Physical and Chemical Sciences

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Browsing Physical and Chemical Sciences by Author "Adebayo, Matthew A."

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    Adsorption isotherms, kinetics and thermodynamic studies of methylene blue dye removal using Raphia taedigera seed activated carbon
    (Caspian Journal of Environmental Science, 2020-04-30) Olasehinde, Emmanuel F.; Abegunde, Segun M.; Adebayo, Matthew A.
    This present work revealed the isotherm, kinetic, and thermodynamic behaviour of methylene blue (MB) dye adsorbed onto acidic activated carbon (AAC) and base activated carbon (BAC) prepared from Raphia taedigera seed by carbonization and chemical activation. AAC and BAC were activated with sulphuric acid and sodium hydroxide respectively. Batch equilibrium studies were done under different experimental conditions such as MB dye concentration and temperature. The equilibrium data were modelled using Langmuir, Freundlich, Elovich, Temkin and Dubinin-Radushkevich isotherms. The Langmuir isotherm model best describes the uptake of MB dye onto AAC and BAC with R 2 > 0.998 in all cases. The pseudo-first-order, pseudo-second-order and intraparticle diffusion equations were used to evaluate the kinetic properties. It was observed that the adsorption of MB dye onto the two activated carbons could best be described by the pseudo-second order equation with 0.999 < R 2 ≤ 1. Thermodynamic parameters such as Gibbs free energy (ΔG0 ), standard enthalpy (ΔH0 ), standard entropy (ΔS0 ), and activation energy (Ea) were determined. The results of ΔG0 indicated a spontaneous and feasible for AAC and non-spontaneous but feasible for BAC. Results of ΔH0 confirmed that the adsorption of MB onto AAC and BAC are endothermic and physical in nature. It can be concluded that AAC and BAC prepared from Raphia taedigera seed could be used as low-cost adsorbent for the removal of MB dye from the wastewater.
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    Cadmium (II) Adsorption from Aqueous Solutions Using Onion Skins
    (SpringerLink, 2019-11-18) Olasehinde, Emmanuel F.; Adegunloye, Ajibola V.; Adebayo, Matthew A.; Oshodi, Aladesanmi A.
    The potential of onion skins for removal of aqueous Cd(II) was investigated. Onion skin powder was chemically modified using thioglycolic acid to develop a suitable, low-cost, and efficient adsorbent for the removal of Cd(II) from aqueous solutions. Influences of temperature, contact time, initial concentration of Cd(II), adsorbent dosage, and pH on the removal of Cd(II) were probed. Optimal adsorption conditions were found at pH 5 and 4, and at 60- and 30-min equilibrium time for the modified and native onion skins, respectively. The equilibrium process was well described by the Freundlich isotherm model. The maximum Cd(II) adsorption capacities, from the Langmuir model, are 17.86 mg/g (modified) and 21.28 mg/g (native). The adsorption process followed the mechanism of physisorption. Pseudo second-order rate equation fitted the kinetic data better than the pseudo first-order rate equation for the two adsorbents. Thermodynamic parameters, such as standard free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°), were calculated for adsorption experimental studies. The results showed that the adsorption of Cd(II) on native/unmodified and modified onion skins was a feasible process and exothermic under the studied conditions. The Cd(II) adsorbed was efficiently desorbed from adsorbent using 0.3 M HCl.
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    Sequestration of Aqueous Lead(II) Using Modified and Unmodified Red Onion Skin
    (Taylor and Francis Online, 2018-05-07) Olasehinde, Emmanuel F.; Adegunloye, Ajibola V.; Adebayo, Matthew A.; Oshodi, Aladesanmi A.
    The efficacy of onion skins, both unmodified and chemically modified with thioglycolic acid, was investigated as alternative low-cost adsorbents for the sequestration of aqueous lead(II) ions from aqueous solution. The adsorbents were characterised using Fourier transform infrared spectroscopy and scanning electron microscopy – energy dispersive X-ray spectroscopy. Adsorption experiments were performed using batch sorption processes. The effects of contact time, pH, initial Pb(II) concentration, adsorbent dose, and temperature were investigated. Optimum sorption conditions were found at pH 4 and a 150 min equilibrium time for the modified onion skin and unmodified onion skin. The Langmuir, Freundlich, DubininRadushkevich and Temkin models were used to characterize the equilibrium experimental results. The equilibrium process was best described by the Freundlich isotherm. The maximum adsorption capacities of 4.878 and 6.173 mg/g were obtained for modified and unmodified adsorbents, respectively, using the Langmuir model. Kinetic studies indicated that the sorption of Pb(II) ions followed a pseudo-second-order model. Thermodynamic parameters such as standard enthalpy change (ΔH°), entropy change (ΔS°), and free energy change (ΔG°) were evaluated from the sorption experimental measurements. The results showed that the sorption process of Pb(II) ions on unmodified and modified onion skins was feasible and exothermic under the conditions used in this study. The sorption process followed the mechanism of physisorption.