Integrating Reactive Chlorine Species Generation with H₂ Evolution in a Multifunctional Photoelectrochemical System for Low Operational Carbon Emissions Saline Sewage Treatment

Abstract

Conventional wastewater treatment plants (WWTPs) suffer from high carbon emissions and are inefficient in removing emerging organic pollutants (EOPs). Consequently, we have developed a low operational carbon emissions multifunctional photoelectrochemical (PEC) system for saline sewage treatment to simultaneously remove organic pollutants, ammonia, and bacteria, coupled with H2 evolution. A reduced BiVO4 (r-BiVO4) photoanode with enhanced PEC properties, ascribed to constructing sufficient oxygen vacancies and V4+ species, was synthesized for the aforementioned technique. The PEC/r-BiVO4 process could treat saline sewage to meet local WWTPs’ discharge standard in 40 min at 2.0 V vs Ag/AgCl and completely degrade carbamazepine (one of EOPs), coupled with 633 μmol of H2 production; 93.29% reduction in operational carbon emissions and 77.82% decrease in direct emissions were achieved by the PEC/r-BiVO4 process compared with large-scale WWTPs, attributed to the restrained generation of CH4 and N2O. The PEC system activated chloride ions in sewage to generate numerous reactive chlorine species and facilitate •OH production, promoting contaminants removal. The PEC system exhibited operational feasibility at varying pH and total suspended solids concentrations and has outstanding reusability and stability, confirming its promising practical potential. This study proposed a novel PEC reaction for reducing operational carbon emissions from saline sewage treatment.

Bias-free driven ion assisted photoelectrochemical system for sustainable wastewater treatment

“…This indicates that the mechanism of ion-electron coupling in our designed PEC system can be widely applied to more ionic electrode materials. Thereafter, to broaden the light harvesting range of the IAPEC system, we employed a bismuth vanadate (BiVO 4 ) photoanode with a visible light absorption band gap 28 , in addition to the previously selected TiO 2 photocatalyst which absorbs UV light. The characterization of the BiVO 4 electrode is presented in Supplementary Fig.…”

“…We compared the degradation rates of target contaminants in tradition PEC (with irradiation, with TiO 2 as photoanode and platinum sheet electrode (1*1 cm 2 ) as the counter electrode, the applied bias is 0, 0.5 and 1 V respectively. ), PC (irradiation only, with TiO 2 photoanode as photocatalyst), electrochemical (the applied bias (1 V) only) 28 . The controls of all experiments were carried out in the same concentration of sodium chloride as IAPEC.…”