (?1.3 kJmol-1K-1). The ?H? values (<45.0
kJmol-1) were in the energy range associated with weak forces of interactions such as Vander Waals, electrostatic, and ?-? interactions.
The sorptions of selected organic and inorganic pollutants were partly surface adsorption and partly partitioning between phases in soils. Organic matter, iron oxides and temperature were major factors controlling sorptions/desorptions. Low levels of organic matter, iron oxides and high temperature may negatively impact biota and aquifer.
Publication Title Synthesis of covalently bonded graphene oxide–iron magnetic nanoparticles and the kinetics of mercury removal
Publication Type journal
Publisher Royal Society of Chemistry
Publication Authors Diagboya PN, Olu-Owolabi BI, Adebowale KO
Year Published 2015-08-08
Abstract Synergistically combined nanomaterials have been applied in various fields in materials science to improve the properties of nanocomposites. However, limited studies focus on the ability of such composites for water treatment. A graphene oxide (GO)–iron oxide (Fe3O4) magnetic nano-particle composite (GOMNP) was synthesized and used to study the Hg2+ adsorption kinetics from aqueous solution at various temperatures. GO was attached to magnetic nanoparticles via the amine group of 3-aminopropyltriethoxysilane which was attached the surface of Fe3O4. The GOMNP nano-composite had a Hg2+ adsorption capacity of 16.6 mg g?1. IR spectra analysis showed that hydroxyl and carboxylate functional groups were mainly responsible for Hg2+ adsorption. Adsorption of Hg2+ by the GOMNP obeyed different adsorption mechanisms at varying adsorption temperatures. The Elovich kinetics model described the Hg2+ adsorption data better than any of the other three models tested. The GOMNP nano-composite is thus a promising nanosorbent for Hg2+ removal from aqueous solutions.
Publication Title Mechanism of dialkyl phthalates removal from aqueous solution using ?-cyclodextrin and starch based polyurethane polymer adsorbents
Publication Type journal
Publisher Elsevier
Publication Authors Okoli CP, Adewuyi GO, Zhang Q, Diagboya PN, Guo, Q
Year Published 2014-12-19
Abstract Phthalate esters have been known as potent endocrine disruptors and carcinogens; and their removal from water have been of considerable concern recently. In the present study, ?-cyclodextrin polyurethane polymer (GPP), ?-cyclodextrin/starch polyurethane copolymer (GSP), and starch polyurethane polymer (SPP) have been synthesized and characterized. Their adsorption efficiencies for the removal of dimethyl phthalate (DMP) and diethyl phthalate (DEP) from aqueous solutions were investigated. The characterization results showed the success of the synthesis. The isotherms were L-type, and both the Langmuir and Freundlich adsorption isotherm gave good fittings to the adsorption data. Adsorption mechanisms suggested that these adsorbents spontaneously adsorb phthalate molecules driven mainly by enthalpy change, and the adsorption process was attributed to multiple adsorbent–adsorbate interactions such as hydrogen bonding, ?–? stacking, and pore filling. The results showed that starch and ?-cyclodextrin polyurethane polymer adsorbents have excellent potential as adsorbent materials for the removal of phthalates from the contaminated water.
Publication Title Microscale scavenging of pentachlorophenol in water using amine and tripolyphosphate-grafted SBA-15 silica: Batch and modeling studies
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Olu-Owolabi BI, Adebowale KO
Year Published 2014-12-15
Abstract Mesoporous silica SBA-15 meets most criteria for selection of water treatment adsorbents such as high specific surface area, large pore-size, chemical inertness, repertory of surface functional groups, good thermal stability, selectivity, regenerability, and low cost of manufacture. However, its use for water treatment is still largely unexplored. SBA-15 and its functionalized derivatives of aminopropyltriethoxysilane (SA) and tripolyphosphate (ST) were synthesized, characterized, and used to investigate pentachlorophenol (PCP) removal from aqueous solutions. Functionalization improved SBA-15 capacity for PCP removal from solution in accordance with the trend SBA-15 < ST < SA. Sorption rate experiments data fit the Lagergren pseudo-second order kinetics model. Intra-particle diffusion indicated that the sorption is controlled by two mechanisms: intra-particle and equilibrium diffusion. Adsorptive pore-filling and electrostatic interactions were implicated in the removal of PCP from solution. Electrostatic interaction led to ?75% increase in sorption upon functionalization. The equilibrium sorption data of the PCP on these mesoporous materials fits the Freundlich isotherm. Desorption hysteresis was low for the pristine SBA-15, but the functionalized SBA-15 materials showed higher hysteresis. The results imply that functionalized SBA-15 sorbents are promising materials for microscale scavenging of PCP in solution.
Publication Title Graphene oxide–tripolyphosphate hybrid used as a potent sorbent for cationic dyes
Publication Type journal
Publisher Elsevier
Publication Authors Diagboya PN, Olu-Owolabi BI, Zhou D, Han BH
Year Published 2014-11-01
Abstract Graphene oxide–tripolyphosphate material (GPM) was synthesized through an ethanolamine (EA) mediated graphene oxide (GO) self-assembly. The synthesis route to GPM is simple and benign. GPM was composed of GO nanosheets as building blocks and the tripolyphosphate as cross-linkers and chelators of cations in solutions. GPM showed higher potency for adsorption of cationic dyes than anionic dyes, and the adsorption process was through electrostatic and ?–? interactions. Adsorption was spontaneous and exothermic, and the adsorption capacity of GPM for cationic dyes (>2540 mg g?1) far exceeded those reported in literature for GO materials.
Publication Title Evaluation of pyrene sorption–desorption on tropical soils
Publication Type journal
Publisher Elsevier
Publication Authors Olu-Owolabi BI, Diagboya PN, Adebowale KO
Year Published 2014-05-01
Abstract Sorption–desorption processes control soil-pollutant interactions. These processes determine the extent of pyrene transport in soils. Understanding sorption characteristics of pyrene is necessary in ascertaining its fate in soil. Laboratory batch experiments were conducted to study the sorptions–desorption of pyrene on eight soils from varying tropical agro-ecological zones (AEZs). The results showed that pyrene sorptions equilibria were attained within 720 min. Solution pH had a reciprocal effect on pyrene sorptions. Sorption was exothermic and increased with pyrene concentration in solution. The quantities of pyrene sorbed by each soil as well as the hysteresis were proportional to the percentage organic matter, and to some degree, the clay mineralogy. Sorption isotherms showed distributed reactivity involving several linear and non-linear isotherms. The present investigation showed that pyrene is likely to be more available to biota and reach the aquifer faster in low organic matter soils than those with relatively higher organic matter and more so in warmer climes.
Publication Title Mechanism of Pb2+ removal from aqueous solution using a nonliving moss biomass
Publication Type journal
Publisher Elsevier
Publication Authors Olu-Owolabi BI, Diagboya PN, Ebaddan WC
Year Published 2012-07-01
Abstract Biosorption of lead (II) ions onto raw biomass of the moss plant Barbula lambarenensis has been studied using the batch equilibrium adsorption method. Equilibrium isotherms, kinetics and thermodynamic parameters have been evaluated. The FT-IR analysis showed that likely functional groups responsible for the adsorption are carboxyl, carbonyl, amides and hydroxyl groups. The pH for optimum adsorption is 5.0. Equilibrium data fit well to the Langmuir isotherm. The estimated maximum adsorption capacity was found to be 62.50 mg/g at 298 K and 90.91 mg/g at 323 K. The kinetic data obeyed the pseudo-second-order model. The free energy changes (?Go) are positive and the reaction is exothermic with decreased randomness at the sorbent/solution interface. Taking into account its good adsorption capacity, ease of sample treatment, as well as availability, the biomass of B. lambarenensis is a promising cost-effective biosorbent for Pb2+ removal from aqueous environment.