Removal of Heavy Metals from Model Mine Wastewater by Adsorption Using Mongolian Natural Zeolites

摘要

Mongolian natural zeolites, whose base components were clinoptilolite, mordenite, and chabazite, were characterized in terms of parameters such as their elemental contents, cation exchange capacities, among others. Since the molar ratios of aluminum to silicon for the Mongolian natural zeolites used in this study were lower than those of pure zeolites, it was surmised that the natural zeolite samples contained substantial amounts of impurities. The cation exchange capacities of the natural zeolite samples were dependent on their aluminum content and were greater for the zeolites with higher aluminum contents. Batch equilibrium adsorptions of heavy metals such as copper, zinc, and manganese from model wastewater using the Mongolian natural zeolites were also carried out. The natural zeolites could adsorb and remove the heavy metals from the aqueous model solutions and also helped to adjust pH of the solutions to appropriate levels. The precipitation of the heavy metals in the form of their hydroxides owing to the addition of natural zeolite also aided the removal of the metals. The amounts of the heavy metals adsorbed at saturation as estimated by the Langmuir equation were almost the same for all the metals. In addition, these amounts increased with the pH of the feed solutions as well as with cation exchange capacities of the natural zeolites. Finally, it was found that the adsorption coefficient in the Langmuir equation was correlated with the hydrated ionic radii of the heavy metals being investigated for removal.