In order to study the ability of bentonites to remove heavy metal ions from waste water and its factors affecting it,batch sorption experiments of Cu2+ were conducted on Ca-bentonite and Na-bentonite under various conditions.The results show that the adsorption process of bentonite accorded with the Freundlich isotherm model and that the sorption results of Na-bentonite are better than those of Ca-bentonite.Adsorption behavior of both bentonites was strongly depending on pH,initial concentration and additional amounts of bentonites.There are three kinds of adsorption mechanism at different ranges of pH values:the competition adsorption between Cu2+ and H+(pH8.3).The removal rate of bentonite decreases with an increase in the initial metal ion concentration.The maximum adsorption capacity of Na-bentonite was 26 mg/g and that of Ca-bentonite 12 mg/g.The removal rate of Cu2+ was practically 100% at the initial concentration of 40 mg/L,when 4 g/L of Na-bentonite and 14 g/L of Ca-bentonite were added to the solution.
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