Surface and pore modification of tripolyphosphate-crosslinked chitosan/polyethersulfone composite nanofiltration membrane; characterization and performance evaluation

A PES-based composite nanofiltration membrane was prepared by spreading a thin layer of sodium tripolyphosphate (STPP)-modified chitosan (CS) on a PES membrane. Two approaches of modification were employed: coating, and injecting the chitosan solution into PES membrane by applying pressure. Physicochemical properties of the prepared membranes were characterized by FTIR-ATR, zeta potential, contact angle, AFM and FE-SEM methods. AFM images showed a denser and more compact surface for STPP-modified membranes compared to the unmodified one. The membranes prepared by the second approach illustrated favorable properties: the increase of both flux and rejection. Engaging of -NH₂ groups in CS with polyanionic phosphate groups of STPP resulted in less availability of functional groups. Furthermore, denser and relatively higher positively charged surface could be the main reasons for higher rejection of membrane composed of 0.05wt% STTP towards copper ions in comparison with the other membranes. Furthermore, the presence of SO ₄ ^2- ions in the CuSO₄ solution slightly changed the positive charge of the membrane surface, resulting in tangible variations in rejection. According to the Donnan exclusion theory, relative increase of the negative charge of the surface in the presence of the highest concentration of STTP caused less NaCl and CuSO₄ rejection compared to the other STPP modified membranes.     

Modification and ionic stimulation of hollow fiber membrane by electric field for water treatment

Hollow fiber membrane (HF) is considered one of the prevalent materials for water treatment; its effectiveness is controlled by permeation and mechanical characteristics. In this study, HF membrane surface was stimulated using electrochemical technique, where binary system of stainless steel cylinder and graphite rod electrodes was used into electrolytic solution of sodium acetate 0.1 M as electrolyte. Two pH of acidic medium (pH = 3.5) and alkaline medium (pH = 8.5) were prepared and different potential between 2 and 10 V were applied. EDX analysis of HF membrane surface revealed the formation of sodium ions on the surface of HF membrane with maximum content of Na⁺ ions 1.84%. Also, HF membrane surface showed variation of roughness (R _a) as, HF membrane surface may undergo distortion by using aggressive conditions of high electric potential (7.5–10 V), The measured raw HF membrane (R _a) was 34.8 nm, while, after electrochemical modification in alkaline medium R _a showed higher values 36, 37, and 41 nm using 2, 2.5, and 5 V, respectively. While, after electrochemical modification in acidic medium (R _a) showed 35, 39, 42, 49, 52 nm for 2, 2.5, 5, 7.5, and 10 V, respectively. Moreover, tensile strength Young's modulus, break stress and break strain were measured after electrochemical modification in both acidic and alkaline mediums and maximum porosity value 76.84% was observed after 30 min in acidic medium.     

SEPARATION OP NITRATE FROM SULPHATE MEDIUM,IN PARTICULAR,FROM CuSO4-SOLUTIONS Br THE USE OF ION EXCHANGERS

From sulphate-containing process solutions, such as CuSO₄-solutions, nitrate can be removed by ion exchange resulting in residual contents not higher than trace amounts (< 10 mg/1). NO₃ ^?adsorption by the ion exchanger increases with increasing total electrolyte content so that, when contacted with > 1 M CuSO₄-solution, 70 % to 80 % of the capacity of traditional ion exchange resins is utilized for adsorbing the NO₃ ^? Even higher adsorption degrees have been achieved by the use of resins type wofatit SN 35 L that are selective for nitrate or a weakly basic resin with di-n-butyl amine functional groups. The resins loaded can be regenerated with alkalies and H₂SO₄. For the latter case, a closed loading-regeneration cycle is proposed which allows the separated NO₃ to be reused as HNO₃.     

Influence of magnetic casting on the permeability and anti-fouling properties of a novel iron oxide/alumina/polysulfone mixed matrix membrane

Novel mixed matrix membranes (MMMs) were fabricated using Fe₃O₄, and Al₂O₃ nanoparticles (NPs) were added to the polysulfone (PSf) and N-methylpyrrolidone (NMP) solution. The nanocomposite membranes were fabricated using the NIPS (non-solvent induced phase separation) method. In order to create preferential permeation pathways for water across the MMMs, membrane formation is accomplished with an external magnetic field. Using magnetic casting cause the targeted placement of NPs in the best location and orientation. The performance of the prepared membranes was examined in terms of pure water flux and fouling parameters. Magnetic casting considerably increased pure water flux and decreased the total resistance of the optimum mixed matrix membrane, which contains 0.2% wt. of Fe₃O₄ NPs to 1175 L/m²h and 13.4 * 10¹¹ (m⁻¹), respectively. This is explained by the ordering of magnetic nanoparticles on the membrane sub-layer cast under the magnetic field of 500 mT, which changed the sub-layer structure. Less rough membrane surface of the mixed matrix membranes offered preferable anti-fouling properties against fouling by BSA proteins. The characterization of fabricated membranes was carried out using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy dispersive X-ray (EDX), and water contact angle measurement methods.     

A thin film composite membrane supported by a hydrophilic poly(vinyl alcohol‐co‐ethylene) nanofiber membrane: Preparation,characterization, and application in nanofiltration

In this study, a fabricated hydrophilic poly(vinyl alcohol‐co‐ethylene) (PVA‐co‐PE) nanofiber membrane was used as the middle support layer to prepare thin film composite (TFC) membranes for nanofiltration. The effects of the supporting nonwoven layer, grams per square meter (GSM) of nanofiber, reaction time, heat treatment, monomer concentration, operating pressure, and pH value on the separation performance of the TFC membranes were analyzed. These results show that the TFC membranes prepared with the PVA‐co‐PE nanofiber membrane can be used to filtrate different metal ions. For NaCl, Na₂SO₄, CaCl₂, CuCl₂, CuSO₄, and methyl orange solutions, the rejection rates of the TFC membrane with nonwoven polyester as the supporting layer and a nanofiber GSM of 12.8 g/m² are 87.9%, 93.4%, 92.0%, 93.1%, 95.8%, and 100%, respectively. This indicates the potential application of the PVA‐co‐PE nanofiber membrane in the preparation of nanofiltration and reverse‐osmosis TFC membranes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46261.     

Development of new hybrid ultrafiltration membranes by entanglement of macromolecular PPSU‐SO3H chains: Preparation,morphologies, mechanical strength,and fouling resistant properties

The present work focuses on the preparation of Polyphenylsulfone (PPSU) membranes with enhanced antifouling surfaces through an incorporation of sulfonated Polyphenylsulfone (PPSU‐SO₃H), which acts as both, surface modifying agent and macromolecular additive. Initially, Sulfonated polyphenylsulfone (PPSU‐SO₃H) was synthesized by using chlosulfonic acid via bulk modification method. The degree of sulfonation (DS, %) of PPSU‐SO₃H was calculated by using NMR (nuclear magnetic resonance).The phase inversion technique was used to prepare all asymmetric membranes by allowing the PPSU‐SO₃H (different wt %) to entangle with the PPSU membrane matrix. All prepared membranes were characterized by using scanning electron microscope (SEM), X‐ray diffraction analysis (XRD), contact angle analysis (CA), mechanical strength analysis, molecular weight cut off (MWCO), porosity (%), mean pore size, and BSA adsorption studies. The performance efficiency of the membranes was evaluated by using BSA protein as a model foulant in terms of permeability, rejection (SR %), R_m (hydraulic resistance), R_c (cake layer resistance), R_p (pore plugging resistance), R_r (reversible fouling), R_ir (irreversible fouling), and FRR (flux recovery ratio). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41986.     

Peroxopolyoxometalate nanoparticles blended PES membrane with improved hydrophilicity,anti-fouling,permeability, and dye separation properties

Poly(ethersulfone) (PES) is one of the polymers most widely used for the fabrication of ultrafiltration or nanofiltration membranes in various applications, but its membrane suffers from fouling. In this study, preparation, characterization, and performance of PES nanocomposite membrane comprising peroxopolyoxometalate nanoparticles was studied to provide improved permeability and anti-fouling properties. The high oxygen ratio of the PW₄ nanoparticles could enhance the hydrophilicity of the membranes. The PW₄ nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction analyses. The mixed matrix membranes were fabricated using a non-solvent induced phase-separation method. The fabricated membranes were characterized using atomic force microscopy, attenuated total reflection, SEM, EDX mapping, total average porosity, thermogravimetric analyze, and water contact angle experiments. The dye flux and rejection, pure water permeability and anti-fouling properties of the membranes were investigated. All of the membranes blended by different contents of the PW₄ nanoparticles presented better performance compared to the unmodified membrane. The filtration performance of the membranes in reactive green 19 (RG19) and reactive yellow 160 (RY160) dye separation showed that all of the PW₄ blended membranes possessed dye rejection greater than 86% and 96% for RY160 and RG19, respectively. The reusability test using bovine serum albumin (BSA) protein and RG19 dye solutions in five cycle experiments presented good reproductivity of the PW₄ blended membranes. The PES membrane containing 1 wt% of PW₄ nanoparticles showed the highest flux recovery ratio (75%) as well as reduced irreversible fouling ratio (8%) through BSA protein filtration.     

Separation performance of a nanofiltration membrane influenced by species and concentration of ions

Nanofiltration (NF), which has been largely developed over the past decade, is a promising technology for the treatment of organic and inorganic pollutants in surface and ground waters. The ESNA 1 membrane from the Nitto Denko Corporation of Japan is made of aromatic polyamide, which provides salt rejection from 50% to 90%. In this paper permeation experiments of aqueous solutions of five chlorides (NH₄Cl, NaCl, KCl, MgCl₂ and CaCl₂), three nitrates (NaNO₃, Mg(NO₃)₂ and Ca(NO₃)₂), and three sulfates (NH₄)₂SO₄, Na₂SO₄ and MgSO₄) were carried out. The effects of species and concentration of salts on the separation performance of the ESNA 1 membrane were investigated. The experimental results showed that the rejection to most salts by the ESNA 1 membrane decreased with the growth of the concentration. Then, the reflection coefficient and solute permeability of ESNA 1 membrane were calculated by the Spiegler-Kedem equation from experimental data. The reflection coefficients of the ESNA 1 membrane to salts are all above 0.95. The salt permeabilities, except for magnesium and calcium salts, increased with the growth of concentration. The sequence of rejection to anions by the ESNA 1 membrane is R(SO²⁻₄) > R(Cl⁻) > R(NO⁻₃) at the same concentration which ranges from 10 mol/m³ to 100 mol/m³. The sequence of rejection to anions by the ESNA 1 membrane can be written as follows: R(Na⁺) > R(K⁺) > R(Mg²⁺) > R(Ca²⁺) at 10 mol/m³ concentration and R(Mg²⁺) > R(Ca²⁺) > R(Na⁺) > R(K⁺) at 100 mol/m³ concentration.     

The Influence of Extractant Structure on the Solvent Extraction of Uranium(VI) and Thorium(IV) from Nitrate Media by Dialkyl Sulphoxides

The solvent extraction of uranium(VI) and thorium(IV) from sodium nitrate solutions (0·20–6·00 M ) by a series of dialkyl sulphoxides with different structures was studied. For sulphoxides with n-alkyl groups (R₂SO, where R = n-hexyl, n-octyl and n-decyl) using 0·20 M solutions in xylene, the extractions of both uranium and thorium are relatively high, and the values of the separation factor β_Th^U are correspondingly low (≈20). Replacement of an n-hexyl group by a cyclohexyl group has little effect on metal extraction, whilst the introduction of a second cyclohexyl group causes a slight decrease in extraction. Similarly, there is little variation in the extraction of uranium and thorium through the series of asymmetrical compounds RR′SO, where R = n-octyl and R′ = cyclopentyl, cyclohexyl or cyclooctyl. When two aromatic (phenyl) rings are introduced into the sulphoxide, however, the extraction of both metals falls to zero. For the series of isomeric compounds R₂SO with C₈ alkyl groups, the separation factors increase in the order: R = n-octyl, 2-ethylhexyl, 2-octyl, 3-octyl, which is also the order of increasing steric bulk of the alkyl group. For these compounds, slope analysis studies are consistent with the formulation of the extracted metal complexes as UO₂(NO₃)₂(R₂SO)₂ and Th(NO₃)₄(R₂SO)₃. © 1997 SCI.     

Copper electrodeposition on pyrolytic graphite electrodes: Effect of the copper salt on the electrodeposition process

The electrodeposition of copper on pyrolytic graphite from CuSO₄ or Cu(NO₃)₂ in a 1.8 M H₂SO₄ aqueous solution was investigated. The Cu deposits were formed potentiostatically and characterized by electrochemical methods, scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy. It was found that the deposition of copper in the presence of CuSO₄ induced the codeposition of sulfate anions. In addition, electrochemical quartz crystal microbalance revealed that the increase of the Cu mass was higher than expected from Faraday's law with the CuSO₄/H₂SO₄ solution. These results confirmed the specific adsorption of anions during the Cu deposition. On the other hand, the use of Cu(NO₃)₂ resulted in a non-contaminated surface with different surface morphologies. The Cu nuclei size, the population density and the surface coverage were monitored as a function of the deposition potential. From the analysis of the chronoamperometric curves, the nucleation kinetics was studied by using various theoretical models. Independently of the Cu source, the nucleation mechanism follows a three-dimensional (3D) process. Copper nucleates according to an instantaneous mode when the deposition potential is more negative than −300 mV versus Ag/AgCl, while the nucleation was interpreted in terms of a progressive mode at −150 mV. The nuclei population densities were also determined by using two common fitting models for 3D nucleation and growth (Scharifker-Mostany and Mirkin-Nilov-Heerman-Tarallo). Their values are reported here as a function of the deposition potential.     

Acrylonitrile-based copolymer membranes containing reactive groups: effects of surface-immobilized poly(ethylene glycol)s on anti-fouling properties and blood compatibility

The anti-fouling properties and blood compatibility of poly(acrylonitrile-co-maleic acid) (PANCMA) membranes were improved by the immobilization of poly(ethylene glycol)s (PEG) on membrane surface. It was found that the reactive carboxyl groups on PANCMA membrane surface could be conveniently conversed into anhydride groups and then esterified with PEG. Chemical and morphological changes as well as biocompatibility on membrane surface were analyzed by Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy, water contact angle, protein adsorption, and platelet adhesion. Results revealed that, with the immobilization of PEG, the hydrophilicity and blood compatibility of the acrylonitrile-based copolymer membranes were improved obviously. The molecular weight of PEG had an obvious influence on the properties of the PEG-immobilized membranes. Permeation behaviors for the studied membranes were investigated by water and bovine serum albumin (BSA) filtration experiments. Compared with the original PANCMA membrane, the membrane immobilized with PEG 400 (M_w=400 g/mol) showed a three-fold increase in a BSA solution flux, a 40.4% reduction in total fouling, and a 57.9% decrease in BSA adsorption.     

Novel and Mild Route to Phthalocyanines and 3‐Iminoisoindolin‐1‐ones via N,N‐Diethylhydroxylamine‐Promoted Conversion of Phthalonitriles and a Dramatic Solvent‐Dependence of the Reaction

Refluxing a mixture of phthalonitrile C₆R¹R²R³R⁴(CN)₂ 1 (R¹–R⁴=H), or its substituted derivatives 2 (R¹, R³, R⁴=H, R²=Me), or 3 (R¹, R⁴=H, R², R³=Cl) (1 equiv.) and N,N‐diethylhydroxylamine, Et₂NOH, (4 equivs.) in methanol for 4 h results ( Route A ) in precipitation of the symmetrical ( 6 and 8 ) and an isomeric mixture of unsymmetrical ( 7 ) phthalocyanines, isolated in good (55–65 %) yields. The reaction of phthalonitriles 1 , 2 , or 4 (R¹, R³, R⁴=H, R²=NO₂) (4 equivs.) with Et₂NOH (8 equivs.) in the presence of a metal salt MCl₂ (M=Zn, Cd, Co, Ni) (1 equiv.) in n‐BuOH or without solvent results in the formation of metallated phthalocyanine species ( 9 – 17 ). Upon refluxing in freshly distilled dry chloroform, phthalonitrile 1 or its substituted analogues 2 , 3 or 5 (R¹–R⁴=F) (1 equiv.) react with N,N‐diethylhydroxylamine (2 equivs.) affording 3‐iminoisoindolin‐1‐ones 18 – 21 ( Route B ) isolated in good yields (55–80 %). All the prepared compounds were characterized with C, H, and N elemental analyses, ESI‐MS, IR, and compounds 18 – 21 also by 1D (¹H, ¹³C{¹H}), and 2D (¹H,¹⁵N‐HMBC and ¹H,¹³C‐HMQC, ¹H,¹³C‐HMBC) NMR spectroscopy.     

Construction strategies of self-cleaning ceramic composite membranes for water treatment

Ceramic membranes have received much popularity due to their high mechanical strength, satisfactory acid/alkali resistance, and long-term stability. However, ceramic membranes are also inevitably fouled by contaminates during the membrane separation process. Therefore, construction strategies of anti-fouling ceramic membranes are a main topic in current research. In this work, we review a better anti-fouling ceramic membrane, which is named “self-cleaning” membrane and membrane process. Date to now, there are four main strategies to construct self-cleaning ceramic membranes: 1) porous piezoelectric ceramic membranes; 2) photo-catalytic ceramic membrane; 3) electrochemical ceramic membranes and 4) self-cleaning ceramic membrane surface. Self-cleaning ceramic membranes can in-situ remove and decompose the pollutants on the membrane surface and recover the water permeance that exhibits a great potential to treat industrial wastewater without backwashing or other methods. The detailed membrane fabrication period, mechanism and important case studies are reported in this review. Self-cleaning ceramic membrane is expected to be next-generation anti-fouling ceramic membrane material for continuous water treatment. It is a first review work that systematically concluded all the strategies for self-cleaning ceramic membranes that can be an important reference in ceramic or membrane fields.     

Simultaneous monitoring of the transport of anions and cations across polypyrrole based composite membranes

A mechanism for the macroscopic charge balance during the transport of anions and cations across polypyrrole based composite membranes is proposed. For the mechanism to be studied, anions and cations were monitored simultaneously across PPy based composite membranes, which are known to have cation exchange (PPy(PSS)), anion exchange (PPy(ClO₄)) and mixed ion exchange properties (PPy(pTS)). Even though none of the membranes were found to be completely permselective, the flux of cations was higher than that of anions across the PPy(PSS) composite membrane, while the flux of anions was higher than that of cations across the PPy(ClO₄) composite membrane. Distinct changes in pH of the receiving solution were also observed. These were a decrease in pH when a predominantly anion exchanging polypyrrole composite membrane was used, and an increase in pH when a membrane that maintains charge balance principally by cation exchange was used. When membranes which display approximately equal permeability towards anions and cations were used the pH of the receiving solution was ca. 6–8. There was only a negligible flux of Ca²⁺ across the PPy(PSS) membrane in the transport experiments carried out with the source solution consisting of either Ca(NO₃)₂ or an equimolar mixture of KNO₃ and Ca(NO₃)₂. The PPy(PSS) composite membrane was impermeable towards NO₃⁻ ions when the source solution was Ca(NO₃)₂ but permeability towards NO₃⁻ was observed when the source solution was either KNO₃ or an equimolar mixture of KNO₃ and Ca(NO₃)₂.     

Fabrication and modification of acrylonitrile–butadiene–styrene‐based heterogeneous ion‐exchange membranes by plasma treatment: Investigation of the nanolayer deposition rate and temperature effects

Our target in this study was the preparation of electrodialysis ion‐exchange membranes with appropriate properties for applications in water recovery and treatment. Composite mixed‐matrix, anion‐exchange membranes were prepared by a solution casting technique with acrylonitrile–butadiene–styrene as a base binder, resin powder as a functional group agent, activated carbon as an adsorptive filler, and an Ag nanolayer as a surface modifier. The Ag nanolayer was used with a magnetron sputtering method. The effect of the nanolayer deposition rate (R_q) and substrate and annealing temperatures on the physicochemical characteristics of the membranes were studied. The X‐ray diffraction results show that average grain size of the nanolayer and membrane crystallinity were improved with increasing R_q. The atomic force microscopy and scanning electron microscopy results show that the membrane roughness was enhanced with increasing R_q. The height distribution results also show the best height distribution for the modified membrane at low R_q. The selectivity and flux decreased with increasing nanolayer R_q in the membranes. The selectivity was also decreased initially with increases in the substrate and annealing temperatures from 300 to 325 K in the membranes and then showed an increasing trend. An opposite trend was found for flux with variations in the temperature. The modified membrane containing a 20‐nm Ag nanolayer at low R_q showed better performance compared to the other modified membranes and the pristine one. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40025.     

Dynamic deposition of polyacids on porous membrane supports

Poly(acrylic acids), poly(styrenesulfonic acid), and their block and random copolymers were tested for their ability to form dynamic membranes on partially cured asymmetric cellulose acetate. Chemically modified porous polypropylene (Celgard) was also used as a support for poly(acrylic acid). Salt rejections, water fluxes, and streaming potentials of membranes were tested under hyperfiltration conditions. Sorption of the polyelectrolytes by the cellulose acetate supports was studied using spectrophotometric, ²²Na tracer, and electron microscopy techniques. The dynamic membrane formation was noted only for poly(acrylic acid) and for its 1:4:1 block copolymer with poly(styrenesulfonic acid). The uneffectiveness of other polyelectrolytes was discussed in terms of a negative zeta potential of cellulose acetate. The increase in salt rejection (R) due to the polyelectrolyte is strongly dependent on the initial R_i of the support. Sharp maxima in the ΔR -versus-R_i curves have been noted for R_i in the range of 40–55%. The most significant improvement in the hyperfiltration characteristics of cellulose acetate was attained with the 1:4:1 block copolymer. Flux of 17 gfd at 350 psi and R = 93% was obtained in short-term tests for a 0.1N feed solution. Long-term tests did not reveal any flux or salt rejection decline for membranes in which poly(acrylic acid) was complexed with phosphoramidic groups grafted onto Celgard.     

Synthesis and characterization of low content of different SiO2 materials composite poly (vinylidene fluoride) ultrafiltration membranes

A comparison of the morphology and performance of virgin poly (vinylidene fluoride) (PVDF) ultrafiltration (UF) membrane, and PVDF-composite membranes with low content of two different SiO₂ (N-SiO₂ and M-SiO₂ particles) was carried out. Cross-sectional area and surface morphology of the membranes were observed by scanning electron microscopy and atomic force microscopy. Surface hydrophilicity of the porous membranes was determined through the measurement of a contact angle. Performance tests were conducted on the composite membranes through water flux and bovine serum albumin (BSA) retention. Average pore size and surface porosity were calculated based on the permeate flux. Thermal stability and mechanical stability were determined by thermogravimetric analysis and tensile stress tests. The results indicate that N-SiO₂/PVDF (P-N) membranes possessed larger average pore size and porosity, which led to higher water flux and a slight decline in BSA retention. On the other hand, M-SiO₂/PVDF (P-M) membranes had better mechanical stability and anti-fouling performance with enhanced membrane hydrophilicity and decreased membrane surface roughness. Both of the P-N and P-M membranes exhibited typical asymmetric morphology and improved thermal stability.     

Development of a conjugated polyaniline incorporated electrospun poly(vinylidene fluoride‐co‐hexafluoropropylene) composite membrane electrolyte for high performance dye‐sensitized solar cells

Different weight percentage (2, 3, 4, and 5 wt %) of polyaniline (PANI) were incorporated into electrospun poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP) composite membranes (esCPMs). The regular morphology, molecular structure, crystallinity, porosity, electrolyte uptake, and leakage of the composite membranes were examined. The esCPMs were activated in liquid electrolyte containing 0.5 M LiI, 0.05 M I₂, and 0.5 M 4‐tert‐butylpyridine and 0.5 M 1‐butyl‐3‐methylimidazoliun iodide in acetonitrile to afford electrospun PVdF‐HFP/PANI composite membrane electrolytes (esCPMEs). The influence of different wt % of PANI on the esCPMEs was studied by electrochemical impedance measurements and Tafel polarization studies. The photovoltaic performance of a dye‐sensitized solar cell assembled using 3 wt % PANI incorporated esCPME exhibits a higher power conversion efficiency of 7.20% than that assembled using esPME (η = 6.42%). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42777.     

Optimizing the incorporation of silica nanoparticles in polysulfone/poly(vinyl alcohol) membranes with response surface methodology

The addition of silica nanoparticles and poly(vinyl alcohol) (PVA) to polysulfone (PSF) membranes was used to modify the membrane morphology and enhance membrane performance. The central composite design of the response surface methodology was used to predict the maximum permeability and real salt rejection (R_real) of the PSF membranes. The factors affecting the permeability and R_real values of the PSF membranes were the silica (0–12 wt % PSF) and PVA (0–2 wt % PSF) contents. The optimized responses, membrane permeability, and R_real obtained experimentally were 61.9260 L m⁻² h⁻¹ bar⁻¹ and 97.5850%, respectively, with deviation from the predicted values of 34.72 and 15.84%, respectively. In the further characterization, the contact angle results showed that PVA was important in stabilizing the nanoparticle surfaces to prevent agglomeration in the polymeric matrix. The tensile strength test confirmed that the addition of silica nanoparticles improved the mechanical strength of the PSF membranes. However, the addition of PVA had a weakening effect on the mechanical strength of the PSF membranes. The addition of silica nanoparticles and PVA affected the typical asymmetric structures of the PSF membrane less, as shown in the scanning electron micrographs. This may have been due to the good incorporation of additives in the PSF membranes, as observed from the energy‐dispersive X‐ray and Fourier transform infrared spectroscopy results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 Liver Transpl, 2011. © 2011 AASLD.     

Photodegradation of imidacloprid insecticide using polyethersulfone membranes modified with iron doped cerium oxide

The widespread accumulation of insecticides in water systems is a growing concern. This study reports efficient photodegradation of imidacloprid (IMD) insecticide using polyethersulfone (PES) membranes modified with iron-doped cerium oxide (Fe-CeO₂). The work focuses on the modification of ultrafiltration polyethersulfone membranes with incremental amounts of Fe-CeO₂ photocatalysts (0.5–2.0 wt.%) using phase inversion method. An increase in Fe-CeO₂ content showed an improvement in surface roughness and porosity of membranes. Pure water flux (PWF) increased from 55.9 L m² h⁻¹ in M0 (PES) to 77.2 (M1, 0.5% Fe-CeO₂-PES), 118.0 (M2, 1% Fe-CeO₂-PES), 128.0 in M3 (1.5 wt.% Fe-CeO₂-PES) and then decreased to 98.5 L m² h⁻¹ in M4 (2 wt.% Fe-CeO₂-PES). This decrease is brought about by the high Fe-CeO₂ content, which minimizes the membranes' surface pores. Fe-CeO₂ photocatalysts are thought to give the membrane both hydrophilic and photocatalytic qualities because of their capacity to absorb light and create radical species that cause the photodegradation of IMD molecules. Consequently, under visible light irradiation, modified membranes demonstrated photocatalytic ability over IMD. Photocatalytic efficiencies of the membranes were found to be 5.2% (M0), 68.9 (M1), 75.8 (M2), 81.8 (M3), and 56.0% (M4), respectively, with M3 membranes showing the highest photocatalytic degradation efficiency and low leaching of metals. The remarkable performance observed by M3 membranes during both water filtration and photocatalytic performance may be an illustration of well dispersed photocatalyst which receives high absorption of light irradiation. Membranes with photocatalytic functionalities are tailored to exploit dual benefits of the membrane filtration and photocatalysis without compromising their original functions. However, maintaining the delicate balance of this phenomenon is still very challenging.