Experimental binding of lead to a low cost on biosorbent:: Nopal (Opuntia streptacantha)

The use of nopal cladodes (Opuntia streptacantha) as raw material for Pb2+ biosorption was investigated. Batch experiments were carried out to determine Pb2+ sorption capacity and the efficiency of the sorption process under different pH, initial Pb2+ and nopal biomass concentrations. The experimental data showed a good fit to Langmuir and Freundlich isotherms models. The maximum adsorption capacity for Pb2+ was 0.14 mmol g(-1) with an efficiency higher than 94% (pH 5.0 and 2.5 g L-1 nopal biomass). The Pb2+ kinetics were best described by the pseudo-second-order rate model. The rate constant, the initial sorption rate and the equilibrium sorption capacity were determined. The practical implication of this study is the development of an effective and economic technology in which the nopal biomass did not undergo any chemical or physical pretreatment, which added to nopal abundance in Mexico and its low cost makes it a good option for Pb2+ removal from contaminated waters. (c) 2007 Elsevier Ltd. All rights reserved.