Photoelectrochemical sewage treatment by sulfite activation over an optimized BiVO<inf>4</inf> photoanode to simultaneously promote PPCPs degradation, H<inf>2</inf> evolution and E. coli disinfection

Abstract

A new photoelectrochemical (PEC) system by means of adding sodium sulfite (Na2SO3) was developed to treat sewage. The PEC system simultaneously promoted pharmaceuticals and personal care products (PPCPs) degradation, H2 evolution and E. coli disinfection using an optimized, visible–light driven BiVO4 photoanode. The PEC reactions were first carried out in 1.5 mM Na2SO3 electrolyte. 92.3% of 2 ppm benzophenone-3 (BZP) was degraded, and 115.36 μmol of H2 was produced in 90 min at 1.0 V vs. Ag/AgCl, which was a significant improvement over cases where the electrolyte was either Na2SO4 or NaCl. The sulfite ions were first activated by holes and then converted into sulfate radicals, which played a dominant role in the degradation of BZP. As the holes were caught by the sulfite, charge separation was also enhanced, increasing H2 evolution. The PEC reactions were also used to treat real sewage, in which case an 82% improvement in the rate constant of BZP degradation, 60% increase of H2 evolution, and 0.78 log enhancement of E. coli disinfection were achieved by adding 1.5 mM Na2SO3. The system was also feasible to degrade various PPCPs, and showed excellent reusability and stability, proving its great potential in sewage treatment.