Unmodified Membrane Research Articles

Hydrogen bonding promoted electrodialysis performance of a novel blend anion exchange membrane

In order to improve the performance of electrodialysis enabled desalination, a simple, efficient and low-cost method for the preparation of high-performance anion exchange membranes (AEM) is required. In this work, we designed a novel hydroxyl quaternized polysulfone (HQPSf) and blended it with environmentally friendly chitosan (CS) for AEM fabrication. Our results demonstrate that hydrogen bonding between HQPSf and CS can promote microphase separation in the resulting blend AEM, and an optimal amount of CS is important in balancing anion permeation and selectivity of the membrane. With a CS percentage of 3 % (by mass), the blend AEM yields the highest current efficiency (η) of 93.30 %, the lowest energy consumption (EC) of 4.23 kWh kg−1, and the highest selective permeability (Pm) of 96.86 % when used for electrodialysis (ED), which are far superior to the performance of unmodified HQPSf membrane (η = 86.79 %, EC = 4.57 kWh kg−1) and the commercial TWEDAI anion exchange membrane (η = 86.74 %, EC = 4.74 kWh kg−1). This work provides a facile, effective strategy to fabricate high performance AEMs for electrodialysis application.

Removal of Phenol from Sour Water by Poly(vinyl Alcohol)/Polyamide‐Reverse Osmosis Membranes

AbstractA commercial thin‐film membrane (unmodified) of polyamide improved by poly(vinyl alcohol) (PVA)‐coated membranes (modified) was investigated for separating phenol in sour water by reverse osmosis. Dependences of pressure and pore surface area on flux and phenol rejection were tested. A graphical correlation was found between the relative flux decline and phenol concentration decrease in the feed. The modified membrane provided rejection of 86 % at 2 bar with the highest permeate flux of 8.46 L m−2h−1. The average contact angle for the former membrane was 58.4°, while that for the modified membrane was 49.1°. The reduction in contact angle enhances the surface hydrophilicity of the membrane leading to the antifouling effect. The modified membrane provides 95.4 % flux recovery compared to the unmodified membrane that provides only 66.2 %.

TiO2 nanoparticle stability via polyacrylic acid-binding on the surface of polyethersulfone membrane: Long-term evaluation

Immobilization of photocatalysts on the membrane surface is a promising approach that produces photocatalytic membranes that could help advance wastewater treatment. This work examined the stability of TiO2 nanoparticles binding to the PES membrane surface via polyacrylic acid. For this aim, the corona-induced grafting technique was used for graft polymerization of PAA to introduce strong binding sites for TiO2 deposition on the PES surface. The stability test was performed in a cross-flow system, which indicated minimal leaching after 72 h of filtration. The results evidenced the firm attachment of TiO2 on the membrane surface after long-term operation. PAA grafted membranes with TiO2-deposited membranes showed better hydrophilicity and higher water flux. Compared to the unmodified PES membrane, the maximum flux of the TiO2 deposited membrane increased by 85 %. Moreover, the photocatalytic ability of the photocatalytic membranes to remove phenol was evaluated under UV irradiation. The prepared membranes showed good photocatalytic performance after three hours of continuous operation. The highest phenol degradation was achieved by PES-PAA-TiO2-0.1 %wt, indicating 62 % removal of the pollutant after three hours. With its remarkable stability during filtration and outstanding photocatalytic performance, the prepared membrane illustrates the excellent potential for long-term processes that could minimize nanoparticles leaching.

Synthesis and Optimization of Superhydrophilic-Superoleophobic Chitosan-Silica/HNT Nanocomposite Coating for Oil-Water Separation Using Response Surface Methodology.

In this current study, facile, one-pot synthesis of functionalised nanocomposite coating with simultaneous hydrophilic and oleophobic properties was successfully achieved via the sol–gel technique. The synthesis of this nanocomposite coating aims to develop a highly efficient, simultaneously oleophobic-hydrophilic coating intended for polymer membranes to spontaneously separate oil-in-water emulsions, therefore, mitigating the fouling issue posed by an unmodified polymer membrane. The simultaneous hydrophilicity-oleophobicity of the nanocoating can be applied onto an existing membrane to improve their capability to spontaneously separate oil-in-water substances in the treatment of oily wastewater using little to no energy and being environmentally friendly. The synthesis of hybrid chitosan–silica (CTS-Si)/halloysite nanotube (HNT) nanocomposite coating using the sol–gel method was presented, and the resultant coating was characterised using FTIR, XPS, XRD, NMR, BET, Zeta Potential, and TGA. The wettability of the nanocomposite coating was evaluated in terms of water and oil contact angle, in which it was coated onto a polymer substrate. The coating was optimised in terms of oil and water contact angle using Response Surface Modification (RSM) with Central Composite Design (CCD) theory. The XPS results revealed the successful grafting of organosilanes groups of HNT onto the CTS-Si denoted by a wide band between 102.6–103.7 eV at Si2p. FTIR spectrum presented significant peaks at 3621 cm−1; 1013 cm−1 was attributed to chitosan, and 787 cm−1 signified the stretching of Si-O-Si on HNT. 29Si, 27Al, and 13H NMR spectroscopy confirmed the extensive modification of the particle’s shells with chitosan–silica hybrid covalently linked to the halloysite nanotube domains. The morphological analysis via FESEM resulted in the surface morphology that indicates improved wettability of the nanocomposite. The resultant colloids have a high colloid stability of 19.3 mV and electrophoretic mobility of 0.1904 µmcm/Vs. The coating recorded high hydrophilicity with amplified oleophobic properties depicted by a low water contact angle (WCA) of 11° and high oil contact angle (OCA) of 171.3°. The optimisation results via RSM suggested that the optimised sol pH and nanoparticle loadings were pH 7.0 and 1.05 wt%, respectively, yielding 95% desirability for high oil contact angle and low water contact angle.

Enhanced CO2-tolerance and hydrogen separation performance of Ba-based ceramic membrane modified by Ce0.9Gd0.1O2-δ surface layer

Interest in mixed conducting ceramic membrane for efficient hydrogen separation is growing. However, the membranes with alkaline earth metal are susceptible to CO2 due to the drastic carbonation and irreversible deterioration of membrane, which significantly impedes their applications. Herein, gadolinium-doped ceria (Ce0.9Gd0.1O2-δ, CGO) with robust chemical stability was employed to modify Ba-based dual-phase membrane BaCe0.85Fe0.15O3-δ-BaFe0.85Ce0.15O3-δ (BCF-BFC) by a simple drop coating method. Due to the improved surface activity on the membrane, the CGO-modified BCF-BFC membrane (CGO/BCF-BFC) exhibited an enhanced H2 separation flux of 0.96 mL min−1 cm−2 at 860 °C, which is nearly 1.3-time improvement than the unmodified BCF-BFC membrane. Furthermore, benefitting from the reduction of CO2 adsorption and suppression of carbonate formation on the surface of membrane, an improved CO2-tolerance was observed over the CGO/BCF-BFC, and a high and stable H2 separation flux of 0.60 mL min−1 cm−2 was retained under CO2-containing atmosphere, while BCF-BFC membrane showcased continually deteriorating H2 separation performance at 900 °C. The achieved H2 separation flux along with the improved CO2-tolerance paves a new way towards the future application of alkaline-earth-metal-containing ceramic membrane for H2 purification.

Characterization of polyamide thin film composite membranes incorporated silver nanoparticles

AbstractIn this study, the polyamide thin film composite membrane surface has been modified by anti‐microbial silver nanoparticles (AgNPs). The membrane surfaces were interwoven with AgNPs by ultraviolet grafting polymerization method using AgNPs with or without poly(ethylene glycol) (PEG). The membrane surface characteristics were determined by scanning electron microscopy–energy dispersive x‐ray spectrometry images, attenuated total reflection–Fourier transforms infrared spectroscopy, water contact angle values, and anti‐bacterial property. The separation performance was determined based on the flux and the ability to remove calcium ions in water. The anti‐biofouling property was appraised through the maintained flux ratios and the irreversible fouling factors of unmodified and modified membranes during 10 h‐filtration of protein bovine serum albumin (BSA) in an aqueous solution, in which, before filtration of BSA, all membranes were immersed in E. coli bacteria solution for 4 days. The results of the experiments corroborated the hydrophilicity and more anti‐microbial property of the membrane surfaces after being incorporated into AgNPs. The water contact angle decreased from around 49° for the unmodified membrane to 36° and 23° for the AgNP‐modified membranes without/with PEG, while no colonies appeared in the medium containing the AgNP‐modified membranes. The separation property of modified membranes was improved, with both membrane flux and antifouling properties, along with the substantial surge of the anti‐biofouling property. After 10 h of BSA filtration, the fluxes of the modified membranes were maintained at 68% and 78% for AgNP‐modified membranes without and with PEG, respectively. Conversely, this value was only 46% for the unmodified one.

A reverse-selective ion exchange membrane for the selective transport of phosphates via an outer-sphere complexation-diffusion pathway.

Specific-ion selectivity is a highly desirable feature for the next generation of membranes. However, existing membranes rely on differences in charge, size and hydration energy, which limits their ability to target individual ion species. Here we demonstrate a nanocomposite ion-exchange membrane material that enables a reverse-selective transport mechanism that can selectively pass a single ion species. We demonstrate this transport mechanism with phosphate ions selectively transporting across negatively charged cation exchange membranes. Selective transport is enabled by the in situ growth of hydrous manganese oxide nanoparticles throughout a cation exchange membrane that provide a diffusion pathway via phosphate-specific, reversible outer-sphere interactions. On incorporating the hydrous manganese oxide nanoparticles, the membrane's phosphate flux increased by a factor of 27 over an unmodified cation exchange membrane, and the selectivity of phosphorous over sulfate, nitrate and chloride reaches 47, 100 and 20, respectively. By pairing ion-specific outer-sphere interactions between the target ions and appropriate nanoparticles, these nanocomposite ion-exchange materials can, in principle, achieve selective transport for a range of ions.

Investigating the effect of polymer-modified graphene oxide coating on RO membrane fouling

The development of novel reverse osmosis (RO) membranes resistant to multiple types of fouling is a need to secure clean water production and meet rising water demands. In this paper, the RO membrane surface-functionalized with antibacterial graphene oxide (GO) and antiscalant maleic acid was prepared and tested. The polymerization of maleic acid on the GO functionalized RO membrane was achieved using microwave radiation. The membrane surface characterization showed a decrease in membrane surface roughness from 74.7 nm to 69.0 nm and an increase in membrane hydrophilicity as the contact angle decreased from 41.7 ± 4.50 to 22.0 ± 1.10. The modified membrane was tested against inorganic scaling and biofouling, and the results demonstrated that the modified membrane has improved resistance to multiple fouling types as compared to the unmodified RO membrane. When tested in the presence of calcium sulfate scaling solution (inorganic fouling), the normalized permeate flux was found to be stable at 0.91 and 0.95 for 0.01 and 0.02 wt% maleic acid-modified RO membranes, respectively. Moreover, the modified membranes also demonstrated bacteriostasis rates of 96.1 %–97.1 % showing their anti-bacterial characteristics. Both types of membrane fouling (inorganic and biofouling) were also studied simultaneously, and the results showed that the RO membranes with dual capabilities can inhibit both mineral formation and biofilm growth concurrently.

Sulfonate-functionalized polybenzimidazole as ion-solvating membrane toward high-performance alkaline water electrolysis

Polybenzimidazole (PBI)-based ion-solvating membranes (ISM) have gained increasing attention for alkaline water electrolysis (AWE). Herein, we designed a series of sulfonate-grafted poly (2,2’-(1,4-naphthalene)-5,5′-benzimidazole) (NPBI) as ISM materials for AWE application. Through the reaction of NPBI and 1,4-butane sultone, butyl sulfonate side chains with different contents were attached to NPBI backbone to afford NPBI-BS-X polymer. Compared to the pristine NPBI membrane, the introduction of hydrophilic sulfonate side chains showed more KOH liquid absorption (59% for NPBI-BS-47 membrane vs. 45% for NPBI), higher hydroxide conductivity (133 vs. 103 mS/cm), and reduced H2 permeability (0.51 vs. 2.05 barrer). Ex situ alkaline stability in 8 M KOH at 80 °C demonstrated that 89% of initial conductivity was retained after 1000 h of testing. As a result, the AWE performance of NPBI-BS-47 was evaluated with 6 M KOH at 80 °C, reaching a current density of 1900 mA cm−2 at 2.0 V, which is much higher than that of the cell with the unmodified NPBI membrane. In the durability test under dynamic operating conditions, the cell with NPBI-BS-47 membrane delivered stable operation for 100 h at a constant current density switching from 0.8 A cm−2 to 1.6 A cm−2 after 20 h of operation at each point. The presented design concept of PBI-based polymer offers new opportunities to develop high-performance ISM for alkaline water electrolysis.

MODIFICATION OF CERAMIC MEMBRANES BY PYROCARBON FROM CARBONIZED POLY(URETHANE UREA)S

Modification of tubular ceramic membranes made of clay minerals, which were obtained by slip casting (produced by the Dumansky Institute of Colloid Chemistry and Water Chemistry of the National Academy of Sciences of Ukraine) was carried out. The membranes were modified with pyrocarbon, which was obtained by carbonization of a precursor – poly(urethane urea)s. The carbonization precursor was synthesized from polyisocyanate (average functionality 2.7) and laprol grade 5003, which was introduced into the membrane by impregnation of the corresponding solutions in ethylacetate. When laprol reacts with polyisocyanate, three-dimensional polyurethane is formed. Since undried reagents were used, water entered the pores of the membrane, which reacted with the NCO groups of the polyisocyanate to form polyurea. The parallel course of these reactions leads to the formation of poly(urethane urea)s in the pores of the membrane. Carbonization was carried at 800 °C in an argon flow. The apparent density and open porosity of the membranes were determined by CCl4 uptake. After modification, the open porosity of the membrane decreased from 29.9 to 27.3 %, the apparent density increased from 1.86 to 1.87 g/cm3. The composition and structure of the membranes were studied by X-ray diffraction analysis and SEM. It is shown that the obtained modifier is pyrocarbon - the relative intensity of reflexes increases at 26,0 - 26,4 and 41,3 and 44,2° 2Θ. Pyrocarbon covers the surface of the pores with a continuous layer, and there are also three-dimensional formations of various shapes and sizes from several nm to several microns. Testing of modified membranes was carried out by water purification from direct scarlet dye and from Ca2+ of calcium chloride using the baromembrane method at a working pressure of 0.7 MPa. The unmodified membrane does not retain direct scarlet dye and Ca2+ at all. Tests of modified membranes have shown that the membranes acquire ultrafiltration properties. The retention factor (R) for direct scarlet dye is 100 % and 25 % for Ca2+.

Antifouling enhancement of thin-film composite polyamide reverse osmosis membrane by surface immersion deposition and in-situ crosslinking method with NaAlg-GA hydrogel

In order to optimize antifouling performance to organic foulants, a commercial polyamide reverse osmosis membrane of composite polyamide material was modified by surface gelation using sodium alginate (NaAlg) as surface coating agent, which was widely known as a natural polymer and environmentally friendly materials. NaAlg-GA hydrogel layer was successfully deposited on commercial membrane surface by combining immersion coating with in-situ crosslinking method and the chemical structure was verified by FT-IR spectroscopy. SEM and AFM was adopted to analyze the changes of morphology and roughness. Zeta potentiometer, and contact Angle analyzer were all used to analyze the hydrophilicity and charge property of relevant NaAlg modified membranes in detail. Specific separation performance was also evaluated by cross-flow filtration tests. Results from above experiments confirmed that NaAlg modified membranes exhibited a surface with more hydrophilic, smoother and more regular, denser negative charge, slightly improved selectivity and lower permeability. Long-term monitored the performance of 100 ppm NaAlg modified membrane, it was found that the rejection rate fluctuated between 98.96% and 99.17%, and the flux ranged from 25.15 ∼ 26.06 L/m2 h during the whole test period, which fully proved that modified membrane had good durability. BSA pollution experiment results showed that the flux attenuation rate of 100 ppm NaAlg modified membrane decreased from 40.87% to 25.01%, and flux recovery rate of contaminated membrane after washing was as high as 90.8%. In addition, the flux of 100 ppm NaAlg modified membrane exceeded that of unmodified membrane after filtrating 20 h. Moreover, with the extension of time, the cumulative flux loss of modified membrane caused by additional resistance at the initial filtration stage would soon be compensated, and it completely exceeded that of unmodified membrane after 40 h. All above results showed that NaAlg-GA hydrogel layer can effectively improve the antifouling performance.

Surface modified basalt membrane as a photothermal material for improved oily wastewater solar evaporation

ABSTRACT Oily wastewater is produced from many processes in petrochemical, food, pharmaceutical, mining, and metal industries. Proper management of oily wastewater discharges is required to mitigate their environmental impacts. Basalt fabric has been reported as being uniquely suitable for oily wastewater purification via solar evaporation due to its robust structure and surface chemistry. In this study, an efficient, low-cost, and scalable 3D photothermal evaporator was prepared by surface modification of basalt fabric with TiO2 nanoparticles for oily wastewater treatment and solar steam generation. The basalt membrane was coated with two types of TiO2 (Degussa P25 and nitrogen-doped TiO2) to enhance its hydrophilicity and photocatalytic properties important for fouling control. The basalt membranes were then tested for their impacts on water evaporation under various salinities and concentrations of gasoline constituents and crude oil. In pure water, the modified membrane system achieved an evaporation rate of 1.65 kg‧m−2‧h−1 under 1 sun irradiation, which is higher than the theoretical value of 1.47 kg‧m−2‧h−1 due to the 3D nature of the structure capable of harvesting energy from the environment. Crude oil significantly decreased the evaporation rate of the unmodified basalt membrane. However, the coating of TiO2 nanoparticles was found to ameliorate the fouling effect by increasing the membrane evaporation efficiency from 0.75 kg‧m−2‧h−1 to 1.42 kg‧m−2‧h−1 in a 2.0 g/L oily water composition. This technology is promising as a new approach to manage oily wastewater storage tanks and evaporation ponds in industry in addition to improving the efficiency of resource recovery.

Modification of Thin Film Composite Membrane by Chitosan-Silver Particles to Improve Desalination and Anti-Biofouling Performance.

Reverse osmosis (RO) desalination is a technology that is commonly used to mitigate water scarcity problems; one of its disadvantages is the bio-fouling of the membranes used, which reduces its performance. In order to minimize this problem, this study prepared modified thin film composite (TFC) membranes by the incorporation of chitosan–silver particles (CS–Ag) of different molecular weights, and evaluated them in terms of their anti-biofouling and desalination performances. The CS–Ag were obtained using ionotropic gelation, and were characterized by Fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The modified membranes were synthetized by the incorporation of the CS–Ag using the interfacial polymerization method. The membranes (MCS–Ag) were characterized by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and contact angle. Bactericidal tests by total cell count were performed using Bacillus halotolerans MCC1, and anti-adhesion properties were confirmed through biofilm cake layer thickness and total organic carbon (%). The desalination performance was defined by permeate flux, hydraulic resistance, salt rejection and salt permeance by using 2000 and 5000 mg L−1 of NaCl. The MCS–Ag-L presented superior permeate flux and salt rejection (63.3% and 1% higher, respectively), as well as higher bactericidal properties (76% less in total cell count) and anti-adhesion capacity (biofilm thickness layer 60% and total organic carbon 75% less, compared with the unmodified membrane). The highest hydraulic resistance value was for MCS–Ag-M. In conclusion, the molecular weight of CS–Ag significantly influences the desalination and the antimicrobial performances of the membranes; as the molecular weight decreases, the membranes’ performances increase. This study shows a possible alternative for increasing membrane useful life in the desalination process.

Preparation of Silica/Graphene Oxide Composite Membranes for Nanofiltration

Graphene oxide (GO) membranes have received widespread attention. However, GO membranes exhibit low structural stability in water. We attempted to solve this problem by cross-linking GO with silica. The water permeance of a silica/GO membrane, which was prepared with a tetraethyl silicate/GO mass ratio of 190 and a reaction time of 3 h, was six times that of an unmodified GO membrane. The molecular weight cutoff of the silica/GO membrane was 800, which was almost the same as that of the unmodified GO membrane.

Durum wheat semolina-modified ceramic membranes as novel porous separators for enhanced power generation and wastewater remediation using microbial fuel cell

This proof-of-concept study describes the enhanced performance efficiency of the dual-chambered microbial fuel cell equipped with the fabricated unmodified ceramic membranes and ceramic membranes modified with 5 % and 10 % (w/w) durum wheat semolina in comparison with the commercially available NafionTM 117 membranes. The chemical oxygen demand removal efficiencies were determined to be 85.6 ± 0.1, 72.1 ± 0.2 and 68.6 ± 0.1 % for microbial fuel cell equipped with 10 % (w/w) semolina-modified, 5 % (w/w) semolina-modified and unmodified ceramic membrane, respectively, which indicated the improved wastewater treatment efficiency with increasing content of semolina. Preliminary studies showed that the 10 % (w/w) semolina-modified ceramic was cost-effective (64 USD/m2) with improved water uptake, good proton mobility, low oxygen diffusion in addition to the enhanced power and current density output. The semolina-modified ceramic membranes have the potential to become a cost-effective alternative for the high-efficiency production of bioelectricity using microbial fuel cells.

Rapid construction of cyclodextrin polyester layer on polyamide for preparing highly permeable reverse osmosis membrane

Hydrophilic modification of reverse osmosis (RO) membrane is a common method to enhance membrane permeance. However, it is usually hard to improve the membrane permeance obviously by introducing hydrophilic substances onto membrane surface as a result of the formation of a new mass transfer resistance layer. Besides, most hydrophilic modification methods are time-consuming, which is not conducive to industrial application. In this work, hydrophilic hydroxyl-rich macrocycles (cyclodextrin, CD) with a hydrophobic lumen and large intrinsic cavity were introduced on polyamide (PA) layer by second interfacial polymerization (IP) between acyl chloride and hydroxyl in only 5 s with the assistance of 4-dimethylaminopyridine (DMAP), forming a highly hydrophilic and loose polyester layer on the top of PA, which is beneficial to water adsorption and transport. The permeances of CD-modified RO membranes are nearly three times as large as the unmodified membrane while maintaining the high rejection (RNaCl = 98.75–98.88%). This work provides a straightforward, industry-friendly, effective, and rapid strategy for preparing highly water permeable RO membranes.

Preparation of Nano-SiO2 Modified PA66 Microfiltration Membrane and Treatment of Oily Wastewater

With the development of industry, more and more oily wastewater is discharged into the water, which brings great harm to the ecological environment and human health. Membrane separation technology is a very promising technology for oily wastewater treatment. In this experiment, a 1:1 mixed solution of formic acid and dichloromethane (FA/DCM) was used as a solvent to prepare a PA66 microfiltration membrane by evaporation method, and nano-SiO2 was used to modify the PA66 with the determined formula. The apparent morphology, hydrophilicity and mechanical properties of the membrane were characterized by scanning electron microscopy, contact angle test and tensile test, and the effect of treating oily wastewater by microfiltration membrane before and after modification was analyzed. The results show that the mechanical strength and hydrophilicity of the microfiltration membrane are improved after modification by SiO2, and the sewage treatment effect is better. The removal rates of unmodified microfiltration membrane to total suspended solids, chemical oxygen demand and oil concentration are 55%~96%, 50%~85% and 55%~92%; the removal rates of modified microfiltration membrane to total suspended solids, chemical oxygen demand and oil concentration are 98%~99%, 91%~95% and 95%~99%.

Synergetic effect of graphene oxide and poly(MMA-co-GMA) copolymer on PSF ultrafiltration membrane for the remediation of potential environmental contaminants

• GO/poly(MMA-co-GMA)/PSF membrane was synthesized by phase inversion method. • GO as a nanofiller showed great influence on pore formation mechanism in membrane. • O/w emulsion flux for GO/poly(MMA-co-GMA)/PSF membrane was six fold to the pristine membrane. • GO/poly(MMA-co-GMA)/PSF membrane exhibited an excellent fouling resistant property. A novel hydrophilic polysulfone (PSF) membranes integrated with graphene oxide (GO) and bifunctional based poly(methyl methacrylate-co-glycidyl methacrylate) (poly(MMA-co-GMA)) copolymer were prepared. The functional groups of synthesized GO, poly(MMA-co-GMA) and PSF membranes were justified using FTIR spectroscopy. The variety of physicochemical analysis helped to demonstrate the presence GO (1.5 wt%) and poly(MMA-co-GMA) (0–2 wt%) and also its impact on morphology and performance of the membranes. Embedding of the pristine GO, affected the pore forming mechanism due to which the modified membrane exhibited uniform finger-like pores as a result of its hydrophilic filler property. PGC-1 membrane was endowed with maximum pore density, porosity and permeability. There was a significant decline in CA and the amount of BSA adsorbed from 81.2° and 0.22 mg/cm 2 for pristine membrane to 59.7° and 0.06 mg/cm 2 , respectively for PGC-2 membrane. By increasing the amount of the copolymer from 0 wt% to 2 wt% the irreversible fouling and total fouling were decreased, which resulted to high flux recovery ratio ( F r r ) for the modified PSF membrane. Besides, the o/w emulsion flux obtained for PGC-2 membrane was 6 times greater than that of the unmodified PSF membrane signifying that the foulants were unable to affect the modified membrane. In general, PSF/GO/poly(MMA-co-GMA) membrane with improved fouling resistance and high separation efficiency open up a way for its great potential for protein separation, oil/water emulsion separation and various other similar domains.

Facile preparation and properties of superhydrophobic nanocellulose membrane

Superhydrophobic nanocellulose membrane was prepared by synergistically modifying biodegradable nanocellulose with low-carbon perfluoroorganosiloxane and ethyl orthosilicate. The effects of four kinds of low-carbon perfluoroorganosiloxanes with different structures and their ratio to ethyl orthosilicate on the hydrophobic properties of nanocellulose membrane were investigated, and then FT-IR, XPS, XRD, SEM, TEM, AFM, TG and contact angle goniometer were used to characterize the structure and hydrophobic properties of nanocellulose membrane before and after modification. It is found that when the molar ratio of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFOTMS) to ethyl orthosilicate (TEOS) is 1, the modified nanocellulose membrane PFOTMS-TEOS-CNF is loaded with silica nanoparticles both inside and on its surface, and a micro-nano hierarchical rough morphology with low surface energy is constructed. At this point, the root-mean-square roughness (Rq) of nanocellulose membrane is 112 nm, and the static contact angle of water droplet is 153.5°, successfully realizing superhydrophobicity. In addition, compared to unmodified nanocellulose membrane, PFOTMS-TEOS-CNF with better thermal stability includes an additional maximum weight loss rate temperature (491.2 °C). The above advantages markedly improve the shortcomings of pristine nanocellulose, such as superhydrophilicity and insufficient thermal stability, and also broadens its high-value application in many fields.

Multi-Layered Branched Surface Fluorination on PVDF Membrane for Anti-Scaling Membrane Distillation.

Membrane distillation (MD) has emerged as a promising technology for hypersaline wastewater treatment. However, membrane scaling is still a critical issue for common hydrophobic MD membranes. Herein, we report a multi-layered surface modification strategy on the commercial polyvinylidene fluoride (PVDF) membrane via plasma treatment and surface fluorination cycles. The repeated plasma treatment process generates more reaction sites for the fluorination reaction, leading to higher fluorination density and more branched structures. MD tests with CaSO4 as the scaling agent show that the modification strategy mentioned above improves the membrane scaling resistance. Notably, the PVDF membrane treated with three cycles of plasma and fluorination treatments exhibits the best anti-scaling performance while maintaining almost the same membrane flux as the unmodified PVDF membrane. This study suggests that a highly branched surface molecular structure with low surface energy benefits the MD process in both membrane flux and scaling resistance. Besides, our research demonstrates a universal and facile approach for membrane treatment to improve membrane scaling resistance.