Rejection Of Pollutants Research Articles

Electro-coagulation pretreatment for improving nanofiltration membrane performance during reclamation of microplastic-contaminated secondary effluent: unexpectedly enhanced membrane fouling and mechanism analysis by MD-DFT simulation

The residue of microplastic in secondary effluent was inevitable with continuous aggravation on nanofiltration membrane fouling. Thus, this study aimed to further evaluate the applicability of electro-coagulation as pretreatment for improving the performance of a nanofiltration-oriented hybrid process during the reclamation of microplastic-contaminated secondary effluent. The electro-coagulation parameters were skillfully optimized and designed for following dynamic nanofiltration experiments. The potential influence of coagulants in different forms as well as their combined effects of microplastics on membrane fouling behaviors and pollutant rejection efficiency was distinguished. Specifically, terminal membrane permeability was reduced by 19% after 0.05 A electro-coagulation, while 0.2 A electro-coagulation almost eliminated the negative effects of microplastics. Mass transfer model analysis excluded the dominance of organic accumulation in the concentration polarization layer on membrane fouling development. Molecular dynamic (MD) simulation and egg-box model demonstrated that humic-Fe network possessed stronger bridging effects and greater porosity. This structure favored the co-deposition of other unlinked bacteria metabolites, which secretion was also facilitated by microplastics as immobilized carriers, on membrane surface. Additionally, density functional theory (DFT) calculation further confirmed that the greater demand for dehydration energy for ferric ions (1124 kcal/mol) inspired the formation of stronger humic-Fe complexes. Besides, residual microplastics in electro-coagulation effluent had different impacts on membrane rejection towards organic and inorganic pollutants, and it depended on the influenced cake-enhanced concentration polarization (CECP) by microplastic affinity with different pollutants.

Machine learning models for predicting the rejection of organic pollutants by forward osmosis and reverse osmosis membranes and unveiling the rejection mechanisms

While forward osmosis (FO) and reverse osmosis (RO) processes have been proven effective in rejecting organic pollutants, the rejection rate is highly dependent on compound and membrane characteristics, as well as operating conditions. This study aims to establish machine learning (ML) models for predicting the rejection of organic pollutants by FO and RO and providing insights into the underlying rejection mechanisms. Among the 14 ML models established, the random forest model (R2 = 0.85) and extreme gradient boosting model (R2 = 0.92) emerged as the best-performing models for FO and RO, respectively. Shapley additive explanations (SHAP) analysis identified the length of the compound, water flux, and hydrophobicity as the top three variables contributing to the FO model. For RO, in addition to the length of the compound and operating pressure, advanced variables including four molecular descriptors (e.g., ATSC2m and Balaban J) and three fingerprints (e.g., C=C double bond and carbonyl group) significantly contributed to the prediction. Besides, the associations between these highly ranked variables and their SHAP values shed light on the rejection mechanisms, such as size exclusion, adsorption, hydrophobic interaction, and electrostatic interaction, and illustrate the role of the operating parameters, such as the FO permeate water flux and RO operating pressure, in the rejection process. These findings provide interpretable predictive models for the removal of organic pollutants and advance the mechanistic understanding of the rejection mechanisms in the FO and RO processes.

Empowering TiO2–coated PVDF membranes stability with polyaniline and polydopamine for synergistic separation and photocatalytic enhancement in dye wastewater purification

Photocatalytic membranes are effective in removing organic dyes, but their low UV resistance poses a challenge. To address this, self-protected photocatalytic PVDF membranes were developed using polyaniline (PANI) and polydopamine (PDA), whaich are anti-oxidation polymers, as interlayers between the membrane and TiO2. PVDF membranes were first modified by a self-polymerization layer of either PANI or PDA and then coated with titanium dioxide (TiO2). The TiO2 remained firmly attached to the PANI and PDA layer, regardless of sonication and prolonged usage. The PANI and PDA layers enhanced the durability of PVDF membrane under UV/TiO2 activation. After 72 h of irradiation, PVDF–PDA–TiO2 and PVDF–PANI–TiO2 membranes exhibited no significant change. This process improved both separation and photocatalytic activity in dye wastewater treatment. The PVDF–PDA–TiO2 and PVDF–PANI–TiO2 membranes showed enhanced membrane hydrophilicity, aiding in the rejection of organic pollutants and reducing fouling. The modified membranes exhibited a significant improvement in the flux recovery rate, attributed to the synergistic effects of high hydrophilicity and photocatalytic activity. Specially, the flux recovery rate increased from 17.7% (original PVDF) to 56.3% and 37.1% for the PVDF–PDA–TiO2 membrane and PVDF–PANI–TiO2 membrane. In dye rejection tests, the PVDF‒PDA‒TiO2 membrane achieved 88% efficiency, while the PVDF‒PANI‒TiO2 reached 95.7%. Additionally, the photodegradation of Reactive Red 239 (RR239) by these membranes further improved dye removal. Despite an 11% reduction in flux, the PVDF–PDA–TiO2 membrane demonstrated greater durability and longevity. The assistance of PANI and PDA in TiO2 coating also improved COD removal (from 33 to 58–68%) and provided self-protection for photocatalytic membranes, indicating that these photocatalytic membranes can contribute to more sustainable wastewater treatment processes.

Amine grafted graphene oxide embedded in polyamide membranes for simultaneous removal of oil, metals, and salts from oily water

As a result of the economic growth and the emergence of industrialization in most economies, water purification has gained increased significance. The nanocomposite nanofiltration membranes can remove salts, hydrocarbons, and environmental pollutants. However, the surface wettability of the membrane materials is crucial since they are utilized to separate emulsified oil/water mixtures. In this study, the polyvinylidene fluoride support membrane was successfully modified to a hydrophilic state in this instance via dip single-step coating by modifying graphene oxide (GO) with (3-aminophenyltriethoxysilane)-trimesic acid-melamine (GO-APTES-TA-MM) polyamide. The separation efficiency and antifouling properties were evaluated by analyzing the flux using a membrane cell tester machine. Scanning electron microscopy (SEM) was used to confirm the morphology of the membrane and EDX was employed to characterize the modified membrane before and after separation testing. The membrane shows good rejection of organic pollutants including pentane, isooctane, toluene, and hexadecane, attaining a removal of >90 % of heavy metals such as strontium, lead, and cobalt, and 86 % rejection of salt ions SO42−, and 42 % for Mg2+. According to the findings, the membrane can be a good choice for simultaneous treatment of wastewater containing a mixture of metal ions, hydrocarbons, and salt mixes from oily water.

Optimizing Reverse Osmosis Feed Spacer Design for Enhanced Dimethylphenol Removal from Wastewater: A Study of Hydrodynamics and Performance Indicators

Due to its high pollutant rejection and low energy usage, the spiral wound module of reverse osmosis (RO) process is the most commonly used technology utilised in wastewater treatment. For a spiral wound module, the presence of a feed spacer is important as a key solution to mitigate the concentration polarisation phenomenon, due to disorderly fluid flow, and to improve the mass transfer coefficient. Undoubtedly, improvements in the spiral wound module design, mainly in the symmetrical shape of the feed spacer, can have a significant impact on the cost and probable use of these modules. Despite the wide interest in appraising the impact of feed spacer geometry and orientation on the performance of a spiral wound module for RO process-based water desalination, the hydrodynamics of feed spacers (pressure drop and mass transfer coefficient) and the associated influences of feed spacer design (the height of the feed spacer, the angle of the filaments, and the porosity) on the removal of pollutants from wastewater have not yet been addressed. The current investigation aims to fill this gap by studying the hydrodynamics and design parameters of the selected parallelogram feed spacer type ultrafiltration (UF−3) for the removal of dimethylphenol from wastewater. Using model-based simulation, the impacts of UF−3 feed spacer design parameters, including the height, angle between the filaments (orientation), and porosity on the pressure drop, friction factor, axial flow fluid velocity, mass transfer coefficient, water flux, dimethylphenol rejection, recovery rate, and specific energy consumption are detailed in this study. The study intends to demonstrate the optimum design features of UF−3 feed spacer that should be considered to assure the highest elimination of dimethylphenol from wastewater in addition to the lowest specific energy consumption.

Hydrogel/mineral-integrated interface for synergistic antifouling membrane

Antifouling performance is significant for practical membrane separation, determining the membrane permselectivity, lifespan and maintenance cost. Integrating multi-component antifouling materials at the membrane interface is a promising solution for maximizing the membrane antifouling potential. Herein, a gel-mineral hybrid interface was constructed on polyvinylidene fluoride (PVDF) membrane via MnO2 mineralization induced by the tannic acid (TA)/polyvinylpyrrolidone (PVP) intermediate hydrogel layer. The resultant membrane exhibited superhydrophilicity and resulted in excellent enhancement in permeability and antifouling performance. The modified ultrafiltration membrane exhibited enhanced water flux, rejection of pollutants, and flux recovery rate (FRR) for organic solutions. The pure water flux of the optimal membrane is 40 % higher than that of PVDF. Most importantly, this hydrogel/mineral hybrid interface collectively resists the adhesion of pollutants and catalytic cleaning to remove pollutants. This integrated interface tailoring strategy paves a way for multi-scale antifouling separation membranes.

Characteristics of polycyclic aromatic hydrocarbons (PAHs) removal by nanofiltration with and without coexisting organics

Polycyclic aromatic hydrocarbons (PAHs) are contaminants of great concern owing to their persistence, toxicity, and bioaccumulation in aquatic environments. In this study, nanofiltration (NF) was used to investigate the removal of naphthalene (NAP) and phenanthrene (PHE) using three membranes of NF270, NF90, and DK. Subsequently, we examined the effects of coexisting organics on PAHs removal. Based on the results, DK was determined to be the optimal membrane for removing PAHs by comparing the membrane flux and pollutant rejection. The membrane flux reached 34.32 L/m2·h, and the NAP and PHE rejections were 92.21% and 97.85%, respectively, at transmembrane pressure (TMP) of 5 bar using DK. Coexisting organics decreased the membrane fluxes of NF270 and DK in the following order: protein > glucose > humic acid. The NAP and PHE rejections were obviously improved using NF270 in the following order: humic acid > protein > glucose. The PHE rejection was slightly improved using DK. A low concentration of organics could reduce the NAP rejection using DK; however, the NAP rejection could be restored at high concentrations of organics, except for humic acid. Coexisting organics could cause severe membrane fouling. The order of the effect of different coexisting organics on membrane fouling was protein > humic acid > glucose. The total investment and operating costs were about 1.47 and 0.187 million dollars, respectively, for treating PAHs solution using DK when the feed flow was 300 m3/d.

Plasmonic titanium nitride-based membranes for solar-driven domestic wastewater distillation treatment

Membrane separation processes have emerged as efficient wastewater treatment technologies due to their reduced footprint, sustainability, cost-effectiveness, ease of operation, high filtration selectivity, and compliance with end-user requirements. Especially solar-driven membrane distillation, known for its low energy requirements and high pollutant rejection rates, has gained prominence as a potential wastewater treatment process that does not need external thermal energy input for water treatment. Herein, we demonstrate plasmonic titanium nitride nanoparticle-incorporated polymeric membranes for the solar-driven membrane distillation of domestic laundry wastewater, specifically focusing on SDBS (sodium dodecylbenzene sulfonate) surfactant removal. Under solar illumination, the plasmonic element within the polymeric matrix enables a localized heating effect driven by photothermal conversion in the proximity of the surface of distillation membranes, thereby producing a vapor pressure enough for water distillation across the hydrophobic membranes. The fabricated photothermal mixed matrix membranes showed incremental distillation flux and derived energy efficiency with the loading of titanium nitride nanoparticles under light illumination, reaching up to 0.47 kg/m2h and 29.79 %, respectively. The rejection rate against SDBS achieved up to 99 %. We also verified that its distinctive surface photothermal heating effect is associated with enhanced plasmonic absorption, surface thermal conductivity, and improved interfacial heat transfer of the membranes in the presence of plasmonic elements. The photothermal membranes proved that the permeate produced by photothermal distillation of real laundry wastewater fulfilled all required parameters for safe use as irrigation water, demonstrating its practical feasibility and viability of solar-driven distillation for domestic wastewater treatment and reuse.

A high flux ultrafiltration membrane with a multi-hydrophilic particle additive and controlled self-assembly of micellar particles

A tri-block-copolymer and dopamine hydrochloride were processed through micellization then mixed with high molecular weight PVP to modify PES membranes, yielding excellent membrane performance in terms of permeability and high pollutant rejection.

R-HGO/MXene composite membrane with enhanced permeability and rejection performance for water treatment

Pure graphene oxide (GO) membranes have a tendency to swell in water and have a relatively low flux, making them impractical for water treatment applications. Herein, a novel two-dimensional (2D) composite membrane based on reduced-holey GO (r-HGO) and MXene materials was developed. As a consequence of synergistic effects arising from its unique heterogeneous structure, the r-HGO/MXene composite membrane exhibited an exemplary performance for water treatment, in terms of its permeability and pollutant rejection, and high physical stability. The preparation conditions, especially the reduction degree of GO and the proportions of r-HGO and MXene, determine the properties and performance of the composite membrane. The water flux of the r-HGO/MXene composite membrane with a r-HGO/MXene mass ratio of 1/1 achieved 121.0 L m−2 h−1·bar−1, which was 23 times higher than that of pure GO membrane (∼5.2 L m−2 h−1·bar−1). The removal rates of Coomassie brilliant blue, Methyl blue, Crystal violet, Rhodamine B, Methylene blue, were all above 90 %. Furthermore, the r-HGO/MXene composite membrane was found to be physically stable for more than a week in an aqueous environment. The results of this work show that the r-HGO/MXene composite membrane has great potential as a separation method in water treatment by overcoming some of the important limitations of other current 2D materials.

Adsorptive Membranes Incorporating Ionic Liquids (ILs), Deep Eutectic Solvents (DESs) or Graphene Oxide (GO) for Metal Salts Extraction from Aqueous Feed.

Water scarcity is a significant concern, particularly in arid regions, due to the rapid growth in population, industrialization, and climate change. Seawater desalination has emerged as a conventional and reliable solution for obtaining potable water. However, conventional membrane-based seawater desalination has drawbacks, such as high energy consumption resulting from a high-pressure requirement, as well as operational challenges like membrane fouling and high costs. To overcome these limitations, it is crucial to enhance the performance of membranes by increasing their efficiency, selectivity, and reducing energy consumption and footprint. Adsorptive membranes, which integrate adsorption and membrane technologies, offer a promising approach to address the drawbacks of standalone membranes. By incorporating specific materials into the membrane matrix, composite membranes have demonstrated improved permeability, selectivity, and reduced pressure requirements, all while maintaining effective pollutant rejection. Researchers have explored different adsorbents, including emerging materials such as ionic liquids (ILs), deep eutectic solvents (DESs), and graphene oxide (GO), for embedding into membranes and utilizing them in various applications. This paper aims to discuss the existing challenges in the desalination process and focus on how these materials can help overcome these challenges. It will also provide a comprehensive review of studies that have reported the successful incorporation of ILs, DESs, and GO into membranes to fabricate adsorptive membranes for desalination. Additionally, the paper will highlight both the current and anticipated challenges in this field, as well as present prospects, and provide recommendations for further advancements.

Rejection of organic micropollutants from greywater with forward osmosis: A matter of time

Forward osmosis (FO) has popularized lately due to its lower fouling propensity, higher pollutant rejection, and potentially lower energy consumption than other membrane technologies. Greywater (GW) is a good candidate for FO treatment for its further reuse due to its lower organic and solids content than other wastewater streams, but it contains organic micropollutants (OMP) that might pose a risk for its reuse. Seawater (NaCl) is widely used as draw solution, but the use of fertilizers instead offers the advantage of applying the diluted draw solution for irrigation. This study evaluated the performance of FO for GW treatment focusing on OMP rejection, by means of tests with fertilizers or NaCl as draw solutions and deionized water or GW as feed solutions. The main GW constituents were well rejected, except for sodium, which diffused to the draw solution. Excellent OMP rejection was obtained (>95% in most cases, average 98.5% rejection at the end of the experiments), which was influenced by experimental conditions and OMP properties. Highest rejections were observed for negatively charged OMP and for neutral/positive charged OMP with large molecular weight. Feed type and contact time between feed and draw solutions had the biggest influence on OMP rejection, which decreased over time and by using GW instead of deionized water as feed solution. The diluted draw solution proved safe for irrigation water reuse purposes although sodium content could be of concern. Further studies on the contact time between the solutions are required to foster further applications of FO, as it clearly influenced the rejection of OMP, aspect that is crucial for safe water reuse applications.

Recent advances in heavy metal removal by thin film nanocomposite membrane

Abstract Rapid industrialization has become one of the root causes of environmental problems, particularly heavy metal pollution. Numerous methods, including chemical precipitation and ion exchange, have been used to remove heavy metal ions from aqueous solutions, but all of them have drawbacks, such as low metal removal effectiveness, significant reagent loss, excessive energy use, and the need for further development of the current techniques. Membrane-based technologies such as reverse osmosis (RO) and nanofiltration (NF) are gaining popularity in the removal of heavy metals due to their high rejection and low formation of secondary pollutants. Among the methods under consideration, the membrane-based approach holds the most promise for wastewater treatment with a focus on heavy metal ion removal due to its ease of manufacture, superior qualities, and increased separation effectiveness. Since membrane performance is typically hampered by fouling, low permeability, and significant contaminant permeation when compared to strict selectivity criteria, the development of novel membrane materials has emerged as an important area of research for academia, industry, and national laboratories. We have therefore reviewed previous initiatives and technological developments in order to achieve more effective heavy metal removal and recovery from industrial wastewater.

Enhancing the Performance of PVDF/GO Ultrafiltration Membrane via Improving the Dispersion of GO with Homogeniser.

In this study, PVDF/GO-h composite membranes were synthesised using a homogeniser to improve the dispersion of GO nanosheets within the composite membrane's structure, and then characterised and contrasted to PVDF/GO-s control samples, which were synthesised via traditional blending method-implementing a magnetic stirrer. By characterizing membrane via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), water contact angle (WCA) and membrane performance. SEM results showed that the number of the finger-like structure channels and pores in the sponge like structure of PVDF/GO-h composite membranes become more compared with PVDF/GO-s membranes. Water contact angle tests showed that the PVDF/GO-h composite membranes have lower contact angle than PVDF/GO-s control, which indicated the PVDF/GO-h composite membranes are more hydrophilic. Results also showed that composite membranes blended using homogeniser exhibited both improved water flux and rejection of target pollutants. In summary, it was shown that the performance of composite membranes could be improved significantly via homogenisation during synthesis, thus outlining the importance of further research into proper mixing.

Antifouling forward osmosis membranes by ε-polylysine mediated molecular grafting for printing and dyeing wastewater: Preparation, characterization, and performance

Membrane fouling during forward osmosis (FO) seriously affects the service life of the membrane and increases the treatment cost. A facile strategy was developed to mitigate membrane surface fouling and simultaneously achieve high pollutants rejection. The amino group on ε-Polylysine (PL) reacted covalently with the active sites (acyl chloride and carboxyl group) on the polyamide (PA), thereby grafting the ε-PL onto the PA active layer of PAN/LiCl supported membrane. Effects of membrane orientation, concentration of draw solution (DS), and pH of feed solution (FS) on pollutants rejection were investigated. Results showed that rejection efficiencies of TOC, Ca, Mg, Sb, Cr, and aniline in wastewater by the 0.5 wt% PL-grafted PAN-1.5LiCl TFC-FO membrane (FO-0.5 PL) attained 93.3%, 96.7%, 99.3%, 98.3%, 99.9%, and 99.8%, respectively. The high rejection efficiencies were mainly attributed to the improvement of the surface hydrophilicity of the grafted membrane, the reduction of the roughness, and the improvement of membrane surface potential. The microbubble-assisted cleaning experiment showed that the flux recovery efficiency of the FO-0.5 PL membrane could reach 98.8%, which is 6% higher than that of the FO-P membrane. The PL-grafted FO membrane simultaneously improves the stability of permeation flux (15.2 L m−2 h−1) and fouling resistance performance of the membrane. This study revealed that the PL grafted method can improve the antifouling performance of the membrane and can be used as a feasible treatment method for printing and dyeing wastewater. The research results provided a new idea for facile preparation and application of FO membranes and had a certain reference value for the development of antifouling FO membrane.

Synthesis of amine-modified graphene integrated membrane as protocols for simultaneous rejection of hydrocarbons pollutants, metal ions, and salts from water

Water pollution endangers water sustainability; it limits the quantity of water available for consumption. Therefore, poor quality of water resources warrants significant ecological and public health concerns. Hence, there is a need for efficient materials and methods for water treatment. In this work, efficient membranes were synthesized by integrating amine-modified graphene in polyamide of m-phenylenediamine and trimesoyl chloride. Scanning electron microscope (SEM), energy dispersive x-ray (EDX), Fourier transform infrared spectroscopy (FTIR), and atomic force microscope (AFM) analyses were used for the characterization of the morphology, and surface characteristics and structure, of the prepared membranes. Filtration experiments were performed to examine the permeability and separation capacity of the membrane against organic contaminants, heavy metals, and salts. The obtained results displayed that permeability of salts and metal ions and separation of oil were considerably improved by integrating the membranes with amine-modified graphene. The synthesized membranes displayed hydrocarbon separation efficiency of ≈ 100%, total metal ions rejection of up to 96%, and average salt rejection of around 80%. The proposed membranes are very promising for real-world applications because of their outstanding stability, high flux, rejection of salt, and rejection of oil.

Dynamics of Topology-dependent Water Purification by Siliceous Zeolite Membranes

• Simulated the effect of topology and pore size of zeolites on water purification. • Compared porous LTA, FAU, and MFI zeolites in purification of Cl - , Pb 2+ , and Co 2+ . • Tersoff and Lennard-Jones hybrid force fields, and TIP3P water models were used. • Applying PMF in MD simulation, the efficiency of zeolite membranes was conceptualized. • Applying a long time of 15 ns, heavy metal ions behaved differently in rejection. The efficiency of pollutant rejection (PR, %) and water purification of the zeolite membranes is highly dependent on their topology, i.e., porosity and chemical composition. Nevertheless, mechanisms controlling such a physicochemical phenomenon have been limitedly discussed. Herein, we provide insights into the physics and dynamics of water purification by zeolite nanosheets in terms of topological variables. The molecular dynamics (MD) simulation pictured the molecular-lever water purification having heavy metal ions (Co 2+ and Pb 2+ ) as typical water contaminants. Three siliceous zeolites having different topologies, i.e., LTA, FAU, and MFI zeolites, were positioned in the simulation space. MD simulation was served under pressure and temperature of 24 MPa and 300 K, respectively, applying the Canonical ensemble (NVT) condition. The intermolecular interactions between contaminant ions, zeolite, and graphene were tracked by hybridizing Tersoff and Lenard-Jones potentials, while the TIP3P model of the CHARMM force field was used to simulate water dynamics. The LAMMPS software and Visual Molecular Dynamics (VMD) were used to collect data and graphics over 15 ns, with early 5 ns devoted to reaching equilibrium. Interestingly, we demonstrated by the aid of potential of the mean force (PMF) pollutant ions which encounter the zeolite pores smaller than their kinetic diameter consume more energy for permeation across the membrane, -reason why LTA appeared selective against Pb 2+ , Co 2+ , and Cl - ions, with PR of 40, 60, and 100%, respectively. The absolute water flux values were monitored, and LTA and FAU fluxes were ∼ 50% higher than MFI zeolite, but 5 ns after equilibrium, LTA flux was overtaken sharply by the simulation because of the larger pore size. Overall, the electrostatic forces showed absolute control over the purification but were governed by the zeolite topology.

Fouling studies on hydrophobic PVDF-bentonite hollow fiber membrane during membrane distillation of palm oil mill effluent

Membrane distillation (MD) is one of the emerging methods that can be adopted for oily wastewater treatment. However, the problems associated with membrane surface fouling may impede its separation efficiency. In this work, we performed a fouling study using self-synthesized polyvinylidene difluoride (PVDF)-bentonite hollow fiber membrane (HFM) to treat palm oil mill effluent (POME) via direct contact membrane distillation (DCMD). To date, there is no report on POME treatment using MD technology based on PVDF-bentonite HFM. The fouling tendency was identified based on the membrane's permeate flux and pollutant rejection. The fouled membranes after POME treatment were characterized based on its morphology, functional group, water contact angle, surface roughness and mechanical strength. The results showed that the average permeate flux of MD was 3.34 kg/m2·h over 72-h operation. The membrane showed good performance in separating pollutants with >95 % removal rate recorded for chemical oxygen demand, nitrate nitrogen, total suspended solid, total dissolved solid, color and turbidity. However, based on the post-characterization analysis, the used membranes still suffered from fouling after 72-h DCMD test. Thus, an in-depth investigation into the prevention and control of membrane fouling is still necessary for the POME treatment using DCMD.

Synthesis, characterization, and performance evaluation of UV light-driven Co-TiO2@SiO2 based photocatalytic nanohybrid polysulfone membrane for effective treatment of petroleum refinery wastewater

This study investigates the effects of cobalt (Co) doped TiO2 @SiO2 photocatalyst in the polysulfone (PSf) membrane that performed a combined membrane filtration and photocatalytic process under UV light irradiation for petroleum refinery wastewater (PRW) treatment. The photocatalyst composites were synthesized using the sol-gel method, and the membranes were prepared using the phase inversion technique. Characterization results showed that the Co doping in TiO2 successfully improved the photo-sensitivity and photocatalytic activity of the composite, suggesting the reduction of the bandgap energy from 3.10 eV to 3.00 eV, which promoted the photocatalytic activity improvement. The addition of Co-TiO2 @SiO2 photocatalyst improved the membrane’s porosity, hydrophilicity, water uptake ability, affinity towards water molecules, and mechanical strength. Furthermore, the PSf/Co-TiO2 @SiO2 membrane also exhibited enhanced performance on permeate flux, pollutant rejection, stability, recyclability, and durability. The fabricated photocatalytic membranes also exhibited superior antifouling performance and flux recovery ability when they performed under UV light irradiation.

Highly permeable and dye-rejective nanofiltration membranes of TiO2 and Bi2S3 double-embedded Ti3C2Tx with a visible-light-induced self-cleaning ability

To conquer the trade-off dilemma of the nanofiltration membranes for both high permeability for water and high rejection for pollutants has long been highly concerned. In this work, TiO2 and Bi2S3 nanoparticles were evenly dispersed successively into the interlayers of Ti3C2Tx nanosheets, and then filtered onto cellulose acetate support membranes. The as-obtained composite membranes exhibited a maximum water flux of 374.4 L m−2 h−1 bar−1, and a high rejection ratio for RhB, GR, MB and BSA at 97.8–100%, apparently higher than those of the Ti3C2Tx and the related membranes in literature. Such a high separation capacity was found quite stable for various dye-containing aqueous solutions, even in a high salinity environment of 5 wt% NaCl. Interestingly, 25% NaCl salt was also rejected accompanying the almost complete rejection of dye pollutants. After the filtering process, the membrane fouling of fouled Ti3C2Tx/TiO2/Bi2S3 membranes was verified quite lower than that of fouled Ti3C2Tx/TiO2 and Ti3C2Tx membranes. Furthermore, the flux recovery rate of the fouled composite membrane could reach 92.1% after washing under visible light, which could be ascribed to the composition of heterojunction causing the red shift of diffuse reflectance UV–vis spectra and the narrowing of the band gap. This study provides a new idea for the preparation of highly permeable and rejective nanofiltration membranes, and lays a foundation for its high-capacity dye removal applications.