An eco-friendly and low-cost approach for separation and recycling of Mo and Cu from molybdenite purification wastewater

[Display omitted] •Molybdenum was almost completely leached out from dried wastewater.•Use of NaOH and Na2CO3 with certain concentrations led to separation of Mo and Cu.•Unlike Na2CO3, addition of H2O2 did not have much effect on Mo leaching efficiency.•By removing Mo, Fe, and Cl– from the electrolyte, Cu electrowinning became possible.•About 95% of Cu content in wastewater was recovered as a cathode with 0.9998 purity. The wastewater resulting from the treatment of molybdenite concentrate contains iron, copper, molybdenum, and significant quantities of ammonium chloride. This research aims to recover copper (Cu) and molybdenum (Mo) from the naturally dried wastewater using calcination, leaching, precipitation, and electrowinning processes. TGA/DTG analysis indicated that significant amounts of ammonia and chloride in the dried wastewater could be removed when heated to a temperature exceeding 300 °C. The alkaline leaching was employed to remove the Mo from the calcined dried wastewater. Alongside the NaOH as a primary leachant, H2O2, and Na2CO3 additives were also used. These additives enhanced the effectiveness of Mo leaching and facilitated the complete separation of Mo from Cu in the dried wastewater. Approximately 99 % of the Mo was extracted from the calcined dried wastewater, with no dissolution of copper in the leaching solution. The most optimal conditions for leaching Mo were attained at a temperature of 80 °C, a duration of 2 h, a NaOH concentration of 2 M, an L/S ratio of 15, and a Na2CO3 concentration of 0.5 M. More than 96 % of Mo was precipitated as molybdenum trisulfide when Na2S was added to leach liquor (after solution acidifying). Then the leach residue was dissolved in 20 vol% sulfuric acid. After iron and chloride ions removal, using 316 stainless steel cathode, lead-calcium anode, and a current density of 250 A/m2 at 45 °C, copper cathode with a purity of 99.98 % was obtained with 91 % cathodic current efficiency.