Reduce Membrane Fouling Research Articles

Development and validation of a model for mitigating particulate fouling in ultrafiltration using water-hammer

Membrane fouling is an endemic problem in ultrafiltration used for many applications. Recently water-hammer pulsing has been shown to reduce membrane fouling. Rapid solenoid-valve closure on the retentate or permeate side of a membrane generates a pressure front that propagates and reflects at the system boundaries at the speed-of-sound. However, the mechanism whereby this mitigation occurs is not well-understood. A predictive model is developed for mitigating fouling using pulsed solenoid-valve closure in the ultrafiltration of particulates. The model assumes the boundary-layer flow that develops after the first pressure-front reflection at the upstream boundary causes an enhanced shear stress on the fouled membrane. This increased shear stress typically occurs for less than 0.01 s during each solenoid-valve closure that occurs once every several seconds. However, it has a significant effect on removing the fouling deposits because it is orders-of-magnitude larger than the shear stress of the steady state crossflow velocity. This model correlates with a Coefficient-of-Determination of 0.997 the fractional flux increase for 44 experiments spanning a range of fluxes, foulant concentrations, pressures, and solenoid-valve-closure frequencies for an aqueous whey-protein feed. The fractional flux increase was 10.7%–124% and averaged 51.2%. However, the model indicates that considerably higher flux increases are possible.

Beneficial role of pre- and post-ozonation in a low rate biofiltration-ultrafiltration process treating reclaimed water

Previous studies have shown that the combination of biological and ozone oxidation processes can achieve a greater performance in treating natural surface water than each process individually. In this work, we designed and tested an ozonation–gravity-driven up-flow slow rate (0.01 m/h) biofiltration–ozonation (O3–GUSB–O3) process for the pre-treatment of reclaimed water prior to ultrafiltration (UF), with the aim of producing high quality drinking water and a significantly reduced degree of UF fouling. Results showed that O3 coupled with GUSB can effectively remove aromatic compounds (∼ 84.8%), dissolved organic carbon (DOC, ∼ 83.4%), and biopolymers in surface water. In addition, post-ozonation greatly contributed to the reduction of the UF membrane fouling (∼ 6 times greater flux). With regard to the disinfection by-product formation potential (DBPFP) of the final treated water, both trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP) were greatly reduced (86.4% and 84.8% for THMs and HAAs, respectively). The relationship between DBPFP and various spectral indexes revealed that aromatic compounds and amino acids were more likely to generate DBPs during the disinfection stage. Among these, humic substances were more likely to generate THMs, while low molecular weight carboxylate and carbonyl organic compounds were associated with the generation of HAAs. Moreover, the dosage of O3 during the post-ozonation stage was found to influence directly the generation of DBPs. Overall, this study has conducted a detailed evaluation of a novel multi-ozone biofilter UF process for treating surface water, and the results provide a valuable basis for subsequent studies at larger scale to demonstrate the potential of the treatment process for practical applications.

A novel bio-flocculation combined with electrodialysis process: Efficient removal of pollutants and sustainable resource recovery from swine wastewater

High organic matter load and nutrient concentration in swine wastewater could lead to soil and water pollution by inappropriate land irrigation. To solve the above problem, this study developed an eco-friendly bio-flocculation combined with electrodialysis (BF-ED) process, in which BF could effectively reduce the probability of ED membrane fouling and replaced subsequent biochemical treatment by ED process. High removal of TS (100 %), TP (100 %), and COD (95.68 %) from raw swine wastewater could be obtained via BF pretreatment, while high recovery efficiency of nutrient ions (98.8 % K+ and 84.3 % NH3-N) was achieved after ED process. Besides, dissolved organic matter was effectively removed after BF treatment, which was beneficial to reduce membrane fouling of ED reactor. Nutrient ions recovery from swine wastewater could be used as agricultural fertilizers. The proposed approach not only solve the problem of swine wastewater purification, but also realize the environmentally sustainable swine wastewater.

Enhanced permeate flux by air micro-nano bubbles via reducing apparent viscosity during ultrafiltration process.

Micro-nano bubbles (MNBs) play important roles in the reduction of membrane fouling during membrane separation; however, such improvements are always attributed to the reduced concentration polarization on the surface of membranes and little attention has been paid on the variations of physicochemical properties of the feed caused by MNBs. In this study, the separation efficiencies of the feed containing humic acid (HA), bovine serum albumin (BSA), sodium alginate (SA) or dyes can be improved by MNBs during ultrafiltration, and the normalized fluxes can be maximally increased to 139% and 127% in the dead-end and cross-flow modes, respectively in the treatment of HA solution. We further reveal that the decreased apparent viscosity of the feed in the presence of MNBs is the key factor that enhances the normalized flux during ultrafiltration. This study gives new insight on the importance of MNBs in membrane separation and provides valuable clues for other chemical processes.

Photocatalytic TiO2@MIL-88A (Fe)/polyacrylonitrile mixed matrix membranes: Characterization, anti-fouling properties, and performance on the removal of natural organic matter.

Photocatalytic membrane reactors (PMRs), coupling photocatalysts and membranes in a single system, have shown a considerable potential to reduce membrane fouling, which is one of the major drawbacks of using membranes to treat water and wastewater. In this study, the visible light-activated photocatalysts were incorporated into the polyacrylonitrile (PAN) casting solution to synthesize the photocatalytic composite membranes. The physicochemical properties and the morphology of the membranes and photocatalysts were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction analysis (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV-visible DRS), photoluminescence (PL), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Brunauer-Emmett-Teller (BET), porosimetry, and contact angle analyses. The performance of the synthesized photocatalytic mixed matrix membranes (MMMs) in treating water containing humic acid, as one of the major components in natural organic matter (NOM) existing in drinking water sources, was investigated. Under visible light irradiation, the PAN/TiO2@MIL-88A (Fe) MMMs simultaneously adopted photocatalysis and membrane separation in the PMR and thereby enhanced humic acid removal and anti-fouling properties. The best synthesized photocatalytic membrane could remove 92.4% of the humic acid once exposed to visible light. The optimum membrane had suitable water permeability, a high flux recovery ratio (99.5%), and a 13.5% decline in the humic acid flux after a 10-h run, considerably lower compared to the corresponding decline of the pristine membrane (37.5% over the same period). The remarkable properties of the PAN/TiO2@MIL-88A (Fe) membrane, including its high anti-fouling specification, confirm the appropriateness of the synthesized MMM for treating water involving humic acid.

Coupling horseradish peroxidase based bioreactor with membrane distillation: Elucidating antibiotics degradation and membrane fouling mitigation

The frequent detection of antibiotics in the surface water bodies increases concerns due to their harmful effect on the biota. In this study, the potential of standalone membrane distillation (MD) and horseradish peroxidase (HRP) enzyme assisted MD treatment (MDHRP) was explored for the removal of 13 antibiotics. A standalone MD system achieved 95 to >99 % removal of the antibiotics from feed solution in ultra-pure water. The enzymatic membrane bioreactor, i.e., MDHRP completely retained both the HRP enzyme and antibiotics (>99 %) in the feed tank, and HRP achieved biocatalytic degradation of antibiotics, thus reducing antibiotics concentration in the feed solution. Overall, 16 to >99 % degradation of the antibiotics retained within MDHRP system was achieved by HRP. Antibiotics degradation was greatly affected by the chemical structure and physicochemical properties of the antibiotics. MDHRP treatment resulted in high removal (>70 %) of antibiotics containing either electron-donating groups (e.g., phenolic group) or both electron-donating group/electron-withdrawing groups (e.g., phenolic and amide groups/carboxylic group) in their structures. When secondary-treated effluent (i.e., effluent from a conventional membrane bioreactor) was spiked with antibiotics and used as a feed in MDHRP system, in addition to the antibiotics degradation, HRP reduced the concentration of bulk organic carbon (30 %) and nitrogen (62 %) from feed during continuous operation. This in turn assisted in reducing membrane fouling and improving the membrane flux.

Layered metal oxides loaded ceramic membrane activating peroxymonosulfate for mitigation of NOM membrane fouling

Catalytic membrane can achieve sieving separation and advanced oxidation simultaneously, which can improve the effluent water quality while reducing membrane fouling. In this study, the catalytic membranes (M2+Al@AM) were fabricated by loading different binary layered metal oxides (M2+Al-LMO: MnAl-LMO, CuAl-LMO and CoAl-LMO) on alumina ceramic substrate membranes (AM) via vacuum filtration followed by calcination process. The performance of the catalytic membranes was investigated by filtering actual surface water. It was found that the presence of peroxymonosulfate (PMS) could mitigate membrane fouling effectively, as evidenced by the increase of normalized flux from 0.28 to 0.62 in CoAl@AM/PMS system, from 0.25 to 0.52 in CuAl@AM/PMS system, and from 0.22 to 0.31 in MnAl@AM/PMS system, respectively. Correspondingly, the CoAl@AM exhibited the highest removal for UV254, TOC and fluorescent components in the surface water, followed by CuAl@AM and MnAl@AM. Quenching effect of phenol and furfuryl alcohol proposed the surface-bound radicals and singlet oxygen were the major reactive oxygen species in the M2+Al@AM/PMS systems. Interface free energy calculations confirmed the in-situ PMS activation could enhance the repulsive interactions between NOM and the membranes, thus mitigating membrane fouling. This work provides an original but simple strategy for catalytic ceramic membrane preparation and new insights into the mechanism of membrane fouling mitigation in catalytic membrane system.

Optimizing dose of coagulant and pH values for membrane fouling control in a submerged membrane bioreactor

AbstractBACKGROUNDThis study assessed the impact of using polyaluminum chloride (PAC) and of changing pH values on the removal efficiency and membrane fouling in a submerged membrane bioreactor (MBR) system utilized to treat real pharmaceutical wastewater.RESULTSThe results revealed that sweep coagulation and a neutral pH were suitable for decreasing soluble microbial products (SMP) in the activated sludge, and the sludge filterability performed better with bridging coagulation and an acidic pH (6.5 < pH < 7). In addition, it was found that membrane fouling was greatly alleviated when PAC was added under the optimized conditions to the MBR (PAC concentration = 100 mg L−1 and pH = 7). Further analyses of membrane fouling mechanisms indicated that adding PAC to the MBR increased the biomass floc size and reduced the SMP concentration and the carbohydrate content in the mixed liquor.CONCLUSIONThe detailed analyses of the membranes' cake layers showed that the presence of PAC decreased the amount of fluorescent organic carbons, proteins, and carbohydrates. These changes in sludge characteristics considerably contributed to the reduction of reversible and irreversible membrane fouling. © 2022 Society of Chemical Industry (SCI).

Achieving high separation of cephalexin in a photocatalytic membrane reactor: What is the best method for embedding catalyst within the polysulfone membrane structure?

The aim of this study is to achieve the best performance for the photocatalytic membrane reactor (PMR) in cephalexin removal. To this end, SrTiO3 photocatalyst with the bandgap of 2.85 eV and crystalline size 50 nm is embedded in the membrane structure using four methods, including blending with membrane matrix (BM), photograft polymerization (GP), interfacial polymerization (IP) and spin coating (SC). Investigation the PMR performance shows that, due to high porosity (68 %), the maximum drug flux (371 L/m2h) passes through the BMi membrane. Because of high flux, BMi membrane suffers from high fouling where presence of SrTiO3 can reduce it by at most 6 %. On the other hand, presence of SrTiO3 across the IPi surface, because of high surface area for performing photocatalytic degradation reactions, causes reduction of membrane fouling by 69 % compared to the raw membrane. The largest share of cephalexin membrane separation (80 %), due to the minimum MWCO (660 g/mol), is related to SCi membrane and the greatest share of the cephalexin photocatalytic degradation (59 %) as the shortest bandgap (3.19 eV) is associated with the GPi membrane. Overall, the highest rate of cephalexin removal (membrane separation plus photocatalytic degradation) is reported for SCi membranes, followed by IPi, GPi and BMi membranes, respectively. Hence, in order to achieve high flux, BMi; low fouling, IPi; high photocatalytic degradation, GPi and high separation, SCi membrane are suggested. Given the challenge ahead of any type of catalytic reactor, the proper method should be chosen for embedding the catalyst within the membrane structure.

Experimental investigation of the performance of anaerobic membrane bioreactor with electrolytic regeneration (AMBER) for challenges and options in wastewater treatment

Significant changes in wastewater services are necessary for achieving the sustainable development goals (SDGs), by utilizing resource recovery, recycle, and reuse in urban wastewater-treatment plants. Based on recent experiences, to improve the filtration behavior of a membrane bioreactor, a hybrid system including an upgraded anaerobic baffled reactor coupled with an electrolysis process and a nanocomposite-membrane was developed. The system, called an anaerobic membrane bioreactor with electrolytic regeneration (AMBER), is a bio-electrochemical process that is expected to be simultaneously efficient in both biogas augmentation and fouling mitigation. The goals were to enhance the stability and efficiency of the anaerobic membrane bioreactor. The integration of the electrolytic process with the ABR (EABR) using a pair of iron electrodes enhanced the removal of contaminants in the ABR while successfully maintained pH in the optimum range for anaerobic digestion (6.8 to 7.2). Then, the performance of AMBER in pollutant removal, including organic load, suspended solids, and microbial load, were investigated over 240 days. The results showed that configuration considerably enhanced permeate flux, as it reduced the deposition of extracellular polymeric substances (EPS) on the surface of the nanocomposite membrane, leading to a reduction in membrane fouling. EPS was extracted and quantified to compare the effect of biogas backwash on the function of the membrane reactor. After 7 d of operation with a daily biogas backwash, the flux reduction was approximately 13 % for the conventional combination of the anaerobic baffled reactor and the membrane bioreactor (AMBR), while it was limited to 4 % in AMBER. After cleaning by the biogas, EPS formation decreased 63 % in AMBER when compared to the AMBR. The results revealed that AMBER can be considered an environmentally competitive bioenergy technology for wastewater treatment with the purpose of water recovery and reuse, employing optimized operational conditions, application of antifouling membranes, and electrically-based strategies.

Graphene Oxide Nanocomposite for Sustainable Pure Water by PES Membrane

The urgent concern of water shortage have promoted to the development of different sustainable technologies with the rapid evolution of nanotechnologies. Graphene oxide (GO) is a water-soluble material that can be constructed into a number of structures such as membranes, and has many applications in environmental sectors. Furthermore enhancing membrane characteristics to improve water flux performance and mitigate fouling is crucial issue for membrane separation technology. GO serves as nanofiller to overcome fouling during filtration as well as water flux improvement. This work aimed to develop PES membranes by phase inversion method and the fabricated membranes subjected to series analysis of FESEM, hydrophilicity and water flux. The results showed that the GO improved the contact angle of the pure PES membrane and the water flux increased from 13 to 16 L/m2.h. Therefore, the PES-GO membrane proved its capability to be used for various applications to reduce membrane fouling.

Fouling behavior and cleaning strategies of ceramic ultrafiltration membranes for the treatment and reuse of laundry wastewater

One of the most promising strategies for maintaining stable water sources for on-site wastewater reuse is greywater reclamation, particularly laundry wastewater reclamation. This study proposes an efficient strategy for the pre-treatment of laundry wastewater, which reduces membrane fouling and improves flux recovery after membrane cleaning. The fouling behavior, organic retention, and flux recovery rates of ceramic ultrafiltration (UF) membranes were comprehensively investigated using synthetic laundry wastewater. Under identical applied pressure and temperature conditions, a fouling resistance that corresponded to the water permeate flux and normalized flux was explored. Total organic carbon (TOC) retention was also tested to investigate the feasibility of using ceramic UF membranes as an effective pre-treatment for laundry wastewater reclamation. Furthermore, four different cleaning strategies for the fouled ceramic membranes were systematically compared, including deionized (DI) water, alkaline, acidic, and combined alkaline and acidic chemical agents to provide an in-depth understanding of the potential recovery rates of the membranes relative to the initial state. The filtration and treatment performance of real laundry wastewater samples collected from a university student dormitory was compared with synthetic laundry wastewater. This work provided valuable information on fouling behavior and cleaning strategies that could advance ceramic UF membrane pre-treatment technology for sustainable laundry wastewater reuse. Despite the challenges associated with the organic fouling and the potential of incomplete flux recovery in engineered systems, our findings provide insights into fouling mechanisms and cleaning strategies that could enable the optimization of engineered wastewater reuse systems.

Enhanced removal of extracellular microcystin-LR using chitosan coagulation-ultrafiltration: Performance and mechanisms

Although many studies have proposed different drinking water treatment strategies to cope with harmful algal blooms (HABs), the removal of dissolved cyanotoxins remains a technical challenge. In this study, well-controlled laboratory experiments were performed to investigate the performance of chitosan as an alternative to traditional metallic coagulants in a hybrid coagulation-ultrafiltration (UF) process for addressing multiple HABs impacts in drinking water treatment. Compared to aluminum chlorohydrate (ACH), chitosan induced the formation of much larger and compact flocs, resulting in about 50% of M. aeruginosa cells removal after simple straining. While coagulation with ACH slightly reduced the rate and extent of UF permeate flux decline, chitosan coagulation at low doses (up to 0.25 mg/L) significantly reduced membrane fouling by 33%. At optimal dose (0.25 mg/L), chitosan coagulation showed a remarkable enhancement effect on the extracellular microcystin-LR (MC-LR) removal by UF membrane, up to 50% higher than those achieved with ACH (20%) coagulation and control condition (15%). However, excessive chitosan dosing would lead to severe membrane fouling. Molecular dynamic simulation results confirmed that chitosan exhibited affinity towards MC-LR via electrostatic interactions and weaker yet prevalent hydrogen bonding. The binding between chitosan and MC-LR would lead to toxin encapsulation within the flocs structure and thus an increased level of toxin retention by UF membrane based on the mechanism of size exclusion.

A new integrated single-chamber air-cathode microbial fuel cell - Anaerobic membrane bioreactor system for improving methane production and membrane fouling mitigation

A novel integrated single-chamber air-cathode microbial fuel cell - anaerobic membrane bioreactor (ScMFC-AnMBR) system was designed. It involved an anaerobic membrane bioreactor (AnMBR) and a single-chamber air-cathode microbial fuel cell (ScMFC) being constructed in a common reaction chamber to enhance methane production and reduce membrane fouling in the AnMBR. Results indicated that ScMFC-AnMBR delivered a stable micro-bioelectric field environment with a voltage output of 95 ± 4 mV. Compared with conventional AnMBR (C-AnMBR), methane production using this system increased by 35.89%. Soluble microbial product (SMP) and extracellular polymeric substances (EPS) dropped by 65.3% and 43.1%, respectively. Particularly, the transmembrane pressure (TMP) in the operating cycle was in a slow growth status with the maximum value of only 18.5 kPa. The bioelectric field helped aceticlastic methanogens (Methanosaeta) replace hydrogenotrophic methanogens (Methanobacterium) as the dominant methanogens via electron transfer under a closed-circuit scenario. As syntrophic bacteria of methanogens (Syntrophobacter, Smithella and Syner-01) and exoelectrogens of Desulfovibrio were selected by the bioelectric field and gained a stable foothold, bio-foulant (Megasphaera) was significantly reduced. The complex microbial synergism in ScMFC-AnMBR greatly improved the methanogenic performance, thus effectively alleviated membrane fouling and prolonged the operation cycle of the system. Demonstrated here is the feasibility of practical application.

Enzymatic Extraction of Sapodilla (Manilkara achras L.) Juice: Process Optimization and Characterization

Conventional treatment of sapodilla pulp yields very viscous, turbid, and low juice recovery. Sapodilla processing for juice requires liquefying enzyme that leads to rectifying flow of juice. This study was conducted to optimize the enzymatic pectolytic conditions of sapodilla fruit processing to extract maximum juice using a central composite design (CCD). The effect of processing variables on recovery of juice, total soluble solids (TSS), viscosity, clarity, and L-value along with physicochemical analysis was investigated. The optimized processing conditions were pectinase concentration (0.120%) at 42.02°C for 167.83 min resulting in juice recovery (62.08 ± 0.38%), viscosity (4.81 ± 0.02cP), TSS (21.48 ± 0.19 °Brix), clarity (0.72 ± 0.05%T), and L-value (28.79 ± 0.96). Optimized sapodilla juice showed higher filterability (24.16 ± 1.04 min−1), conductivity (69.46 ± 0.30 S/m), total phenolic content (35.86 ± 0.60 mg/100 mL), ascorbic acid (6.38 ± 0.58 mg/100 mL), moisture content (84.85 ± 0.21% WB), and titratable acidity (0.143 ± 0.0% citric acid) as compared to control sample (60.5 ± 1.80 min−1, 30.43 ± 0.35 S/m, 30.68 ± 0.85 mg/100 mL, 4.64 ± 0.0 mg/100 mL, 83.69 ± 0.18%, and 0.130 ± 0.0%). Optimized sapodilla juice was lower in sedimentation index (0.73 ± 0.11%), turbidity (13.73 ± 1.10 NTU), ash (0.57 ± 0.031%), and β-carotene (0.173 ± 0.008 μg/100 mL) as compared to control sample (1.07 ± 0.02%, 79 ± 0.75 NTU, 0.65 ± 0.031%, and 0.306 ± 0.007 μg/100 mL). The flow behavior index (n) was closer to 1 in both juice samples, which indicated Newtonian-like flow behavior. Conclusively, sapodilla juice extraction at optimal condition (0.120% of pectinase concentration) and 42.02°C/167.83 min would be potentiated to the beverage industry. The use of pectinase might reduce membrane fouling and facilitates processing operation efficiently.

Antifouling BaTiO3/PVDF piezoelectric membrane for ultrafiltration of oily bilge water.

Barium titanate/polyvinylidene fluoride (BaTiO3/PVDF) piezoelectric membrane was successfully prepared and generated in-situ vibrations to reduce membrane fouling by applying alternating current (AC) signal for oily bilge water ultrafiltration. The effect of in-situ vibration on membrane fouling was investigated through changing in the excitation alternating voltage and its frequency, pH, crossflow rate. The results indicated that the piezoelectric membrane by applying AC signal remarkably alleviated the membrane fouling for bilge water ultrafiltration. The membrane fouling decreased with increasing the AC signal voltage. The final steady-state permeate flux from the piezoelectric membrane for bilge water ultrafiltration increased with the AC signal voltage, raising it by up to 63.4% at AC signal voltage of 20 V compared to that of the membrane without applying AC voltage. The high permeate flux was obtained at the resonant frequency of 220 kHz. During the 50-h ultrafiltration of bilge water with the piezoelectric membrane excited at 220 kHz and 15 V, the permeate flux from the membrane was stable. The oil concentration in outflow from the piezoelectric membrane was below 14 ppm, which met the discharged level required by IMO convention. The total organic carbon removal rate in bilge water was over 94%.

Efficient synergism of K2FeO4 preoxidation/ MIEX adsorption in ultrafiltration membrane fouling control and mechanisms

This study examined the combination of potassium ferrate (K2FeO4) preoxidation with magnetic ion exchange resin (MIEX) adsorption as a strategy to reduce membrane fouling caused by the treatment of natural surface water pollutants before ultrafiltration (UF). The mechanism leading to the improvement of the combined process in the reduction of membrane fouling behaviors was systematically analyzed. The combined K2FeO4-MIEX-UF process was used to reduce membrane fouling by evaluating the decline in the accumulation rate and reversibility of membrane fouling. The reversible filtration resistance of the K2FeO4-MIEX-UF process was reduced by 77.2% compared with that of the MIEX-UF process and by 31.2% compared with that of the K2FeO4-UF process. The interfacial forces of pollutants-hydroxide flocs and pollutants-MIEX were 0.46 mN m−1 and 0.62 mN m−1. They were 1.24 and 1.68 times greater than the interfacial force of pollutants-membrane, respectively. The synergistic mechanism of K2FeO4 preoxidation and MIEX adsorption in pollutant removal was further elucidated by analyzing the organic matter in the feed water. The K2FeO4-MIEX-UF process enhanced the removal of organics from water. Therefore, the K2FeO4 preoxidation, MIEX adsorption and UF combined process is an effective strategy for reducing membrane fouling in the UF process.

Marriage of membrane filtration and sulfate radical-advanced oxidation processes (SR-AOPs) for water purification: Current developments, challenges and prospects

• The combination technology of SR-AOPs and membrane filtration (MF) was summarized. • The current scenario of various integrated catalytic filtration membranes methods was centralized. • SR-AOPs/MF was used to remove pollutants and reduce membrane fouling. • The future opportunities and challenges of this technology are discussed. Integration of membrane filtration (MF) and sulfate radical-advanced oxidation processes (SR-AOPs) has progressively attracted extensive attention for environmental remediation because of simultaneous degradation and filtration of pollutants in wastewater. Current development of the integration of MF and SR-AOPs can be divided into three main categories: (1) peroxymonosulfate (PMS)/peroxydisulfate (PDS) are activated by membrane materials to achieve the purpose of synergistic oxidation-filtration process; (2) removal of contaminants was achieved by filtering through the membrane, and then adding PMS/PDS to regenerate the membrane; (3) the membrane can be directly used as an oxidant-catalyst/water contactor to promote SR-AOPs. On this basis, this review comprehensively summarizes the classification, preparation methods and properties of different types of membrane-based materials and filtration devices. In addition, the antifouling effect and self-purification regeneration ability of different SR-AOPs systems on the membrane are highlighted. Moreover, the main mechanisms including the analysis of active sites, the generation of free radicals, and the theoretical calculations in integration of MF and SR-AOPs are defragmented and discussed. Finally, the technical challenges of coupling technology in wastewater treatment are discussed, and the development and application prospects of the collaborative mixing process are prospected.

Study on the Control of Membrane Fouling by Pulse Function Feed and CFD Simulation Verification.

A complex-function fluid controller placed in front of a membrane module was used to control the velocity change with feed fluid and reduce membrane fouling. Using humic acid as the simulated pollutant, the effects of the square wave function, sine function, reciprocal function, and power function feeding on the membrane flux were investigated. For sine function feeding, the membrane-specific flux was the largest and was maintained above 0.85 under the intermittent frequency of 9 s. Compared with the final membrane-specific flux with steady-flow feeding of 0.55, functional feeding could significantly reduce membrane fouling. SEM results showed that sine feeding led to slight contamination on the membrane surface. Furthermore, the Computational Fluid Dynamics (CFD) simulation results showed that the shear force of sine function feeding was about three times that of the steady flow (6 × 105 N). Compared with steady feeding, functional feeding could significantly improve the shear force on the membrane surface and reduce membrane fouling.

Mussel primed grafted zwitterionic phosphorylcholine based superhydrophilic/underwater superoleophobic antifouling membranes for oil-water separation

One of the most successful methods for reducing membrane fouling in filtration and separation applications is zwitterionic surface modification. Herein, poly[(2-methacryloyloxyethyl phosphorylcholine)-co-(glycidyl methacrylate)] (poly(MPC-co-GMA)) was synthesized as a zwitterionic polymer and grafted onto the polysulfone (PSF) microfilter membrane using polydopamine chemistry. The stepwise modifications and formation of the zwitterionic PgEDgMG membrane were established by analyzing chemical structure, surface morphology, charge, and wetting properties. The antifouling properties were established by bovine serum albumin (BSA) protein adsorption as low as 3.71 ± 0.78 µg cm−2, fluorescence imaging, and in-situ BSA adsorption via zeta potential measurements. After zwitterionization, the in-air and underwater oil wetting tests demonstrate the formation of superhydrophilic and superoleophobic membranes, which are critical for oil-water separation. Finally, the prepared membranes were evaluated in batch and continuous mode for soybean and silicone oil-water emulsion separation. The modified membrane demonstrated nearly complete oil rejection (>99%) and flux recovery up to 99% after a continuous 10-cycle operation along with retention of initial flux during continuous filtration for 12 h. Overall, the combination of polydopamine and poly(MPC-co-GMA) created a robust zwitterionic antifouling surface which induces superhydrophilic character and can be used for long-term water purification and sep-aration applications.