Statistical Evaluation of Factors Affecting the Leaching Process of Waste Electrical and Electronic Equipment using Sodium Persulfate

Abstract

Recycling of waste electrical and electronic equipment (WEEE) is important not only to reduce the amount of waste requiring treatment, but also to promote the recovery of valuable materials. Implementation of the European Directive on WEEE and recycling targets imposed in the European Union will require new processes to be developed and applied to recover metals from WEEE. This study aims to provide an alternative process for the dissolution of metals from WEEE which contains Cu and Zn based on our previous research. The effects of leaching parameters, such as temperature, Na2S2O8 concentration, and leaching time, were separately investigated on leaching of copper, zinc, and brass (alloy composition −35% zinc and 65% copper) in Na2S2O8 solution (0.1, 0.2 and 0.3 M). Box–Behnken experimental design (BBD) method was used to determine the number and the condition of necessary leaching experiments. Statistical analysis of variance (ANOVA) was performed to see whether process parameters such as leaching time, temperature, and oxidant concentration are statistically significant or not on the leaching performance. Results show leaching time as the most influential factor in the dissolution process, for the first six models. Two extended models have been developed to optimize the parameters of the investigated process. In these models, we consider the metal composition as a model input next to the earlier investigated parameters. Optimal condition for maximum copper and zinc dissolution in Na2S2O8 environment can be found for parameter values: temperature 45°C, oxidant concentration 0.1 M and leaching time 35 min.