Removal of Zinc from Wastewater through the Reduction Potential Determination and Electrodeposition Using Adsorption-Desorption Solutions

The rubber product manufacturing industry generates large volumes of wastewater containing on average 10 ppm of zinc. Presently, zinc is removed via a chemical precipitation process generating hazardous precipitate that requires secure disposal. This study evaluated the removal of zinc through adsorption on Palm Shell Activated Carbon (PSAC) and subsequent desorption in hydrochloric, nitric (0.1 and 0.2 M) and citric (0.2 and 0.5 M) acids to produce solutions for the electrodeposition of zinc to achieve the permissible discharge level of 2 ppm. The highest desorption efficiency was achieved using HCl. Cyclic Voltammetry (CV) was applied to determine the reduction potential of zinc in desorption solutions. The presence of KCL and a buffer solution improved the electrodeposition of zinc. The chloride-based solution showed the best electroreduction behavior of zinc with a well-defined reduction peak as compared to the nitrate and citrate-based solutions, with a wider reduction peak and no peak, respectively. The chloride-based solution, selected for the electrodeposition experiments, showed 64 % reduction in zinc concentration within 10 min. The prolonged to 30 min electrodeposition resulted in only 7 % of further increment. Overall, the obtained results confirm the feasibility of zinc removal through the electrodeposition from the adsorption-desorption solution, which provides an effective alternative to the currently industrially used chemical precipitation method.