Synthesis and characterization of ZSM-5 zeolite from rice husk ash and their adsorption of Pb2+ onto unmodified and surfactant-modified zeolite

Local rice husk ash was precleaned with chemical treatment using NaOH and HCl solutions and well incorporated with other components forming zeolites; under hydrothermal conditions, to synthesize ZSM-5. ZSM-5 zeolites were characterized with several techniques including XRD, FT-IR and N-2 adsorption. The effect of Na2O/SiO2 ratio, on ZSM-5 preparation was investigated. The results clearly show that Na+ cation plays a structure directing role as well as a charge balancing role. Lead binding was most effective when the zeolite was treated with surfactant solutions. TPABr-zeolite in aqueous suspension (10 g/L) sorbed up to 85% of Pb2+ from solutions containing 50-140 ppm Pb2+. The results suggested that TPABr modified zeolites had higher adsorption for Pb2+ than the unmodified zeolite or modified by n-PA or TBABr or CTAB. The adsorption conditions were optimized, and the mechanisms of adsorption are briefly discussed. (C) 2011 Elsevier B.V. All rights reserved.