Novel Ag3PO4/ZnWO4-modified graphite felt electrode for photoelectrocatalytic removal of harmful algae: Performance and mechanism.

A novel Ag3PO4/ZnWO4-modified graphite felt electrode (AZW@GF) was prepared by drop coating method and applied to photoelectrocatalytic removal of harmful algae. Results showed that approximately 99.21% of chlorophyll a and 91.57% of Microcystin-LR (MCLR) were degraded by the AZW@GF-Pt photoelectrocatalytic system under the optimal operating conditions with a rate constant of 0.02617 min-1 and 0.01416 min-1, respectively. The calculated synergistic coefficient of photoelectrocatalytic algal removal and MC-LR degradation by the AZW@GF-Pt system was both larger than 1.9. In addition, the experiments of quenching experiments and electron spin resonance (ESR) revealed that the photoelectrocatalytic reaction mainly generated •OH and •O2- for algal removal and MC-LR degradation. Furthermore, the potential pathway for photoelectrocatalytic degradation of MC-LR was proposed. Finally, the photoelectrocatalytic cycle algae removal experiments were carried out on AZW@GF electrode, which was found to maintain the algae removal efficiency at about 91% after three cycles of use, indicating that the photoelectrocatalysis of AZW@GF electrode is an effective emergency algae removal technology.

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.

Mechanistic insight into humic acid-enhanced sonophotocatalytic removal of 17ß-estradiol: Formation and contribution of reactive intermediates.

In this study, humic acid (HA) enhanced 17ß-estradiol (17ß-E2) degradation by Er3+-CdS/MoS2 (ECMS) was investigated under ultrasonic and light conditions. The degradation reaction rate of 17ß-E2 was increased from (14.414 ± 0.315) × 10-3 min-1 to (122.677 ± 1.729) × 10-3 min-1 within 90 min sonophotocatalytic (SPC) reaction with the addition of HA. The results of quenching coupled with chemical probe experiments indicated that more reactive intermediates (RIs) including reactive oxygen species (ROSs) and triplet-excited states were generated in the HA-enhanced sonophotocatalytic system. The triplet-excited states of humic acid (3HA*), hydroxyl radical (•OH), and superoxide radical (•O2-) were the dominant RIs for 17ß-E2 elimination. In addition, the energy- and electron-transfer process via coexisting HA also account for 12.86% and 29.24% contributions, respectively. The quantum yields of RIs in the SPC-ECMS-HA system followed the order of 3HA* > H2O2 > 1O2 > â€¢O2-> •OH. Moreover, the spectral and fluorescence characteristics of HA were further analyzed during the sonophotocatalytic reaction process. The study expanded new insights into the comprehension of the effects of omnipresent coexisting HA and RIs formation for the removal of 17ß-E2 during the sonophotocatalytic process.

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.

Co-doped Fe3O4/α-FeOOH for highly efficient peroxymonosulfate activation to degrade trimethoprim: Occurrence of hybrid non-radical and radical pathways.

Trimethoprim (TMP), as a widely used chemotherapeutic antibiotic agent, has caused potential risks to the aquatic environment. In this study, magnetic Co-doped Fe3O4/α-FeOOH was fabricated by a facile one-step ageing method and used for activation of peroxymonosulfate (PMS) in TMP degradation. It was found that low catalyst (0.5 g/L) and PMS addition (0.2 mM) led to the high degradation efficiency of TMP (97.2%, kobs = 0.11211 min-1) over a wide range of pH. The oxidation of active radical (SO4·-) and non-radical singlet oxygen (1O2) co-acted on TMP degradation. Besides, PMS was activated through the cycles between Co(II)/Co(III) and Fe(II)/Fe(III). Fifteen degradation intermediates of TMP were identified by LC-MS, and three possible degradation pathways including hydroxylation, demethylation, and cleavage were proposed. The recovered catalysts exhibited high stability and reusability, maintaining 80% TMP removal efficiency with inappreciable metal leaching (0.012 mg/L of Co, 0.113 mg/L of Fe) after six cycles. Besides, the Co-Fe3O4/α-FeOOH/PMS system was highly tolerant to inorganic anions and actual water bodies (river water, lake water, tap water, and sewage plant effluent). Overall, this work provided a promising way to the potential application of Fe-based binary metal oxide for PMS activation.

Enhanced Solubilization and Biodegradation of HMW-PAHs in Water with a Pseudomonas mosselii-Released Biosurfactant.

The treatment and reuse of wastewater are crucial for the effective utilization and protection of global water resources. Polycyclic aromatic hydrocarbons (PAHs), as one of the most common organic pollutants in industrial wastewater, are difficult to remove due to their relatively low solubility and bioavailability in the water environment. However, biosurfactants with both hydrophilic and hydrophobic groups are effective in overcoming these difficulties. Therefore, a biosurfactant-producing strain Pseudomonas mosselii MP-6 was isolated in this study to enhance the bioavailability and biodegradation of PAHs, especially high-molecular-weight PAHs (HMW-PAHs). FTIR and LC-MS analysis showed that the MP-6 surfactant belongs to rhamnolipids, a type of biopolymer, which can reduce the water surface tension from 73.20 mN/m to 30.61 mN/m at a critical micelle concentration (CMC = 93.17 mg/L). The enhanced solubilization and biodegradation of PAHs, particularly HMW-PAHs (when MP-6 was introduced), were also demonstrated in experiments. Furthermore, comprehensive environmental stress tolerance tests were conducted to confirm the robustness of the MP-6 biosurfactant, which signifies the potential adaptability and applicability of this biosurfactant in diverse environmental remediation scenarios. The results of this study, therefore, have significant implications for future applications in the treatment of wastewater containing HMW-PAHs, such as coking wastewater.

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.

Photocatalytic inactivation of algae in a fluidized bed photoreactor with an external magnetic field.

Practical applications of photocatalysis in algae removal often involve the use of photoreactors, which can be of many different configurations. In this study, a fluidized bed photoreactor (FBPR) with an external magnetic field was designed and constructed to achieve algae inactivation continuously and stably. Magnetic photocatalyst ZnFe2O4/Ag3PO4/g-C3N4 attached to Fe3O4 aggregate, was dispersed and fixed at the bottom of the reactor to form a flower-like structure, which can not only increase the effective irradiation area of the photocatalyst, but also enhances mass transfer by inducing flow disturbance. Under the optimal operating conditions, i.e., 0.04 m/s flow rate, 200 mT magnetic field strength, and 0.025 g photocatalyst loading, the photoreactor can effectively remove algae cells within 6 h. During the continuous operation experiment, the quality of the magnetic photocatalyst and aggregate did not decrease significantly, and there was still a 90% removal efficiency after 18 h of continuous operation. Furthermore, in the experiment where humic acid was added to simulate actual water environment, certain advantages can still be observed with the FBPR. As a continuous reactor using a magnetic photocatalyst, the FBPR has the characteristics of high availability, low cost, and low energy consumption.

Sono-photo hybrid process for the synergistic degradation of levofloxacin by FeVO4/BiVO4: Mechanisms and kinetics.

A novel FeVO4/BiVO4 heterojunction photocatalyst was synthesized by hydrothermal method. The FeVO4/BiVO4 nanostructures were characterized by XRD, SEM, XPS, UV-vis, and photoluminescence spectroscopy. The effects of catalyst dosage, contaminant concentration, initial hydrogen peroxide (H2O2) concentration, and pH value on the degradation of levofloxacin were investigated and several repeated experiments were conducted to evaluate the stability and reproducibility. The optimized process parameters were used for mineralization experiments. Reactive oxygen species, degradation intermediates, and possible catalytic mechanisms were also investigated. The results showed that the sonophotocatalytic performance of the FeVO4/BiVO4 heterojunction catalyst was better than that of sonocatalysis and photocatalysis. In addition, the Type II heterojunction formed by the material still had good stability in the degradation of levofloxacin after 5 cycles. The possible degradation pathway and mechanism of levofloxacin by sonophotocatalysis were put forward. This work develops new sono-photo hybrid process for potential application in the field of wastewater treatment.

Magnetically separable ZnFe2O4/Ag3PO4/g-C3N4 photocatalyst for inactivation of Microcystis aeruginosa: Characterization, performance and mechanism.

Water eutrophication leads to increasingly serious harmful algal blooms (HABs), which poses tremendous threats on aquatic environment and human health. In this work, a novel magnetically separable ZnFe2O4/Ag3PO4/g-C3N4 (ZFO/AP/CN) photocatalyst with double Z-scheme was constructed for Microcystis aeruginosa (M. aeruginosa) inactivation and Microcystin-LR (MC-LR) degradation under visible light. The photocatalyst was characterized by XRD, SEM, EDS, TEM, XPS, FTIR, UV-vis, PL, and VSM. Approximately 96.33% of chlorophyll a was degraded by ZFO/AP/CN (100 mg/L) after 3 h of visible light irradiation. During the photocatalytic process, the malondialdehyde (MDA) of M. aeruginosa increased, the activities of superoxide dismutase (SOD) and catalase (CAT) increased initially and decreased afterwards. Furthermore, the photocatalytic removal efficiency of M. aeruginosa (OD680 ≈0.732) and MC-LR (0.2 mg/L) reached 94.31% and 76.92%, respectively, in the simultaneous removal of algae and algal toxin experiment. Reactive species scavenging experiments demonstrated that·O2- and·OH played key roles in inactivating M. aeruginosa and degrading MC-LR. The excellent recoverability and stability of ZFO/AP/CN were proved by cycling photocatalytic experiment which using magnetic recovery method. In summary, the synthesized magnetically separable ZFO/AP/CN photocatalyst has remarkable photocatalytic activity under visible light and shows promising potential for practical application of alleviating HABs.

Migration and abiotic transformation of estrone (E1) and estrone-3-sulfate (E1-3S) during soil column transport.

Steroid estrogens have received worldwide attention and given rise to great challenges of aquatic ecosystems security, posing potential adverse effects on aquatic organisms and human health even at low levels (ng/L). The present study focused on understanding the mobility and abiotic transformation of estrone (E1) and estrone-3-sulfate (E1-3S) over spatial and time scales during soil transport. Column transport experiments showed that the migration capacity of E1-3S was far stronger than E1 in soil. The calculated groundwater ubiquity score and leachability index values also indicated the high leaching mobility of E1-3S. The hydrolysis of E1-3S and abiotic transformation into estradiol and estriol was observed in the sterilized soil. Furthermore, possible transformation products (e.g., SE239, E2378, E1 dimer538, E1-E2 dimer541) of E1 and E1-3S in soil were analyzed and identified after the column transport experiments. The estrogenic activity was estimated by 17ß-estradiol equivalency values during the transport process in aqueous and soil phases. Additionally, the potential leaching transport to groundwater of E1-3S requires further critical concern.

Enhanced degradation capability of white-rot fungi after short-term pre-exposure to silver ion: Performance and selectively antimicrobial mechanisms.

Azo dyes in wastewater have great threats to environment and human health. White-rot fungi (WRF) have broad-spectrum potential for such refractory organics bioremediation; however, their applications are largely restrained by the poor viability owning to microbial invasion under non-sterile conditions. In this study, short-term pre-exposure to silver ion (Ag+) was demonstrated to be a practical, economic, and green method to enhance the perdurability of azo dyes decoloration by WRF Phanerochaete chrysosporium under non-sterile conditions. In control (without Ag+ pre-exposure), decoloration deactivated since cycle 7 (<10%), whereas in Ag+ pre-exposure groups, the decoloration ratios remained 91.5%-94.7% after 7 cycles. Variations in decoloration-related extracellular lignin enzyme activities were consistent with the decoloration effectiveness. The enhanced decoloration capability in Ag+ pre-exposure groups under non-sterile conditions could be ascribed to the selectively antimicrobial action by Ag+. The released Ag+ from the self-assembled silver nanoparticles (AgNPs) could selectively "stimulate" the proliferation and viability of P. chrysosporium, and simultaneously inhibit the growths of invasive microorganisms. The pyrosequencing results indicated that genus Sphingomonas (24.1%-31.3%) was the main invasive bacteria in Ag+ pre-exposure groups after long-term operation owing to the AgNPs passivation. As control, the invasive fungi (Asterotremella humicola) and bacteria (Burkholderia spp.) occurred in control after short-term operation, and genus Burkholderia (74.9%) dominated after long-term operation, leading to decoloration deactivation. Overall, these findings offer a new insight into the bio-nano interactions between WRF and invasive microorganisms in response to Ag+ or biogenic AgNPs, and could extend WRF application perspective under non-sterile conditions in future.

Effects of low impact development on the stormwater runoff and pollution control.

The frequent urbanization and extreme rainfall events have posed the threat to the urban environment. The implementation of low impact development (LID) practices with great potential for control urban flood and overflow pollution is not comprehensively understood yet due to the influence of complex factors (i.e., hydrological pattern, installation location, and vertical parameter setting). In this study, the hydraulic and water quality model were used to analyze the hydrological and pollution reduction of outfall and storage under different hydrological patterns, vertical parameter setting, and green infrastructure installation locations, which can determine the best implementation of the scheme for overflow pollution control. The results showed that nine parameters of the vertical layer regarding the four parameters impacted the peak value and load of suspended solids (SS). The combination scheme of the LID practices was further proposed based on the selection and analysis of the single LID practice. Besides, considering the installation location, the downstream installed location was a better choice. The horizontal connection of overflow runoff and pollution could be reduced by up to 9.75% and 36.46%, respectively. In addition, the horizontal connection can effectively reduce the peak value of inflow and pollutants at the time of assessing storage tank impact, which reach the maximum of 14.08% and 29.25%, respectively. The pollutants distribution became uniform and showed better resilience against rainfall intensity, which is beneficial to the management of stormwater. Our findings can provide guidance for Sponge City construction and effectively alleviate the combined sewer overflow.

Metagenomics reveals functional species and microbial mechanisms of an enriched thiosulfate-driven denitratation consortia.

In this study, thiosulfate-driven denitratation (TDD) system was successfully established under optimal S/N molar ratio of 1.00, with nitrite accumulation efficiency (NAE) of 82.24 ± 17.09%. This work highlighted that thiosulfate significantly preferred the reduction of nitrate than nitrite. However, after the depletion of thiosulfate, the in-situ formed intermediate product element sulfur (S0) served as the main electron donor, and significantly favored the reduction of nitrite than nitrate, which constrained nitrite accumulation and nitrate removal. In addition, metagenomic sequencing revealed that the functional denitratation species might be Thiobacillus_sp._65-29, but the occurrence of Nir-annotated species would decrease nitrite accumulation. Under S/N ratio of 1.00, the decreased abundant Nir-annotated species (e.g., Thiobacillus_sp.), as well as the down-regulated quorum sensing interactions between Nar- and Nir-annotated species were key microbial metabolisms of high NAE in the TDD system. Overall, this work provides new sight into the metagenome-base functional species and metabolic potential of thiosulfate-driven denitratation.

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.

Self-floating photocatalytic hydrogel for efficient removal of Microcystis aeruginosa and degradation of microcystins-LR.

Cyanobacterial harmful algal blooms (CyanoHABs) and the release of cyanotoxins have posed adverse impacts to aquatic system and human health. In this study, a novel self-floating Ag/AgCl@LaFeO3 (ALFO) photocatalytic hydrogel was prepared via freeze-thaw method for removal of Microcystis aeruginosa (M. aeruginosa). The ALFO hydrogel performed an excellent photocatalytic activity with a 99.4% removal efficiency of chlorophyll a within 4 h. It can still remove above 95% chlorophyll a after six consecutive recycles. Besides it has also shown excellent mechanical strength and elasticity, which can ensure its use in practical applications. The mechanisms of M. aeruginosa inactivation are attributed to •O2- and •OH generated by the ALFO hydrogel under visible light radiation. In addition, •O2- and •OH can further oxidative degrade and even mineralize the leaked algae organic matter, avoiding the recurrence of CyanoHABs. What's more, the ALFO hydrogel owns good photocatalytic degradation performance for microcystins-LR (MC-LR) with a 97% removal efficiency within 90 min. A possible photocatalytic degradation pathway of MC-LR was proposed through the identification of the intermediate products during the photocatalytic reaction, which confirmed the reduction of MC-LR toxicity. This work develops recyclable a self-floating ALFO hydrogel to simultaneously inactivate M. aeruginosa and degrade MC-LR, providing a prospective method for governing and controlling CyanoHABs in practical application.

Mussel-Inspired Immobilization of Photocatalysts with Synergistic Photocatalytic-Photothermal Performance for Water Remediation.

The serious problem of pharmaceutical and personal care product pollution places great pressure on aquatic environments and human health. Herein, a novel coating photocatalyst was synthesized by adhering Ag-AgCl/WO3/g-C3N4 (AWC) nanoparticles on a polydopamine (PDA)-modified melamine sponge (MS) through a facile layer-by-layer assembly method to degrade trimethoprim (TMP). The formed PDA coating was used for the anchoring of nanoparticles, photothermal conversion, and hydrophilic modification. TMP (99.9%; 4 mg/L) was removed in 90 min by the photocatalyst coating (AWC/PDA/MS) under visible light via a synergistic photocatalytic-photothermal performance route. The stability and reusability of the AWC/PDA/MS have been proved by cyclic experiments, in which the removal efficiency of TMP was still more than 90% after five consecutive cycles with a very little mass loss. Quantitative structure-activity relationship analysis revealed that the ecotoxicities of the generated intermediates were lower than those of TMP. Furthermore, the solution matrix effects on the photocatalytic removal efficiency were investigated, and the results revealed that the AWC/PDA/MS still maintained excellent photocatalytic degradation efficiency in several actual water and simulated water matrices. This work develops recyclable photocatalysts for the potential application in the field of water remediation.

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.

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.