Competitive adsorption of malachite green and Pb ions on natural zeolite

A natural zeolite was employed as adsorbent for removal of malachite green and Pb2+ ions from aqueous solution. A batch system was applied to study the adsorption behaviour of the dye and heavy metal in single and binary systems on the natural zeolite. Kinetic studies indicate that malachite green and Pb2+ adsorption on the natural zeolite in a single component system follows the first-order kinetics and the adsorption is diffusion process with single-stage for Pb2+ and two-stage for malachite green. For the single system, malachite green adsorption isotherm follows the Langmuir model while Pb adsorption follows the Freundlich isotherm. The adsorption capacities of malachite green and Pb at 30 degrees C, pH 6 are 5 x 10(-5) and 10 x 10(-5) mol/g, respectively. In the binary system, malachite green and Pb2+ exhibit competitive adsorption on the natural zeolite. The adsorption is reduced to 90 and 80% of single component of Pb2+ and malachite green, respectively. However, the total adsorption is higher. In the binary system, Pb2+ exhibits relative higher affinity and selectivity to be adsorbed on zeolite. The dynamic adsorption of malachite green and Pb2+ still follows the first-order kinetics. (c) 2007 Elsevier Inc. All rights reserved.