Leaching kinetics of copper flotation tailings in aqueous ammonia/ammonium carbonate solution



The experiments of agitation leaching were carried out in aqueous ammonia/ammonium carbonate solution, to recover copper from the flotation tailings of waste copper oxide residue. The main copper minerals contained in the flotation tailings are chrysocolla, malachite, and cuprite, with the copper grade of 1.12%. Effects of lixiviant concentration, solid-to-liquid ratio, stirring speed, and reaction temperature on copper leaching ratios at various time were investigated. It is found that the leaching ratio almost cannot be affected by time after 90 min of leaching. The optimised processing conditions have been determined, under which the leaching ratio of 70.6% is obtained. Kinetics analysis indicates that the copper leaching ratio is controlled by diffusion through the product layer in the initial 60 min of leaching, and corresponding measures to strengthen the copper extraction is proposed, with the activation energy of 32.3 kJ/mol. © 2012 Canadian Society for Chemical Engineering