Modification of natrolite zeolite with iron(III) nitrate: Application for cyanide removing from industrial wastewaters

An iron oxide–Natrolite system was synthesized by adding natural Natrolite zeolite to an iron nitrate solution under strongly basic condition. A combination of XRD, XRF and FTIR spectroscopies, as well as TG/DSC thermal analyses provided information on the type of Fe species located on the zeolite surface. According to cyanide adsorption experiments, the Fe–Natrolite system is a promising new material since it adsorbs significantly larger cyanide concentrations than unmodified Natrolite. The effects of different parameters such as pH, amount of adsorbent and contact time have been studied. The experimental data obtained for optimum conditions were selected for modeling the adsorption behavior of the materials using 6 isotherm equations (Freundlich, Langmuir, Langmuir-Freundlich, Dubinin-Radushkevich, Redlich- Peterson, Toth). The obtained modeling results indicated that, although the three-parameter models, taking into account the surface heterogeneity, provided the closest approach to the measurement data, the parameters estimates could be highly biased. On the other hand, the two-parameter Langmuir isotherm was sufficient to describe the process equilibrium in terms of smallest number of adjustable parameters and approximation of the sorption capacity. The modified zeolite has been used for removing of cyanide from industrial wastewaters.