Adsorption Efficiency of Bentonite Clay and Parrotia persica During Acid Mine Drainage Treatment for the Removal of Turbid Material

Abstract

We conducted jar tests on the efficacy of using various mixtures of pulverized bentonite clay and Parrotia persica plant to treat AMD from a mine in Mogale City, South Africa without adding alkalinity. Two nearly identical sets of experiments were conducted using the same materials after they were rinsed using distilled and potable waters, respectively, to remove impurities, and then dried in an oven at 60 °C for 24 h, after which they were pulverized again. The pH, electrical conductivity, oxidation reduction potential, turbidity, and metal concentrations were measured before and after the experiments. The samples were treated in a jar test using standard procedures, i.e. rapid and slow mixing and settling for 1 h. The results showed that increasing the concentration of P. persica relative to the bentonite improved treatment effectiveness and that the highest turbidity removal (> 96.8%) was produced by rinsing the mixtures with potable water, drying them, and then pulverizing them again. Potentially toxic metals were removed by more than 93.7%. The morphological structure of the SEM micrographs indicate that the removal mechanism involves both physical and chemical phenomena and that the clay and P. persica are both important, particularly to the physical aspects.