Different refractory organic substances degradation and microbial community shift in the single-chamber bio-photoelectrochemical system.

The single-chamber bio-photoelectrochemical system (BPES) with a BiOBr photocathode was developed for acid orange 7 (AO7), 2,4 dichlorophenol (2,4-DCP) and chloramphenicol (CAP) degradation under solar irradiation. Photoelectrochemical characterizations showed that the optimized BiOBr-photocathode exhibited great light-response property and excellent electrochemcial performance. Moreover, desired TOC removals were achieved for various organic pollutants, with the values of 90.97% (AO7), 81.41% (2,4-DCP) and 78.47% (CAP). Besides, the lower cathode potentials in the illuminated BPESs were favorable to efficient pollutants degradation. Significant microbial community shifts were observed among the inoculation and anodic biofilms from the BPES, and the most dominated species in anodic biofilms acclimated to various pollutants were Geobacter and Pseudomonas, which have the abilities of extracellular electrons transfer and organics degradation. Some other species that different from the inoculation were also identified from the BPES biofilms. This study suggested that BPES had great potential for refractory organics degradation.

Photocathode optimization and microbial community in the solar-illuminated bio-photoelectrochemical system for nitrofurazone degradation.

To further enhance the bio-photoelectrochemical system (BPES) performance for nitrofurazone (NFZ) degradation and current output, the g-C3N4/CdS photocathode was optimized, and microbial community shift from inoculation to the BPES was analyzed. Results showed that photocathode with g-C3N4/CdS (mass ratio of 1:9) loading of 7.5 mg/cm2 exhibited the best performance, with NFZ removal of 83.14% (within 4 h) and current of ~9 mA in the BPES. Proteobacteria accounted for the largest proportion: 66.53% (inoculation), 71.89% (microbial electrolysis cell (MEC) anode), 74.67% (BPES anode) and 57.31% (BPES cathode), respectively. In addition, Geobacter was the most dominant genus in MEC and BPES anode and cathode, which occupied 31.64%, 67.73% and 41.34%, respectively. The microbial compositions of BPES anode and cathode were similar, but different from that of MEC anode. Notably, Rhodopseudomonas, a photosynthetic species, was detected in the BPES. Cognition of microbial community in the BPES is important for advancing its development.

Nitrofurazone degradation in the self-biased bio-photoelectrochemical system: g-C3N4/CdS photocathode characterization, degradation performance, mechanism and pathways.

In this study, a self-biased bio-photoelectrochemical system (SB-BPES) was constructed using a bioanode and the g-C3N4/CdS heterojunction photocathode for nitrofurazone (NFZ) degradation under solar irradiation. The physio-chemical properties and optical performance of photocatalysts were characterized, and photo-electrochemical properties of various photocathodes were analyzed. Results showed that g-C3N4/CdS exhibited the broadest visible light absorption range (to 594 nm) and the most efficient e--h+ separation; and its corresponding photocathode showed the highest photocurrent (9.8 µA), and the lowest charge transfer resistance (5.43 ☓ 103 Ω). In the solar-illuminated SB-BPES with g-C3N4/CdS photocathode, about 80% of NFZ removal rate was achieved within 10 h. More importantly, TOC removal of 62.6% was achieved in 24 h, which was 1.8 times of that from the open circuit SB-BPES, and 4.3 folds of that from microbial degradation; also, about 1.5 times of those from SB-BPES with g-C3N4 and CdS photocathodes. Besides, reproducible current generations (∼1.0 mA) were produced. These verified that it was a self-sustained system for spontaneously pollutants degradation and electricity generation. Moreover, possible degradation mechanism and pathways were proposed according to the identified intermediates. This study provides inspiration for synchronic improving refractory organics degradation and net energy recovery.

Bio-photoelectrochemcial system constructed with BiVO4/RGO photocathode for 2,4-dichlorophenol degradation: BiVO4/RGO optimization, degradation performance and mechanism.

A single-chamber bio-photoelectrochemical system (BPES) constructed with BiVO4/reduced graphene oxide (RGO) photocathode was proposed for 2,4-dichlorophenol (2,4-DCP) degradation under simulated solar irradiation. The BiVO4/RGO (B/G) composites were synthesized, optimized and characterized by various techniques to analyze their physico-chemical and photocatalytic properties. Results showed that B/G (5 wt% - 9 h - 150 °C) exhibited the best photocatalytic activity for 2,4-DCP degradation, which was 1.5 times of that of BiVO4, due to its better light absorption, faster electrons transfer, and more efficient photo-generated e- - h+ separation. Reactive species trapping experiments revealed that ·OH was the main radical leading to 2,4-DCP degradation, and h+ also influenced 2,4-DCP removal. The 2,4-DCP (20 mg/L) removal rate and current output from the illuminated BPES were much higher than those of the unilluminated reactor (68.5 % vs. 41.8 %, 60.31 A/m3 vs. 40.07 A/m3) in 24 h, and the cathode potential was more negative, indicating that photocathode catalytic process was favorable to pollutants degradation and energy generation. Intermediates of 2,4-DCP degradation in the BPES were identified, and accordingly, possible degradation pathway and mechanism were proposed. This research advanced the development of efficient photocathode and mechanism of recalcitrant wastewater treatment in the BPES.