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Photocatalytic disinfection with high performance is thought to be a promising way for water purification. Herein, plasmonic Ag doped urea-derived graphitic carbon nitride (g-C 3 N 4 ) composites were fabricated via in-situ photo-deposition at room temperature as the visible-light photocatalyst. Scan electron microscopy and transmission electron microscopy images showed the uniform dispersion of Ag nanoparticles on the surface of g-C 3 N 4 sheet, which facilitated the synergistic effect of antibacterial performance from Ag and photocatalytic property from Ag/g-C 3 N 4 composites. Photocatalytic water disinfection against Escherichia coli with visible light was performed to demonstrate the improved photocatalytic property with assistance of Ag. The 3-Ag/g-C 3 N 4 exhibited the best bactericidal performance by inactivating all bacteria within 120 min with damaged cell membranes of Escherichia coli observed by scan electron microscopy and transmission electron microscopy images. Photoluminescence spectra, steady-state surface photovoltage spectra, photocurrent response, and electrochemical impedance spectra results revealed that Ag nanoparticles inhibited the recombination of photo-generated e - and h + pairs and further reinforced the photocatalytic performance of g-C 3 N 4 . Scavenger experiments indicated that h + produced on valence band of g-C 3 N 4 dominated the photocatalytic disinfection process against Escherichia coli. This work further proved Ag/g-C 3 N 4 showed great potential in photocatalytic water disinfection under visible-light irradiation., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In this study, the feasibility of a novel Ca-Ag 3 PO 4 composite with visible light irradiation for the phenanthrene (PHE) degradation and algae inactivation in artificial seawater was firstly investigated. The experimental findings revealed that Ag 3 PO 4 phase was sucessfully formed on the Ca-based material, and the presence of Ca-based material could effectively keep Ag 3 PO 4 particles stable. An excellent performance on PHE degradation or algae inactivation was observed from Ca-Ag 3 PO 4 composite under visible light irradiation. The degradation of PHE or inactivation of algae not only could be efficiently achieved in the single mode, but also could be successfully achieved in the coexisting mode. Above 96% of PHE and algae were simultaneously removed within 12 h in the Ca-Ag 3 PO 4 /visible light system. It was further observed that the degradation of PHE and/or inactivation of algae increased with the increase of Ca-Ag 3 PO 4 dosage. HO was the primary radical responsible for PHE degradation, whereas HO and Ag + released from Ca-Ag 3 PO 4 mainly contributed to the algae inactivation. A possible mechanism involving the catalytic removal of PHE and algae by Ca-Ag 3 PO 4 under visible light irradiation was proposed. This study provides helpful guide for the simultaneous removal of various pollutants in real seawater., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Waterborne viruses with a low infectious dose and a high pathogenic potential pose a serious risk for humans all over the world, calling for a cost-effective and environmentally-friendly inactivation method. Optimizing operational parameters during the disinfection process is a facile and efficient way to achieve the satisfactory viral inactivation efficiency. Here, the antiviral effects of a metal-free visible-light-driven graphitic carbon nitride (g-C 3 N 4 ) photocatalyst were optimized by varying operating parameters with response surface methodology (RSM). Twenty sets of viral inactivation experiments were performed by changing three operating parameters, namely light intensity, photocatalyst loading and reaction temperature, at five levels. According to the experimental data, a semi-empirical model was developed with a high accuracy (determination coefficient R 2  = 0.9908) and then applied to predict the final inactivation efficiency of MS2 (a model virus) after 180 min exposure to the photocatalyst and visible light illumination. The corresponding optimal values were found to be 199.80 mW/cm 2 , 135.40 mg/L and 24.05 °C for light intensity, photocatalyst loading and reaction temperature, respectively. Under the optimized conditions, 8 log PFU/mL of viruses could be completely inactivated by g-C 3 N 4 without regrowth within 240 min visible light irradiation. Our study provides not only an extended application of RSM in photocatalytic viral inactivation but also a green and effective method for water disinfection., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Natural organic matter (NOM) continues to increase in drinking water sources due to many factors, including changes in land use and global climate. Water treatment facilities will need to evaluate the best treatment options to account for these higher NOM levels. The UV/H₂O₂ advanced oxidation process (AOP) is one treatment option that has shown success at reducing high levels of NOM. As a result, this study evaluated the UV/H₂O₂ for the reduction of NOM in a high NOM water matrix, the Florida Everglades. In addition to liquid H₂O₂, sodium percarbonate and sodium perborate were used as oxidants to evaluate their performance as alternatives to liquid H₂O₂. Results showed that all three oxidants were able to reduce aromatic carbon (UV₂₅₄) by 46-66% and dissolved organic carbon (DOC) by 11-19% at UV fluences of 2.6-2.7 J cm(-2) and an H₂O₂ dose of 100 mg L(-1). When the UV fluences were increased to 21.8-26.1 J cm(-2) at an H₂O₂ dose of 100 mg L(-1), UV₂₅₄ reduction increased to 79-97% and DOC to 42-82% for all three oxidants. All three oxidants performed statistically similar for UV₂₅₄ reduction. However, for DOC reduction, H₂O₂ performed statically better than both percarbonate and perborate, and perborate performed statistically better than percarbonate. While the UV/H₂O₂ AOP is effective for NOM reduction in high NOM waters, advances in electrical efficiency are needed to make it economically feasible., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Samples of riverine and coastal, filtered (filter pore size 0.2 microm) water were exposed to short-term sunlight irradiation which reduced their absorbance in the UV and visible regions. Absorbance losses in coastal chromophoric dissolved organic matter (CDOM) were up to 10-fold smaller than those in riverine CDOM. Accompanying changes of absorbance spectra shapes (increased slope parameter) were, probably, a result of decrease of the mean molecular size of light absorbing organic matter. The potential of coastal CDOM to photodegradation was smaller and was exhausted during the course of a day-long experiment. A distinctive feature of spectral changes after sunlight exposure was a maximum absorbance decrease which appeared at approximately 300 nm in riverine and at approximately 280 nm in coastal water. That selective absorbance loss has been ascribed in both cases to the disappearance of chromophores of terrestrial origin which, in coastal water, had a lower mean molecular size (due to flocculation and/or prior photodegradation) but, nevertheless, retained their molecular properties.