Abstract: The removal of zinc cations from aqueous solution by Ca-bentonite and Na-exchanged bentonite was studied.Such factors of affecting the adsorption of bentonite as the initial concentration of Zn²⁺, the liquid-to-solid ratio, pH value, adsorption time, stirring speed, temperature, and bentonite particle are investigated.The results showed that the removal of Zn²⁺ by Ca-bentonite and Na-exchanged bentonite can be equal at 2 h.The removal rate of Zn²⁺ by bentonite can be improved in various degree by increasing pH value, adsorption temperature, stirring speed, time extension, and decreasing bentonite particle, the initial concentration of Zn²⁺, and the liquid-to-solid ratio.In a complex system, Pb²⁺ has not influenced the removal of Zn²⁺ by both of bentonites, while Cr⁶⁺ can decease it.

Key words: Bentonite, Zn²⁺, Adsorption