Visible-light-driven heterostructured g-C3N4/Bi-TiO2 floating photocatalyst with enhanced charge carrier separation for photocatalytic inactivation of Microcystis aeruginosa

• Bi doping in TiO₂ enhanced the separation of photo-generated electron-hole. • The performance of photocatalytic degradation of MC-LR was improved. • Coexisting substances have no influence on algal removal performance. • The key reactive oxygen species were h⁺ and ^•OH in the photocatalytic process. The increase in occurrence and severity of cyanobacteria blooms is causing increasing concern; moreover, human and animal health is affected by the toxic effects of Microcystin-LR released into the water. In this paper, a floating photocatalyst for the photocatalytic inactivation of the harmful algae Microcystis aeruginosa (M. aeruginosa) was prepared using a simple sol-gel method, i.e., coating g-C₃N₄ coupled with Bi-doped TiO₂ on Al₂O₃-modified expanded perlite (CBTA for short). The impact of different molar ratios of Bi/Ti on CBTA was considered. The results indicated that Bi doping in TiO₂ inhibited photogenerated electron-hole pair recombination. With 6 h of visible light illumination, 75.9% of M. aeruginosa (initial concentration= 2.7 × 10⁶ cells/L) and 83.7% of Microcystin-LR (initial concentration= 100 μg/L) could be removed with the addition of 2 g/L CBTA-1% (i.e., Bi/Ti molar ratio= 1%). The key reactive oxygen species (ROSs) in the photocatalytic inactivation process are h⁺ and ^•OH. The induction of the Bi⁴⁺/Bi³⁺ species by the incorporation of Bi could narrow the bandgap of TiO₂, trap electrons, and enhance the stability of CBTA-1% in the solutions with coexisting environmental substances.     

Assessing combined toxic effects of tetracycline and P25 titanium dioxide nanoparticles using Allium cepa bioassay

• UVA pre-irradiation to TiO₂ NPs enhanced its toxicity toward plant A. cepa. • UVA TiO₂ NPs increased intracellular ROS, resulting in more cell damage. • Cell death enhanced cell permeability and increased uptake of NPs. • Being highly toxic (EC₅₀ = 0.097 µmol/L), TC did not increase ROS generation. • Even at a low dose, TC enhanced the toxic potential of TiO₂ NPs significantly. Usage of titanium dioxide nanoparticles (TiO₂ NPs) and tetracycline (TC) has increased significantly in the present era. This leads to their release and accumulation in the environment. Both the compounds, individually, can have adverse toxic effects on the plants. Their binary mixtures can increase this degree of damage. The present study aimed to evaluate the toxicity of both the contaminants in individual and binary mixtures in Allium cepa. Further, the toxicity of TiO₂ NPs upon UVA pre-irradiation was also measured. Results showed that UVA pre-irradiated NPs (UVA-TiO₂ NPs) had a significant decrease in cell viability than their non-irradiated counterparts (NI-TiO₂), denoting an increase in photocatalytic activity upon UVA pre-irradiation. Very low concentrations of TC (EC₁₀ = 0.016 µmol/L) mixed with TiO₂ NPs significantly increased the toxicity for both UVA-TiO₂ and NI-TiO₂ NPs. Intracellular ROS generation was significantly high for UVA-TiO₂ NPs. However, TC did not have any effects on ROS production. Both the compounds exhibited genotoxic potential in A. cepa. Different chromosomal abnormalities like anaphase bridges, telophase bridges, laggard chromosomes, binucleate cells, etc. were observed. The binary mixture of UVA-TiO₂ NPs and TC showed the highest chromosomal aberrations (64.0%±1.26%) than the mixture with NI-TiO₂ or the individual contaminants. This decreased significantly after recovery (46.8%±1.92%), denoting the self-repair processes. This study proved that UVA-TiO₂ NPs were more toxic and could be enhanced further when mixed with a sub-lethal concentration of TC. This work will help to assess the risk of both compounds in the environment.     

Mechanism of dichloromethane disproportionation over mesoporous TiO2 under low temperature

• Mechanism of DCM disproportionation over mesoporous TiO₂ was studied. • DCM was completely eliminated at 350℃ under 1 vol.% humidity. • Anatase (001) was the key for disproportionation. • A competitive oxidation route co-existed with disproportionation. • Disproportionation was favored at low temperature. Mesoporous TiO₂ was synthesized via nonhydrolytic template-mediated sol-gel route. Catalytic degradation performance upon dichloromethane over as-prepared mesoporous TiO₂, pure anatase and rutile were investigated respectively. Disproportionation took place over as-made mesoporous TiO₂ and pure anatase under the presence of water. The mechanism of disproportionation was studied by in situ FTIR. The interaction between chloromethoxy species and bridge coordinated methylenes was the key step of disproportionation. Formate species and methoxy groups would be formed and further turned into carbon monoxide and methyl chloride. Anatase (001) played an important role for disproportionation in that water could be dissociated into surface hydroxyl groups on such structure. As a result, the consumed hydroxyl groups would be replenished. In addition, there was another competitive oxidation route governed by free hydroxyl radicals. In this route, chloromethoxy groups would be oxidized into formate species by hydroxyl radicals transfering from the surface of TiO₂. The latter route would be more favorable at higher temperature.     

UV-LED/P25-based photocatalysis for effective degradation of isothiazolone biocide

• UV-LED with shorter wavelength was beneficial for photocatalytic degradation. • SRNOM dramatically inhibit the degradation. • ·OH acts as the active radical in photocatalytic degradation. • Degradation mainly undergoes oxidation, hydrolysis and chain growth reactions. In this work, LED-based photocatalysis using mixed rutile and anatase phase TiO₂ (P25) as the photocatalyst could effectively remove 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) and methylisothiazolone (MIT) simultaneously, with removal efficiencies above 80% within 20 min. The photocatalytic degradation of both CMIT and MIT could be modeled using a pseudo-first-order rate equation. The photocatalytic degradation rates of CMIT and MIT under LED280 illumination were higher than under LED310 or LED360 illumination. At concentrations below 100 mg/L, the degradation rate of CMIT and MIT under LED illumination significantly increased with increasing catalyst dosage. Additionally, the effects of the chloride ion concentration, alkalinity and dissolved organic matter on the photocatalytic degradation reaction were also investigated. The ·OH free radicals were determined to play the primary role in the photocatalytic degradation reaction, with a degradation contribution of >95%. The photocatalytic degradation of CMIT and MIT mainly occurred via oxidation, hydrolysis, and chain growth reactions. Finally, the possible photocatalytic degradation pathways of CMIT and MIT over LED/P25 are proposed.     

TiO2@palygorskite composite for the efficient remediation of oil spills via a dispersion-photodegradation synergy

• A novel and multi-functional clay-based oil spill remediation system was constructed. • TiO₂@PAL functions as a particulate dispersant to break oil slick into tiny droplets. • Effective dispersion leads to the direct contact of TiO₂ with oil pollutes directly. • TiO₂ loaded on PAL exhibits efficient photodegradation for oil pollutants. • TiO₂@PAL shows a typical dispersion-photocatalysis synergistic remediation. Removing spilled oil from the water surface is critically important given that oil spill accidents are a common occurrence. In this study, TiO₂@Palygorskite composite prepared by a simple coprecipitation method was used for oil spill remediation via a dispersion-photodegradation synergy. Diesel could be efficiently dispersed into small oil droplets by TiO₂@Palygorskite. These dispersed droplets had an average diameter of 20–30 mm and exhibited good time stability. The tight adsorption of TiO₂@Palygorskite on the surface of the droplets was observed in fluorescence and SEM images. As a particulate dispersant, the direct contact of TiO₂@Palygorskite with oil pollutants effectively enhanced the photodegradation efficiency of TiO₂ for oil. During the photodegradation process, •O₂⁻and •OH were detected by ESR and radical trapping experiments. The photodegradation efficiency of diesel by TiO₂@Palygorskite was enhanced by about 5 times compared with pure TiO₂ under simulated sunlight irradiation. The establishment of this new dispersion-photodegradation synergistic remediation system provides a new direction for the development of marine oil spill remediation.     

Translocation and biotoxicity of metal (oxide) nanoparticles in the wetland-plant system

• Aquatic plants are more likely to absorb TiO₂ NPs that are beneficial to them. • Ag NPs inhibited the growth of aquatic plants under both 5- and 60-day exposure. • CeO₂ NPs had positive/negative impact on plant in 5/60-day exposure, respectively. • TiO₂ NPs presence could enhance the photosynthesis and increase the plant biomass. • The ENPs changed plant activity, which resulted in changes of wetland performance. Engineered nanoparticles (ENPs) threaten the environment through wastewater discharging. Generally, constructed wetlands (CWs) are efficient methods for ENPs removal. However, the biotoxicity of ENPs on plants in CWs is unclear. Here, we investigated the distribution and bio-impacts of different ENPs (Ag NPs, TiO₂ NPs, and CeO₂ NPs) in plants under 5- and 60-day exposure to 1 and 50 mg/L concentrations. Results showed that ENPs appeared in the vascular bundle and mesophyll cell space, which induced the variation in antioxidase activities (e.g., superoxide dismutase [SOD], peroxidase [POD], and catalase [CAT] activities) as well as overproduction of malondialdehyde (MDA). Additionally, Ag NPs inhibited photosynthesis rate and root activity during two exposure phases. CeO₂ NPs had positive and negative impacts on plants in 5- and 60-day exposure, respectively. Inversely, TiO₂ NPs enhanced photosynthesis and root activity under 60-day exposure. Finally, the contents of the C, N, and P elements in plants fluctuated in response to ENPs stress. All results have a positive correlation with the wetland performance under ENPs exposure except for TiO₂ NPs treatment. Overall, our study systematically reveals aquatic plants' responses to ENPs and provides a reference for building ecological treatment systems to purify wastewater containing ENPs.     

Photocatalytic degradation of the acetaminophen by nanocrystal-engineered TiO2 thin film in batch and continuous system

• Photocatalytic activity was improved in TiO₂ thin film by rapid thermal annealing. • Photoreactor was designed for TiO₂ thin film. • Considerable reusability and durability of prepared photocatalysts were studied. Un-biodegradable pharmaceuticals are one of the major growing threats in the wastewaters. In the current study, TiO₂ thin film photocatalysts were designed by nanocrystal engineering and fabricated for degradation of the acetaminophen (ACE) in a photocatalytic reaction under UV light irradiation in batch and continuous systems. The photocatalyst was prepared by sputtering and then engineered by thermal treatment (annealing at 300℃ (T300) and 650℃ (T650)). The annealing effects on the crystallinity and photocatalytic activity of the TiO₂ film were completely studied; it was found that annealing at higher temperatures increases the surface roughness and grain size which are favorable for photocatalytic activity due to the reduction in the recombination rate of photo-generated electron-hole pairs. For the continuous system, a flat plate reactor (FPR) was designed and manufactured. The photocatalytic performance was decreased with the increase of flow rate because the higher flow rate caused to form the thicker film of the liquid in the reactor and reduced the UV light received by photocatalyst. The reusability and durability of the samples after 6 h of photocatalytic reaction showed promising performance for the T650 sample (annealed samples in higher temperatures).     

Composition,dispersion, and health risks of bioaerosols in wastewater treatment plants: A review

• Bioaerosols are produced in the process of wastewater biological treatment. • The concentration of bioaerosol indoor is higher than outdoor. • Bioaerosols contain large amounts of potentially pathogenic biomass and chemicals. • Inhalation is the main route of exposure of bioaerosol. • Both the workers and the surrounding residents will be affected by the bioaerosol. Bioaerosols are defined as airborne particles (0.05–100 mm in size) of biological origin. They are considered potentially harmful to human health as they can contain pathogens such as bacteria, fungi, and viruses. This review summarizes the most recent research on the health risks of bioaerosols emitted from wastewater treatment plants (WWTPs) in order to improve the control of such bioaerosols. The concentration and size distribution of WWTP bioaerosols; their major emission sources, composition, and health risks; and considerations for future research are discussed. The major themes and findings in the literature are as follows: the major emission sources of WWTP bioaerosols include screen rooms, sludge-dewatering rooms, and aeration tanks; the bioaerosol concentrations in screen and sludge-dewatering rooms are higher than those outdoors. WWTP bioaerosols contain a variety of potentially pathogenic bacteria, fungi, antibiotic resistance genes, viruses, endotoxins, and toxic metal(loid)s. These potentially pathogenic substances spread with the bioaerosols, thereby posing health risks to workers and residents in and around the WWTP. Inhalation has been identified as the main exposure route, and children are at a higher risk of this than adults. Future studies should identify emerging contaminants, establish health risk assessments, and develop prevention and control systems.     

Simultaneous removal of NOx and chlorobenzene on V2O5/TiO2 granular catalyst: Kinetic study and performance prediction

• A V₂O₅/TiO₂ granular catalyst for simultaneous removal of NO and chlorobenzene. • Catalyst synthesized by vanadyl acetylacetonate showed good activity and stability. • The kinetic model was established and the synergetic activity was predicted. • Both chlorobenzene oxidation and SCR of NO follow pseudo-first-order kinetics. • The work is of much value to design of multi-pollutants emission control system. The synergetic abatement of multi-pollutants is one of the development trends of flue gas pollution control technology, which is still in the initial stage and facing many challenges. We developed a V₂O₅/TiO₂ granular catalyst and established the kinetic model for the simultaneous removal of NO and chlorobenzene (i.e., an important precursor of dioxins). The granular catalyst synthesized using vanadyl acetylacetonate precursor showed good synergistic catalytic performance and stability. Although the SCR reaction of NO and the oxidation reaction of chlorobenzene mutually inhibited, the reaction order of each reaction was not considerably affected, and the pseudo-first-order reaction kinetics was still followed. The performance prediction of this work is of much value to the understanding and reasonable design of a catalytic system for multi-pollutants (i.e., NO and dioxins) emission control.     

The source and transport of bioaerosols in the air: A review

• Emission of microbe from local environments is a main source of bioaerosols. • Regional transport is another important source of the bioaerosols. • There are many factors affecting the diffusion and transport of bioaerosols. • Source identification method uncovers the contribution of sources of bioaerosols. Recent pandemic outbreak of the corona-virus disease 2019 (COVID-19) has raised widespread concerns about the importance of the bioaerosols. They are atmospheric aerosol particles of biological origins, mainly including bacteria, fungi, viruses, pollen, and cell debris. Bioaerosols can exert a substantial impact on ecosystems, climate change, air quality, and public health. Here, we review several relevant topics on bioaerosols, including sampling and detection techniques, characterization, effects on health and air quality, and control methods. However, very few studies have focused on the source apportionment and transport of bioaerosols. The knowledge of the sources and transport pathways of bioaerosols is essential for a comprehensive understanding of the role microorganisms play in the atmosphere and control the spread of epidemic diseases associated with them. Therefore, this review comprehensively summarizes the up to date progress on the source characteristics, source identification, and diffusion and transport process of bioaerosols. We intercompare three types of diffusion and transport models, with a special emphasis on a widely used mathematical model. This review also highlights the main factors affecting the source emission and transport process, such as biogeographic regions, land-use types, and environmental factors. Finally, this review outlines future perspectives on bioaerosols.     

Removal of odors and VOCs in municipal solid waste comprehensive treatment plants using a novel three-stage integrated biofilter: Performance and bioaerosol emissions

• TSIBF was composed of ABRS, FRS and HBRS. • THIBF can effectively remove various odors, VOCs and bioaerosols. • Different reaction segments in TSIBF can remove different types of odors and VOCs. • TSIBF can reduce the emission of bioaerosols through enhanced interception. A novel three-stage integrated biofilter (TSIBF) composed of acidophilic bacteria reaction segment (ABRS), fungal reaction segment (FRS) and heterotrophic bacteria reaction segment (HBRS) was constructed for the treatment of odors and volatile organic compounds (VOCs)from municipal solid waste (MSW) comprehensive treatment plants. The performance, counts of predominant microorganisms, and bioaerosol emissions of a full-scale TSIBF system were studied. High and stable removal efficiencies of hydrogen sulfide, ammonia and VOCs could be achieved with the TSIBF system, and the emissions of culturable heterotrophic bacteria, fungi and acidophilic sulfur bacteria were relatively low. The removal efficiencies of different odors and VOCs, emissions of culturable microorganisms, and types of predominant microorganisms were different in the ABRS, FRS and HBRS due to the differences in reaction conditions and mass transfer in each segment. The emissions of bioaerosols from the TSIBF depended on the capture of microorganisms and their volatilization from the packing. The rational segmentation, filling of high-density packings and the accumulation of the predominant functional microorganisms in each segment enhanced the capture effect of the bioaerosols, thus reducing the emissions of microorganisms from the bioreactor.     

Utilizing transparent and conductive SnO2 as electron mediator to enhance the photocatalytic performance of Z-scheme Si-SnO2-TiOx

• A novel Z-scheme Si-SnO₂-TiO_x with SnO₂ as electron mediator is first constructed. • Transparent and conductive SnO₂ can pass light through and promote charge transport. • V_O from SnO₂ and TiO_x improve photoelectrochemical performances. • Efficient photocatalytic degradations originate from the Z scheme construction. Z-scheme photocatalysts, with strong redox ability, have a great potential for pollutants degradation. However, it is challenging to construct efficient Z-scheme photocatalysts because of their poor interfacial charge separation. Herein, by employing transparent and conductive SnO₂ as electron mediator to pass light through and promote interfacial charge transportation, a novel Z-scheme photocatalyst Si-SnO₂-TiO_{x (1<x<2)} was constructed. The Z-scheme photocatalyst displayed an order of magnitude higher photocurrent density and a 4-fold increase in open-circuit potential compared to those of Si. Moreover, the onset potential shifted negatively for approximately 2.2 V. Benefiting from these advantages, this Z-scheme Si-SnO₂-TiO_x exhibited efficient photocatalytic performance toward phenol degradation and mineralization. 75% of the phenol was degraded without bias potential and 70% of the TOC was removed during phenol degradation. Other typical pollutants such as bisphenol A and atrazine could also be degraded without bias potential. Introducing a transparent and conductive electron mediator to construct Z-scheme photocatalyst gives a new sight to the improvement of photocatalytic performance in Z scheme.     

One-pot hydrothermal fabrication of BiVO4/Fe3O4/rGO composite photocatalyst for the simulated solar light-driven degradation of Rhodamine B

• BiVO₄/Fe₃O₄/rGO has excellent photocatalytic activity under solar light radiation. • It can be easily separated and collected from water in an external magnetic field. • BiVO₄/Fe₃O₄/0.5% rGO exhibited the highest RhB removal efficiency of over 99%. • Hole (h⁺) and superoxide radical (O₂^•−) dominate RhB photo-decomposition process. • The reusability of this composite was confirmed by five successive recycling runs. Fabrication of easily recyclable photocatalyst with excellent photocatalytic activity for degradation of organic pollutants in wastewater is highly desirable for practical application. In this study, a novel ternary magnetic photocatalyst BiVO₄/Fe₃O₄/reduced graphene oxide (BiVO₄/Fe₃O₄/rGO) was synthesized via a facile hydrothermal strategy. The BiVO₄/Fe₃O₄ with 0.5 wt% of rGO (BiVO₄/Fe₃O₄/0.5% rGO) exhibited superior activity, degrading greater than 99% Rhodamine B (RhB) after 120 min solar light radiation. The surface morphology and chemical composition of BiVO₄/Fe₃O₄/rGO were studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. The free radicals scavenging experiments demonstrated that hole (h⁺) and superoxide radical (O₂^•−) were the dominant species for RhB degradation over BiVO₄/Fe₃O₄/rGO under solar light. The reusability of this composite catalyst was also investigated after five successive runs under an external magnetic field. The BiVO₄/Fe₃O₄/rGO composite was easily separated, and the recycled catalyst retained high photocatalytic activity. This study demonstrates that catalyst BiVO₄/Fe₃O₄/rGO possessed high dye removal efficiency in water treatment with excellent recyclability from water after use. The current study provides a possibility for more practical and sustainable photocatalytic process.     

Size and shape effects of MnFe2O4 nanoparticles as catalysts for reductive degradation of dye pollutants

• Size and shape-dependent MnFe₂O₄ NPs were prepared via a facile method. • Ligand-exchange chemistry was used to prepare the hydrophilic MnFe₂O₄ NPs. • The catalytic properties of MnFe₂O₄ NPs toward dye degradation were fully studied. • The catalytic activities of MnFe₂O₄ NPs followed Michaelis–Menten behavior. • All the MnFe₂O₄ NPs exhibit selective degradation to different dyes. The magnetic nanoparticles that are easy to recycle have tremendous potential as a suitable catalyst for environmental toxic dye pollutant degradation. Rationally engineering shapes and tailoring the size of nanocatalysts are regarded as an effective manner for enhancing performances. Herein, we successfully synthesized three kinds of MnFe₂O₄ NPs with distinctive sizes and shapes as catalysts for reductive degradation of methylene blue, rhodamine 6G, rhodamine B, and methylene orange. It was found that the catalytic activities were dependent on the size and shape of the MnFe₂O₄ NPs and highly related to the surface-to-volume ratio and atom arrangements. Besides, all these nanocatalysts exhibit selectivity to different organic dyes, which is beneficial for their practical application in dye pollutant treatment. Furthermore, the MnFe₂O₄ NPs could be readily recovered by a magnet and reused more than ten times without appreciable loss of activity. The size and shape effects of MnFe₂O₄ nanoparticles demonstrated in this work not only accelerate further understanding the nature of nanocatalysts but also contribute to the precise design of nanoparticles catalyst for pollutant degradation.     

Dual-functional sites for synergistic adsorption of Cr(VI) and Sb(V) by polyaniline-TiO2 hydrate: Adsorption behaviors,sites and mechanisms

• PANI/Ti(OH)_n^(4–n)+ exhibited excellent adsorption capacity and reusability. • Adsorption sites of Cr(VI) were hydroxyl, amino/imino group and benzene rings. • Sb(V) was adsorbed mainly through hydrogen bonds and Ti-O-Sb. • The formation of Cr-O-Sb in dual system demonstrated the synergistic adsorption. • PANI/TiO₂ was a potential widely-applied adsorbent and worth further exploring. Removal of chromium (Cr) and antimony (Sb) from aquatic environments is crucial due to their bioaccumulation, high mobility and strong toxicity. In this work, a composite adsorbent consisting of Ti(OH)_n^(4–n)+ and polyaniline (PANI) was designed and successfully synthesized by a simple and eco-friendly method for the uptake of Cr(VI) and Sb(V). The synthetic PANI/TiO₂ composites exhibited excellent adsorption capacities for Cr(VI) and Sb(V) (394.43 mg/g for Cr(VI) and 48.54 mg/g for Sb(V)), wide pH applicability and remarkable reusability. The adsorption of Cr(VI) oxyanions mainly involved electrostatic attraction, hydrogen bonding and anion-π interactions. Based on X-ray photoelectron spectroscopy and FT-IR analysis, the adsorption sites were shown to be hydroxyl groups, amino/imino groups and benzene rings. Sb(V) was adsorbed mainly through hydrogen bonds and surface complexation to form Ti-O-Sb complexes. The formation of Cr-O-Sb in the dual system demonstrated the synergistic adsorption of Cr(VI) and Sb(V). More importantly, because of the different adsorption sites, the adsorption of Cr(VI) and Sb(V) occurred independently and was enhanced to some extent in the dual system. The results suggested that PANI/TiO₂ is a promising prospect for practical wastewater treatment in the removal of Cr(VI) and Sb(V) from wastewater owing to its availability, wide applicability and great reusability.     

Experimental and computational assessment of 1,4-Dioxane degradation in a photo-Fenton reactive ceramic membrane filtration process

• 1,4-Dioxane was degraded via the photo-Fenton reactive membrane filtration. • Degradation efficiency and AQY were both enhanced in photocatalytic membrane. • There is a tradeoff between photocatalytic degradation and membrane permeation flux. • Degradation pathways of 1,4-Dioxane is revealed by DFT analysis. The present study evaluated a photo-Fenton reactive membrane that achieved enhanced 1,4-Dioxane removal performance. As a common organic solvent and stabilizer, 1,4-Dioxane is widely used in a variety of industrial products and poses negative environmental and health impacts. The membrane was prepared by covalently coating photocatalyst of goethite (α-FeOOH) on a ceramic porous membrane as we reported previously. The effects of UV irradiation, H₂O₂ and catalyst on the removal efficiency of 1,4-Dioxane in batch reactors were first evaluated for optimized reaction conditions, followed by a systematical investigation of 1,4-Dioxane removal in the photo-Fenton membrane filtration mode. Under optimized conditions, the 1,4-Dioxane removal rate reached up to 16% with combination of 2 mmol/L H₂O₂ and UV₃₆₅ irradiation (2000 µW/cm²) when the feed water was filtered by the photo-Fenton reactive membrane at a hydraulic retention time of 6 min. The removal efficiency and apparent quantum yield (AQY) were both enhanced in the filtration compared to the batch mode of the same photo-Fenton reaction. Moreover, the proposed degradation pathways were analyzed by density functional theory (DFT) calculations, which provided a new insight into the degradation mechanisms of 1,4-Dioxane in photo-Fenton reactions on the functionalized ceramic membrane.     

Locally enhanced electric field treatment (LEEFT) for water disinfection

• Nanowire-assisted LEEFT is applied for water disinfection with low voltages. • LEEFT inactivates bacteria by disrupting cell membrane through electroporation. • Multiple electrodes and device configurations have been developed for LEEFT. • The LEEFT is low-cost, highly efficient, and produces no DBPs. • The LEEFT can potentially be applicable for water disinfection at all scales. Water disinfection is a critical step in water and wastewater treatment. The most widely used chlorination suffers from the formation of carcinogenic disinfection by-products (DBPs) while alternative methods (e.g., UV, O₃, and membrane filtration) are limited by microbial regrowth, no residual disinfectant, and high operation cost. Here, a nanowire-enabled disinfection method, locally enhanced electric field treatment (LEEFT), is introduced with advantages of no chemical addition, no DBP formation, low energy consumption, and efficient microbial inactivation. Attributed to the lightning rod effect, the electric field near the tip area of the nanowires on the electrode is significantly enhanced to inactivate microbes, even though a small external voltage (usually<5 V) is applied. In this review, after emphasizing the significance of water disinfection, the theory of the LEEFT is explained. Subsequently, the recent development of the LEEFT technology on electrode materials and device configurations are summarized. The disinfection performance is analyzed, with respect to the operating parameters, universality against different microorganisms, electrode durability, and energy consumption. The studies on the inactivation mechanisms during the LEEFT are also reviewed. Lastly, the challenges and future research of LEEFT disinfection are discussed.     

One-step ball milling-prepared nano Fe2O3 and nitrogen-doped graphene with high oxygen reduction activity and its application in microbial fuel cells

• Nano Fe₂O₃ and N-doped graphene was prepared via a one-step ball milling method. • The maximum power density of Fe-N-G in MFC was 390% of that of pristine graphite. • Active sites like nano Fe₂O₃, pyridinic N and Fe-N groups were formed in Fe-N-G. • The improvement of Fe-N-G was due to full exposure of active sites on graphene. Developing high activity, low-cost and long durability catalysts for oxygen reduction reaction is of great significance for the practical application of microbial fuel cells. The full exposure of active sites in catalysts can enhance catalytic activity dramatically. Here, novel Fe-N-doped graphene is successfully synthesized via a one-step in situ ball milling method. Pristine graphite, ball milling graphene, N-doped graphene and Fe-N-doped graphene are applied in air cathodes, and enhanced performance is observed in microbial fuel cells with graphene-based catalysts. Particularly, Fe-N-doped graphene achieves the highest oxygen reduction reaction activity, with a maximum power density of 1380±20 mW/m² in microbial fuel cells and a current density of 23.8 A/m² at –0.16 V in electrochemical tests, which are comparable to commercial Pt and 390% and 640% of those of pristine graphite. An investigation of the material characteristics reveals that the superior performance of Fe-N-doped graphene results from the full exposure of Fe₂O₃ nanoparticles, pyrrolic N, pyridinic N and excellent Fe-N-G active sites on the graphene matrix. This work not only suggests the strategy of maximally exposing active sites to optimize the potential of catalysts but also provides promising catalysts for the use of microbial fuel cells in sustainable energy generation.     

PM-support interfacial effect and oxygen mobility in Pt,Pd or Rh-loaded (Ce,Zr,La)O2 catalysts

• Pt/CZL exhibits the optimum catalytic performance for HC and NO_x elimination. • The strong PM-Ce interaction favors the oxygen mobility and DOSC. • Pd/CZL shows higher catalytic activity for CO conversion due to more O_latt species. • Great oxygen mobility at high temperature broadens the dynamic operation window. • The relationship between DOSC and catalytic performance is revealed. The physicochemical properties of Pt-, Pd- and Rh- loaded (Ce,Zr,La)O₂ (shorted for CZL) catalysts before/after aging treatment were systematically characterized by various techniques to illustrate the relationship of the dynamic oxygen storage/release capacity and redox ability with their catalytic performances for HC, NO_x and CO conversions. Pt/CZL catalyst exhibits the optimum catalytic performance for HC and NO_x elimination, which mainly contribute to its excellent redox ability and dynamic oxygen storage/release capacity (DOSC) at lower temperature due to the stronger PM (precious metals)-support interaction. However, the worse stability of Pt-O-Ce species and volatile Pt oxides easily result in the dramatical decline in catalytic activity after aging. Pd/CZL shows higher catalytic activity for CO conversion by reason of more O_latt species as the active oxygen for CO oxidation reaction. Rh/CZL catalyst displays the widest dynamic operation window for NO_x elimination as a result of greater oxygen mobility at high temperature, and the ability to retain more Rh-O-Ce species after calcined at 1100°C effectively restrains sintering of active RhO_x species, improving the thermal stability of Rh/CZL catalyst.     

Fabrication of highly efficient Bi2WO6/CuS composite for visible-light photocatalytic removal of organic pollutants and Cr(VI) from wastewater

• A novel Bi₂WO₆/CuS composite was fabricated by a facile solvothermal method. • This composite efficiently removed organic pollutants and Cr(VI) by photocatalysis. • The DOM could promoted synchronous removal of organic pollutants and Cr(VI). • This composite could be applied at a wide pH range in photocatalytic reactions. • Possible photocatalytic mechanisms of organic pollutants and Cr(VI) were proposed. A visible-light-driven Bi₂WO₆/CuS p-n heterojunction was fabricated using an easy solvothermal method. The Bi₂WO₆/CuS exhibited high photocatalytic activity in a mixed system containing rhodamine B (RhB), tetracycline hydrochloride (TCH), and Cr (VI) under natural conditions. Approximately 98.8% of the RhB (10 mg/L), 87.6% of the TCH (10 mg/L) and 95.1% of the Cr(VI) (15 mg/L) were simultaneously removed from a mixed solution within 105 min. The removal efficiencies of TCH and Cr(VI) increased by 12.9% and 20.4%, respectively, in the mixed solution, compared with the single solutions. This is mainly ascribed to the simultaneous consumption electrons and holes, which increases the amount of excited electrons/holes and enhances the separation efficiency of photogenerated electrons and holes. Bi₂WO₆/CuS can be applied over a wide pH range (2–6) with strong photocatalytic activity for RhB, TCH and Cr(VI). Coexisiting dissolved organic matter in the solution significantly promoted the removal of TCH (from 74.7% to 87.2%) and Cr(VI) (from 75.7% to 99.9%) because it accelerated the separation of electrons and holes by consuming holes as an electron acceptor. Removal mechanisms of RhB, TCH, and Cr(VI) were proposed, Bi₂WO₆/CuS was formed into a p-n heterojunction to efficiently separate and transfer photoelectrons and holes so as to drive photocatalytic reactions. Specifically, when reducing pollutants (e.g., TCH) and oxidizing pollutants (e.g., Cr(VI)) coexist in wastewater, the p-n heterojunction in Bi₂WO₆/CuS acts as a “bridge” to shorten the electron transport and thus simultaneously increase the removal efficiencies of both types of pollutants.