Efficient removal of As, Cu and Cd and synthesis of photo-catalyst from Cu-smelting waste acid through sulfide precipitation by biogenic gaseous H2S produced by anaerobic membrane bioreactor

Abstract

The proper disposal of Cu-smelting waste acid (CSWA) is a major challenge in sulfide ores pyrometallurgy industry due to its high content of H2SO4, extremely high concentration of As and multiple toxic metals. The neutralization precipitation using cheap CaO is the most widely used process in tackling CSWA. However, a large amount of hazardous wastes covering As and other heavy metals which requires further disposal is generated, and the valuable H2SO4 cannot be reused. Herein, anaerobic membrane bioreactor (AnMBR) is used to continuously produce gaseous H2S for sulfide precipitation of the refractory CSWA and simultaneous fabrication of photo-catalyst for the first time. The 200L AnMBR respectively gained the highest total H2S production of 6.41 g/h and the highest gaseous H2S production of 5.05 g/h under the optimal conditions, being 3–9 times higher than previous reports by other types of bioreactors. And the sulfide precipitation triggered by the maximum gaseous H2S of 5.05 g/h harvested almost 100 % removal for Cu, As and Cd from CSWA within a short time from 0.35 to 3.69 days. Moreover, the phase 1 precipitate covering Cu-S compounds displayed an efficient photo-catalytic activity. The sulfide precipitation by AnMBR showed an application potential in tackling the refractory CSWA and fabrication of valuable nanoparticle photo-catalyst.