Removal of Fe(III) ion from aqueous solution by adsorption on raw and treated clinoptilolite samples

Iron (III) adsorption from aqueous solutions onto raw and pretreated clinoptilolite was investigated here. Various parameters for iron removal; initial solution pH, contact time and metal ion concentration were optimized. The equilibrium data were modeled by both the Langmuir and Freundlich adsorption isotherms at optimal conditions. Adsorption capacities of raw samples and those pretreated with Na2S2O8 at 20 °C , 70 °C and with HNO3 at 20 °C were all similar but samples pretreated with HNO3 at 70 °C were significantly different; iron (III) removal from samples pretreated with HNO3 decreased with increasing pretreatment temperature. Tests with Fe+3 solutions containing phenol, CsCl or KCl, indicated the continued presence of these ions in zeolite which either promoted or retarded the adsorption of iron. The Fe+3 adsorption capacity of clinoptilolite pretreated with HNO3 at 70 °C was about two times greater with, than without, CsCl and KCl. The kinetics of iron adsorption from aqueous solution were also investigated using the first-order Lagergren equation and a pseudo-second-order model.