Effect of magnesium carbonate on the uptake of aqueous zinc and lead ions by natural kaolinite and clinoptilolite

Adsorption behavior of Zn 2+ and Pb 2+ ions on kaolinite and clinoptilolite, originating from natural resources, was studied as a function of contact time and concentration. Zn 2+ and Pb 2+ ions are quickly adsorbed on both minerals and the uptake of the latter is more favored. The uptake of both ions was then examined on kaolinite–MgCO3 and clinoptilolite–MgCO3 mixtures over a metal ions range from 1 to 10000 mg/L. The sorption behavior of Zn 2+ and Pb 2+ on pure MgCO3 was also studied. MgCO3 is much more effective in the retention of Zn 2+ and Pb 2+ ions, in particular at higher concentrations. The large increase in the retarded amounts of both ions was associated with formation of the hydroxy-carbonate phases; namely hydrozincite for Zn 2+ , and cerussite and hydrocerussite in the case of Pb 2+ .