Abstract:

Wastewaters 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+.