Single, binary and multi-component adsorption of some anions and heavy metals on environmentally friendly Carpobrotus edulis plant

A low-cost adsorbent and environmentally friendly adsorbent from Carpobrotus edulis plant was used for the removal of NO3-, H2PO4-, Pb2+ and Cd2+ ions from single, binary and multi-component systems. The efficiency of the adsorbent was studied using batch adsorption technique under different experimental conditions by varying parameters such as pH, initial concentration and contact time. In single component systems, the dried C edulis has the highest affinity for Pb2+, followed by NO3-, Cd2+ and H2PO4-, with adsorption capacities of 175 mg/g, 125 mg/g, 28 mg/g and 26 mg/g, respectively. These results showed that the adsorption of NO3- and H2PO4- ions from single and binary component systems can be successfully described by Langmuir and Freundlich isotherms. Freundlich adsorption model, showed the best fit to the single and binary experimental adsorption data. These results also indicated that the adsorption yield of Pb2+ ion was reduced by the presence of Cd2+ ion in binary metal mixture. The competitive adsorption of NO3-, H2PO4- Pb2+ and Cd2+ ions on dried C. edulis plant shows that NO3- and H2PO4- anions are able to adsorb on different free binding sites and Pb2+ and Cd2+ cations are able to adsorb on the same active sites of C. edulis particles. The dried C. edulis was found to be efficient in removing nitrate, phosphate, cadmium and lead from aqueous solution as compared to other adsorbents already used for the removal of these ions. (C) 2010 Elsevier B.V. All rights reserved.