An insight into underlying purification mechanism of tannery wastewater based on carbon/sulfur segmented tracing strategy in electrochemical membrane reactor

Abstract

Relying on co-precipitation and thermally induced phase separation methods, a novel triple-layered heterojunction catalytic electrode membrane (PVDF/La/Sm/CeO2, LMOHCEM) was developed and applied in coupled microbial fuel cell and membrane bioreactor (CMMS), achieving enhanced performance for treating tannery wastewater. Hydrophobic LMOHCEM exhibits increased electrochemical activity (qT* 3.53 × 10-3C cm−2, qo* 2.2 × 10-3C cm−2), indicating superior electron transfer efficiency. The oxygen reduction reaction (ORR) process mediated by LMOHC follows a 2 × 2 e- transfer pathway, and density functional theory (DFT) calculations demonstrates a negative Bader charge (-60 |e|) for the synthesized catalyst. To serve for engineering, the CMMS was implemented in the operation of continuous-flow for tannery wastewater treatment, the system achieved optimized pollutant removal property (COD 98.3%, Cr 99.1%, Sulfide and Sulfate 100%). Based on the segmented tracing strategy, the whole process of carbon/sulfur production of the electrochemical membrane reactor was analyzed. Microbial community analysis confirmed the dominant functional bacteria in the reactor. Elucidated multiple removal pathways and underlying purification mechanisms related to chromium and organic matter in the CMMS were proposed. Overall, this work provides a perspective for exploring an electrochemical membrane reactor with enhanced removal features for efficient electroplating wastewater treatment through typical element tracing analysis.