REMOVAL OF SILVER(I) FROM AQUEOUS SOLUTION USING JAPANESE NATURAL ZEOLITES (MORDENITE AND CLINOPTILOLITE): A COMPARATIVE STUDY

Abstract

The adsorption of silver ion in aqueous solution onto Japanese natural zeolites, i.e., mordenite (MZ) and clinoptilolite (CZ), from Iizaka mine, Fukushima Prefecture and Koriyama mine, Kagoshima Prefecture, respectively, is analyzed in this study. The effects of various parameters, i.e., solution pH, adsorbent dosage, adsorption time, silver ion solution concentration, and temperature, on silver ion adsorption onto the Japanese natural zeolites are investigated as a comparative study. For both zeolites, the optimum pH for silver adsorption is determined to be 3–4, and the adsorption processes can be described better using the Langmuir isotherm model than the Freundlich isotherm model. The calculated maximum adsorption capacities of MZ and CZ are 0.728 mmol‧g^-1 and 0.546 mmol‧g^-1, respectively. Adsorption kinetics studies are conducted, and the results show that the adsorption processes for both zeolites correspond to the pseudo-second-order kinetics model instead of the pseudo-first-order model. These results suggest Japanese natural zeolites have a potential for removing silver ion from aqueous solution.