Hardness and chloride removal in dewatering system: Modeling and optimization of electrochemical reaction

The electrocoagulation (EC) process is a novel approach in the mining industry, especially to recycle water in the dewatering system of a mineral processing plant. In this research, the electrocoagulation process was studied to remove the hardness and chloride ions from concentrate thickener overflow water under different operating conditions: retention time (5–15 min), initial pH (4–10), current density (41.6–166.6 A/m2) and electrode type (Fe, Fe-Al, Al). Four factors with three levels with the D-optimal response surface design were applied for optimization. As a result, the optimal situation for the electrocoagulation process was characterized by a retention time of 15 min, initial pH of 9.08, the current density of 139.59 A/m2, and electrode type Fe-Al. In this situation, the maximum removal efficiency of hardness (60.11%) and chloride (98.38%) were yielded with a desirability value of 0.989. These results illustrated the effectiveness of the EC process as an influence method for the removal of hardness and chloride in terms of separation.