Department of Chemical Sciences

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Browsing Department of Chemical Sciences by Subject "Agrowaste"

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    Solar-active clay-TiO2 Nanocomposites Prepared via Biomass Assisted Synthesis: Efficient Removal of Ampicillin, Sulfamethoxazole and Artemether from Water
    (Elsevier, 2020-10-01) Omorogie, Martins
    New solar-active nanocomposites free from toxic reagents or precious metals were developed. They were prepared from natural kaolinite clay, Na2WO4, titania, and biomass. The photocatalytic activity of the nanocomposites against two antibiotics [Ampicillin (AMP) and Sulfamethoxazole (SMX)] and an antimalarial drug [Artemether (ART)] under sunlight suggests an unusually fast photodegradation that is >90% complete in 30 min especially with the photocatalytic nanocomposite prepared from Musa paradisiaca peels (plantain peels) @ 500 °C (TZPP5). The presence of both biomass and TiO2 is essential for the effective function of the photocatalytic nanocomposites. With TZPP5, ca. 80% and ca. 50% mineralisation of AMP and SMX, respectively, was observed after 60 min. The photocatalytic reaction releases inorganic by-products (SO42-, NO3- and NH4+) at levels below WHO permissible limits for drinking water. The presence of anions reduces the efficiency of TZPP5, indicating that it releases electrons and reactive oxygen species that are also responsible for photodegradation of the drugs. However, changing concentrations of electrolyte (NaCl) do not influence its efficiency, suggesting that adsorption may not precede photocatalysis, contrary to common models. Reuse studies suggest a slight loss in photodegradation efficiency (≈6%) of the nanocomposite for AMP in the first two cycles followed by subsequent stability at 70% for subsequent cycles. This is different for SMX, which maintained ≈58% removal for all cycles after the 1st cycle. With efficient treatment of raw wastewater from an abattoir, a river, and a hand-dug well for drinking water, the photocatalytic nanocomposite shows potential for treating drinking water especially in point-of-use water treatment devices.
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    Solid Phase Extraction of Hazardous metals from Aqua System by Nanoparticle Modified Agrowaste Composite Adsorbents
    (Elsevier, 2014-03-15) Omorogie, Martins
    This study reports for the first time the adsorption of Cd(II) and Hg(II) ions from simulated wastewaters onto Nauclea diderrichii agrowaste (NDS) modified with mesoporous SiO2 (MND) and mesoporous SiO2 + graphene oxide (GND). Modification of NDS with mesoporous SiO2 and graphene oxide improved its adsorption capacity for Cd(II) and Hg(II) in aqueous solution with surface area increasing from 5.4 m2/g (in NDS) to 209 m2/g (in MND) and 267 m2/g (in GND) respectively. The modification of NDS also improved its rate of uptake of both metal ions with uptake rate of Hg(II) being more than that of Cd(II). Kinetic data obtained gave better fit to the pseudo-second order kinetic model than to pseudo-first order, Elovich, modified pseudo-first order, ion exchange or Weber–Morris intraparticle diffusion kinetic models. Data obtained from the Weber–Morris intraparticle diffusion model suggests that pore diffusion mechanism may have played a significant role in the adsorption process. Thermodynamic data showed negative and positive values for ΔG⸰ and ΔH⸰ respectively for the adsorption systems, which supports the fact that the adsorption of both Cd(II) and Hg(II) by MND and GND adsorbents was feasible, spontaneous and endothermic in nature.