Removal of Heavy Metals (Fe, Mn and Cd) from Aqueous Solutions by Natural Zeolite and FeS Media

Objectives : The adsorption characteristics of Fe, Cd, and Mn in aqueous solution using zeolite and FeS media were investigated by the adsorption isotherm and kinetic model analysis.Methods : The adsorption characteristics of the heavy metals (Fe, Mn, Cd) were investigated using Langmuir or Freundlich adsorption isotherm. The analysis of pseudo-first or pseudo-second order reaction was also attempted to evaluate the rate limiting factor such as molecular diffusion or chemical adsorption on the absorbents.Results and discussion : The adsorption of the heavy metals on the zeolite and FeS media was more suitable for the Langmuir adsorption isotherm, representing that mono-layer absorption on the surface and no interaction between the absorbed solutes. The order of adsorption preference to zeolite was Fe > Cd > Mn, whereas the order of adsorption preference to FeS media was Cd > Fe > Mn. The adsorption kinetics of zeolite and FeS media were more suitable for pseudo-secondary reactions than for pseudo-primary reaction.Conclusions : The absorption capacity of FeS media for the heavy metals (Fe, Cd and Mn) in aqueous solution was higher than that of zeolite. The adsorption pattern was suitable for the Langmuir adsorption isotherm, and has kinetic characteristic by chemisorption.