Mechanical-Electrical dewatering (EDW) of mine Tailings: Influence of voltage level on water recovery and moisture reduction

This study aims to investigate the potential of mechanical–electrical dewatering (EDW) on the recovery of process water from tailings slurry of Miduk copper mine. The EDW experiments were carried out using three voltage levels, including 50, 70 and 90 V, and the mechanical pressures of 3 and 6 bar for 120 min. The moisture content and the pH values of the filtered tailings were determined at the end of the process. Moreover, the electrical resistivity and the electric energy consumption were calculated. To investigate the energy efficiency of the recovered/removed water, four indices were calculated including, water removal (WR), additional water removal (AWR), specific energy (SE) and normalised specific energy (NSE). Mechanical filtration extracted 63% and 71% of the process water at 3 and 6 bar, respectively. Also, EDW experiments recovered 8–31% more additional water. A higher rate was achieved for the process water by applying more voltage while increasing energy consumption. The EC and pH values of the recovered water were in a suitable range of the process water for Miduk copper mine. The average moisture content of filtered tailings reduced to 3.7–12.7% and indicated an ascending trend from anode to cathode sides. Although the pH values of the filtered tailings in the anode side decreased to the point of zero charge, the reverse electro-osmosis process did not significantly affect the potential of EDW. Due to the joined impact of moisture variation, temperature and hydrolysis process, the interpretation of electrical resistivity was complex. Overall, the least amount of energy consumption for removing the additional process water was achieved by applying a voltage level of 70 V. However, a combination of a mechanical pressure of 3 bar and a voltage of 90 V recovered up to 92% of water by the optimal values of SE and NSE indices.