Shortage of water resources and deterioration of water quality have urged the need to develop new technologies for removal of contaminants from water. Heavy metals, produced by municipal and industrial activities, are among the most toxic contaminants present in natural and waste waters. Finding new appropriate and eco-friendly methods for elimination of these contaminants from water resources is vital to recycle anduse water efficiently. Adsorption is an effective and economic method for the water purification purposes. Clays and natural polymers have been widely used as adsorbents, due to their natural abundance, low cost and high specific surface area. If these adsorbents used as a hybrid material, some of their physical and chemical restrictions would be alleviated. In this study, alginate-bentonite and polyacrylic acid-bentonite hybrids were used for removal of lead (Pb) from aqueous solutions. Adsorption of Pb by alginate:bentonite composites in 2:1, 4:1 and 8:1 ratios and polyacrylic acid–bentonite hybrids were studies in batch systems. Besides, effects of pH, flow rate and initial Pb concentration on Pb retention were investigated in fixed-bed column systems. Results of the batch studies showed that Langmuir and Freundlich isotherm models were appropriate to describe equilibrium Pb sorption data. Pb sorption by the sorbents increased with the rise in solution pH from 4 to 6. Among the sorbents, the 2:1 alginate:bentonite hybrid showed the greatest Pb sorption capacity at pH values of 4 (111/9 mg g -1 ) and 6 (152.2 mg g -1 ). Based on C e-rel (av), S R , T R and ? f coefficients calculated from break-through curves, lower flow rates and initial Pb concentrations and higher pH values resulted in greater Pb removal from the solutions. It can be concluded that alginate:bentonite hybrid is a superior adsorbent for Pb removal from contaminated waters. Keywords : composite, polyacrylic acid, alginate, polymer, clay, fixed-bed column, adsorption, lead.
