Recovery of copper as CuS from artisanal gold smelting wastewater via sulfide precipitation and its utilization as an H₂O₂-based AOP catalyst

School of Chemical, Biological, and Materials Engineering and Sciences, Mapúa University, Intramuros, Manila 1002 Philippines

^* Corresponding author: kgnquiton@mapua.edu.ph

Abstract

The characterization of gold smelting wastewater from Meycauayan City, Bulacan revealed significant copper pollution exceeding WHO, US EPA, and DENR standards. Utilizing batch sulfide precipitation, three parameters—pH level, precipitant dose, and stirring speed—were examined for copper removal. The ANOVA for Quadratic Model demonstrated a strong fit for copper removal efficiency, with pH level and precipitant dose as the significant parameters. Optimal solutions for copper removal were identified as pH 8.64, 0.5 g L^-1 precipitant dose, and 120 rpm stirring speed which led to 99.32% copper removal efficiency. The recovered copper precipitates as the H₂O₂-based AOP catalyst were utilized in these solutions, thus, enhancing the degradation of Congo Red and Malachite Green dyes. The chemical degradation of dyes highlighted the efficacy of the recovered catalyst in facilitating the process, increasing degradation percentages significantly by 98.75% Congo Red degradation and 99.23% Malachite Green degradation. These findings highlight the potential of recovered copper in improving chemical degradation processes and contributing to sustainable water management practices. Therefore, the study offers valuable insights into using recovered copper as a catalyst for more efficient wastewater treatment.