ASSISTANT LECTURER, MICHAEL OKPARA UNIVERSITY OF AGRICULTURE UMUDIKE ABIA STATE NIGERIA
THIS IS THE DETOXIFICATION OF INDUSTRIAL EFFLUENTS USING BIO-MATERIAL THAT IS ENVIRONMENTAL FRIENDLY
Wasteswaters from industries should be treated before discharge. The pollution problems posed by toxic heavy metals to the environment have been a concern. The use of unmodified and mercaptoacetic acid modified kolanut pod husk as biosorbents in detoxifing Cd2+, Ni2+ and Pb2+ ions from aqueous solutions were investigated using a batch sorption process.Biosorption was carried out in a batch process at various contact time and dose with initial metal ions concentration of 100 mg/l using 250 µm size of the of the unmodified and modified kolanut pod husks respectively at a temperature of 25 0C and pH of 7.5. Maximum biosorption capacities of unmodified kolanut pod husk were observed at 3g, values given as 98.999 mg/g, 89.870 mg/g for Cd2+, Ni2+ and 89.890 mg/g for Pb2+ at 2g while that of modified kolanut pod husk indicated 99.952 mg/g at 2g for Cd2+ and 99.776 mg/g, 99.021 mg/g for Ni2+ and Pb2+ ions at 3g. More so at 60 minutes for Cd2+, 90 minutes for Ni2+ and 10 minutes for Pb2+, values given as 99.986 mg/g, 99.999 mg/g and 99.999 mg/g by the unmodified kola nut pod husk while modified kolanut pod husk gave 99.666 mg/g at 30 minutes for Cd2+, 99.664 mg/g at 30 minutes for Ni2+ and 96.164 mg/g at 90 minutes for Pb2+. Generally maximum biosorption were all favoured at low doses and at low contact time. The kinetic of metal ions biosorption on unmodified and modified kola nut pod husks have also been studied by fitting the data in Lagergren’s first-order, Ho-Mckay’s pseudo-second-order kinetics hypothesis and Elovich adsorption model. It was observed that the removal of metal ions over the biosorbent showed a better fit with the pseudo-second-order process and Elovich adsorption model than the pseudo -first-order. From this work kolanut pod husk had proven to be a good biosorbent for Cd2+, Ni2+ and Pb2+
Abstract: The biosorption of cadmium(II) ions on Oedogonium sp. is studied in a batch system with respect to initial pH, algal dose, contact time and the temperature. The algal biomass exhibited the highest cadmium(II) uptake capacity at 25 degrees C, at the initial pH value of 5.0 in 55 min and at the initial cadmium(II) ion concentration of 200 mg L(-1). Biosorption capacity decreased from 88.9 to 80.4 mg g(-1) with an increase in temperature from 25 to 45 degrees C at this initial cadmium(II) concentration. Uptake kinetics follows the pseudo-second-order model and equilibrium is well described by Langmuir isotherm. Isotherms have been used to determine thermodynamic parameters of the process, viz., free energy change, enthalpy change and entropy change. FTIR analysis of algal biomass revealed the presence of amino, carboxyl, hydroxyl and carbonyl groups, which are responsible for biosorption of metal ions. Acid pretreatments did not substantially increase metal sorption capacity but alkali like NaOH pretreatment slightly enhanced the metal removal ability of the biomass. During repeated sorption/desorption cycles at the end of fifth cycle, Cd(II) sorption decreased by 18%, with 15-20% loss of biomass. Nevertheless, Oedogonium sp. appears to be a good sorbent for removing metal Cd(II) from aqueous phase.
Pub.: 19 Oct '07, Pinned: 30 Aug '17
Abstract: The biosorption characteristics of Pb(II) and Cd(II) ions from aqueous solution using the macrofungus (Amanita rubescens) biomass were investigated as a function of pH, biomass dosage, contact time, and temperature. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherm of the metal ions by A. rubescens biomass. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The maximum biosorption capacity of A. rubescens for Pb(II) and Cd(II) was found to be 38.4 and 27.3mg/g, respectively, at optimum conditions of pH 5.0, contact time of 30min, biomass dosage of 4 g/L, and temperature of 20 degrees C. The metal ions were desorbed from A. rubescens using both 1M HCl and 1M HNO(3). The recovery for both metal ions was found to be higher than 90%. The high stability of A. rubescens permitted ten times of adsorption-elution process along the studies without a decrease about 10% in recovery of both metal ions. The mean free energy values evaluated from the D-R model indicated that the biosorption of Pb(II) and Cd(II) onto A. rubescens biomass was taken place by chemical ion-exchange. The calculated thermodynamic parameters, DeltaG degrees , DeltaH degrees and DeltaS degrees showed that the biosorption of Pb(II) and Cd(II) ions onto A. rubescens biomass was feasible, spontaneous and exothermic under examined conditions. Experimental data were also tested in terms of biosorption kinetics using pseudo-first-order and pseudo-second-order kinetic models. The results showed that the biosorption processes of both Pb(II) and Cd(II) followed well pseudo-second-order kinetics. Based on all results, It can be also concluded that it can be evaluated as an alternative biosorbent to treatment wastewater containing Pb(II) and Cd(II) ions, since A. rubescens is low-cost biomass and has a considerable high biosorption capacity.
Pub.: 11 Oct '08, Pinned: 30 Aug '17
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