Uptake of toxic metals from wastewater by activated carbon from agro industrial by-product

Activated carbon prepared from neem oilcake, by pyrolysis accompanied with microwave oven activation is evaluated for the adsorption of Cd(II) and Ni(II) from wastewater. Parameters such as pH, agitation time, metal ion concentration and adsorbent dose are studied. The percent removal increased with pH from 2.0 to 7.0. The adsorption data fit well with Langmuir, Freundlich and Temkin isotherm models. The adsorption capacity (qe) calculated from Langmuir isotherm are 54.95 mg Ni(II)/g and 23.70 mg Cd(II)/g at an optimal pH of 7.0 at 30°C for the particle size 0.120-0.075 mm. Adsorption of Cd(II) and Ni(II) by activated carbon from neem oilcake follows pseudo-second-order kinetic model. Desorption studies with dilute hydrochloric acid indicate that quantitative recovery of cadmium and nickel ions are possible. The mechanism of adsorption seems to follow ion exchange process. As neem oilcake is discarded as waste from oil processing industries, the carbon could be exploited for metal ions recovery from wastewater.