Treatment of wastewater produced during the hydrometallurgical extraction of silver from in-mold structural electronics

Abstract

Hydrometallurgical processes utilize aqueous solutions to extract metals from ores, concentrates, or waste, resulting in a substantial consumption of freshwater and wastewater generation. This study investigates the treatment of wastewater produced during the hydrometallurgical silver extraction from in-mold structural electronics (IMSEs), aiming at minimizing discharge and ensuring water reuse. IMSE is an emerging technology that offers a lighter, cost-effective alternative to traditional PCBs. The generated wastewater contains high levels of COD (14.48 g/L) and iron (8.69 g/L). It was treated using a Fenton process by adopting a 22-full factorial design with center points to identify the best operative conditions. Following the analysis of variance (ANOVA) and model determination for COD abatement, Fisher's test was conducted to evaluate whether incorporating curvature into the model would enhance its fit to the experimental data. To further refine the process optimization, star points were added, resulting in a central composite design (CCD). The treatment resulted in a 93.6 % reduction in COD and a 99.9 % reduction in iron, with lime addition aiding in iron precipitation for water reuse. A quadratic model for COD removal indicated a high fit (R2 = 0.96), demonstrating the process's efficiency in reducing pollutants and promoting water reuse. Preliminary cost analysis revealed a total expenditure of 81.60 €/m³, significantly lower than the typical disposal costs of hydrometallurgical wastewater.

Keywords

• Wastewater treatment
• Fenton process
• In-mold structural electronics
• Minimal liquid discharge
• Sustainable water management