Photoelectrocatalytic degradation of sulfadiazine by Ag3PO4/MoS2/TiO2 nanotube array electrode under visible light irradiation

Photoheterotrophic extracellular reduction of ferrihydrite activates diverse intracellular metabolic pathways in Rhodopseudomonas palustris for enhanced antibiotic degradation

Anoxygenic photosynthetic bacteria (APB) have been frequently detected as a photoautotrophic Fe-carbon cycling drivers in photic and anoxic environment. However, the potential capacity of these bacteria for photoheterotrophic extracellular reduction of iron-containing minerals and their impact on the transformation of organic pollutants remain currently unknown. This study investigated the capacity of R. palustris, a purple non-sulfur anoxygenic photosynthetic bacterium, to reduce ferrihydrite (Fh) and its correlation with sulfamethazine (SDZ) degradation were firstly investigated. The results revealed that R. palustris could undergo photoheterotrophic extracellular reduction of Fh to form goethite through direct contact, facilitating the formation of conductive bands and enter the interior of cells with a maximum Fe(II)/Fe(T) ratio of up to 39 % within 8 days which led to 13 % increase in assimilation rate of acetate carbon and 53.2 % increase in SDZ degradation rates, as compared with those by R. palustris alone. Moreover, the intermediates generated during the degradation of SDZ by R. palustris-Fh exhibited relatively lower developmental toxicity compared with the original SDZ molecule. The extracellular reduction of Fh significantly up-regulated the expression of genes related to photosynthetic metabolic enzymes, extracellular electron transporters, and extracellular degrading enzymes in R. palustris. This enhancement promoted the photoheterotrophic metabolism and extracellular secretion of photosensitive active compounds in R. palustris, thereby enhancing both the biodegradation and photosensitive degradation of SDZ.

A novel alginate-embedded magnetic biochar-anoxygenic photosynthetic bacteria composite microspheres for multipollutant removal: Mechanisms of photo-bioelectrochemical enhancement and excellent reusability performance

Existing wastewater treatment technologies face the key challenge of simultaneously removing emerging contaminants and nutrients from wastewater efficiently, with a simplified technological process and minimized operational costs. In this study, a novel alginate-embedded magnetic biochar-anoxygenic photosynthetic bacteria composite microspheres (CA-MBC-PSB microspheres) was prepared for efficient, cost-effective and one-step removal of antibiotics and NH4+-N from wastewater. Our results demonstrated that the CA-MBC-PSB microspheres removed 97.23% of sulfadiazine (SDZ) within 7 h and 91% of NH4+-N within 12 h, which were 21.23% and 38% higher than those achieved by pure calcium alginate-Rhodopseudomonas palustris microspheres (53% and 45.7%), respectively. The enhanced SDZ and NH4+-N removal were attributed to the enhanced photoheterotrophic metabolism and excretion of extracellular photosensitive active substances from R. Palustris through the photo-bioelectrochemical interaction between R. Palustris and magnetic biochar. The long-term pollutants removal performance of the CA-MBC-PSB microspheres was not deteriorated but continuously improved with increasing ruse cycles with a simultaneous removal efficiency of 99% for SDZ and 92% for NH4+-N after three cycles. The excellent stability and reusability were due to the fact that calcium alginate acts as an encapsulating agent preventing the loss and contamination of R. palustris biomass. The CA-MBC-PSB microspheres also exhibited excellent performance for simultaneous removal of SDZ (89% in 7 h) and NH4+-N (90.7% in 12 h) from the secondary effluent of wastewater treatment plant, indicating the stable and efficient performance of CA-MBC-PSB microspheres in practical wastewater treatment.

Enhanced photodegradation of antibiotics based on anoxygenic photosynthetic bacteria and bacterial metabolites: A sustainably green strategy for the removal of high-risk organics from secondary effluent

Antibiotic residues in effluents discharged from wastewater treatment plants (WWTPs) have been considered high-risk organics due to biorefractory property and potential toxicity. Secondary pollution and unsustainability existed in advanced treatment of secondary effluent are currently in urgent need of improvement. In this study, a sustainably green strategy based on Rhodopseudomonas palustris (R.palustris) by regulating the structure of extracellular polymeric substances (EPS) was proposed for the first time to achieve efficiently removal of sulfadiazine (SDZ). Results showed that 0.2 V was the optimal external potential for R.palustris to efficiently remove SDZ, where the biodegradation rate constant obtained at this potential was 4.87-folds higher than that in open-circuit mode and a complete removal was achieved within 58 h in the presence of EPS extracted at this potential. Three-dimensional excitation-emission matrix (3D-EEM) spectra analysis suggested that tryptophan protein-like, tyrosine protein-like, humic acid-like and fulvic acid-like substances present in EPS were the main effective components which was responsible for the indirect photodegradation of SDZ. The quenching experiments showed that ³EPS* was the dominant reactive species which accounted for 90% of SDZ removal. This study provides new implications for the advanced treatment of secondary effluent organic matters by developing eco-friendly bioaugmentation technology and biomaterials.

Preparing a dual-function BiVO4/NiFe-LDH composite photoanode for enhanced photoelectrocatalytic wastewater treatment and simultaneous hydrogen evolution

The proposed PEC degradation over the BiVO4/NiFe-LDH photoelectrode under visible light irradiation and simultaneous hydrogen evolution at the cathode.

Applications of anodized TiO2 nanotube arrays on the removal of aqueous contaminants of emerging concern: A review

The presence of contaminants of emerging concern (CECs) in various water bodies and the associated threats to eco-system and human society have raised increasing concerns. To fight against such a problem, TiO₂ photocatalysis is considered to be a powerful tool. In recent decades, TiO₂ nanotube array (TNA) fabricated by electrochemical anodization emerged as a viable immobilized catalyst and its applications on CECs removal have gained a considerable amount of research interest. We herein present a critical review on the development of TNA and its applications on the removal of aqueous CECs. In this work, the CECs removal in different TNA based processes, the CECs removal mechanisms, the role of TNA properties, the role of operational parameters, and the role of water matrices are discussed. Moreover, perspectives on the current research progress are presented and recommendations on future research are elaborated.