Microfiltration Membranes Research Articles

Evaluation of Organic and Inorganic Foulant Interaction Using Modified Fouling Models in Constant Flux Dead-End Operation with Microfiltration Membranes.

The goal of this study was to elucidate the interaction of complex feed solutions under modified membrane fouling models for constant flux operation. The polyvinylidene fluoride membrane (PVDF) was tested for three types of solutions containing inorganic foulants (Al, Mn, and Fe), organic foulants, and suspended solids at 0.5 mM Ca2+ ionic strength. The membrane's performance was evaluated by measuring the increase in transmembrane pressure (TMP) during two different filtration scenarios: continuous filtration lasting 1 h and cyclic filtration lasting 12 min, with 3 min backwashing cycles included. Statistical analysis (linear regression results (R2), p-value) was used to verify the fouling model propagation along with the determination of the contributing constant of each fouling model. An increasing TMP percentage of 164-302%, 155-300%, and 208-378% for S1 (HA + Ca2+), S2 (inorganics + kaolin + Ca2+), and S3 (HA + inorganics + kaolin + Ca2+) was recorded for 1 h filtration, respectively. Furthermore, a five percent increase in irreversible resistance was noted for the S3 solution due to the strong adsorption potential of foulants for the PVDF membrane caused by the electrostatic and hydration forces of foulants. In addition to that, the participation equation elucidated the contribution of the fouling model and confirmed that complete blocking and cake layer contribution were dominant for the S1 and S3 solutions, while standard blocking was dominant for the S2 solution with a high significance ratio. Moreover, R2 and cyclic filtration analysis also confirmed the propagation of these fouling models. The statistical confirmation and regression results analysis of the modified model gave comparative results and satisfied the filtration mechanism and can be used for the constant flux dead filtration analysis of water treatment.

Modification of microfiltration membranes by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/n-hydroxy sulfosuccinimide coupling mediated antimicrobial peptides grafting for biofouling mitigation

Microfiltration membrane separation is widely applied for water and wastewater but biofouling is a challenging task in real applications. In this work, we fabricated a novel antibiofouling polyvinylidene fluoride (PVDF) membrane by grafting non-drug-resistant antimicrobial peptides (AMPs) on the membranes via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxy sulfosuccinimide (EDC/Sulfo-NHS) chemistry. Effects of AMPs concentration on the membrane basic properties, antibacterial and antibiofouling behaviors of the modified membranes were systematically investigated. Membrane surface characterization demonstrated that the AMPs were successfully grafted onto the base PVDF membranes. The AMPs modified membrane showed enhanced hydrophilicity, consistent permeability and prominent antimicrobial ability (i.e., >90% of antibacterial efficiency against both Escherichia coli and Staphylococcus aureus). Batch filtration tests exhibited that the modified membranes with the concentration of AMPs less than or equal to 0.7 mg/mL had lower flux decline rate compared to the pristine membrane (M0). According to the images from confocal laser scanning microscopy analysis, less total cells as well as more dead cells were observed on the AMPs modified membrane compared to M0. Furthermore, the grafted AMPs on the membranes also displayed favorable stability suffered from a cycle involving biofouling and chemical cleaning. This grafting protocol for AMPs highlights a robust way to fabricate antibiofouling membranes for water and wastewater treatment.

A novel approach for sterilization and concentration of traditional functional drinks: Membrane‐based nonthermal processes

AbstractThe applicability of microfiltration (MF) and osmotic membrane distillation (OMD) for sterilization and concentration of traditional functional drink constituents, such as Curcuma xanthorrhiza, ginger, lime, Java tea, and sappan wood extracts, was evaluated in this study. MF showed excellent performance in microorganisms elimination, turbidity reduction, and maintaining antihyperglycemic activity performance. However, a reduction of total phenol and antioxidant activity were observed due to the retention by MF. Fouling in MF was challenging and resulted in rapid flux decline. The concentration of sterilized extracts by OMD operation resulted in a concentration factor of 1.15, 1.13, 1.10, 1.24, and 1.24 for ginger, lime, C. xanthorrhiza, Java tea, and sappan wood, respectively. The active compounds were well preserved, with a maximum of 20% reduction compared to sterilized extracts. Despite insignificant foulant deposition, the OMD flux in tests using C. xanthorrhiza, ginger, and lime as the feed decreased over time, indicating reduced driving force.Practical applicationsThe application of membrane technology for juices and liquid foods sterilization and concentration has been widely researched. In this research, we evaluated the performance of MF and OMD for the sterilization and concentration of traditional functional drinks. The results indicated that the functional drink can be sterilized by MF with excellent preservation of the active compounds, such as those responsible for the antihyperglycemic and antioxidant activities. The OMD could also concentrate the traditional functional drink, even though concentration polarization posed a challenge to flux stability. The degradation of phenolic compounds and antioxidant activity of the concentrated traditional functional drink was at a minimal value, indicating the promising application of MF and OMD. We believe this article provides new and exciting insights to push forward the sterilization and concentration process in industrial scale.

Performance evaluation of submerged membrane bioreactor for the removal of microalgae from the source water of a water treatment plant

Freshwater algal blooms negatively impact the operations of water treatment plants when they are present in the source water. In the present study, an application of a low-cost submerged microfiltration membrane bioreactor for the removal of microalgae from a source water reservoir of a water treatment plant was evaluated. The experiments were conducted in different phases to systematically evaluate how different fouling control methods such as air scouring and water backwashing in combination with vibration technique can enhance the flux and removal efficiency of microalgae in a submerged flat sheet microfiltration membrane bioreactor. Combining backwashing with air scouring (Phase 3) positively enhanced the flux by reducing the TMP, but it did not improve the permeate quality in terms of microalgae and turbidity removal. The results of Phase 4 studies confirmed that vibration had a profound effect on microalgae removal compared to backwashing technique while reducing the TMP from 105 to 103 kPa. The average turbidity removal was increased from 76.75% to 82% when vibration is applied. Combining all fouling control methods such as air scouring, backwashing and vibration methods did not appear to be effective for the removal of microalgae and turbidity (Phase 5). In order to signify the energy input on membrane fouling control, flux in each phase was assessed with respect to total power input. In overall, air scouring at a rate of 7 L/min with 50 Hz of vibration appeared to be an optimum condition in controlling fouling without any frequent backwashing.

The antimicrobial substance's content influences the membrane blocking mechanism in cross-flow filtration – Flow cytometric assessment of the membrane's activity

The study aims to investigate the antibacterial properties of carvacrol-loaded cellulose acetate membranes in cross-flow filtration using an advanced microbiological flow cytometry method and analyze the influence of carvacrol's presence on the pore-blocking mechanisms. The commercial cellulose acetate microfiltration membranes were impregnated with carvacrol using supercritical carbon dioxide as a solvent and transport medium. This technique enables active substance distribution throughout the whole polymer volume on the molecular level. Carvacrol loadings of up to 30 % were obtainable, whereby the membranes preserved their microstructure and functionality for loadings of up to 25 %. The protocol for flow cytometric assessment of the cell deposition on the membrane surface during the cross-flow filtration was developed. The results showed that the presence of carvacrol considerably decreased Staphylococcus aureus deposition on the membrane (from the order of magnitude 107/(cm2membrane surface·mLpermeate) to 105/(cm2membrane surface·mLpermeate)). The membranes containing 20 % and 25 % carvacrol showed the largest permeate flux and the smallest number of deposited bacteria. The largest fraction of dead bacteria (42 %) was detected in the membrane containing 25 % carvacrol. Mathematical modeling showed that the pore-blocking mechanism changed with the increase in carvacrol content, from the cake filtration phenomenon via the intermediate blocking towards standard and complete blocking mechanisms.

Alaska Treatment Plant Tackles Climate Change, Treatment Challenges

After seven years in the making, a state‐of‐the‐art microfiltration membrane facility and new source water intake is being celebrated by the City of Sitka, Alaska.

Effect of granular activated carbon adsorption on mitigating microfiltration membrane fouling by algal organic matter

Abstract Algal blooms can seriously affect the operation of water treatment processes including low-pressure (micro- and ultrafiltration) and high-pressure (nanofiltration and reverse osmosis) membranes mainly due to the accumulation of algae-derived organic matter (AOM). This study investigated the effect of granular activated carbon (GAC) pretreatment on PVDF microfiltration performance for the removal of AOM. Dissolved organic matter (DOM) solution of commercial humic acid, extra- and intracellular organic matter from two species of algae, and Cyanobacteria were used for the investigation of the fouling potential of the membrane. A comparison study of different DOM removal and fouling behaviors of microfiltration (MF) after GAC adsorption as pretreatment was evaluated under variable GAC dosage and solution pH. Almost 15–20% improvement in flux and decline in irreversible fouling occurred due to the pretreatment using 1.0 g/L of GAC for an hour. The intracellular material caused higher membrane fouling than humic acid due to the hydrophilic nature of the AOM. Membrane fouling and decline in flux increased with increasing pH in the range of 5.0–8.0. The comparison results might help to provide insights into the real challenge of dealing with the treatment of algal-laden water.

EFFECT OF POLYMER MODIFIER ON THE MOR­PHO­LOGICAL AND SEPARATION PROPERTIES OF ASYMMETRIC MICROFILTRATION MEMBRANES

Modifying membranes is a common approach to improve their separation ability. In this work, a series of the membranes, which reject colloidal particles of a wide diapason of their size, was obtained by modifying acetylcellulose microfiltration membranes with such rigid polymer as polymetylmetacrilate. Modifying was carried out by precipitation of the polymer in the membrane pores, the depo­sition occurred from the solutions of different concentrations. Other way was multistage modifying membranes with a solution of the same concentration. Depending on the modifying conditions, the content of polymetylmetacrilate in the membrane was 12–44 %. Morphology of the composite membranes was investigated by optical and scanning electron microscopy. Water test was also performed at 0.5–2 bar. The membranes obey Darcy law in this pressure diapason: thus, the pore radius can be approximately estimated from the Hagen – Poiseuille equation (18–63 nm). Moreover, the modifier minimizes the membrane compression: a decrease of the permeate flux is 19 % (pristine membrane) and 8% for membranes containing high amount of the modifier. Colloidal solutions of water-soluble linear polymer, vegetable protein and sol of hydrated iron oxide were also used for the membrane testing. The selectivity of composite membranes enhances in the row: polyvinylpyrollidone < iron oxide < albumin. In the case of vegetable protein, the membrane selectivity is 30–91% depending on the modifier content. The membrane with highest separation ability was used for clarification of goiaba juice: the selectivity towards total solids was found to reach 33–73%. The permeate can be used for the production of beverages, the concentrate is recommended for confectionery industry. Polymethylmetacrylate can be recommended for the membrane modifying as a binding component in the composite containing also hydrophilic agent.

Effects of Different TiO2/CNT Coatings of PVDF Membranes on the Filtration of Oil-Contaminated Wastewaters.

Six different TiO2/CNT nanocomposite-coated polyvinylidene-fluoride (PVDF) microfilter membranes (including -OH or/and -COOH functionalized CNTs) were evaluated in terms of their performance in filtering oil-in-water emulsions. In the early stages of filtration, until reaching a volume reduction ratio (VRR) of ~1.5, the membranes coated with functionalized CNT-containing composites provided significantly higher fluxes than the non-functionalized ones, proving the beneficial effect of the surface modifications of the CNTs. Additionally, until the end of the filtration experiments (VRR = 5), notable flux enhancements were achieved with both TiO2 (~50%) and TiO2/CNT-coated membranes (up to ~300%), compared to the uncoated membrane. The irreversible filtration resistances of the membranes indicated that both the hydrophilicity and surface charge (zeta potential) played a crucial role in membrane fouling. However, a sharp and significant flux decrease (~90% flux reduction ratio) was observed for all membranes until reaching a VRR of 1.1-1.8, which could be attributed to the chemical composition of the oil. Gas chromatography measurements revealed a lack of hydrocarbon derivatives with polar molecular fractions (which can act as natural emulsifiers), resulting in significant coalescent ability (and less stable emulsion). Therefore, this led to a more compact cake layer formation on the surface of the membranes (compared to a previous study). It was also demonstrated that all membranes had excellent purification efficiency (97-99.8%) regarding the turbidity, but the effectiveness of the chemical oxygen demand reduction was slightly lower, ranging from 93.7% to 98%.

Improving anti-fouling properties of alumina tubular microfiltration membranes through the use of hydrophilic silica nanoparticles for oil/water separation

ABSTRACT In this study, hydrophilic silica nanoparticles (Si NPs) were used to modify α-alumina tubular membranes to improve their performance in terms of flux, oil rejection, and anti-fouling properties. Our work focuses on enhancing membrane performance, particularly for difficult applications such as produced water treatment. The prepared membranes were applied for oil-in-water emulsion treatment. After coating hydrophilic Si NPs, the oil contact angle improved from 133.8° to 171.4°. To prevent Si NPs from leaching off the surface of α-alumina tubular membranes, polyvinyl alcohol was used to coat the membranes as a pre-treatment step before Si NP modification. After coating the membrane with Si NPs, the roughness of the membrane surface decreased, likely leading to less fouling. After coating Si NPs, Total Organic Carbon rejection increased from 93.1% for pristine α-alumina tubular membranes to 97.7% for silica-modified membranes because of hydrophilic improvements of the modified membranes. The Si NP coating improved the anti-fouling property of membranes with the flux recovery ratio increasing from 71.3% for pristine α-alumina tubular membranes to 85.9% for silica-modified membranes. Scanning Electron Microscopy, Energy-dispersive X-ray spectroscopy, oil contact angle, and Atomic Force Microscopy characterization tests were done. The tests showed successful Si NPs impregnation and altered wettability.

Microfiltration, ultrafiltration and nanofiltration as a post-treatment of biological treatment process with references to oil field produced water of Moran oilfield of Assam

The selection of an apt technology for the treatment of Oilfield Produced Water (OFPW) depends mainly on the quality of OFPW and methods of pre-and post-treatment processes. The most challenging part of the OFPW treatment process is the removal of Suspended Solid (SS), Oil & Grease (O&G) and dissolved organics. SS and O&G pose an acute problem to the membrane filtration system by fouling the membrane surface which increases operation & maintenance costs and decreases the life of the membrane. Fouling of the membrane surface is mainly attributed to the presence of low molecular weight aromatic compounds and naphthenic acids in the suspended and dissolved organic compounds. Thus, the removal of these suspended and dissolved organic compounds before membrane filtration proffers a challenge to the researchers. In this research, bioremediation process has been applied to remove the organic compounds and the performance and fouling behaviour of hollow fibre Microfiltration (MF), Ultrafiltration (UF) and Nanofiltration (NF) membranes after the bioremediation process has been analyzed in detail. The level of toxicity was determined by comparing the pollutants with the safe discharge limit for disposal into the environment set by Central Pollution Control Board (CPCB), India. The research presents its novelty by using a hydrocarbon-degrading bacteria, Pseudomonas aeruginosa for the Reduction of Organic Loads (ROL) from OFPW of Moran oil field of Upper Assam as a pre-treatment to membrane filtration. The Total Sum Corrected Area (TSCA) method through chromatographic analyses was used for this. The organic loads removal from OFPW by the TSCA method was found to be 67–100%, 100% and 100% after 7, 14 and 21 days of bioremediation respectively. The major parameters in feed OFPW of Moran oil field were found to be pH (7.5–9.3), Total Dissolved Solid (TDS) (1.79–4.75) ppt, O&G (1.78–2.8) ppt, Salinity (2.94–6.98) ppt, Chloride (Cl−) (1.6–3.86) ppt, Bicarbonate (HCO3−) (2.89–4.03) ppt. It was observed that the ranges of pollutants removal by NF was highest such as TDS (26–86%), salinity (81–86%), turbidity (78–94%), hardness (67–75%), O&G (96–99%), Cl− (80–89%) and HCO3− (95–97%).

Identification and control of gas-producing bacteria isolated from the swollen bagged soy sauce

The swelling of soy sauce bags seriously affects product quality and causes food safety problems, which has become an urgent problem to solve in the condiment industry. Here, gas-producing bacteria in the swollen bagged soy sauce were isolated and identified to provide an effective control method for inhibiting their growth and solving the swelling of soy sauce bags. It was found that three gas-producing bacteria isolated from the swollen bagged soy sauce were confirmed as Bacillus amyloliquefaciens (G1), Bacillus sp. (G2) and Bacillus subtilis (P3) using 16S rDNA analysis. The strains' morphologies, growth rates, and physiological and biochemical characteristics were also compared. Further studies yielded the optimal growth time, temperature and pH for the three gas-producing bacteria (B. amyloliquefacien: 24 h, 37 °C, and pH 7; Bacillus sp.: 18 h, 30 °C, and pH 6.5–7.5; B. subtilis: 36 h, 30 °C, and pH 8). Bacillus sp. was more salt tolerant than the other two. Then the antibacterial effect of the combination was tested by the physicochemical index. The results showed that filtering through a 0.22 μm inorganic micro-filtration membrane, sterilizing at 121 °C for 2 min, and adding 1 g/kg potassium sorbate was effective methods to inhibit three gas-producing bacteria and control the swelling of soy sauce.

Effects of peroxide types on the removal performance and mechanism of sulfonamide antibiotics using graphene-based catalytic membranes

This study reports in situ catalytic oxidation processes using graphene-based catalytic membranes to activate peroxydisulfate (PDS), peroxymonosulfate (PMS), and hydrogen peroxide (H2O2). Sulfonamide antibiotics in water, including sulfamethoxazole (SMX), sulfadiazine (SDZ), sulfamerazine (SMR), and sulfamethazine (SM2), were used as target pollutants. The composites of reduced graphene oxide and nitrogen-doped carbon nanotubes were loaded onto nylon microfiltration membranes at 8 g·m–2 mass dosage. The PDS-based systems exhibited the highest efficiency in removing SDZ (≥ 98%) and SMX (> 93%) during continuous 10 h filtration. In contrast, PMS was more suitable for oxidizing SMR (≥ 99%) and SM2 (≥ 90%) in a single pass. Based on functional group characterization and density functional theory calculations, structural defects and pyridinic/graphitic nitrogen species in carbon mats were identified as the main active centers for peroxide activation. Moreover, PDS, PMS and H2O2 exhibited distinct adsorption behaviors on defective and nitrogen-doped graphitic carbon, influencing the cleavage of peroxide bonds to generate reactive oxygen species. The reaction mechanism was investigated through electron paramagnetic resonance and chemical quenching tests. Surface-active species and singlet oxygen dominated in the PDS- and PMS-based systems, representing non-radical pathways, that selectively oxidize sulfonamides in real water matrices more effectively than the hydroxyl radicals involved in H2O2-based systems. PDS activating exhibited significant performance in organic fouling polishing, lowering the transmembrane pressure during continuous filtration. These findings offer valuable insights into implementing in situ catalytic oxidation processes in actual water purification.

Membrane Functionalization Approaches toward Per- and Polyfluoroalkyl Substances and Selected Metal Ion Separations.

Adsorption and ion exchange technologies are two of the most widely used approaches to separate pollutants from water; however, their intrinsic diffusion limitations continue to be a challenge. Pore functionalized membranes are a promising technology that can help overcome these challenges, but the extents of their competitive benefits and broad applicability have not been systematically evaluated. Herein, three types of adsorptive/ion exchange (IX) polymers containing strong/weak acid, strong base, and iron-chitosan complex groups were synthesized in the pores and partially on the surface of microfiltration (MF) membranes and tested for the removal of organic and inorganic cations and anions from water, including arsenic, per- and polyfluoroalkyl substances (PFAS), and calcium (hardness). When directly compared with beads (0.5-6 mm) and crushed resins (0.05 mm), adsorptive/IX pore-functionalized membranes demonstrated an increased relative sorption capacity, up to 2 orders of magnitude faster kinetics and the ability to regenerate up to 70-100% of their capacity while concentrating the initial solution concentration up to 12 times. The simple and versatile synthesis approach used to functionalize membranes, notably independent of the polymer type of the MF membrane, utilized pores throughout the entire cross section of the membrane to immobilize the polymers that contain the functional groups. Utilizing the pore volume of commercial membranes (6-112 mL/m2), the scientific weight capacity of the polymer (3.1-11.5 mequiv/g), and the synthesis conditions (e.g., monomer concentration), the theoretical adsorption/IX capacities per area of the membranes were calculated to be as high as 550 mequiv/m2, substantially higher than the 175 mequiv/m2 value needed to compete with commercially available IX resins. This work therefore shows that pore functionalized membranes are a promising path to tackle water contamination challenges, lowering separation diffusion limitations.

Wet dispersion of graphene assisted constructing multiple interface pores of PVDF hollow fiber membranes via melt-spinning and stretching

In this work, in order to further improve the permeability of poly(vinylidene fluoride) (PVDF) hollow fiber microfiltration membranes through melt-spinning and stretching (MS-S), we doped graphene (GE) in the forming membrane system of the previous work via wet dispersion and successfully prepared PVDF hollow fiber microfiltration membranes with multiple interface pores. GE could be uniformly dispersed and embedded in the PVDF matrix through the wet dispersion, which could obviously improve the interface layer between the matrix phase (PVDF) and the dispersed phase (GE) due to their poor compatibility of organic/inorganic phases. In addition, the stress concentration would be generated at the interface between GE and PVDF, which resulted in PVDF forking to many tiny fibers. Thus, the multiple interface pores between organic/organic (PVDF/polysulfone(PSf)) and organic/inorganic (PVDF/GE) phases could occur and be controlled precisely through the further stretching. The results showed that GE could improve the pore size and porosity of the prepared membranes obviously. In addition, the pore size of the prepared membranes could be controlled from 0.258 to 1.066 µm by changing the stretching ratios. Accordingly, pure water flux increased from 174.5 to 2782.9 L m-2 h-1. Applied to filter the active sludge suspension, the prepared PVDF microfiltration membranes exhibited a high rejection (＞99.5%), and the turbidity decreased obviously (˂0.5 NTU). In particular, there were not any hazardous solvents used in the preparation process, which could achieve green preparation of PVDF membranes.

Construction of transfer-free regular through-pore polyimide composite microfiltration membranes via amphiphilic dendron-assisted breath-figure method for water treatment

Regular through-pore membranes exhibit extremely high productivity and size-selective capabilities. Previous studies have demonstrated that the use of a polymer alone on a solid substrate surface hinders the formation of regular through-pore membranes. In this study, amphiphilic dendrons were used as surfactants to concentrate the functional groups and strengthen the weak bonding forces between the molecules, which is conducive to the formation of regular through-pores in the membrane. The amphiphilic dendrons were mixed with commercial-grade polyimide (PI) using chloroform as the solvent, and the solution was evenly coated on the surface of the filter paper. Using the breath-figure method, an ultrathin regular through-pore PI layer was formed directly on the surface of the filter paper. The SEM image shows that regular through-pores were formed only on the surface of the substrate. The preparation process used in this study eliminates the need to transfer ultrathin and weak membranes to the substrate surface, which simplifies the membrane-making process. Pure water and yeast solution filtration tests were conducted on the composite membrane prepared with a 5 mg/ml dendron solution. A pure water permeance of 118,826 L m-2h−1 bar−1 (LMH/bar) was obtained, the yeast solution permeance and rejection are 17,410 LMH/bar and 92.85 %, respectively. The yellow, turbid, muddy water was successfully purified to clean water. The original performance of the fouled membrane was restored after only 30 s of water flushing. This study proposes a new approach to fabricate high-efficiency regular through-pore PI composite microfiltration membranes.

PPS composite membrane preparation based on aramid and glass fiber woven fabric support

Polyphenylene sulfide@aramid fiber (PPS@AF) composite membrane was synthesized using the dip drawing method. This involved coating a PPS separating membrane over both sides of AF support via the thermally induced phase separation (TIPS) method. In order to overcome the drawbacks of a dense skin and limited flux, we explored the influence of PPS concentration in the casting solution on membrane morphology and PPS composite membrane performance. Compared to the 6.7 N of PPS membrane, the prepared composite membrane displayed a tensile strength up to 445 N. The pure water flux of PPS composite membrane can reach 888.15 L⋅m−2⋅h−1 ⋅bar−1, which is 20.7 times greater than that of PPS membrane. We also successfully developed a PPS composite membrane with superior mechanical properties which was uniformly coated by PPS membrane on both sides of a glass fiber woven fabric (GFWF) using the TIPS membrane scraping method. The ratio of Benzoin (BZ) and Benzophenone (DPK) in casting solution were adjusted to control the surface structure of composite membrane, which was systematically characterized. The results revealed that when the casting solution contained 25 % DPK, the composite membrane supported by GFWF reached a tensile strength of 207.84 N, 31 times stronger than that of PPS membrane. When the casting solution contained 10 % DPK, the pure water flux of PPS/GFWF microfiltration membrane was 75.3 L⋅m−2⋅h−1⋅bar−1, 1.75 times higher than that of PPS membrane.

A Comparative Study of the Self-Cleaning and Filtration Performance of Suspension Plasma-Sprayed TiO2 Ultrafiltration and Microfiltration Membranes.

This study investigated the performance of photocatalytic titanium dioxide microfiltration membranes with an average pore size of approximately 180 nm and ultrafiltration membranes with an average pore size of around 40 nm fabricated with the suspension plasma spray process. The membranes were evaluated for their filtration performance using SiO2 particles of different sizes and polyethylene oxide with molecular weights of 20 kDa to 1000 kDa, and the fouling parameters were characterized. The rejection rate was enhanced by increasing the thickness of the membranes. This effect was more pronounced with the ultrafiltration membranes. The rejection rate of the ultrafiltration membrane was improved significantly after filling the larger pores on the surface with agglomerates of titanium dioxide nanoparticles. The self-cleaning performance of the membranes was assessed under visible light. Both ultrafiltration and microfiltration membranes showed a flux recovery under visible light illumination due to the photocatalytic activity of titanium dioxide. The membranes also show a flux recovery of more than 90%.

Guanidinium manipulated interfacial polymerization for polyamide nanofiltration membranes with ultra-high permselectivity

Polyamide (PA) nanofiltration (NF) membranes with excellent permeability and selectivity have always been the ultimate pursuit of desalination technology. Herein, we present a guanidinium manipulated interfacial polymerization strategy to develop guanidyl-integrated PA NF membranes with ultra-high permselectivity. A nylon microfiltration membrane is utilized as the support to conduct spatial-temporal regulation of amine monomers along with controllable diffusion reaction. Through introducing 1,3-diaminoguanidine (DAG) or triaminoguanidine (TAG) into the aqueous piperazine solution, the free volumes of PA membranes could be well modulated at the sub-angstrom scale. Consequently, the TAG-integrated PA membrane exhibited high water permeance of 33.1 LMH bar−1 and superior Na2SO4 rejection of 99.2%. Meanwhile, this membrane achieved outstanding anion sieving capability (Cl−/SO42− ∼ 343) and nearly 100% tetracycline removal, which is superior to the “state-of-the-art” PA NF membranes. The DAG-integrated PA membrane attained ultra-high water permeance of 46.5 LMH bar−1 due to its relatively large free volume. In addition, the nylon composite PA membranes displayed desirable anti-pressure and organic solvent-resistant abilities. This study provides a convenient and scalable preparation strategy for highly permselective NF membranes, which holds great application potential in desalination and resource recovery.

A Review of Microfiltration Membrane in Separating Folic Acid from Fermented Dark Green Leafy Vegetables (DGLVs), Legumes, Beans, and Cereal for Nutraceutical Application

DGLVs (spinach, broccoli), legumes (soybean, mung bean, kidney bean), and cereal (corn) are well recognized for human health benefits due to the presence of natural folate (vitamin B9) with essential micronutrients. Folate is among the most unstable vitamins for the normal functions of the human body. The recent development of membrane-based methods for the separation of folic acid (FA) is reviewed from the selected literature and covers the result of significant research that has been performed in the last five years on the use of the microfiltration (MF) method. This is coupled with the fermentation process to support and achieve separation or recovery of FA from their selected plant-based food source. The nixtamalization, fermentation, separation, and purification of DGLVs, legumes, and beans, as well as corn, were conducted using the MF (pore size 0.15 µm) membrane separation method. The results showed that the MF membrane was able to separate FA components in permeate from fermented spinach and broccoli, soybean, mung bean, kidney bean, and corn, namely 7.14 and 3.79, 197.00, 325.37 and 242.93, and 121.10 µg/mL, respectively. Meanwhile, FA content in retentate from fermented spinach and broccoli, soybean, mung bean, kidney bean, and corn was 58.90 and 28.10, 362.07, 254.07 and 506.07, and 212.84 µg/mL, respectively. The applications of membrane techniques were used as an alternative to some unit operations in the solving of separation issues as well as the development of selected new fermented plant-based food sources. The contemporary pressure-driven membranes, such as MF, and the main applications were related to pre-treatment, selected fermented plant-based food sources, and alternative technology for extending the shelf life of natural folate. The utilization of MF membranes in the nutraceutical field holds significant promise, particularly in the creation of value-added products from minor compounds.