Composite Microporous Membrane Research Articles

Uranium removal from contaminated groundwater using goethite-loaded composite microporous membrane

In this study, we have coupled adsorption and membrane separation for the removal of uranium from contaminated groundwater in environmentally relevant conditions at low energy requirements. This study mainly focuses on elucidating uranium, U(VI), adsorption mechanisms using surface complexation modeling approach in a novel goethite-loaded composite microfiltration membrane (GLM). This experiment involved immobilizing goethite nanorods in a microporous (0.22 μm pore size) poly (vinylidene fluoride) (PVDF) membrane. The effect of varying goethite loading and hydraulic residence time on U(VI) removal was investigated at field-relevant pH (i.e. pH 8.5). U(VI) adsorption (i.e. 4.95 μg·mg−1) was optimum at a goethite loading 1.20 mg·cm−2. The effect of varying hydraulic residence time had no impact on U(VI) removal which was also confirmed via performing batch adsorption kinetic experiments. GLM membrane loaded at 1.2 mg·cm−2 could treat 275 L of U(VI) contaminated water having 200 μg of U L−1 below WHO drinking water limit (i.e. 30 μg of U L−1) with 1 m2 of membrane surface area with a adsorption capacity of 6.12 μg·mg−1. Varying the pH of aqueous solution, containing U(VI) from pH 4.0 to pH 10.0, showed a significant impact on uranium uptake ranging from 0.7 μg·mg−1 to 2.63 μg·mg−1 by the composite membrane. The adsorption mechanism of uranium onto goethite was explained via the formation of bidentate surface complexes using the Surface Complexation Model (SCM). The results of batch pH edge experiments and SCM have been compared with pH experiments performed using GLM. The results of SCM predicted the batch pH edge experiment within a RMSE of 0.055. The trend of U(VI) removal in membrane experiments was observed to be similar to that of batch pH edge experiments and was well predicted SCM model. Our results showed that the novel goethite-loaded membrane has the potential for the effective removal of uranium with a lower specific energy consumption.

Combined effects of nanoparticle and stretch‐induced orientation on crystal structure and properties of UHMWPE/TiO2 composite microporous membranes

AbstractThe nanocomposite microporous membrane of ultra‐high molecular weight polyethylene (UHMWPE) and nano‐titanium dioxide (nano‐TiO2) system was prepared by combining the thermally induced phase separation (TIPS) technique with the extrusion‐casting process using liquid paraffin (LP) as the diluent. The effects of variations of TiO2 content and melt draw ratio on the properties of composite microporous membranes were studied and the optimal processing parameters were further investigated. ATR‐FTIR demonstrated that nanocomposite microporous membranes were successfully prepared. The crystallization behavior and morphological evolution of membranes were systematically investigated by WAXD, 2D‐SAXS, and SEM. It was found that the stretch‐induced orientation of UHMWPE was promoted and the shish‐kebab structure was formed for the reason of addition of TiO2. The mechanism of combined effects of nanoparticles and stretch‐induced orientation on the crystallization behavior of UHMWPE was further discussed and explained. Compared to pure UHMWPE film, the permeability of the optimum performance film was significantly improved, with porosity of 49% and pure water flux of about 193 L m−2 h−1. Mechanical studies showed that nanoparticles and DR have significant effects on tensile strength and elongation at break. In addition, the thermal stability of composite microporous membranes was found to be improved with the increase of TiO2 content and melt draw ratio. Thus, this investigation delivers inspiration for the expansion of excellent performance microporous membranes used for battery separators and filtration devices.

Surface modification of UHMWPE/fabric composite membrane via self‐polymerized polydopamine followed by mPEG‐NH2 immobilization

ABSTRACTIn this work, a novel approach to improve the antifouling properties of membrane surfaces was developed. First, a polydopamine layer was attached onto the surface of an ultrahigh molecular weight polyethylene/fabric composite microporous membrane based on dopamine self‐polymerization and adhesive behavior. Then, methoxy polyethylene glycol amine was covalently bonded with the polydopamine layer via a Schiff base reaction. The physicochemical properties of the modified composite membrane surface were investigated, and the results indicated this modification could effectively enhance the membrane surface hydrophilicity. Furthermore, the protein fouling resistance of both dopamine‐coated and methoxy polyethylene glycol amine immobilized composite membranes was evaluated. It was found that a dopamine coating cannot obviously enhance the membrane antifouling properties due to its strong bioadhesion behavior. However, the antifouling properties of the composite membranes were significantly improved after being immobilized with a methoxy polyethylene glycol amine layer. Consequently, a layer‐by‐layer modified composite membrane with excellent antifouling property was obtained. The pure water flux and flux recovery ratio of the resultant membrane were 764 L m−2 h−1 and 83%, respectively. The aim of this paper was to provide an effective approach to optimizing the separation efficiency and antifouling performance of the ultrahigh molecular weight polyethylene/fabric composite membrane. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46428.

A novel MD-ZVI integrated approach for high arsenic groundwater decontamination and effluent immobilization

A highly effective novel system of direct contact membrane distillation (DCMD) integrated with acid-purged zero-valent iron (APZ) technology has been developed. Compared to conventional processes of arsenic removal which reconstitute secondary contamination at disposal site, this system proves capable of simultaneous removal and immobilization of arsenic from contaminated water with great efficiency and improved water flux. Using composite microporous membranes of polytetrafluoroethylene (PTFE) and polypropylene (PP) integrated with APZ in a DCMD-APZ configuration, varying residual arsenic concentrations were injected anoxically into ≤2g acid-washed Fuchen (XK 13-201) reduced Fe powder at a flow rate of 0.33mL/min and pH 6±1.0 at 60°C. Results from this unique configuration show advantages including maximum distillate flux production of 55.5kg/m2h with greater than 95% arsenic rejection efficiency using PTFE/PP composite membrane, fast adsorption and immobilization of rejected arsenic on APZ at t1/2≤30min, and electrochemical reduction of As(V) and/or As(III) to sparsely soluble As(0) as confirmed by macroscopic wet chemistry, adsorption kinetic model and X-ray photoelectron spectroscopic (XPS) analysis conducted within 5 days of experimental period. Since the arsenic adsorption/reduction process is a thermodynamically assisted phenomenon, integrated configuration of the DCMD-APZ technology stands out as a promising technique to mitigate the unresolved challenges of arsenic contamination and re-dissolution in groundwater.

Development and evaluation of UHMWPE/woven fabric composite microfiltration membranes via thermally induced phase separation

We demonstrate a new kind of ultra-high molecular weight polyethylene (UHMWPE)/woven fabric composite microporous membrane via a thermally induced phase separation (TIPS) method. A dilute UHMWPE/liquid paraffin (LP) solution with a concentration lower than 8 wt% was used in the preparation of the composite membrane. The polyester-cotton (P-C) blended woven fabric was pretreated to remove the polyester component and then the UHMWPE/LP solution was pressed into the interstices of the pretreated woven fabric and wrapped the cotton fibers, then the composite membrane was prepared via the TIPS method. The cloud points and dynamic crystallization temperatures of the UHMWPE/LP solution were determined by optical microscopy and differential scanning calorimetry (DSC), respectively. The results show that the cloud points were similar to the crystallization temperatures, indicating that only solid–liquid (S–L) phase separation occurred during the thermally induced phase separation (TIPS) method of the UHMWPE/LP solution. The mechanical properties and thermal stability of composite membranes were also tested. The parameters such as the concentration and the viscosity molecular weight (Mη) of UHMWPE were optimized and a type of composite microporous membrane was prepared with good penetrating pore flow, dramatically high water flux and excellent bovine serum albumin (BSA) rejection. The composite membrane prepared from 5 wt% UHMWPE with a Mη of 4000000 had the largest BSA rejection of 76% and extremely high water flux of 621 L m−2 h−1. The antifouling effect of the composite membrane was also assessed in bovine serum albumin (BSA) aqueous solution.

PVDF-based composite microporous gel polymer electrolytes containing a novelsingle ionic conductor SiO2(Li+)

In this paper, a novel silica sol conductor SiO2(Li+) was synthesized from tetraethylorthosilicate (TEOS) and γ-(2,3-epoxypropoxy) propyltrimethoxysilane via sol–gel hydrolysis followed by neutralized with lithium hydroxide. The prepared SiO2(Li+) were incorporated into poly(vinylidene fluoride) (PVdF) by standard solution-casting technique coupled with phase inversion process to fabricate a composite microporous membrane. Then the resultant composite microporous gel polymer electrolyte (CMGPE) was obtained by simply immersing the dried composite microporous membrane into liquid electrolyte and being gelled. The physicochemical properties of the CMGPEs were characterized by FTIR, DSC, XRD, TG, stress–strain response and electrochemical measurements. They exhibit a higher porosity and a higher electrolyte uptake with a proper addition of SiO2(Li+), while, the degree of crystallization of composite microporous membranes decrease with it. In addition, the ionic conductivity of CMGPEs can also be enhanced by vast amount of Li+ ions on the added SiO2(Li+). When the content of SiO2(Li+) was 5wt%, ionic conductivity of the CMGPEs reached to 10−3Scm−1 order of magnitudeat at room temperature and its electrochemical stability window was 5.2V. A proper content of SiO2(Li+) in PVdF-based membrane makes it a potential candidate for application as polymer electrolyte in devices.

A New Class of P(VdF-HFP)-CeO2-LiClO4-Based Composite Microporous Membrane Electrolytes for Li-Ion Batteries

Composite microporous membranes based on Poly (vinylidene fluoride–co-hexafluoro propylene) P(VdF-co-HFP)-CeO2were prepared by phase inversion and preferential polymer dissolution process. It was then immersed in 1M LiClO4-EC/DMC (v/v=1:1) electrolyte solution to obtain their corresponding composite microporous membrane electrolytes. For comparison, composite membrane electrolytes were also prepared by conventional phase inversion method. The surface morphology of composite membranes obtained by both methods was examined by FE-SEM analysis, and their thermal behaviour was investigated by DSC analysis. It was observed that the preferential polymer dissolution composite membrane electrolytes (PDCMEs) had better properties, such as higher porosity, electrolyte uptake (216 wt%), ionic conductivity (3.84 mS⋅cm−1) and good electrochemical stability (4.9 V), than the phase inversion composite membrane electrolytes (PICMEs). As a result, a cell fabricated with PDCME in between mesocarbon microbead (MCMB) anode and LiCoO2cathode had better cycling performance than a cell fabricated with PICME.

Investigation on Preparation and Porosity of YSZ/PTFE Microporous Membrane Modified by PTFE Resin Emulsion

In this paper, YSZ/PTFE composite microporous membrane was prepared by mechanical tensile method, using PTFE resin emulsion as material and YSZ micro/nanoparticles as reinforcer. The performance of YSZ/PTFE composite microporous membrane was characterized by mechanical property testing. The effects of the dispersant PVA, the draw ratio, YSZ content and calcination temperature on the porosity of composite microporous membrane were systematically investigated. The results showed that the porosity increased significantly as PVA added; with the increase of YSZ content, the porosity gradually increased, but the YSZ content was not over 20%; the porosity reached 73.09% when the draw ratio 3.5 times, YSZ content 8%, and the calcination temperature 320?.

LiFAP-based PVdF–HFP microporous membranes by phase-inversion technique with Li/LiFePO4 cell

Polyvinylidenefluoride-hexafluoropropylene-ba- sed (PVdF-HFP-based) gel and composite microporous membranes (GPMs and CPMs) were prepared by phase- inversion technique in the presence 10 wt% of AlO(OH)n nanoparticles. The prepared membranes were gelled with 0.5-M LiPF3(CF2CF3)3 (lithium fluoroalkylphosphate, Li- FAP) in EC:DEC (1 : 1v /v) and subjected to various char- acterizations; the AC impedance study shows that CPMs ex- hibit higher conductivity than GPMs. Mechanical stability measurements on these systems reveal that CPMs exhibit Young's modulus higher than that of bare and GPMs and addition of nanoparticles drastically improves the elonga- tion break was also noted. Transition of the host from α to β phase after the loading of nanosized filler was confirmed by XRD and Raman studies. Physico-chemical properties, like liquid uptake, porosity, surface area, and activation energy, of the membranes were calculated and results are summa- rized. Cycling performance of Li/CPM/LiFePO4 coin cell was fabricated and evaluated at C/10 rate and delivered a

Effect of functionalized montmorillonite addition on the thermal properties and ionic conductivity of PVDF–PEG polymer electrolyte

Composite microporous polymer electrolyte membranes comprising poly(vinylidene fluoride), PVDF, poly(ethylene glycol), PEG, and 1-ethyl-3-methylimidazolium tetrafluoroborate functionalized montmorillonite (EMIm-MMT) were prepared by a phase inversion method. The EMIm-MMT was subjected to FTIR, WXRD, TGA and element analysis in order to better understand the intercalation of imidazolium cations in sodium montmorillonite (Na-MMT) through exchange with intermellar sodium ions and improved thermal stability compared to organic-montmorillonite (O-MMT). The studies of porosity, weight uptake, and ionic conductivity of composite microporous membrane were performed as a function of EMIm-MMT content. The addition of EMIm-MMT can greatly enhance the thermal stability of the polymer electrolyte membrane. The maximum conductivity at 25 °C was found to be 7.77 mS cm −1 for PVDF–PEG/6wt% EMIm-MMT.

Manufacturing of new nano-structured ceramic–metallic composite microporous membranes consisting of ZrO 2, Al 2O 3, TiO 2 and stainless steel

Frequently, the membrane employed in a traditional nano-filtration (NF) or gas separation (GS) membrane device consists of a polymeric material, having significant disadvantages including a restricted mechanical, chemical and thermal stability. As an alternative for the polymeric membranes, ceramic membranes with an improved stability have been introduced, but the current membranes still suffer from stability problems (e.g. brittle material, restricted chemical stability in water vapour). This paper reports the preparation of novel hybrid metallic–ceramic membranes, based on a porous 316L stainless-steel support material. The optimized membranes were made by deposition of a fine suspension with a particle size of ~ 180 nm, a colloidal sol with a particle size of ~ 30 nm and a nano-particle sol with a particle size of ~ 5 nm and show a comparable multilayer structure as current ceramic membranes for micro-, ultra- and nano-filtration and gas separation. The essential new features of the membranes include the use of an alternative metallic support material, which provides a high mechanical stability to the membrane, and the application of zirconia- and titania based functional membrane layers, which display a high chemical and thermal stability for potential filtration or gas separation applications.

Removal of airborne bacteria by filtration using a composite microporous membrane made of a pyridinium-type polymer showing strong affinity with microbial cells.

A composite microporous membrane made of poly(N-benzyl-4-vinylpyridinium chloride) that showed strong affinity with bacterial cells was prepared as a filter material for removing airborne bacteria. Thickness, pore diameter and porosity of the membrane were 0.72 mm, 14.5 microm and 63%, respectively. Electron micrographic analysis revealed that the membrane consisted of a very large number of connected beads of 1.4 microm in diameter made of the pyridinium-type polymer. Filtration using the membrane was performed easily at low flow rates with insignificant pressure drop across the membrane. Filtration at 63.7 cm/sec gave 99.98% and 99.996% removal (3.7 and 4.4 log10-unit reduction in concentration) of Escherichia coli and Pseudomonas aeruginosa, respectively. Staphylococcus aureus was not detected in filtrates. Since pores of the membrane were much larger than these bacteria, the efficient removal was best explained in terms of the affinity of the polymer with bacterial cells.

Removal of virus from air by filtration using a composite microporous membrane made of crosslinked poly( N-benzyl-4-vinylpyridinium chloride)

A composite microporous membrane made of a functional polymer that showed remarkable affinity with viruses was developed as a filter material for removing viruses from air. A 0.83-mm thick membrane with pore diameter of 14.3 μm and porosity of 42% was prepared that consisted of a large number of connected minute beads of 1.7 μm in diameter made of crosslinked poly( N-benzyl-4-vinylpyridinium chloride) and reinforced by nonwoven cloth. Filtration experiments were performed using bacteriophage T4 as a test virus. When influent concentration was in the order of 10 6 PFU/ml, filtration using one sheet of the membrane showed 99.9994–99.9998% removal (5.2–5.7 log 10-unit reduction in concentration) of the virus from air. Percentage of removal increased with decrease of influent concentration, and the virus was not detected in the filtrate when influent concentration was in the order of 10 5 PFU/ml. Since pore of the membrane was greatly larger than the virus, the excellent removal can be attributed to the special and remarkable affinity of the pyridinium-type polymer with viruses.

Immobilization of bacteria and Saccharomyces cerevisiae in poly(tetrafluoroethylene) membranes

A novel method for immobilization of bacteria and Saccharomyces cerevisiae cells is described. Microorganisms may be entrapped in a matrix of poly(tetrafluoroethylene) (PTFE) fibrils. Cells are blended with an aqueous emulsion of PTFE stabilized with Triton X-100 surfactant to form a thick paste. The paste is calendered biaxially in a standard rubber mill. This process causes fibrillation of the PTFE and formation of the fibril matrix, which serves only to impart physical integrity to the composite microporous membrane. The cells trapped in the membrane were shown to be viable by incubation of the membrane on solid media and in broth culture. This bioactive membrane represents a new means of immobilization of cells for bioprocessing.