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A study of kinetics and successive sorption/desorption of Zn and Cd uptake onto iron-modified zeolite

The sorption properties of iron-modified zeolite (IMZ) and kinetics of zinc and cadmium uptake have been investigated by the batch method. Two kinetic stages have been observed, fast uptake up to 240 min, followed by slow uptake up to equilibration. In order to investigate the rate limiting step, kinetic results were fitted to the reaction and diffusion kinetic models. The results indicate intraparticle diffusion as the rate limiting step. The Vermeulen's approximation model was used to predict the quantity of removed Zn and Cd per gram of IMZ. The results of successive sorption of Zn and Cd and their desorption with different electrolyte solutions have shown the best desorption efficiency in sodium salts solutions. A successive repetition of four sorption/desorption cycles has shown a small difference between the amount of sorbed and desorbed Zn and Cd from the second to the fourth cycle. This indicates excellent sorption/regeneration properties of IMZ.

iron-modified zeolite ; zinc ; cadmium ; kinetics ; sorption ; desorption

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