Photoelectrochemical sewage treatment by a multifunctional g-C3N4/Ag/AgCl/BiVO4 photoanode for the simultaneous degradation of emerging pollutants and hydrogen production, and the disinfection of E. coli

Abstract

This study describes the photoelectrochemical (PEC) treatment of authentic sewage from Hong Kong for H2 production and degradation of emerging pollutants (EP’s) simultaneously, and disinfection of E. coli. The g-C3N4/Ag/AgCl/BiVO4 (CAB-1) coated thin film acted as the photoanode in a three-electrode configuration PEC cell and real sewage as the electrolyte. Electrochemical studies revealed the near reversible, diffusion-controlled and high electron transfer reaction at the electrode-electrolyte surface. For CAB-1, the achieved photocurrent density was 0.1–0.2 mA cm−2 at 1.23 V vs. RHE exhibiting the highest PEC degradation efficiency (11.15% h−1 cm−2) compared to other base materials like g-C3N4/BiVO4 (6.88% h−1 cm−2) or Ag/AgCl/BiVO4 (4.06% h−1 cm−2). During the same reaction, the evolved 118 μmol of H2 gas corresponds to a Faradic efficiency of 69.38%. The composition of sewage was found to influence the overall PEC efficiency. The higher amount of total suspended solids, turbidity, and anionic species decreased the efficiency while as the other parameters like alkaline pH increased the PEC efficiency. Photo-electrochemically, the CAB-1 also effectively disinfected the E. coli present in the sewage with a final discharge of ≤1000 CFU/mL which is within the permissible discharge limits (≤1500 CFU/mL), in Hong Kong.