Ultrathin g-C3N4 composite Bi2WO6 embedded in PVDF UF membrane with enhanced permeability, anti-fouling performance and durability for efficient removal of atrazine

Interfacial hydrophilicity induced CoAl-LDH/Ti3C2Tx@PVDF Fenton-like catalytic filtration membrane for efficient anti-fouling and water decontamination

The catalytic filtration membrane, combining the interfacial hydrophilic effect with PMS based Fenton-like oxidation processes, demonstrates great potential as an advanced solution for alleviating membrane fouling and removing contaminants. Herein, a novel type of hollow fiber CoAl-LDH/Ti3C2Tx@PVDF membranes was successfully fabricated. The well-designed hybrid membrane incorporating 0.5 wt% of CoAl-LDH/Ti3C2Tx (denoted as M-0.5) as PMS activator exhibited excellent anti-fouling behavior and remarkable TC degradation efficiency. The anchored hetero-structural CoAl-LDH/Ti3C2Tx was pivotal in driving the reaction, where the synergistic redox cycles (Ti+/Ti2+, Ti2+/Ti3+ and Co2+/Co3+) facilitated the activation of PMS. Concurrently, the plentiful hydrophilic groups especially -OH of CoAl-LDH/Ti3C2Tx endowed M-0.5 with robust interfacial hydrophilicity, extremely boosting interactions among CoAl-LDH/Ti3C2Tx, PMS and TC at the surface of M-0.5. Mechanism analysis revealed that the formed ∙OH, SO4·-, ·O2- and 1O2 collectively contributed to the non-selective degradation of TC. Moreover, the M-0.5 +PMS system showed exceptional stability in the presence of various environmental interferences and continuous flow device. Ultimately, the degradation pathways and toxicological assessment of TC and its intermediates further substantiated the impressive catalytic oxidation performance of the M-0.5 +PMS system. This insightful work cleverly integrates the macro/micro-scale design of membrane structure, promising to unlock novel opportunities for the development of water treatment.

Fabrication of anti-fouling and self-cleaning PHI modified PVDF membranes for high-flux dye removal

The large pore size of ultrafiltration membranes presents a challenge in rejecting small molecules and the accumulated contaminants on the membrane surface severely restrict the treatment efficiency and shorten the lifespan of separation membranes. Herein, poly(heptazine imide) (PHI) is utilized as a modifier to fabricate anti-fouling and self-cleaning polyvinylidene fluoride (PVDF) membranes for high-flux dye removal. The introduction of PHI does not affect the rejection performance of bovine serum albumin (>97%), whilst improving the water permeability and mechanical strength of membranes. The anti-fouling ability is also significantly enhanced with a flux recovery ratio of 91.61%. In addition, the rejection performance of PHI modified PVDF (PHI/PVDF) membranes for anionic dyes, especially for those of low molecular weight, is obviously improved. The rejection ratios of Congo red (CR) and orange G are 99.8% and 87.4%, respectively, and rejection performance for methyl orange is increased from 22.0% (pure PVDF membrane) to 62.5% (M3 membrane with 3 g PHI added). Furthermore, in the presence of anionic dye (such as CR), 99.3% of methylene blue, 91.8% of malachite green and 95.9% of basic red 46 can be rejected and approximately 613 L m-2 of 50 mg per L CR solution can be processed after 2 h of operation, with the rejection ratio consistently above 98%. The accumulated CR dyes on PHI/PVDF membranes can be easily self-cleaned within 60 min by the H2O2-assisted photocatalytic reaction, effectively solving the problem of membrane fouling.

A Review on Bi2WO6-Based Materials for Photocatalytic CO2 Reduction

Photocatalytic reduction of CO2 (PCR) technology offers the capacity to transmute solar energy into chemical energy through an eco-friendly and efficacious process, concurrently facilitating energy storage and carbon diminution, this innovation harbors significant potential for mitigating energy shortages and ameliorating environmental degradation. Bismuth tungstate (Bi2WO6) is distinguished by its robust visible light absorption and distinctive perovskite-type crystal architecture, rendering it highly efficiency in PCR. In recent years, numerous systematic strategies have been investigated for the synthesis and modification of Bi2WO6 to enhance its photocatalytic performance, aiming to achieve superior applications. This review provides a comprehensive review of the latest research progress on Bi2WO6 based materials in the field of photocatalysis. Firstly, outlining the fundamental principles, associated reaction mechanisms and reduction pathways of PCR. Then, the synthesis strategy of Bi2WO6-based materials is introduced for the regulation of its photocatalytic properties. Furthermore, accentuating the extant applications in CO2 reduction, including metal-Bi2WO6, semiconductor-Bi2WO6 and carbon-based Bi2WO6 composites etc. while concludes with an examination of the future landscape and challenges faced. This review hopes to serve as an effective reference for the continuous improvement and implementation of Bi2WO6-based photocatalysts in PCR.

Performance, progress, and mechanism of g-C3N4-based photocatalysts in the degradation of pesticides: A systematic review

In the modern world, humans are exposed to an enormous number of pesticides discharged into the environment. Exposure to pesticides causes many health disorders, such as cancer, mental retardation, and endocrine disruption. Therefore, it is a priority to eliminate pesticides from contaminated water before discharge into aquatic environments. Conventional treatment systems do not efficiently accomplish pesticide remediation. Applying graphitic carbon nitride (g-C3N4; GCN)-based materials as highly efficient and low-cost catalysts can be one of the best methods for adequately removing pesticides. This study aims to review the most relevant studies on the use of GCN-based photocatalytic processes for degrading well-known pesticides in aqueous solutions. Thus, in the current state-of-the-art review, an overview is focused not only on how to use GCN-based photocatalysts towards the degradation of pesticides, but also discusses the impact of important operational factors like solution pH, mixture temperature, catalyst dosage, pesticide concentration, photocatalyst morphology, light intensity, reaction time, oxidant concentration, and coexisting anions. In this context, four common pesticides were reviewed, namely 2,4-dichlorophenoxyacetic acid (2,4-D), malathion (MTN), diazinon (DZN), and atrazine (ATZ). Following the screening procedure, 55 full-text papers were chosen, of which the most were published in 2023 (n = 10), and the most publications focused on the elimination of ATZ (n = 33). Among the GCN modification methods, integrating GCN with other photocatalysts showed the best performance in enhancing photocatalytic activity towards the degradation of pesticides. All GCN-based photocatalysts showed a degradation efficiency of > 90% for pesticides under optimum operating conditions. This review provides a detailed summary of different GCN modification methods to select the most promising and cost-effective photocatalyst degradation of pesticides.

Optimization of AgIO3/Bi4Ti3O12 composite photocatalyst to achieve enhanced photocatalytic performance by adjusting internal electric field via oxygen defect engineering

The construction of heterojunction is an effective and conventional method to improve the photocatalytic activity of photocatalysts. On this basis, how to further regulate the separation and migration of photogenerated carrier is worthy of further investigation. As a mature and efficient modification method, oxygen defect engineering was used to regulate the S-scheme heterojunction composed of AgIO3 and Bi4Ti3O12 to further enhance the photocatalytic activity of the constructed heterojunction in this study. In addition to improving the visible light absorption of the photocatalyst and providing active sites, the introduction of oxygen vacancies can also strengthen the internal electric field between the two semiconductors by expanding the Fermi level gap, which can be verified by Mott-Schottky experiment and DFT calculations, resulting in more efficient photogenerated carrier separation efficiency. As a result, compared with AgIO3/Bi4Ti3O12, the AgIO3/Bi4Ti3O12 heterojunction modulated by oxygen defect engineering exhibited excellent photocatalytic activity, which proves the feasibility of the regulation of the interfacial electric field. This work provides a new idea for the modulation strategy of the interface electric field.

Deep degradation of atrazine in water using co-immobilized laccase-1-hydroxybenzotriazole-Pd as composite biocatalyst

The efficient and green removal technology of refractory organics such as atrazine in water has been an important topic of research in water treatment. A novel membrane composite biocatalyst Lac-HBT-Pd/BC as prepared for the first time by co-immobilizing laccase, mediator 1-hydroxybenzotriazole (HBT) and metal Pd on functionalized bacterial cellulose (BC) to investigate the removal of atrazine and degradation of its intermediates under mild ambient conditions. It was found that atrazine could be completely degraded in 5 h by the catalysis of Lac-HBT-Pd/BC, and the removal rate of degradation intermediates from atrazine was about 85% after continuous catalysis, which achieved deep degradation of atrazine. The effect of electrochemical activity and radical stability of the membrane composite biocatalysts loaded with Pd was investigated. The possible degradation pathways were proposed by identifying and analyzing the deep degradation products of atrazine. The Lac-HBT-Pd/BC demonstrated deep degradation of atrazine and favorable reusability as well as considerable adaptability to various water qualities. This work provides an important reference for preparing new kinds of biocatalysts to degrade refractory organic pollutants in water.

Bi2WO6 nanoparticles anchored on membrane by grafting via in-situ polymerization for the treatment of antibiotic and pesticides wastewater

Antibiotics, natural organic matter, and pesticides are detected in the ecosystem's domestic water, surface water, and groundwater and are largely applied in pharmaceuticals and agriculture. Polymeric membranes are effectively remove the various pollutants in the water bodies, but fouling is one of the major limitations of commercial membranes. Herein, we modified the polymeric membrane surface with inorganic photocatalytic nanoparticles. In this work, the hydrothermal method is used for the synthesis of Bi2WO6 nanoparticles and as-synthesized nanoparticles grafted onto the various polymeric membranes, including polyetherimide (PEI), cellulose acetate (CA), polyvinylidene fluoride (PVDF), and polysulfone (PSF). The functional group studies confirmed the existence of nanoparticles and hydroxyl groups on the hybrid membrane. Further, finger-like voids, top-surface morphology, and roughness on the membrane surface were validated via Field Emission Scanning Electron Microscopy (FESEM) and Atomic force microscopy (AFM), respectively. The significant rejection of tetracycline, humic acid, and fulvic acid + atrazine was noted with the synthesized membranes in the following order: PVDF (81.1%, 78.8%, 80.6%) > CA (70.1%, 69.3%, 71.7%) > PSF (72.5%, 73.6%, 67.1%) > PEI (75.9%, 65.5%, 63.7%). The photodegradation efficiency of hybrid membranes against tetracycline, humic acid, and fulvic acid + atrazine was observed in the order: PEI (28.5%, 25.8%, 30.2%) < CA (46.5%, 42.4%, 40.5%) < PSF (46.9%, 37.7%, 44.7%) < PVDF (67.7%, 62.1%, 64.3%). These membranes exhibit an outstanding permeate flux recovery ratio to the neat membrane. Therefore, the grafting of Bi2WO6 nanoparticles creates a potential bonding with PVDF membranes than other polymeric membranes, thus exhibiting an outstanding rejection than hybrid and neat membranes.

Chemical-free vacuum ultraviolet irradiation as ultrafiltration membrane pretreatment technique: Performance, mechanisms and DBPs formation

Membrane fouling induced by natural organic matter (NOM) has seriously affected the further extensive application of ultrafiltration (UF). Herein, a simple, green and robust vacuum ultraviolet (VUV) technology was adopted as pretreatment before UF and ultraviolet (UV) technology was used for comparison. The results showed that control effect of VUV pretreatment on membrane fouling was better than that of UV pretreatment, as evidenced by the increase of normalized flux from 0.27 to 0.38 and 0.73 after 30 min UV or VUV pretreatment, respectively. This is related to the fact that VUV pretreatment exhibited stronger NOM degradation ability than UV pretreatment owing to the formation of HO•. The steady-state concentration of HO• was calculated as 3.04 × 10-13 M and the cumulative exposure of HO• reached 5.52 × 10-10 M s after 30 min of VUV irradiation. And the second-order rate constant between NOM and HO• was determined as 1.36 × 104 L mg-1 s-1. Furthermore, fluorescence EEM could be applied to predict membrane fouling induced by humic-enriched water. Standard blocking and cake filtration were major fouling mechanisms. Moreover, extension of UV pretreatment time increased the disinfection by-products (DBPs) formation, the DBPs concentration was enhanced from 322.36 to 1187.80 μg/L after 210 min pretreatment. However, VUV pretreatment for 150 min reduced DBPs content to 282.57 μg/L, and DBPs content continued to decrease with the extension of pretreatment time, revealing that VUV pretreatment achieved effective control of DBPs. The variation trend of cytotoxicity and health risk of DBPs was similar to that of DBPs concentration. In summary, VUV pretreatment exhibited excellent effect on membrane fouling alleviation, NOM degradation and DBPs control under a certain pretreatment time.

Bromine Ion-Intercalated Layered Bi2WO6 as an Efficient Catalyst for Advanced Oxidation Processes in Tetracycline Pollutant Degradation Reaction

The visible-light-driven photocatalytic degradation of pharmaceutical pollutants in aquatic environments is a promising strategy for addressing water pollution problems. This work highlights the use of bromine-ion-doped layered Aurivillius oxide, Bi2WO6, to synergistically optimize the morphology and increase the formation of active sites on the photocatalyst's surface. The layered Bi2WO6 nanoplates were synthesized by a facile hydrothermal reaction in which bromine (Br-) ions were introduced by adding cetyltrimethylammonium bromide (CTAB)/tetrabutylammonium bromide (TBAB)/potassium bromide (KBr). The as-synthesized Bi2WO6 nanoplates displayed higher photocatalytic tetracycline degradation activity (~83.5%) than the Bi2WO6 microspheres (~48.2%), which were obtained without the addition of Br precursors in the reaction medium. The presence of Br- was verified experimentally, and the newly formed Bi2WO6 developed as nanoplates where the adsorbed Br- ions restricted the multilayer stacking. Considering the significant morphology change, increased specific surface area, and enhanced photocatalytic performance, using a synthesis approach mediated by Br- ions to design layered photocatalysts is expected to be a promising system for advancing water remediation.