Simple recycling of copper by the synergistic exploitation of industrial wastes: a step towards sustainability

A Green Recycling process for copper recovery by the synergistic treatment of two different industrial wastes is presented. Firstly, the solid waste generated during the processing of epoxy modeling compounds was treated with the waste nitric acid solution produced in the sputter cleaning. A faster leaching rate of copper without any effect of temperature was noticed, which can be attributed to the intermediate-controlled kinetics along with the autocatalytic behaviour of Cu2+ present in the waste solution. An increase in pulp density above 25% adversely affected the solubilisation of copper because of the decreased lixiviant acidity corresponding to the metals being leached. Subsequently, the key experimental parameters for liquid-liquid separation of copper using LIX 84-I after Fe-removal with D2EHPA, viz. equilibrium pH, extractant concentration, temperature, and phase ratio (O/A), were optimized and correlated with complexation chemistry. The extraction equilibrium constant (log K-ex = 1.67) under the studied conditions of nitrate media was determined by the log-log plot of D-star[H+](aq)(2) vs. ([HR](2))(org) Thermodynamic properties indicated a strong affinity of LIX 84-I towards Cu2+ due to the emergence of spontaneous inner-sphere coordination with disrupted hydration. A counter-current study for the separation and recovery of copper was performed under the optimized conditions, which has successfully validated the results of extraction and stripping isotherms exhibited by the McCabe-Thiele plots. The unfolded hydro-metallurgical process described in this study has a potential for sustainable utilization of wastes to recover the metal of interest at a 46% lower energy cost than the processing of primary ores.