Optimization of copper recovery from electronic waste using response surface methodology and Monte Carlo simulation under uncertainty

Electronic waste (e-waste) production is currently the largest growing waste stream in the world. These wastes contain the precious metals such as gold, silver, and platinum, and the base metals including copper, lead, nickel, iron, and zinc. Therefore, economically and environmentally, the valuable and basic metals recovery from e-waste is important. Before the cyanidation leaching, sulfuric acid and hydrogen peroxide are used as leaching and oxidizing agents, respectively, for the dissolution of base metals. The most important operational parameters affecting the base metals leaching are sulfuric acid concentration, acid to oxidant ratio, temperature, pulp density, and leaching time. Using the response surface analysis, the maximum copper leaching recovery of 97.52% was achieved under the optimal conditions: temperature = 50 °C, leaching time = 4 h and 35 min, pulp density = 5%, sulfuric acid concentration = 4 M, and acid/oxidant ratio = 4. To overcome the errors of experiments caused by the preparation of sample, weighing, analysis, etc., and consequently, the uncertainty in results, Monte Carlo simulation for modeling under uncertainty conditions was used. Accordingly, first, the type and characteristics of the probability distribution function were determined for each of the operational parameters. Then, the distribution function characteristics of copper leaching recovery were obtained. The results showed that the uncertainty of achieving a recovery percentage higher than 97.52% under the optimal conditions is 5.8%.