Controllable H₂S supply via membrane contactors for safe and efficient arsenic precipitation from acidic wastewater

Sulfide precipitation is a popular technique for the treatment and resource recovery of arsenic-containing dirty acid wastewater. However, this approach frequently suffers from toxic hydrogen sulfide (H₂S) escape and agent wastage issues. Herein, a safe and efficient technique is proposed based on a polytetrafluoroethylene membrane contactor wherein the mass transfer resistance of the gas, membrane, and liquid phases can be easily and independently regulated to control the H₂S supply. Additionally, H₂S is transferred in bubble-free form, fundamentally avoiding the issue of gas escape, and uniform membrane distribution contributes to evenly distributed H₂S delivery. The results demonstrated that 99.3 % arsenic precipitation could be achieved and the H₂S emission ratio was limited to < 0.12 %, which was significantly better than traditional methods. Thus, highly efficient separation and resource recovery of heavy metals in wastewater can be achieved using this unique and controllable low-dose H₂S supply method. The separation factor between copper and arsenic was as high as 7490.9. This study provides a safe, reliable, and promising new approach for the treatment of arsenic-containing acidic wastewater.