Equilibrium ion exchange studies of Zn super(2+), Cr super(3+), and Mn super(2+) on natural bentonite

Bentonite is a clay mineral often used in ion exchange processes due to its high ion exchange capacity. In the present study, a commercially available in Greece market bentonite was obtained and characterized by XRD, XRF, FTIR, BET, and TG/DTA analysis. Monmorillonite was the main component of bentonite sample (>80%). Ion exchange equilibria of Zn super(2+), Cr super(3+), and Mn super(2+) on bentonite was examined by use of batch equilibrium isotherms, distribution coefficients, and maximum exchange levels (MELs) under the same normality for all metals (0.01 N) at 25 plus or minus 2 degree C. The equilibrium isotherms for the metals studied exhibit a favorable-type isotherm. Selectivity series deduced from equilibrium isotherms are Cr super(3+) > Zn super(2 +) > Mn super(2+), and the same occurs for MELs. The Langmuir and Freundlich models were applied and fitted the equilibrium data for the metal ion uptake. A detailed literature review on heavy metals-bentonite equilibrium is provided.