Synthesis of kaolin supported nZVI and evaluation for the removal of Cr(VI) and Ni from waste streams

This study involved the synthesis of kaolin-supported nano zero valent iron (K-nZVI) and the evaluation of its performance for the removal of chromates and nickel from contaminated waters. K-nZVI was prepared by mixing a kaolin sample with a FeCl3 solution, followed by the addition of sodium borohydride for the reduction of Fe(III) to the zero valent state. The effectiveness of kaolin supported nZVI for Cr(VI) and Ni removal was evaluated by conducting batch experiments. The investigated parameters included the amount of K-nZVI per solution volume, the concentration of contaminants and the effect of pH. K-nZVI was found to be more efficient for the treatment of Cr(VI) contaminated waters than for the removal of Ni. Using 1 gram of K-nZVI per liter of solution, it was possible to reduce 20 mg/L of Cr(VI) to less than 5 mg/L within 3 hours. Starting with the same concentration of Ni, i.e.20 mg/L, the final concentration after 3 hours was aproximately 17 mg/L at pH 5.6, and dropped to 10 mg/L when the pH of the suspension was regulated to the value of 7.5. The results suggest the K-nZVI has a rather limited efficiency for Ni removal.