High Pure Water Permeability Research Articles

Novel thin film nanocomposite membrane modified with Boron Nitride Nanosheets for water treatment

This paper provides a simple method for modifying the boron nitride (BN) surface using cyclopentadienyl. In this study, CBNs were fabricated and incorporated into the thin polyamide (PA) layer of thin-film composite. The developed materials were characterized by FE-SEM, BET, AFM, XPS, and contact angle analyzer and the performance of the membrane. The results indicated that CBNs-incorporated Thin-film composite (TFC) membranes had enhanced surface hydrophilicity due to the increased carboxyl groups produced in the PA layer by the CBNs. Due to the hydropholicity of CBNs nanocomposite,The polyamide-CBNs membranes has higher pure water permeability (330 L.m-2.h-1.bar-1) compared to TFC membranes (3.80 L.m-2.h-1.bar-1). As a result, CBNs increased the attraction between water molecules and membrane surfaces, resulting in enhanced TFN membrane water flux. Upon incorporation of CBNs, the resultant TFN membrane achieved a 95% removal rate for Na2SO4 along with 22.10% higher water flux than the pristine membrane and gives the membrane strong antibacterial properties against Escherichia coli for water purification.

Recycling of aged RO membranes as NF/UF membranes: Biosafety evaluation and aging process

With dramatic growth of reverse osmosis (RO) in water treatment, more than 1.5 million waste RO membrane modules will be generated worldwide annually, which will lead to waste of resources and environmental pollution if not properly disposed. The present study aims at evaluating the feasibility of using aged RO membranes in NF/UF process. And ultraviolet (UV) irradiation was used to simulate the aging process. In addition to the conventional separation performance, virus (bacteriophage MS2) removal rate was used to evaluate the ability that membranes ensure the biosafety of the permeate. After 48 h continuous UV irradiation (313 nm, 1 W/m2), the membrane maintained high Na2SO4 rejection (88%) and phage MS2 removal rate (>4 log), which was comparable to NF-like membrane. After 96 h, the membrane manifested sound virus removal rate (>3.4 log) and high pure water permeability (122.6 L·m−2·h−1·bar−1), but the ability for salt rejection was rather weak, which approximated to a UF-like membrane. It was noteworthy that the aged membrane maintained a high virus removal rate within 0–96 h, which ensured the biosafety of the permeate. The results provided a basis for direct recycling of aged membranes.

Tailored nanofiltration membranes with enhanced permeability and antifouling performance towards leachate treatment

The leachate generated from the sanitary landfill or incineration poses serious environmental threats and it's difficultly disposed due to its complexity containing high concentration of organic matters and inorganic salts etc. Membrane technology stands out as a potential solution for leachate because of its beneficial advantages. Nanofiltration (NF) can reject organic compounds and separate divalent ions from mixed salts, which alleviates fouling and increases separation efficiency and flux of reverse osmosis (RO) in the popular combined processes (MBR-NF/RO) applicable for leachates. However, NF is often subject to low water permeance and membrane fouling for traditional polyamide thin film composite (PA-TFC) membranes. This work develops a high-performance NF membrane by grafting bipyridinium derivative monomer (BBD), an alternative antibacterial by interfering with the bacterial metabolism and reproduction and a hydrophilic compound endowing membrane hydrophilicity, onto PA-TFC membranes through the esterification reaction toward the leachate treatment. Resultantly, the BBD-TFC membrane achieves a reasonably high pure water permeability of 31.6 ± 2.1 L m−2 h−1 bar−1, ∼ 4 times higher than that of the pristine polyamide membrane. Notably, the resultant membrane exhibits excellent antifouling and antibacterial properties in the treatment of the leachate benefiting from the more hydrophilic surface and negative potential on BBD-TFC. Meanwhile, high rejection ratio of divalent ions and organic matter (R > 95%) was also attained companying with high separation efficiency of divalent/monovalent ions. The current work may provide an effective strategy to design high performance NF membranes for the leachate treatment or other wastewater treatment.

Fabrication of microporous polyamide selective layer on macroporous ceramic hollow fibers via direct interfacial polymerization for nanofiltration applications

Polyamide (PA) thin-film composite (TFC) membranes have been widely applied to nanofiltration applications and separation processes due to their high water permeability and solute rejection. However, commercial PA-TFC membranes with organic flat-sheet substrates, such as polysulfone, have a low resistance to organic solvents and a maximum operating temperature no higher than 50 °C. To alleviate this problem, recent research has focused on the development of ceramic substrates to provide robust membrane support. In this study, we successfully developed a novel alumina hollow fiber (AHF) substrate for PA-TFC membrane synthesis via interfacial polymerization. For the first time, a PA thin film was directly fabricated on a macroporous ceramic hollow fiber substrate without an intermediate layer. Herein, to make the support compatible with the PA thin film, AHF with a smooth, hydroxyl group-abundant, and ultrahydrophilic surface was prepared. The HF substrate demonstrated a porous structure with a mean pore size of 219.4 nm and high pure water permeability of 4593 ± 139 LMH/bar. In addition, the nanofiltration performance of the PA-TFC membrane was thoroughly evaluated in this study and compared to previous reports, and it was found that it possessed a molecular weight cut-off (MWCO) of 340 g/mol, pure water permeability (PWP) of 9.5 ± 0.4 LMH/bar, and high rejection of dyes (>97.0%). Our AHF substrate demonstrated its potential as an ideal material for fabricating high-performance PA-TFC membranes for nanofiltration applications. Moreover, our enhanced process of synthesizing PA-TFC membranes via direct interfacial polymerization promises wide applicability in future membrane studies.

Bulk cross-linked hydroxyethyl cellulose-silica composite membrane for acid-stable nanofiltration

This work focused on the construction of an acid-resistant composite nanofiltration membrane with the selective layer of bulk cross-linked hydroxyethyl cellulose (HEC)-silica and a support of porous polypropylene. Membranes were fabricated through in-situ sol-gel reaction and slot-die coating method employing tetraethyl orthosilicate (TEOS) as the silica precursor and cross-linking agent of HEC. Membrane structure and performance were tuned by controlling the hydrolysis time of TEOS and differentiating TEOS and HEC contents, and systematically characterized in terms of physico-chemical property, permeation attribution and acid stability. It was found that membrane performance was strongly correlated with the relative contents of C–O–Si and Si–O–Si bonds of the formed HEC-silica selective layer. High content of C–O–Si bond formed via condensation reaction of HEC and TEOS endowed the selective layer with denser network structure and good rejection ability. Both insufficient and excessive hydrolysis led to a poor rejection ability of formed membrane. The optimized HEC-silica membrane possessed an average pore size of about 1.43 nm within the scope of nanofiltration membrane, a high pure water permeability coefficient of around 10.5 LMH/bar, and a medium rejection of 85.2% to 500 mg/l Na2SO4 aqueous solution at 5.0 bar. No changes in both chemical structure and separation performance occurred with the HEC-silica composite membrane after being soaked in aqueous H2SO4 solution of 4.9 wt% for 7 days, while evident structure destruction and serious performance degradation occurred with the compared polyamide-based commercial membrane NF270. Long-term soaking test using 15.0 wt% H2SO4 aqueous solution for 30 days also demonstrated that the acid resistance HEC silica membrane was comparable with those reported acid stable nanofiltration membranes. Furthermore, the HEC-silica membrane also maintained its water permeation and solute rejection abilities during a 30-day continuous filtration of aqueous solution of 4.9 wt% H2SO4 and 50 mg/l polyethylene glycol fraction (PEG2000). The good acid resistance of the HEC-silica composite membrane was attributed to its bulk cross-linked network structure composed of C–O–Si, Si–O–Si and C–C bonds.

Polyarylester thin films with narrowed pore size distribution via metal-phenolic network modulated interfacial polymerization for precise separation

Traditional nanofiltration (NF) membranes meet a bottleneck in throughput due to the lack of flexibility in pore structure control of the polyamide selective layer. This work developed a highly-permselective NF membrane by creating a controlled polyarylester selective layer via a facile method of metal-phenolic network (MPN) modulated interfacial polymerization between 5,5,6′,6′-tetrahydroxy-3,3,3′,3′-tetramethyl spirobisindane (TTSBI) and trimesoyl chloride (TMC). It was hypothesized that in the presence of FeCl3, the catechol groups of TTSBI first formed a Fe3+/TTSBI complex to construct the MPN and subsequently reacted with TMC, eliminating structural defects in the selective layer. The solution chemistry studies and membrane optimization results verified the significant role of Fe3+ in forming metal-phenolic coordination and thus defectless pore structure. The resulted Fe-TTSBI-TMC membrane exhibited greatly reduced pore size of 0.68 nm and narrow pore size distribution. The rigid and twisted feature of TTSBI endowed the polyarylester layer with high porosity. This ingeniously designed synergistic effect rendered the resulted membrane with a high pure water permeability of 15 L m−2 h−1 bar−1, about 3 times higher than typical polyamide NF membrane prepared by piperazine and TMC; while achieved high salt and molecular rejections (e.g., 98% rejection of Na2SO4, 100% rejection of vitamin B12), exhibiting superior perm-selective properties as compared to most NF membranes incorporating microporous materials. Accurate separation between molecules of different sizes of vitamin B2 and vitamin B12 was achieved with 100% efficiency. Hence, this work provides a promising alternative for skillful control of NF membrane pore structure towards efficient and precise molecular separation.

Engineering novel high-flux thin-film composite (TFC) hollow fiber nanofiltration membranes via a facile and scalable coating procedure

A novel defect-free polyamide/(polyether sulfone/poly(vinylidene fluoride)) PA/(PES/PVDF) thin-film composite (TFC) hollow fiber membrane (HFM) with desirable separation characteristics were developed through a facile and scalable coating procedure. By the introduction of piperazine (PIP) monomers into the PES coating solutions, the functional monomer-enriched PES coating layer was formed on the shell side of porous matrix-reinforced hollow fiber (HF) support through phase inversion process. Subsequently, PIP and TMC was interfacial polymerized during the fiber coating line to form a thin and defect-free polyamide (PA) functional layer for TFC HFM with high water permeability. Furthermore, the introduction of aqueous monomers only into the PES layer allowed economizing the cost of membrane manufacturing compared with bulk modification of the membrane substrate. Interestingly, the formation of bowl-like structures endowed the separation layer with higher permeation surface area and thus favored high water permeability. On combining these separation features, the optimized TFC membranes presented a high pure water permeability (PWP) of 13.8 L·m−2·h−1·bar−1, approximately twice than that of conventional TFC membrane, with a satisfying Na2SO4 rejection of 98.2%. Moreover, the PA/(PES/PVDF) TFC HFM exhibited excellent stability, backwash ability and anti-fouling ability, suggesting its huge potential for the water purification. Compared with the conventional two-step IP process on flat sheet membrane, the in-situ IP procedure performed on HF greatly simplifies the manufacturing process, shortens the production period and reduces monomer usage while the high packing density and great surface area per unit volume are obtained. This work may provide a simple and economical strategy for engineering high-performance TFC HFM.

The effect of polyvinylpirrolidone on the performance of polyvinylidene fluoride membranes

In this investigation, polyvinylidene fluoride membranes were resulted by a phase inversion technique with polyvinylpyrrolidone (PVP) as an agent to form pores, as well as n-methyl pyrrolidone as a solvent. In addition, the effect of PVP concentration (1-4%) was investigated to prepare membranes with better membrane antifouling performance and characteristics. Furthermore, functional groups, morphological structures, and membrane porosity were analysed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and membrane porosity calculation. The surface SEM images revealed that the size of the modified membrane pores increased. The increase of the PVP concentration added, resulted in the number of modified membrane pores. FTIR spectra confirmed that PVP functional groups were dispersed in the PVDF membrane matrix. Optimum pure water permeability (PWP) of 60 L/(m2?h?bar) was achieved using 3% PVP, resulting in a humic acid rejection percentage of 80% and a water flux recovery ratio (FRR) of 85%. These findings indicate that the utilization of PVP as a pre-forming agent resulted in higher PWP, lower humic acid rejection, and good antifouling properties.

Enhanced water flux and bacterial resistance in cellulose acetate membranes with quaternary ammoniumpropylated polysilsesquioxane

An enhanced water flux and anti-fouling nanocomposite ultrafiltration membrane based on quaternary ammoniumpropylated polysilsesquioxane (QAPS)/cellulose acetate (QAPS@CA) was fabricated by in situ sol-gel processing via phase inversion followed by quaternization with methyl iodide (CH3I). Membrane characterizations were performed based on the contact angle, FTIR, SEM, and TGA properties. Membrane separation performance was assessed in terms of pure water flux, rejection, and fouling resistance. The 7%QAPS@CA nanocomposite membrane showed an increased wettability (46.6° water contact angle), water uptake (113%) and a high pure water permeability of ∼370 L m−2 h−1 bar−1. Furthermore, the 7%QAPS@CA nanocomposite membrane exhibited excellent bactericidal properties (∼97.5% growth inhibition) against Escherichia coli (E. coli) compared to the bare CA membrane (0% growth inhibition). The 7%QAPS@CA nanocomposite membrane can be recommended for water treatment and biomedical applications.

Development of a photocatalytic zirconia-titania ultrafiltration membrane with anti-fouling and self-cleaning properties

A photocatalytic Ce-Y-ZrO2/TiO2 ultrafiltration membrane was successfully prepared on a ZrO2/SiC support by a modified sol-gel process. The top active layer is 2 µm thick, uniform and defect-free. The membrane presented a molecular weight cut-off (MWCO) of 19 kDa (equivalent to a pore size of 6 nm) and a high pure water permeability, 160 Lm−2h−1bar−1. The high hydrophilicity and negative surface charge of the membrane favoured its great retention of proteins (bovine serum albumin, whey protein, and hemoglobin), indigo dye, and humic acid. The membrane was effective in photodegrading phenol and humic acid under simulated sun light irradiation. During humic acid filtration tests, the membrane presented better anti-fouling properties (smaller flux decline) and higher permeate flux under irradiation compared to the filtration in the dark. Moreover, self-cleaning properties were observed by irradiating the membrane, which enabled recovering up to 97% of the original flux. Consequently, a longer operation without chemical cleaning is possible, reducing costs and the process footprint. Further investigation would allow the development of innovative treatments for dinking and wastewaters by combining filtration and advanced oxidation processes for the abatement of contaminants of emerging concern in the presence of natural organic matter.

A new method for preparing α-alumina ultrafiltration membrane at low sintering temperature

α-Al2O3 has attracted much attention owing to its excellent organic solvent resistance and acid-base corrosion resistance. However, the preparation of α-Al2O3 ultrafiltration membranes by sol-gel method is still a challenge, because the formation of α-phase requires high temperature calcination and is accompanied by rapid grain growth. To reduce the phase transition temperature and obtain smaller grains, we started from a polymeric sol with particle size of approximately 3.7 nm, which was converted into α-Al2O3 at a low temperature of 1000 °C. Moreover, graphene oxide (GO) as the sacrificial layer was used to prevent the sol from penetrating into the macroporous support, and to obtain a high permeability α-Al2O3 ultrafiltration membrane. Because GO can be pyrolyzed at temperature above 500 °C, an ultra-thin and high pure water permeability α-Al2O3 ultrafiltration membrane was obtained at a low temperature of 1000 °C. The prepared α-Al2O3 ultrafiltration membrane showed a pure water permeability of up to 390 L m−2 h−1 bar−1 and a pore size of approximately 20 nm.

Physicochemical characteristics of polysulfone nanofiber membranes with iron oxide nanoparticles via electrospinning

AbstractHydrophilicity is one of the ideal properties for water treatment membrane. In addition, higher surface area with a porous structure results in extraordinary permeability and selectivity, thus making it a good candidate for water permeability. This study used iron oxide nanoparticles (IONPs) as polysulfone (PSf) membrane nanofillers to enhance the physicochemical properties. Nanofiber membranes were characterized in terms of morphology, wettability, and pure water permeability (PWP). The concentration of IONPs was varied from 0.5% to 2.0% (w/v). From the scanning electron microscope images, all produced membranes were smooth and contain bead‐free nanofibers. The produced nanofiber membrane with 1% (w/v) of IONPs concentration was found to be optimum since it had the highest porosity, lower contact angle, and desirable fiber thickness and diameter. In order to find the best PSf solution concentration, the loadings of PSf were varied from 18% to 27% (w/v). The PSf/IONPs with 25% (w/v) provided the best results in terms of fiber thickness and diameter, porosity and morphology. The contact angle also confirmed that in the presence of IONPs, the nanofiber structure produced with 25% PSf was less hydrophobic and had the highest PWP (70.27 L/m2 h bar).

In situ growth of multifunctional porous organic polymer nanofilms with molecular sieving and catalytic abilities

Porous organic polymers (POPs) have evinced a huge potential for membrane-based separations owing to their impressive surface areas, high mesopore ratio, superior chemical stabilities, and catalytic abilities. In this study, for the first time, an o-hydroxy porous organic polymer (POP) thin film was in situ generated atop a (polyacrylonitrile) HPAN membrane support via diazo-coupling reaction under mild conditions. Analysis by FT-IR, XPS and SEM confirmed the successful formation of a coherent, thin POP nanofilm. Zeta potentials and water contact angle measurements demonstrated that the resultant POP film was hydrophilic (water contact angle = 48°) and negatively charged because of the abundance of hydroxyl groups. The roles of synthesis parameters (e.g., the solution pH and the reaction time) in the membrane microstructure and separation performance were explored in detail. The best-performing composite membranes show a high pure water permeability (66.5 L m−2h−1 bar−1), superior dye retentions (RCR = 99.6%, RDR = 98.0%, RMB = 98.8%), and low divalent salt retention (<15.0%), thus promising for separation of dye/salt mixtures. In addition, the thus-obtained POP film was utilized as the catalyst to yield propylene carbonate in aqueous solution with a high conversion rate of 80% at room temperature. The significance of this study is expected to provide a useful guideline of in situ fabrication of multifunctional POP membranes for separation of dye/salt mixtures and catalysis.

Highly permeable thin film composite hollow fiber membranes for brackish water desalination by incorporating amino functionalized carbon quantum dots and hypochlorite treatment

A novel strategy has been demonstrated to synergistically improve the separation performance of thin film composite (TFC) hollow fiber membranes for brackish water reverse osmosis (BWRO) desalination. It consists of two steps. Firstly, a series of amino functionalized carbon quantum dots (CQDs) were synthesized and incorporated into the polyamide layer of TFC membranes. The modified TFC membrane with the optimal amino functionalized CQDs has a pure water permeability (PWP) of 5.50 LMH/bar and a NaCl rejection of 98.0% against a 2000 ppm NaCl feed solution at 15 bar. Comparing with the unmodified TFC membrane, the modified TFC membrane has a 42.1% higher PWP without compromising the salt rejection. Then the modified TFC membrane was treated by a sodium hypochlorite solution at different concentrations. Chlorine was bonded to the polyamide layers, enhancing their repulsion against charged solutes and making the polyamide network less cross-linked. As a result, both PWP and NaCl rejection of the TFC membranes could be improved. After being treated with a sodium hypochlorite aqueous solution at 4000 ppm for 3h, the aforementioned modified TFC membrane displays a PWP of 10.13 LMH/bar and a NaCl rejection of 98.9% against a 2000 ppm NaCl solution at 15 bar, which demonstrates a great potential for brackish water desalination. This study may mark a milestone for the development of future BWRO membranes based on the use of amino functionalized CQDs and hypochlorite treatment.

Bioinspired: A 3D vertical silicon sponge-inspired construction of organic-inorganic loose mass transfer nanochannels for enhancing properties of polyimide nanofiltration membranes

Nowadays, the separation efficiency and stability of nanofiltration (NF) membrane are of widespread concern. Inspired by the biomineralization phenomenon and its unique structure with siliceous framework, a polyimide (PI) NF membrane decorated with “silica hard phase-polymer soft phase” 3D interwoven sponge bionic structure was fabricated via a simple and effective one-step phase inversion strategy. The obtained membranes demonstrated high pure water permeability of 65 L/(m2·h) and rejections of Na2SO4 (91.55%) and NaCl (30.21%) at 0.4 MPa, respectively. Moreover, siliceous sponge-like structures were determined by SEM analysis, with the degree of cross-linking after membrane pore regulated as high as 88.89%. The integrity and long-term stability of the membrane in different organic solvents, including methanol, cyclohexane, acetone, ethyl acetate, n-heptane, absolute ethanol and toluene were maintained for 72 h at 0.8 MPa. Furthermore, the PI/SiO2 membrane with siliceous sponge biologically unique structure gives rise to a scope of bioinspired membranes and shows promising prospect for the treatment of solutions in extreme environments.

Novel polysulfone ultrafiltration membranes incorporating polydopamine functionalized graphene oxide with enhanced flux and fouling resistance

Novel PSF composite UF membranes incorporating low loadings of polydopamine-functionalized graphene oxide particles (rGO-PDA) were fabricated and investigated. The functionalization was confirmed using FTIR-UATR, Raman spectra, XPS, and SEM. Pristine PSF, PSF/GO, and PSF/rGO-PDA MMMs were then prepared using the phase inversion technique and analysed using FTIR, SEM, AFM, and contact angle (CA). The cross-section SEM images showed better distribution of rGO-PDA particles in the pores and polymer wall whereas the pristine GO particles aggregate and partially block the pores. Thus, the pure water flux increased with the addition of rGO-PDA without affecting the rejection properties, while the flux decreased with the embedding of pristine GO particles. The highest pure water permeability (PWP) was obtained with PSF/rGO-PDA-0.1 to be approximately twice that of the pristine PSF and PSF/GO-0.1. All membranes exhibited complete rejection of BSA and HA, and showed almost similar performance against different dyes. The FRRs of the pristine PSF after three fouling cycles (FRR3) against BSA and HA were recorded to be 57.8% and 70.7% respectively. FRR3 was enhanced by around 30% with PSF/rGO-PDA composites. The MMMs prepared in this work are expected to have great potential on ultrafiltration and similar studies on other membrane processes.

Validity of Three-Dimensional Tortuous Pore Structure and Fouling of Hemoconcentration Capillary Membrane Using the Tortuous Pore Diffusion Model and Scanning Probe Microscopy.

Hemoconcentration membranes used in cardiopulmonary bypass require a pore structure design with high pure water permeability, which does not allow excessive protein adsorption and useful protein loss. However, studies on hemoconcentration membranes have not been conducted yet. The purpose of this study was to analyze three-dimensional pore structures and protein fouling before and after blood contact with capillary membranes using the tortuous pore diffusion model and a scanning probe microscope system. We examined two commercially available capillary membranes of similar polymer composition that are successfully used in hemoconcentration clinically. Assuming the conditions of actual use in cardiopulmonary bypass, bovine blood was perfused inside the lumens of these membranes. Pure water permeability before and after bovine blood perfusion was measured using dead-end filtration. The scanning probe microscopy system was used for analysis. High-resolution three-dimensional pore structures on the inner surface of the membranes were observed before blood contact. On the other hand, many pore structures after blood contact could not be observed due to protein fouling. The pore diameters calculated by the tortuous pore diffusion model and scanning probe microscopy were mostly similar and could be validated reciprocally. Achievable pure water permeabilities showed no difference, despite protein fouling on the pore inlets (membrane surface). In addition, low values of albumin sieving coefficient are attributable to protein fouling that occurs on the membrane surface. Therefore, it is essential to design the membrane structure that provides the appropriate control of fouling. The characteristics of the hemoconcentration membranes examined in this study are suitable for clinical use.

How to fabricate a negatively charged NF membrane for heavy metal removal via the interfacial polymerization between PIP and TMC?

The potential toxicity of heavy metals arising from the discharge of industrial wastewater has become a serious public concern. Fabrication of a thin film composite (TFC) NF membrane with desirable rejection of heavy metal ions is an attracting route to solve this problem. Hereon, we proposed a facile strategy for fabricating a TFC NF membrane with excellent heavy metal removal. The ratio of PIP and TMC was greatly enlarged by decreasing the concentration of TMC to an exceptional low extent. Thus a polyamide film with weak electronegativity and small pore size was successfully constructed on an ultrafiltration substrate membrane. Comprehensive characterizations were adopted to reveal the micro-variation of the resulted NF membranes when regulating TMC concentration. The optimized membrane prepared only with PIP and TMC can exhibit a high pure water permeability of 14.6 L m−2 h−1 bar−1, desirable rejection of over 98% against Ni2+, Zn2+, Cu2+, and >92.7% against Cd2+. This performance could go beyond most of the reported candidates which were prepared with other complicated methods. The simplicity, low cost and scaling up feasibility of the current strategy is expected to well meet the requirements of industrial production of TFC NF membrane for heavy metal removal.

Preparation of antifouling polypropylene/ZnO composite hollow fiber membrane by dip-coating method for peat water treatment

Dip-coating is a facile method for membrane modification. In this work, composite polypropylene-based membrane (PP) with improved anti-organic fouling is prepared by coating polysulfone (PSf)/PEG400/ZnO layer on PP hollow fiber membrane. Separation properties and organic fouling tendency of the composite membrane are investigated during the peat water filtration. Results show that PSf/PEG400/ZnO layer is successfully deposited on PP membrane evidenced by scanning electron microscopy and fourier-transform infrared spectroscopy analysis. ZnO particles increase membrane hydrophilicity shown by decreasing water contact angle from ∼97.7 to 77.1, which results in higher pure water permeability (from ∼16 to ∼46 L.m−2. h−1. bar−1). Higher hydrophilicity also reduces organic fouling tendency of the membrane during peat water treatment. The flux recovery ratio increases from 63 % to 66 % while relative flux reduction decreases from 53 % to 44 %. The composite PP membrane (M-ZnO-40 %) is able to remove ∼70 % humic substances from peat water. Results of this study show that the addition PSf/PEG400/ZnO layer can effectively improve membrane permeability, selectivity, and anti-organic fouling of PP hollow fiber membrane.

Performance enhancement of ultrafiltration membrane via simple deposition of polymer-based modifiers

Ultrafiltration (UF) membrane is extensively utilized in water treatment for the removal of colloidal particles, dissolved organic matters and microorganisms. These colloidal particles and organic matters are prone to being adsorbed on membrane surface known as membrane fouling, which increases operational costs and lowers down membrane efficiency. In this work, a group of synthesized hydrophilic random copolymers and homopolymer were utilized to enhance PES UF membrane performance by a simple deposition of a thin layer. Despite the increased intrinsic resistance as a result of the thin modification layer, higher pure water permeability and recovery rate were observed for the modified Polyethersulfone (PES) membrane during Bovine Serum Albumin (BSA) fouling test in comparison to the virgin membrane. Moreover, the stability of the adsorbed polymer layers was evaluated by a cyclic fouling test and chemical cleaning endurance assessment. The membrane surface morphology and topography were characterized by field emission scanning electron microscopy (FESEM) and atom force microscope (AFM). The chemical composition before and after clcylic fouling test and chemical cleaning were studied with attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy. The results show that the random copolymer modified membrane exhibited average 26 % rises in water permeability compared with the virgin PES UF membrane when 0.5 wt% BSA solution was used as feed. The stable permeability and flux recovery rate during the cyclic study with chemical cleaning suggest good affinity of the newly synthesized random copolymer with the PES membrane and water. This strategy successfully enhanced the UF membrane anti-fouling performance.