Adsorption of lead(II) from aqueous solution using Africa elemi seed, mucuna shell and oyster shell as adsorbents and optimization using Box–Behnken design

Abstract

The aim of this study was to model and optimize the adsorption of Pb(II) ions from an aqueous solution using Africa elemi seed, mucuna shell and oyster shell modified with orthophosphorous acid used as adsorbents. The influence of operational parameters such as adsorbent dosage, initial pH and contact time was evaluated by response surface methodology (RSM). The interactions between the operational parameters were evaluated using Box–Behnken design of response surface methodology. The optimum conditions for maximum removal of Pb(II) ions were observed at pH of 2.0, 100 mg adsorbent dosage and 70 min of contact time, with correlation coefficient R2, 0.996 for Africa elemi seed adsorbent; pH of 6.0, 100 mg adsorbent dosage and 40 min contact time with R2 0.996 for mucuna shell adsorbent; and pH of 6.0, 100 mg adsorbent dosage and contact time of 40 min for oyster shell adsorbent. The ANOVA results obtained from the RSM were analyzed using second-order polynomial equations, and the contour plots showed the interaction among the variables of the adsorption. This shows that the prepared low-cost adsorbents can be effectively adopted for the removal of Pb(II) ions from industrial wastewaters.