Fertilizer-driven FO and MD integrated process for shale gas produced water treatment: Draw solution evaluation and PAC enhancement.

It is a great challenge for effective treatment of shale gas produced water (SGPW), a typical industrial wastewater with complex composition. Single forward osmosis (FO) or membrane distillation (MD) process has been widely used for desalination of SGPW, with membrane fouling not well addressed. Fertilizer draw solution (DS) with high osmotic pressure is less likely to cause FO fouling and can be used for irrigation. An integrated process using fertilizer-driven FO (FDFO) and MD process was proposed for the first time for SGPW treatment, and characteristics of fertilizer DS and powdered activated carbon (PAC) enhancement were assessed. The DS using KCl and (NH4)2SO4 had high MD fluxes (36.8-38.8 L/(m2·h)) and low permeate conductivity (below 50 µS/cm), increasing the contact angle of the MD membrane by 113 % than that without FO, while the DS using MgCl2 and NH4H2PO4 produced a lower reverse salt flux (0.9-3.2 g/(m2·h)). When diluted DS was treated using PAC, the MD permeate conductivity was further reduced to 35 µS/cm without ammonia, and the membrane hydrophobicity was maintained to 71-83 % of the original. The mechanism of the FDFO-MD integrated process for mitigating MD fouling and improving permeate quality was analyzed, providing guidance for efficient SGPW treatment.

Enhancing microfiltration membrane performance by sodium percarbonate-based oxidation for hydraulic fracturing wastewater treatment.

Low pressure membrane takes a great role in hydraulic fracturing wastewater (HFW), while membrane fouling is a critical issue for the stable operation of microfiltration (MF). This study focused on fouling mitigation by sodium percarbonate (SPC) oxidation, activated by ultraviolet (UV) and ferrous ion (Fe(II)). The higher the concentration of oxidizer, the better the anti-fouling performance of MF membrane. Unlike severe MF fouling without oxidation (17.26 L/(m2·h)), UV/SPC and Fe(II)/SPC under optimized dosage improved the final flux to 740 and 1553 L/(m2·h), respectively, and the latter generated Fe(III) which acted as a coagulant. Fe(II)/SPC oxidation enabled a shift in fouling mechanism from complete blocking to cake filtration, while UV/SPC oxidation changed it to standard blockage. UV/SPC oxidation was stronger than Fe(II)/SPC oxidation in removing UV254 and fluorescent organics for higher oxidizing capacity, but the opposite was noted for DOC removal. The deposited foulants on membrane surface after oxidation decreased by at least 88% compared to untreated HFW. Correlation analysis showed that UV254, DOC and organic fraction were key parameters responsible for membrane fouling (correlation coefficient＞0.80), oxidizing capacity and turbidity after oxidation were also important parameters. These results provide new insights for fouling control during the HFW treatment.

Gravity-driven membrane integrated with membrane distillation for efficient shale gas produced water treatment.

Substantial volumes of hazardous shale gas produced water (SGPW) generated in unconventional natural gas exploration. Membrane distillation (MD) is a promising approach for SGPW desalination, while membrane fouling, wetting, and permeate deterioration restrict MD application. The integration of gravity-driven membrane (GDM) with MD process was proposed to improve MD performance, and different pretreatment methods (i.e., oxidation, coagulation, and granular filtration) were systematically investigated. Results showed that pretreatment released GDM fouling and improved permeate quality by enrich certain microbes' community (e.g., Proteobacteria and Nitrosomonadaceae), greatly ensured the efficient desalination of MD. Pretreatment greatly influences GDM fouling layer morphology, leading to different flux performance. Thick/rough/hydrophilic fouling layer formed after coagulation, and thin/loose fouling layer formed after silica sand filtration improved GDM flux by 2.92 and 1.9 times, respectively. Moreover, the beneficial utilization of adsorption-biodegradation effects significantly enhanced GDM permeate quality. 100 % of ammonia and 53.99 % of UV254 were efficiently removed after zeolite filtration-GDM and granular activated carbon filtration-GDM, respectively. Compared to the surged conductivity (41.29 µS/cm) and severe flux decline (>82 %) under water recovery rate of 75 % observed in single MD for SGPW treatment, GDM economically controlled permeate conductivity (1.39-19.9 µS/cm) and MD fouling (flux decline=8.3 %-27.5 %). Exploring the mechanisms, the GDM-MD process has similarity with Janus MD membrane in SGPW treatment, significantly reduced MD fouling and wetting.

Improving membrane distillation performance by Fe(II) activated sodium percarbonate oxidation during the treatment of shale gas produced water.

Membrane distillation (MD) offers promise for recycling shale gas produced water (SGPW), while membrane fouling is still a major obstacle in standalone MD. Herein, sodium percarbonate (SPC) oxidation was proposed as MD pretreatment, and the performance of the single MD, SPC-MD hybrid process and Fe(II)/SPC-MD hybrid process for SGPW treatment were systematically evaluated. Results showed that compared to raw SGPW, the application of SPC and Fe(II)/SPC led to the decrease of the fluorescent organics by 28.54 % and 54.52 %, respectively. The hydrophobic fraction decreased from 52.75 % in raw SGPW to 37.70 % and 27.20 % for SPC and Fe(II)/SPC, respectively, and the MD normalized flux increased from 0.19 in treating raw SGPW to 0.65 and 0.81, respectively. The superiority of SPC oxidation in reducing the deposited membrane foulants and restoring membrane properties was further confirmed through scanning electron microscopy observation, attenuated total reflection fourier transform infrared, water contact angle and surface tension analyses of fouled membranes. Correlation analysis revealed that hydrophobic/hydrophilic matters and fluorescent organics in SGPW took a crucial role in MD fouling. The mechanism of MD fouling mitigation by Fe(II)/SPC oxidation was attributed to the decrease in concentrations and hydrophobicity of organic by synergistic oxidation, coagulation and adsorption.

Feasibility of replacing proton exchange membranes with pressure-driven membranes in membrane electrochemical reactors for high salinity organic wastewater treatment.

Membrane electrochemical reactor (MER) shows superiority to electrochemical oxidation (EO) in high salinity organic wastewater (HSOW) treatment, but requirement of proton exchange membranes (PEM) increases investment and maintenance cost. In this work, the feasibility of using low-cost pressure-driven membranes as the separation membrane in MER system was systematically investigated. Commonly used pressure-driven membranes, including loose membranes such as microfiltration (MF) and ultrafiltration (UF), as well as dense membranes like nanofiltration (NF) and reverse osmosis (RO), were employed in the study. When tested in a contamination-free solution, MF and UF exhibited superior electrochemical performance compared to PEM, with comparable pH regulation capabilities in the short term. When foulant (humic acid, Ca2+ and Mg2+) presented in the feed, UF saved the most energy (43 %) compared to PEM with similar removal rate of UV254 (∼85 %). In practical applications of MER for treating nanofiltration concentrate (NC) of landfill leachate, UF saved 27 % energy compared to PEM per cycle with the least Ca2+ and Mg2+ retention in membrane and none obvious organics permeation. For fouled RO and PEM with ion transport impediment, water splitting was exacerbated, which decreased the percentage of oxidation for organics. Overall, replacing of PEM with UF significantly reduce the costs associated with both the investment and operation of MER, which is expected to broaden the practical application for treating HSOW.

Mineral scaling induced membrane wetting in membrane distillation for water treatment: Fundamental mechanism and mitigation strategies.

The scaling-induced wetting phenomenon seriously affects the application of membrane distillation (MD) technology in hypersaline wastewater treatment. Unlike the large amount of researches on membrane scaling and membrane wetting, scaling-induced wetting is not sufficiently studied. In this work, the current research evolvement of scaling-induced wetting in MD was systematically summarized. Firstly, the theories involving scaling-induced wetting were discussed, including evaluation of scaling potential of specific solutions, classical and non-classical crystal nucleation and growth theories, observation and evolution of scaling-induced processes. Secondly, the primary pretreatment methods for alleviating scaling-induced wetting were discussed in detail, focusing on adding agents composed of coagulation, precipitation, oxidation, adsorption and scale inhibitors, filtration including granular filtration, membrane filtration and mesh filtration and application of external fields including sound, light, heat, electromagnetism, magnetism and aeration. Then, the roles of operation conditions and cleaning conditions in alleviating scaling-induced wetting were evaluated. The main operation parameters included temperature, flow rate, pressure, ultrasound, vibration and aeration, while different types of cleaning reagents, cleaning frequency and a series of assisted cleaning measures were summarized. Finally, the challenges and future needs in the application of nucleation theory to scaling-induced wetting, the speculation, monitoring and mitigation of scaling-induced wetting were proposed.

The shifting research landscape for PAH bioremediation in water environment: a bibliometric analysis on three decades of development.

Polycyclic aromatic hydrocarbons (PAHs) with their carcinogenic, teratogenic, and mutagenic effects can cause great damage to the ecosystem and public health when present in water. With bioremediation, PAH contamination in water environment can be greatly reduced in an eco-friendly manner. It has thus become the research focus for many environmental scientists. In this study, a bibliometric analysis on three-decade (1990-2022) development of PAH bioremediation in water environment was conducted from temporal and spatial dimensions using CiteSpace. A total of 2480 publications, obtained from Web of Science core collection database, were used to explore the basic characteristics, hotspots, and prospects of the research area. The results showed that (1) bioremediation/biodegradation of PAHs in water environment has been getting researchers' attention since 1990, and is gaining even more traction as time goes on. (2) In terms of countries, China and the USA were the major contributors in this research area, while at the institutional level, the Chinese Academy of Sciences has produced the most research results. However, international cooperation across regions was lacking in the field. (3) Environment Science and Technology, Chemosphere, Applied and Environment Microbiology, Journal of Hazardous Materials, and Environment Pollution were the 5 most cited journals in this field. (4) There were three major stages the field has gone through, each with distinct research hotspots, including initial stage (1990-1994), mechanism investigation (1995-2000), and application exploration (2001-2010; 2011-2022). Finally, research perspectives were proposed, covering three directions, namely, bioavailability, immobilization, and viable but nonculturable (VBNC) bacteria.

Integrated membrane electrochemical reactor-membrane distillation process for enhanced landfill leachate treatment.

Treatment of recalcitrant landfill leachate (LFL) induces huge energy consumption and carbon emissions due to its complex composition. Although membrane distillation (MD) exhibits good potential in LFL treatment with waste heat utilization, membrane fouling and ammonia rejection are still the major problems encountered that hinder its application. Herein, membrane electrochemical reactor (MER) was coupled with MD for simultaneous membrane fouling control and resource recovery. LFL pretreatment with membrane-less electrochemical reactor (EO) and without pretreatment were also purified by MD for comparison. Results showed that the MER-MD system rejected almost all CODCr, total phosphorus, metal salts, and ammonia nitrogen (increased by 33.5%-43.5% without chemical addition), and recovered 31% of ammonia nitrogen and 48% of humic acid in the raw LFL. Owing to the effective removal of hardness (61%) and organics (77%) using MER, the MER-MD system showed higher resistance to the membrane wetting and fouling, with about 61% and 14% higher final vapor flux than those of the MD and EO-MD systems, respectively, and the pure water flux could be fully recovered by alkaline solution cleaning. Moreover, SEM-EDS, ATR-FTIR and XRD characterization further demonstrated the superiority of the MD membrane fouling reversibility of the MER-MD system. Energy consumption and carbon emissions analysis showed that the MER-MD system reduced the total energy consumption/carbon emissions by ∼20% and ∼8% compared to the MD and EO-MD systems, respectively, and the ammonia nitrogen recovered by MER could offset 8.25 kg carbon dioxide equivalent. Therefore, the introduction of MER pretreatment in MD process would be an option to decrease energy consumption and reduce carbon emissions for MD treatment of LFL.

Mapping the research on desulfurization wastewater: Insights from a bibliometric review (1991-2021).

Desulfurization wastewater in coal-fired power plants (CFPPs) is a great environmental challenge. This study aimed at the current status and future research trends of desulfurization wastewater by bibliometric analysis. The desulfurization wastewater featured with high sulfate (8000 mg/L), chlorite (8505 mg/L), magnesium (2882 mg/L) and calcium (969 mg/L) but low sodium (801.82 mg/L), and the concentrations of the main contaminants were critically summarized. There was an increasing trend in the annual publications of desulfurization wastewater in the period from 1991 to 2021, with an average growth rate of 15%. Water Science and Technology, Desalination and Water Treatment, Energy & Fuels, Chemosphere, and Journal of Hazardous Materials are the top 5 journals in this field. China was the most productive country (58.3% of global output) and the core country in the international cooperation network. Wordcloud analysis and keyword topic trend demonstrated that removal/treatment of pollutants dominated the global research in the field of desulfurization wastewater. The primary technologies for desulfurization wastewater treatment were systematically evaluated. The physicochemical treatment technologies occupied half of the total treatment methods, while membrane-based integrated processes showed potential applications for beneficial reuse. The challenges and outlook on desulfurization wastewater treatment for achieving zero liquid discharge are summarized.

An innovative S-scheme AgCl/MIL-100(Fe) heterojunction for visible-light-driven degradation of sulfamethazine and mechanism insight.

The development of high efficient photocatalysts for antibiotics contamination in water remains a severe challenge. In this study, a novel step-scheme (S-scheme) photocatalytic heterojunction nanocomposites were fabricated from integrating AgCl nanoparticles on the MIL-100(Fe) octahedron surface through facile multi-stage stirring strategy. The S-scheme heterojunction structure in AgCl/MIL-100(Fe) (AM) nanocomposite provided a more rational utilization of electrons (e-) and holes (h+), accelerated the carrier transport at the junction interface, and enhanced the overall photocatalytic performance of nanomaterials. The visible-light-driven photocatalysts were used to degrade sulfamethazine (SMZ) which attained a high removal efficiency (99.9%). The reaction mechanisms of SMZ degradation in the AM photocatalytic system were explored by electron spin resonance (ESR) and active species capture experiments, which superoxide radical (•O2-), hydroxyl radical (•OH), and h+ performed as major roles. More importantly, the SMZ degradation pathway and toxicity assessment were proposed. There were four main pathways of SMZ degradation, including the processes of oxidation, hydroxylation, denitrification, and desulfonation. The toxicity of the final products in each pathway was lower than that of the parent according to the toxicity evaluation results. Therefore, this work might provide new insights into the environmentally-friendly photocatalytic processes of S-scheme AM nanocomposites for the efficient degradation of antibiotics pollutants.

Enhancing the antifouling and rejection properties of PVDF membrane by Ag3PO4-GO modification.

Ultrafiltration is an environmentally friendly water treatment technology, but membrane fouling significantly impacts membrane performance and service life. Photocatalytic modification of membrane is regarded as an effective way for membrane fouling control. In this study, graphite oxide (GO), Ag3PO4 and Ag3PO4-GO nanomaterials were applied in polyvinylidene fluoride (PVDF) ultrafiltration membranes modification, and the membranes was denoted as P-GO, P-AgP and P-AgP@GO, respectively. Filtration of humic acid (HA) at different operating conditions was adopted in evaluation of membrane performance. Among them, P-AgP@GO had the best permeation, rejection and antifouling performances, and could maintain excellent properties when operation conditions (HA concentration, operation pressure, pH and ionic strength) were changed. Furthermore, the effect of photocatalysis on the self-cleaning performance and its mechanism were revealed. The overall performance of P-AgP@GO could be enhanced by visible light irradiation, and extending the visible illumination time during the filtration was conducive to the reusability.

Integrated loose nanofiltration-electrodialysis process for sustainable resource extraction from high-salinity textile wastewater.

Effective extraction of useful resources from high-salinity textile wastewater is a critical pathway for sustainable wastewater management. In this study, an integrated loose nanofiltration-electrodialysis process was explored for simultaneous recovery of dyes, NaCl and pure water from high-salinity textile wastewater, thus closing the material loop and minimizing waste emission. Specifically, a loose nanofiltration membrane (molecular weight cutoff of ~800 Da) was proposed to fractionate the dye and NaCl in the high-salinity textile wastewater. Through a nanofiltration-diafiltration unit, including a pre-concentration stage and a constant-volume diafiltration stage, the dye could be recovered from the high-salinity textile wastewater, being enriched at a factor of ~9.0, i.e., from 2.01 to 17.9 g·L-1 with 98.4% purity. Assisted with the subsequent implementation of electrodialysis, the NaCl concentrate and pure water were effectively reclaimed from the salt-containing permeate coming from the loose nanofiltration-diafiltration. Simultaneously, the produced pure water was further recycled to the nanofiltration-diafiltration unit. This study shows the potential of the integration of loose nanofiltation-diafiltration with electrodialysis for sufficient resource extraction from high-salinity textile wastewater.

Recyclable self-floating A-GUN-coated foam as effective visible-light-driven photocatalyst for inactivation of Microcystis aeruginosa.

In this work, a recyclable self-floating A-GUN-coated (Ag/AgCl@g-C3N4@UIO-66(NH2)-coated) foam was fabricated for effective inactivation of Microcystis aeruginosa (M. aeruginosa) under visible light. The floating photocatalyst was able to inactivate 98% of M. aeruginosa within 180 min under the visible-light irrigation, and the floating photocatalyst exhibited a stable performance in various conditions. Moreover, the inactivation efficiency can still maintain nearly 92% after five times recycle experiments, showing excellent photocatalytic stability. Furthermore, effects of A-GUN/SMF floating catalyst on the physiological properties, cellular organics, and algal functional groups of M. aeruginosa were studied. The floating photocatalyst can not only make full use of excellent photocatalytic activities of A-GUN nanocomposite, but also promote contact between catalyst and algae, and realize the effective recovery of the photocatalyst. Finally, possible photocatalytic inactivation mechanisms of algae were obtained, which provides references for removing cyanobacteria blooms in real water bodies.

An innovative cation regulation-based anaerobic fermentation strategy for enhancing short-chain fatty acids production from waste activated sludge: Metal ion removal coupled with Na+-regulation.

This study proposed a cation-regulation strategy based on metal ion removal coupled Na+-regulation for enhancing anaerobic fermentation of waste activated sludge. The optimal treatment condition was: cation-exchange resin dosage of 1.75 g/g SS for 1-day treatment, followed by Na+-enhanced anaerobic fermentation at NaCl concentration of 20 g/L. The CER induced sludge solubilization and the Na+-regulation treatment triggered secondary hydrolysis of CER-solubilized sludge, causing remarkable sludge disintegration and extracellular polymeric substance (EPS) disruption. Numerous SCOD of 6588 mg/L (SCOD/TCOD = 40.6%) was released within 2 days, and the short-chain fatty acids (SCFAs) of 439.9 mg COD/g VSS was produced through 4-day anaerobic fermentation. More than 59% of the SCFAs was composed of acetate and propionate. Nitrogen-free organic matters (i.e. SCFAs and carbohydrates) accounted for 77.9% of SCOD, while considerable sludge solid reduction (51.6% of total VSS) was achievable, which was beneficial for fermentative liquid utilization and sludge disposal.

Microbial community dynamic shifts associated with sulfamethoxazole degradation in microbial fuel cells.

Though sulfamethoxazole (SMX) degradation at the low or medium concentration (SMX< 30 mg/L) has been reported in the microbial fuel cell (MFC), further exploration is still urgently required to investigate how the high concentration of SMX affect the anode biofilm formation. In this study, the degradation mechanism of SMX and the response of microbial community to SMX at different initial concentrations (0, 0.5, 5 and 50 mg/L) were investigated in MFCs. The highest SMX removal efficiency of 98.4% was obtained in MFC (5 mg/L). SMX at optimal concentration (5 mg/L) could serve as substrate accelerating the extracellular electron transfer. However, high concentration of SMX (50 mg/L) conferred significant inhibition on the electron transfer with SMX removal decline to 84.4%. The 16S rRNA high-throughput sequencing revealed the significant shift of the anode biofilms communities with different initial SMX concentrations were observed in MFCs. Thauera and Geobacter were the predominant genus, with relative abundance of 31.9% in MFC (50 mg/L SMX) and 52.7% in MFC (5 mg/L SMX). Methylophilus exhibited a huge increase with the highest percentage of 16.4% in MFC (50 mg/L). Hence, the functional bacteria of Thauera, Geobacter and Methylophilus endowed significant tolerance to the selection pressure from high concentration of SMX in MFCs. Meanwhile, some bacteria including Ornatilinea, Dechloromonas and Longilinea exhibited a decrease or even disappeared in MFCs. Therefore, initial concentrations of SMX played a fundamental role in modifying the relative abundance of predominant populations. This finding would promote theories support for understanding the evolution of anode biofilm formation related to the different initial concentrations of SMX in MFCs.

Efficient integration of plasmonic Ag/AgCl with perovskite-type LaFeO3: Enhanced visible-light photocatalytic activity for removal of harmful algae.

A novel plasmonic Ag/AgCl@LaFeO3 (ALFO) photocatalyst was successfully synthesized by a simple in-situ synthesis method with enhanced photocatalytic activity under visible light for harmful algal blooms (HABs) control. The structure, morphology, chemical states, optical and electrochemical properties of the photocatalyst were systematically investigated using a series of characterization methods. Compared with pure LaFeO3 and Ag/AgCl, ALFO-20% owned a higher light absorption capacity and lower electron-hole recombined rate. Therefore, ALFO-20% had higher photocatalytic activity with a near 100% removal rate of chlorophyll a within 150 min, whose kinetic constant was 15.36 and 9.61 times faster than those of LaFeO3 and Ag/AgCl. In addition, the changes of zeta potential, cell membrane permeability, cell morphology, organic matter, total soluble protein, photosynthetic system and antioxidant enzyme system in Microcystis aeruginosa (M. aeruginosa) were studied to explore the mechanism of M. aeruginosa photocatalytic inactivation. The results showed that ALFO-20% could change the permeability and morphology of the algae cell membrane, as well as destroy the photosynthesis system and antioxidant system of M. aeruginosa. What's more, ALFO could further degrade the organic matters flowed out after algae rupture and die, reducing the secondary pollution and avoiding the recurrence of HABs. Finally, the species of reactive oxygen species (ROS) (mainly •O2- and •OH) produced by ALFO were determined through quenching experiments, and a possible photocatalytic mechanism was proposed. Overall, ALFO can efficiently remove the harmful algae under the visible light, providing a promising method for controlling HABs.

A solar photo-thermochemical hybrid system using peroxydisulfate for organic matters removal and improving ultrafiltration membrane performance in surface water treatment.

Solar energy is considered one of the most promising energy sources for the degradation of pollutants in the water treatments. An innovative solar photo-thermochemical system involving peroxydisulfate (PDS) as an oxidant and xenon lamp as a solar irradiation light source was applied with hopes to degrade organic matters and alleviate the ultrafiltration (UF) membrane fouling when treating the real surface water. Moreover, heat-activated PDS pretreatment was used as a comparison to explore the respective proportions of solar light and heating effects, finding that solar light effect dominated the activation of PDS to degrade natural organic matters (NOMs) when the reaction temperature was below 50 °C and they both contributed to the production of free radicals at the temperature of >50 °C. The results indicated that solar-activated PDS pretreatment significantly alleviated membrane fouling caused by Songhua River water with the highest transmembrane pressure (TMP) reduction of approximately 69.6% at 70 °C. Organic substances (characterized by DOC, UV254 and the maximum florescent intensity) and micropollutant (atrazine) in the feed water were better degraded in the presence of solar light. Both total fouling index (TFI) and hydraulic irreversible fouling index (HIFI) were moderate correlated with the UV254 and DOC, whereas remarkably correlated with the Fmax of component 2 (C2) and component 3 (C3). In addition, no significant correlation was observed between fouling indexes (TFI and HIFI) and the Fmax of component 1 (C1). The membrane irreversible fouling was attributed to the accumulation of cake layers mainly composed of protein-like substances on the membrane surface. Solar-activated PDS pretreatment would efficiently degrade the protein-like substances and terrestrially derived humic-like matters to control UF membrane fouling. The findings are beneficial to develop new strategies for membrane fouling alleviation based on the solar irradiation and PDS oxidation.

Fabrication of heterostructured Ag/AgCl@g-C3N4@UIO-66(NH2) nanocomposite for efficient photocatalytic inactivation of Microcystis aeruginosa under visible light.

In this work, a novel Ag/AgCl@g-C3N4@UIO-66(NH2) heterojunction was constructed for photocatalytic inactivation of Microcystis aeruginosa (M. aeruginosa) under visible light. The photocatalyst was synthesized by a facile method and characterized by XRD, SEM, TEM, BET, XPS, FT-IR, UV-vis DRS, PL and EIS. The nanocomposite can not only provide lots of active sites, but also improve capacities to utilize visible-light energy and effectively transfer charge carriers, thus enhancing removal efficiencies of cyanobacteria (99.9% chlorophyll a was degraded within 180 min). Various factors in photodegradation of chlorophyll a were studied. Besides, changes on cellular morphologies, membrane permeability, physiological activities of M. aeruginosa during photocatalysis were investigated. Moreover, the cycle test indicated that Ag/AgCl@g-C3N4@UIO-66(NH2) exhibits excellent reusability and photocatalytic stability. Finally, a possible mechanism of M. aeruginosa inactivation was proposed. In a word, Ag/AgCl@g-C3N4@UIO-66(NH2) can efficiently inactivate cyanobacteria under visible light, thus providing useful references for further removal of harmful algae in real water bodies.

Double photoelectron-transfer mechanism in Ag-AgCl/WO3/g-C3N4 photocatalyst with enhanced visible-light photocatalytic activity for trimethoprim degradation.

Antibiotic contamination is increasing scrutinized recently. In this work, the Ag-AgCl/WO3/g-C3N4 (AWC) nanocomposites were successfully synthesized using a two-step process involving electrostatic self-assembly and in-situ deposition for trimethoprim (TMP) degradation. The as-prepared photocatalysts were investigated and characterized by XRD, FTIR, XPS, TGA, SEM, TEM, UV-vis, PL and EIS. The experimental results indicated that 99.9% of TMP (4 mg/L) was degraded within 60 min when the concentration of AWC was 0.5 g/L. Reactive species scavenging experiments and electron spin resonance (ESR) experiments illustrated that superoxide radical (•O2-) and photogenerated holes (h+) were the main active species. The functional theory calculation and identification of intermediates via HPLC-MS revealed the possible degradation pathways of TMP. A double photoelectron-transfer mechanism in AWC photocatalyst was proposed. Five cycling photocatalytic tests and reactions under different solution matrix effects further supported that the AWC was a promising photocatalyst for the removal of TMP from the aquatic environment.

A Critical Review of Membrane Wettability in Membrane Distillation from the Perspective of Interfacial Interactions.

Hydrophobic membranes used in membrane distillation (MD) systems are often subject to wetting during long-term operation. Thus, it is of great importance to fully understand factors that influence the wettability of hydrophobic membranes and their impact on the overall separation efficiency that can be achieved in MD systems. This Critical Review summarizes both fundamental and applied aspects of membrane wetting with particular emphasis on interfacial interaction between the membrane and solutes in the feed solution. First, the theoretical background of surface wetting, including the relationship between wettability and interfacial interaction, definition and measurement of contact angle, surface tension, surface free energy, adhesion force, and liquid entry pressure, is described. Second, the nature of wettability, membrane wetting mechanisms, influence of membrane properties, feed characteristics and operating conditions on membrane wetting, and evolution of membrane wetting are reviewed in the context of an MD process. Third, specific membrane features that increase resistance to wetting (e.g., superhydrophobic, omniphobic, and Janus membranes) are discussed briefly followed by the comparison of various cleaning approaches to restore membrane hydrophobicity. Finally, challenges with the prevention of membrane wetting are summarized, and future work is proposed to improve the use of MD technology in a variety of applications.