Zeolite facilitated adsorption of selected metals associated with mine drainage

Abstract

South Africa (SA) is a water scarce country, with 34 % of SA’s total population living in rural areas with very limited access to safe surface and groundwater sources. The pollution of these water sources is caused by many natural and anthropic causes, with industrial effluents being of the greatest impact. Adsorption column experiments were conducted to investigate the influence of pH, water hardness and mineral characteristics on the adsorptive capacity of the zeolite, clinoptilolite, for the removal of heavy metals prevalent in mine drainage (MD) besieging in SA. Clinoptilolite is a natural, commonly available, and inexpensive zeolite found in SA, which can be used by impoverished communities for MD contaminated surface and groundwater treatment. The results indicated that the adsorption capacity of the clinoptilolite increases with a decrease in pH, albeit an indication that the adsorption is better when the solution is closer to a neutral pH with the Freundlich isotherm describing the adsorption capacity. It was indicated that the activated clinoptilolite used, is suited both for acid and alkaline mine drainage. A Pseudo-second order kinetic model best described the adsorption of the investigated heavy metals. Furthermore, it was indicated that due to its crystal structure, the impurity quartz, does not consist of a large adsorption capacity.