Removal of lead from solution by combination of natural zeolite-kaolin-bentonite as a new low-cost adsorbent

Recently several kinds of low-cost adsorbents were developed for the extreme environmental and waste treatment processes. The adsorption capacity and physico-mechanical properties of adsorbent are basically affected by mixing ratio of the used materials. These requirements cause to apply the technique of experiment to optimize mentioned properties. In the present investigation commercial zeolite, bentonite and kaolin were used in experimental design algorithm due to their abilities in removal of heavy metal ions. Different amounts of used powders were mixed according to mixture design algorithm and shaped by extrusion technique in the form of Raschig ring. The test rings were calcined at 600 and 700 degrees C after drying in laboratory oven and characterized by determining porosity, diametrical compressive strength and adsorption capacity. In order to manufacture applicable adsorbent, the response surface analysis method was used to optimize mixing ratio of materials. The investigation was concluded that the strength and adsorption capacity can be simultaneously optimized by the addition of 66.67, 29.17 and 4.16 wt.% zeolite, bentonite and kaolin respectively. In the next part of work, the kinetics and adsorption isotherm of lead on selected composition was mathematically investigated. The Langmuir isotherm and pseudo second order kinetic model showed the acceptable accuracy in prediction of adsorption data. The possibility of lead immobilization by fabricated rings can be useful in industrial practice. (C) 2011 Elsevier B.V. All rights reserved.