Betel-nut Peel as an Adsorbent in the Removal of Cd, Cr and Pb from Aqueous Solutions

The ability of Betel-nut Peel BP, an agricultural waste material, for the removal of chromium (Cr3+), cadmium (Cd2+) and lead (Pb2+) from aqueous solution has been investigated. In the batch tests experimental parameters were studied, including solution pH, contact time, adsorbent dose, initial solution volume of metal ions and initial metal ions concentration. The adsorbent exhibited good sorption potential at pH 4.0. Maximum removal of Cr, Cd and Pb (96-98.0) % with (60 mg/ mL) of sorbent was observed at 10 mg/L sorbate concentration. Removal of about 50-60% occurred in 50 min, and equilibrium was attained at around 90 min for all the three metal ions. The functional groups (C=O, S=O, OH) present on the carbon surface of BP were responsible for the adsorption of metal ions. The adsorption parameters were analyzed using both the Freundlich and Langmuir models. The value of KF is large and 1/n is 0.1-0.69, indicating that BP has high adsorption capacities for Cr3+, Cd2+ and Pb2+. The desorption studies were carried out using HCl. Maximum desorptions of 72% for Cd and Pb and 67% for Cr were attained with 6M HCl.