Adsorption of Hg2+ and Cd2+ by ethylenediamine modified peanut shells

In this study, an absorbent material was prepared using peanut shells modified with epichlorohydrin and ethylenediamine. Peanut shells were modified by mixing with 10 mL ethylenediamine, 100 mL water and 1 g NaCO3 per 10 g shells at 60 °C for 2 h. Factors affecting the adsorption behavior of Hg2+ and Cd2+, such as pH, initial metal concentration and adsorption time, were then investigated. Results suggested that optimal Hg2+ adsorption by modified peanut shells can be obtained by adding 0.2 g modified peanut shells per 25 mL of 10 mg/L Hg2+ and mixing at a fixed pH of 3.0 for 30 min. The adsorption rate was merely 37%, while after modification the adsorption rate can reach 100% for Hg2+. Data also suggested that separation of Hg2+ and Cd2+ can be achieved by maintaining the solution acidity to less than pH 2.5.