Investigation on tank and column leaching capability of a copper oxide ore by Ammonia reactants

Ammonia and Ammonium salts have been focused by the researchers of leaching process for several years due to low toxicity and cost, easy recovery and high selective recovery of metal, although the extent of researches were less than the chemical agents used in acid leaching. In this research, tank and column leaching methods of Meskani mine copper oxide ore using ammonium hydroxide and ammonium carbonate reagents have been studied. For the tank leaching experiments, response surface methodology (RSM) with input parameters as the ammonium hydroxide concentration, liquid to solid ratio and time was used. The high correlation coefficient obtained (0.96) indicates a good conformity of the proposed quadratic model with experimental data. Copper recovery under optimal conditions (88 g/L ammonium hydroxide concentration, liquid to solid ratio of 7 and leaching time of 120 minutes) was found to be 96.22 percent.For the column leaching experiments, selected parameters were ammonium hydroxide concentration, flow rate, size and leaching time, designed and analyzed in three levels using L9 array of Taguchi method. According to the results, the optimum value of abovementioned parameters were estimated at 40 gr/L, 15.6 L/m2h, 1-4.75 mm and 10 days, respectively. Also the most important parameters influencing leaching process were identified as ammonium hydroxide concentration, size and leaching time, respectively. Recovery of 80.6 percent was obtained at the proposed optimum conditions confirming the model obtained from the regression. Finally, kinetics of copper column leaching was studied briefly and it was found that the diffusion mechanism shows a good conformity with experimental data.