Department of Chemical Sciences
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Browsing Department of Chemical Sciences by Author "Bayode, Ajibola Abiodun"
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- ItemCarbon-mediated Visible-light Clay-Fe2O3–graphene Oxide Catalytic Nanocomposites for the Removal of Steroid Estrogens from Water(Journal of Water Process Engineering, 2020-12) Bayode, Ajibola AbiodunGraphene oxide (GO). These nanocomposites were used for the removal of steroid estrogens (E1, E2, E3 and EE2)from water under visible-light. The use of these photocatalytic nanocomposites lead to complete oxidation of the steroid estrogens at >80 % even under simultaneous presence of all estrogens in water. Complete mineralization was obtained for these estrogens with the range of 58–73 %. The presence of Fe-oxide in the nanocompositesincreased the photocatalytic efficiency but addition of GO further improved the photocatalytic efficiency. Thisimproved efficiency was further doubled when the nanocomposites were prepared with a carbon source (caricapapaya seeds). The presence of carbon in the nanocomposite matrix was confirmed using X-ray Photoelectron Spectroscopy and Elemental Analysis. The main contributors to photocatalytic efficiency of the nanocomposites are superoxide radicals (· ) and holes (h+). Under competitive conditions, the catalysts are still active although the extent of estrogen oxidation is somewhat lower. Changes in the ionic strength did not significantly influence the efficiency of the photocatalyst. This signifies that adsorption only plays a minor role in estrogen removal from water. Toxicity tests show that the treated water is safe for human consumption and the most efficient nanocomposite can be recycled three times without any significant loss of performance. Overall, the nanocomposite shows high potential for the effective removal of a cocktail of estrogens in raw wastewater, tap and rain water, attaining contamination levels that are within WHO safe limits
- ItemClean Technology for Synchronous Sequestration of Charged Organic Micro-pollutant onto Microwave-assisted Hybrid Clay Materials(Journal of Environmental Science and Pollution Research, 2020-03) Bayode, Ajibola AbiodunThe Sustainable Development Goal 6 (SDG #6) of the United Nations (UN) is hinged on the provision, availability, and sustainability of water for the global populace by 2030. In a bid to achieve this goal, the quest to seek for ubiquitous and low-cost adsorbents to treat effluents laden with industrial dyes, such as methylene blue (MB), is on the increase in recent years. Acute exposure of humans to (MB) dye causes cyanosis, necrosis, and jaundice and even leads to death. In this research, zinc-modified hybrid clay composite adsorbent (materials from kaolinite and biomass (crushed Carica papaya seeds and/or plantain peel)) was developed via microwave route. This adsorbent was characterized using field emission scanning electron microscopy (FE-SEM),Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray (EDX), and high-resolution transmission electron microscopy (HR-TEM). These characterization techniques confirmed the success achieved in doping hybrid clay with Zn. These adsorbents were used to sequester cationic dye (MB) from aqueous solutions and textile effluent under various experimental conditions. The adsorption and desorption data obtained were analyzed using various kinetic models, which are two-step kinetics, pseudo-first order, pseudo-second order, fractal kinetics, first-order desorption, second-order desorption, and modified statistical rate theory (MSRT) desorption models. Results showed that the adsorption of the dye occurred via several chemical interactions, while the latter models (for desorption) indicated that desorption occurred in two different desorption sites on the adsorbent surfaces, which showed that the adsorption of MB dye onto the adsorbents was stable without the emergence of any secondary pollution. Adsorption of MB was achieved within 15 min for aqueous solutions and 900 min for textile effluent, which is an improvement on previous results from other studies. The three adsorption-desorption cycles for MB uptake by the adsorbents showed that it is pragmatically applicable to treat textile effluents. Hence, low-cost composite adsorbents have a potential for the effective remediation of MB dye from textile effluents as this study confirmed
- ItemOccurrence and Management of Selenium Oxyanions in Water(Springer Nature, 2021-07) Bayode, Ajibola AbiodunSelenium is a metalloid and an essential micronutrient needed by animals and humans at low concentrations but extremely toxic at high concentrations. It is found in the natural environment and can be present in soil, food, air, plant, and water. The chemistry of Se is linked to its different chemical forms. Se mobility and toxicity are strongly dependent on its redox state; from highly soluble oxyanions like selenate, selenite, and hydroselenite to elemental Se. However, selenate and selenite are the two predominant Se species in the water system because of their high solubility and low adsorption by sediments and soil. This provides most techniques the platform to focus on the removal of both selenite and selenate among other Se species. This chapter is focused on the occurrence and effective management of Selenate and Selenite in water.
- ItemThe Sequestral Capture of Fluoride, Nitrate and Phosphate by Metal-doped and Surfactant-modified Hybrid Clay Materials(Journal of Environmental Science and Pollution Research, 2018) Bayode, Ajibola AbiodunToxic anions removal for increased access to potable water remains a problem that has not been adequately addressed. This study, reports the successful preparation and modification of kaolinite-papaya seed based adsorbents under vacuum (VHYCA) for the removal of Nitrate (NO3⁻), Fluoride (F⁻) and Phosphate (PO4³⁻). Modified adsorbents via metal-doping using Zinc were more efficient in removing these anions from aqueous solution compared with surfactant-modified adsorbents. However, both type of adsorbents showed a higher preference for NO3⁻ removal with Zn-VHYCA and Fe-VHYCA adsorbents having 98 and 85% removal of the anion from aqueous solution, respectively. The removal of F⁻ and PO4³⁻ was best achieved by Ortho-phenylenediamine (OP) and N,N,N′,N′-Tetramethyl-1,4-phenyldiaminedihydrochloride (TPD) modified VHYCA, respectively. However, Zn-VHYCA adsorbent showed comparable results with TPD-VHYCA in the removal of PO4³⁻ from aqueous solution. Overall, the metal-doped hybrid clay adsorbents showed better efficiency for the removal of anions than the surfactant-modified hybrid clay adsorbents.
- ItemTuning ZnO/GO pn Heterostructure with Carbon Interlayer Supported on Clay for Visible-light Catalysis: Removal of Steroid Estrogens from Water(Chemical Engineering Journal, 2020-12) Bayode, Ajibola AbiodunThis study demonstrates the efficiency of a new visible-light p-n ZnO/GO heterostructured composite catalyst supported on clay with carbon interlayer. This photocatalyst was prepared via microwave assisted technique for the removal of four steroid estrogens in water: Estrone (E1), 17-β-estradiol (E2), Estriol (E3) and the synthetic estrogen 17-α ethinylestradiol (EE2). The prepared catalyst was characterized by different techniques: FE-SEM, EDX, RAMAN, ATR-FTIR, XPS, BET, UV-VIS, and PL. Studies confirmed that the presence of carbon interlayer (from carica papaya seeds) and Graphene Oxide (GO) were important for the visible-light efficiency of the photocatalyst. In single solute systems, estrogen removal was >89% and as high as 98% and this was not significantly different in a competitive system. In real wastewater samples, efficiency was 63-78% estrogen removal. A reuse study suggested that the photocatalyst efficiency was slightly >80% after 3 reuse cycles. The presence of Humic acid reduced the efficiency to ≥70% for all estrogens while the addition of 1% H2O2 raised photodegradation of estrogens to 100% in 10 min. However, using the chemical oxidation demand test, the actual oxidation level of steroid estrogens after photodegradation was 51-77% for the various steroid estrogens. Important reactive oxygen species responsible for photodegradation was hydroxyl radical (HO.) via superoxide radical (.O2⁻) and hole (h⁺) formation from the photocatalytic composite. Test with cerio daphnia silvestrii suggests very mild toxicity from treated water which is below the acute level of these estrogens (LC50 = ca. 0.89 mg/L).