Adsorption of Cd (II) From Aqueous Solution by Activated Charcoal Derived from Lapsi Seeds

Abstract

The potential and effectiveness of activated carbon derived from carbonization of Lapsi (Choerospondias axillaris) seed for adsorptive removal of cadmium (II) was examined by adsorption technique. The carbon obtained from Lapsi seed was chemically modified by treating with 1:1 HNO3 at 60o C. Boehm method was used to estimate the oxygen containing acidic functional groups. The acidic functional group, specific surface area and adsorptive capacity all greatly increased with chemical treatment with nitric acid. The specific surface area of the charcoal, after chemical treatment, increased to 600 m2/g from 45 m2/g. The ash, moisture and carbon contained in modified charcoal were found to be 3.5%, 0.2 % and 96.3 % respectively. The performance of the adsorbent was in par with commercial activated charcoal. Various parameters such as contact time, adsorbent dose, pH and metal ion concentrations on adsorption were studied, optimized and applied in the present study. The maximum adsorption capacity of charcoal to adsorb Cd(II) was found to be 12.53 mg/g at optimum pH of 6 and equilibrium was attained within 150 minutes. The adsorption of cadmium followed pseudo second order kinetic model and the rate constant of the process was found to be 1.73x10-3 g mg-1 min-1. Results indicated that the Langmuir model gave a better fit to the experimental data in comparison with the Freundlich isotherm.