Adsorption of Cr(VI) and Pb(II) from aqueous solution using agricultural solid waste.

Areca nut shell, an agricultural solid waste by-product, has been studied for the removal of heavy metals Cr(VI) and Pb(II) from aqueous solution. Parameters, such as equilibrium time, effect of initial metal ion concentration, effect of pH on the removal, were analyzed. An initial pH of 4.0 was found most favourable for Cr(VI) removal and 5.0 for Pb(II) removal. Two theoretical isotherm models, namely Langmuir and Freundlich, were analyzed for the applicability of the experimental data. The Langmuir adsorption capacity (Q0) was calculated. The results of thermodynamic parameters suggest the exothermic nature of the adsorption. The desorption studies were carried out using dilute hydrochloric acid. Maximum desorption of 88% for Cr(VI) and 91% for Pb(II) were achieved. Areca nut shell waste, the low cost adsorbent is found to be effective in the removal of Cr(VI) and Pb(II) ions, and hence it can be applied for the removal of heavy metals from industrial wastewater.