Browsing by Author "Olasehinde, E. F."
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Item Biosorption of Cadmium (II) and Chromium (VI) from Aqueous Solution by Chemically Modified Tithonia Diversyfolia Biomass(Journal of American Science, 2014-08-06) Olasunkanmi, O.; Okoronkwo, A. E.; Aiyesanmi, A.F.; Olasehinde, E. F.; Adepoju, T.S.The search for alternative and innovative treatment technologies for the effective removal of heavy metals from aqueous wastes has been a research of concerted effort due to the inherent limitations exhibited by the conventional methods such as less efficiency, sensitive operating conditions, energy requirements and generation of toxic sludge or other waste products. Biosorption, the passive uptake of heavy metals by biomaterials has been studied recently because of its high efficiency and cost effectiveness. Therefore, the biosorption capacity of Tithonia diversyfolia biomass chemically modified with sodium hydroxide for the removal of cadmium and chromium ions from aqueous solution was investigated. The effects of temperature, contact time, initial concentration of metal ions, adsorbent dosage and pH on the biosorption of Cd2+ and Cr6+ ions were assessed. Thermodynamic parameters such as free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) during the biosorption were evaluated. The results showed that the biosorption process of Cd2+ and Cr6+ by chemically modified Tithonia diversyfolia (CMTD) biomass was feasible and exothermic under the studied conditions. The equilibrium process was well described by the Langmuir isotherm model, with a maximum biosorption capacity of 46.75mg/g and 48.00mg/g for Cadmium and Chromium ions, respectively. Kinetic studies indicated that the biosorption of metal ions followed a pseudo-second order equation.Item Extraction of Cu, Zn, and Ni from waste silica-rich integrated circuits by sulfation roasting and water leaching(Springer Link, 2020-02-01) Ajiboye, E. A.; Olasehinde, E. F.; Adebayo, A. O.; Ajayi, O. O.; Ghosh, M. K.; Basu, S.High-tech electrical and electronic equipment contain large numbers of silica-rich integrated circuits (SRICs) which after its end of life generate huge amount of waste; however, its valuable metal contents can be properly recycled. Extraction of Cu, Ni, and Zn from pulverized SRIC obtained from discarded waste electrical and electronic equipments (WEEE) by sulfation roasting followed by water leaching was studied. Co-extraction of other metals such as Fe, Al, and Pb present in the sample was also explored. Effects of H2SO4/SRIC ratio, roasting temperature, time, and varying water leaching conditions on the extraction efficiencies were evaluated. The optimum conditions for Cu, Zn, and Ni extractions were determined as H2SO4/SRIC ratio 0.5, roasting temperature 300 °C, roasting time 60 min, leaching temperature 50 °C, leaching time 60 min, and liquid–solid ratio = 10:1 (i.e., 100 mL/10 g) with extraction efficiencies of 61.9, 84.9, and 93.6% for Cu, Ni, Zn, and co-extractions of Fe and Al were 71.1 and 55.6, respectively. Under the optimum conditions, approximate 20% Fe3+ was naturally precipitated which is advantageous for the subsequent step. Comparatively, higher extraction efficiencies of Cu, Zn, and Ni were observed in water leaching of H2SO4-roasted sample than direct H2SO4 leaching of raw sample keeping other leaching conditions constant. Lead retained in the roasted–leached residue was extracted with dilute HCl leaving silica and Al in the final leached residue. Process flow sheet for the extraction of Cu, Ni, Zn, and Pb and reuse of silicon from waste SRICs was proposed.Item Reaction Kinetics for Nitrosation of DAF-2 in Air Saturated Nitric Oxide Solution(Science Publishing Group, 2012-12-31) Olasehinde, E. F.; Ogunsuyi, H.O.; Abata, E. O.; Sakugawa, H.Understanding the reaction rate constant of a probe compound with its target molecule is essential for its selection and use in biological and non-biological systems. Over the past decade, the probe, 4, 5-diaminofluorescein (DAF-2) has been widely employed for the detection and imaging of nitric oxide (NO•) in various media. However, the rate constant for the nitrosation of DAF-2 in air-saturated nitric oxide solution is far from being understood. For the first time, we have determined the second order rate constant for the reaction of DAF-2 with NO• (k2) in airsaturated solution using competition kinetics method. An alternative competition kinetics method which involves a reciprocal plot of the reactant (DAF-2) and triazolofluorescein (DAF-2T), the product formed from the reaction of DAF-2 with NO• was developed and compared to the standard competition kinetics method. Our particular approach in this system is based on the use of oxy-hemoglobin (HbO2), a potent scavenger of NO• against the DAF-2 which serves as the detector molecule. The product, DAF-2T, is separated from the reaction mixture by reversed-phase high performance liquid chromatography and its fluorescence intensity signals were measured at excitation and emission of 495 and 515 nm respectively. The results showed that the second order reaction rate constant of DAF-2 with NO• in air-saturated aqueous solution are comparable, with the average value of (6.28 ± 0.45) × 10 6 M-1s -1 . Also, DAF-2 can react with NO• directly thereby by-passing the N2O3-mediated formation of DAF-2T at low NO• formation rates