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Exchange of cadmium and lead on sodium clinoptilolite zeolite

İşler, Hakan Murat
Heavy metal ions, such as cadmium and lead, should be removed from wastewaters to prevent bioaccumulation. Among many other separation processes, one of the alternatives is ion exchange involving a low cost packing material, clinoptilolite. Clinoptilolite is a natural zeolite and contains exchangeable cations such as Na+, K+, Mg2+, and Ca2+ in its structure. Aim of this study is to determine binary and multicomponent ion exchange behaviors of sodium enriched form of Gördes clinoptilolite for lead and cadmium ions. For this purpose, Pb+2 – Na+, Cd+2 – Na+ binary and Pb+2 – Cd+2 – Na+ ternary systems were investigated in column operations for concentrations between 0.005 to 0.02 N and flow rates between 5 to 20 mL/min at 25 ˚C. For determination of optimum particle size, 5/6, 8/10, 14/18, 20/30, 35/60, and 70/140 ASTM E-11 standard mesh ranges were tested and the optimum particle size, under the experimental conditions was found as 35/60. Furthermore, although the clinoptilolite has a theoretical ion exchange capacity of 2.14 meq/g based on its aluminum content, under experimental conditions maximum exchange level was determined as 1.08 meq/g. For binary and ternary experiments, it is observed that the clinoptilolite has affinity for both Pb2+ and Cd2+ ions. However, clinoptilolite has greater affinity to Pb2+ than Cd2+ ion. Therefore, selectivity sequence was determined as Pb2+>Cd2+>Na+. Additionally, for column studies, flow rates less than 10 mL/min and influent concentrations up to 0.01 N, sodium enriched form of Gördes clinoptilolite holds great potential to remove Pb2+ and Cd2+ ions from wastewaters.