Activated charcoal‐loaded composite membranes of sodium alginate in pervaporation separation of water‐organic azeotropes

Composite membranes of sodium alginate prepared by incorporating nanosized‐activated charcoal particles were prepared and characterized for the extent of cross‐linking, thermal stability, and mechanical strength properties using Fourier transform infrared, differential scanning calorimetry, and universal testing machine, respectively. The membranes were tested for pervaporation (PV) dehydration of isopropanol (IPA), ethanol (EtOH), 1,4‐dioxane (1,4‐D), and tetrahydrofuran (THF) at their azeotropic compositions. Improved PV performances of the composite membranes were observed compared with plain sodium alginate membrane for all the azeotropes. Sorption was studied to evaluate the extent of interactions between liquids and membranes as well as degree of swelling of the membranes in the chosen aqueous‐organic mixtures. Adding different amounts of activated charcoal into NaAlg offered high water selectivity values of 99.7, 99.1, 99.4, and 99.41%, respectively, for IPA, THF, 1,4‐D, and EtOH. Arrhenius activation parameters were computed from the temperature versus flux plots, which showed systematic trends for different liquids that depended upon their interactions with membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sorption and diffusion of volatile organic compounds in fluoroalkyl methacrylate‐grafted PDMS membrane

Pervaporation is known as an excellent method for the purification of contaminated water, the extraction of aroma compounds, etc., and has been widely studied. The prediction of permeation is important for treatment, extraction, and quantitative analysis. To predict permeation, a solution–diffusion mechanism is proposed. The octanol–water partition coefficient (Pow) has been generally used in expressing hydrophobicity. The hydrophobicity, Pow, is closely related to the solubility of organic compounds. Also, the molecular volume is closely related to the diffusion of organic compounds. In this study, we improved polydimethylsiloxane (PDMS) membranes by plasma grafting of fluoroalkyl methacrylates (FALMA) to enhance the affinity of PDMS to volatile organic compounds (VOCs). Furthermore, we investigated the pervaporation through the plasma‐grafted PDMS membrane and the PDMS membrane and the solution–diffusion mechanism of various VOCs. The permselectivity of tetrachloroethylene (PCE) and toluene determined by the sorption and the diffusion characteristics permeating in the membrane was high. Because the molecular volume of the VOCs is greated than that of water and the permeates quickly penetrate in rubbery membranes like PDMS, permselectivity was not affected by the diffussivity. Solubility significantly affected the permselectibity during pervaporation through a hydrophobic rubbery membrane. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 773–783, 2000     

Pervaporation separation of IPA‐water mixtures through 4A zeolite‐filled sodium alginate membranes

Incorporation of zeolites into natural polymers has been shown experimentally to enhance both the flux and selectivity in pervaporative dehydration separation of organic compounds. Pervaporation is a promising membrane technique for separation of volatile organic compounds (VOCs)/water mixtures. In this study, hydrophilic sodium alginate (SA) mixed membranes were prepared using solution casting technique by incorporating zeolites into the polymer matrix. The prepared membranes were characterized by ATR‐Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), Thermal Gravimetric Analysis (TGA), and differential scanning calorimetry (DSC) were tested in a laboratory scale pervaporation experimental set‐up. The effect of experimental parameters such as the type and composition of zeolites on permeation flux and selectivity was investigated. When tested on IPA‐water mixtures, the zeolite‐filled membrane was found to give much higher selectivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characteristics of the nanofiltration composite membranes based on PVA and sodium alginate

Chemically stable nanofiltration (NF) composite membranes based on poly(vinyl alcohol) (PVA) and sodium alginate (SA) (hereafter, these membranes are called PVA/SA composite membranes) were prepared by coating microporous polysulfone (PSF) supports with dilute PVA/SA blend solutions. The PSF supports were pretreated with small monomeric compounds to reduce their pore size and to improve their hydrophilicity before coating with the PVA/SA blend solutions. The concentration of the PVA/SA blend solutions ranged from 0.1 to 0.3 wt %. The membranes prepared in this study were characterized with various methods such as SEM, FTIR, permeation tests, and z‐potential measurements. Especially, chemical stabilities of the membranes were tested, using three aqueous solutions with different pHs such as a HCl solution (pH 1), a K₂CO₃ solution (pH 12.5), and a NaOH solution (pH 13). Their chemical stabilities were compared with that of a polyamide (PA) composite membrane prepared from piperazine (PIP) and trimesoyl chloride (TMC). In this study, it was found that the PVA/SA composite membranes prepared showed not only good chemical stabilities but also good permeation performances in the range from pH 1 to 13. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2471–2479, 2001     

纤维素/海藻酸钠共混膜的制备及力学性能

将纤维素和海藻酸钠分别溶于氢氧化钠/尿素/硫脲体系,制得纤维素膜和纤维素/海藻酸钠共混膜,通过正交实验和单因素实验法分析,确定制备纤维素膜的最佳工艺条件,在此基础上研究了纤维素/海藻酸钠共混膜的制备工艺。结果表明:质量分数为4.5%的纤维素溶液所制得的膜在25℃的5%的硫酸溶液中凝固15 min,20%的甘油溶液中塑化30 min,其膜的拉伸强度较佳为5.2 MPa;纤维素/海藻酸钠共混膜的较佳工艺:质量分数分别为4.5%的纤维素溶液和3%的海藻酸钠溶液按质量比100/5共混后先浸入5%硫酸溶液中反应15 min,再放入10%氯化钙溶液中凝固10 min,用15%甘油溶液塑化15 min后,共混膜的拉伸强度达到3.50 MPa。     

Synthesis and characterization of polyacrylamide‐grafted sodium alginate copolymeric membranes and their use in pervaporation separation of water and tetrahydrofuran mixtures

Polyacrylamide‐grafted sodium alginate (PAAm‐g‐Na‐Alg) copolymeric membranes have been prepared, characterized, and used in the pervaporation separation of 10–80 mass % water‐containing tetrahydrofuran mixtures. Totally three membranes were prepared: (1) neat Na‐Alg with 10 mass % of polyethylene glycol (PEG) and 5 mass % of polyvinyl alcohol (PVA), (2) 46 % grafted PAAm‐g‐Na‐Alg membrane containing 10 mass % of PEG and 5 mass % of PVA, and (3) 93 % grafted PAAm‐g‐Na‐Alg membrane containing 10 mass % of PEG and 5 mass % of PVA. Using the transport data, important parameters like permeation flux, selectivity, pervaporation separation index, swelling index, and diffusion coefficient have been calculated at 30°C. Diffusion coefficients were also calculated from sorption gravimetric data of water–tetrahydrofuran mixtures using Fick's equation. Arrhenius activation parameters for the transport processes were calculated for 10 mass % of water in the feed mixture using flux and diffusion data obtained at 30, 35, and 40°C. The separation selectivity of the membranes ranged between 216 and 591. The highest permeation flux of 0.677 kg/m² h was observed for 93% grafted membrane at 80 mass % of water in the feed mixture. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 272–281, 2002     

Sorption,diffusion, and swelling characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) in water–acetic acid mixtures

Sorption, diffusion, and swelling characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) were investigated for water–acetic acid mixtures by using a gravimetric method at 30, 40, and 50°C. The membranes were characterized by X‐ray diffraction and Fourier transform infrared techniques. Concentration‐independent diffusion coefficients were obtained by applying Fick's relationship before completion of equilibrium sorption. Permeation coefficients were calculated from sorption and diffusion coefficients. Concentration profiles of liquids were computed considering the sheet geometry for the membrane by solving Fick's equation under suitable boundary conditions. Arrhenius activation parameters were computed for the transport processes. Experimental results and calculated quantities were discussed to understand membrane–solvent interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1139–1150, 2004     

Preparation and characterization of novel sodium alginate/chitosan two ply composite membranes

Sodium alginate/chitosan (SA/CS) two ply composite membranes were prepared by casting and solvent evaporation technique. NaHCO₃ was used as a porogen additive to form pores in the interior of the composite membranes and glycerol was introduced as a plasticizer. The water uptake capacity, mechanical strength, oxygen permeation property, and in vitro cytotoxicity were evaluated to test the feasibility to utilize the composite membranes for wound dressing. The average pore size, water uptake capacity, and oxygen permeation property of the composite membranes could be adjusted by the ratio of NaHCO₃ in the SA solution. The SA/CS two ply composite membranes showed high water uptake capacity, suitable mechanical strength, excellent oxygen permeability, and good biocompatible. It indicates that the SA/CS two ply composite membranes are suitable for wound dressing application. It provides a simple but promising platform to fabricate wound dressing using natural polymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

有机分子在聚乙烯膜中扩散过程的分子动力学模拟

引言聚乙烯(PE)是由乙烯单体聚合而成的相对分子质量较高的线性烷烃,是合成树脂中应用最广泛的品种。扩散系数是描述传递现象的基本物性参数,在聚合物材料开发方面具有重要的理论特性和广阔的应用前景。用实验方法测定扩散系数时,操     

高亲水性海藻酸钠膜渗透汽化分离甲醇水溶液

在海藻酸钠基质中引入磷钨酸颗粒,制备了一种高亲水性渗透汽化杂化膜。由热失重等分析手段对膜进行了表征,并在不同温度下（30～60 ℃）通过分离80%～95%的甲醇水溶液,测试了杂化膜的渗透汽化性能,实验结果表明：添加了磷钨酸的杂化膜,其分离性能显著高于纯海藻酸钠膜,当磷钨酸含量为6%时,30 ℃下分离水含量5%的溶液,膜通量达到318.2 g/(m2?h),分离因子达到656.9,分别是纯海藻酸钠膜的3.7倍和26.3倍。利用阿累尼乌斯关系式考察了膜通量与温度之间的关系,发现溶液通过膜的活化能随着磷钨酸含量的增加而降低。表明,磷钨酸的加入使得渗透物在杂化膜内更容易透过。     

Sorption/diffusion of aqueous mixtures of 1,4‐dioxane/tetrahydrofuran through blend membranes of poly(vinyl alcohol) and sodium alginate: Their compatibility and pervaporation separation studies

Blend membranes of poly(vinyl alcohol) (PVA) and sodium alginate (NaAlg) were prepared by solution casting and crosslinked with glutaraldehyde (GA). Polymer blend compatibility was studied in water by measuring solution viscosity at 30°C. From the viscosity data, interaction parameters were determined to find the blend compatibility. Thickness of the membranes ranged between 35 and 40 μm. Circular disc‐shaped samples were cut from the thin membranes to perform gravimetric sorption experiments in water + 1,4‐dioxane and water + tetrahydrofuran mixtures at 30°C. Diffusion coefficients were calculated using Fick's equation. Concentration profiles of liquids were computed by solving Fick's equation under suitable boundary conditions. Diffusion coefficients show a dependence on the composition of the blends as well as composition of binary mixtures. A correlation was attempted between concentration profiles and diffusion coefficients of the transporting liquids. Degree of swelling and sorption coefficients were calculated from the gravimetric sorption data. Sorption kinetics was studied using an empirical equation to understand the nature of sorption–diffusion anomalies. Membrane selectivity for water + 1,4‐dioxane and water + tetrahydrofuran mixtures were calculated from the pervaporation experiments. A correlation between sorption and membrane selectivity was attempted. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 178–188, 2005     

无机杂化海藻酸钠渗透汽化膜的制备与分离性能对比

为提高海藻酸钠（SA）膜的渗透汽化分离性能,分别采用纳米氧化铝、纳米氧化锆和纳米氧化钛对SA膜进行改性,对比分析了3种不同杂化膜渗透汽化分离性能的差异,并将分离性能较好的杂化膜应用到乙酸与乙醇酯化反应脱水的体系中。系统考察了无机纳米粒子含量对SA膜渗透汽化分离性能的影响,对杂化膜进行了接触角、傅里叶红外（FTIR）、扫描电子显微镜（SEM）、热重/差示扫描量热（TG/DSC）、X射线衍射（XRD）和拉伸强度等表征与分析。结果表明,无机纳米粒子能提高SA膜的热稳定性、机械强度和渗透通量,当无机纳米粒子与SA质量比为0.3时,掺杂TiO₂、ZrO₂和Al₂O₃的杂化膜二碘甲烷的接触角依次升高,同时渗透通量也依次升高。SA-0.3Al₂O₃杂化膜亲水性较好,然而SA-0.3ZrO₂杂化膜分离性能最优,50℃下分离水含量10%的乙醇-水溶液,膜渗透通量达到336 g·m^-2·h^-1,渗透侧水含量99.97%,分离因子29990。酯化反应脱水实验表明,在80℃时,酯化反应脱水实验乙酸转化率均高于无脱水实验乙酸转化率,平衡转化率不断被打破,反应12 h后,转化率由平衡时的79.3%提高到93.9%。     

Synthesis and characterization of pH‐ and salt‐responsive hydrogels based on etherificated sodium alginate

Hydrogels composed of etherificated sodium alginate (ESA), sodium acrylic acid (NaAA), and poly (vinyl alcohol) (PVA) were synthesized by aqueous solution polymerization. The effects of reaction variables such as terminal pH, ions, and ionic strength on hydrogel swelling ratio (SR) were determined and compared. SR was influenced strongly by pH and ionic strength. SR increased with increasing pH but tended to decrease with PVA content. At a given ionic strength, SR of ESA/NaAA/PVA hydrogel was dependent on the valence of anion; SR was higher in multivalent anion salt solution than in monovalent anion salt solution, i.e., SR_K2SO4 > SR_KCl and SR_Na2SO4 > SR_NaCl. The swelling kinetic of the hydrogels showed Fickian kinetic diffusion in acidic media and non‐Fickian behavior in alkaline media. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Sorption,diffusion, and pervaporation separation of water–acetic acid mixtures through the blend membranes of sodium alginate and guar gum‐grafted‐polyacrylamide

Nonporous homogeneous dense membranes were prepared from the blends of sodium alginate (Na–Alg) with guar gum‐grafted polyacrylamide (GG‐g‐PAAm) in the ratios of 3 : 1 and 1 : 1 and these were tested for the pervaporation separation of water–acetic acid mixtures at 30°C. Blend compatibility was studied in solution by measuring the viscosity and the speed of sound. Membranes were crosslinked by glutaraldehyde. The GG‐g‐PAAm polymer and the crosslinked blend membranes were characterized by Fourier transform infrared spectra. High separation selectivity was exhibited by the pure Na–Alg membrane for water–acetic acid (HAc) mixtures containing 20 mass % of water. The permeation flux increased with increasing mass percent of water in the feed as well as with an increase in the amount of GG‐g‐PAAm in the blend, but separation selectivity decreased. Sorption selectivity was higher for the Na–Alg membrane than for the blend membranes, but it decreased with increasing mass percent of GG‐g‐PAAm in the blends. Diffusion selectivity values vary systematically with the blend composition, but not with the amount of water in the feed. Diffusion coefficients of the water–HAc mixtures were calculated from Fick's equation using sorption data and compared with those calculated from flux values obtained in pervaporation experiments. The Arrhenius activation parameters were calculated for the 20 mass % of water in the feed using flux and diffusion data obtained at 30, 40, and 50°C. The diffusion and pervaporation results are explained in terms of solution–diffusion concepts. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 259–272, 2002     

Temperature sensitive semi‐IPN microspheres from sodium alginate and N‐isopropylacrylamide for controlled release of 5‐fluorouracil

Semi‐interpenetrating network (IPN) of sodium alginate (NaAlg) and N‐isopropylacrylamide (NIPAAm) microspheres were prepared by water‐in‐oil (w/o) emulsification method. The microspheres were encapsulated with 5‐fluorouracil (5‐FU) and release patterns carried in 7.4 pH at temperatures of 25 and 37°C. The semi‐IPN microspheres were characterized by Fourier transform infrared spectroscopy (FTIR). Differential scanning calorimetry (DSC) and scanning electron microscopic studies were done on the drug‐loaded microspheres to confirm the polymorphism of 5‐FU and surface morphology of microspheres. These results indicated the molecular level dispersion of 5‐FU in the semi‐IPN microspheres. Particle size and size distribution were studied by laser light diffraction technique. Microspheres exhibited release of 5‐FU up to 12 h. The swelling studies were carried in 1.2 and 7.4 pH buffer media at 25 and 37°C. Drug release from NaAlg‐NIPAAm semi‐IPN microspheres at 25 and 37°C confirmed the thermosensitive nature by in vitro dissolution. The micro domains have released in a controlled manner due the presence of NIPAAm in the matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Multi‐responsive hydrogels based on N‐isopropylacrylamide and sodium alginate

Hydrogels consisting of sodium alginate and N‐isopropylacrylamide covalently crosslinked with N,N′‐methylenebisacrylamide were prepared. The mixed‐interpenetrated networks obtained were characterized using elemental analysis, Fourier transform infrared and Raman spectroscopy, swelling measurements and environmental scanning electron microscopy. The thermo‐ and pH‐responsive properties of these hydrogels were evidenced by their swelling behaviour, which depended also on the amount of crosslinking agent and hydrogel composition. Copyright © 2010 Society of Chemical Industry     

Pervaporation separation of water‐isopropyl alcohol mixtures with blend membranes of sodium alginate and poly(acrylamide)‐grafted guar gum

The blend membranes of sodium alginate (Na‐Alg) and poly(acrylamide)‐grafted guar gum (PAAm‐g‐GG) in the ratios of 3:1 and 1:1 were prepared and studied for the pervaporation separation of water–isopropyl alcohol mixtures over the entire range of mixture composition at 30°C. Membranes prepared from neat Na‐Alg (M‐1) and the 1:1 blend of Na‐Alg and PAAm‐g‐GG (M‐3) showed the highest separation selectivity for 10 mass % water in the feed mixture, whereas membranes prepared with the 3:1 blend ratio of Na‐Alg to PAAm‐g‐GG showed the highest separation selectivity of 20 mass % water in the feed. Selectivity decreased with increasing amount of water in the feed for all the membranes, but these values show an increase with increasing amount of grafted copolymer in the blend mixture. Flux increased with increasing amount of water in the mixture, but the flux values did not change markedly with the PAAm‐g‐GG content in the blend membrane at the lower mass % water. At higher mass % of water, the flux values of the blends increase systematically with increasing amount of PAAm‐g‐GG in the blend polymer. For the 10 mass %‐containing binary mixtures, the pervaporation separation experiments were performed at 30, 40, and 50°C, and the resulting data were used to calculate the Arrhenius activation parameters. These data indicated activated pore‐type diffusion of the permeants in the membranes. Dynamic sorption studies were also performed on up to 40 mass % water–isopropyl alcohol mixtures at 30°C. These results, when analyzed by the empirical equation, indicated Fickian transport in all the cases. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2014–2024, 2002     

Structure and properties of collagen‐konjac glucomannan‐sodium alginate blend films

A new kind of blend film was made by mixing the solutions of collagen, konjac glucommnnan (KGM), and sodium alginate. The structure of the blend film was characterized by FTIR, XRD, atomic absorption spectrophotometer, and SEM, respectively. The effects of weight ratio between the polymers on light transmittance, tensile strength, elongation at break, water permeability, and water absorption of the film were studied. The results showed that there were strong interactions and good compatibility between collagen, KGM, and sodium alginate in the film. The film possesses good mechanical properties. Therefore, it can be applied in biomedicine as a new type of biomaterial. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of polyacrylamidegrafted sodium alginate membranes for pervaporation separation of water + isopropanol mixtures

Polyacrylamide‐grafted‐sodium alginate copolymers were prepared by persulfate‐induced radical polymerization by using polymer‐to‐monomer ratios of 2 : 1 and 1 : 1. Polymers were characterized by Fourier transform infrared spectroscopy, differential thermal analysis, and viscosity. Membranes were prepared from the polymers, crosslinked with glutaraldehyde, and used in the pervaporation separation of water + isopropanol mixtures at 30°C. Equilibrium swelling experiments were performed for mixtures containing 10 to 80 mass % of water in the feed. Both the grafted copolymer membranes were ruptured while separating 10 mass % of water in the feed mixture. However, beyond 20 mass % of water in the feed mixture, flux increased with increasing grafting ratio, while selectivity decreased. Pervaporation separation experiments were carried out at 30, 40, and 50°C for 20 mass % of water in the feed mixture. By increasing the temperature, flux increased, whereas selectivity decreased. Arrhenius activation parameters for pervaporation and diffusion decreased with increasing grafting ratio of the membranes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2030–2037, 2004     

Antifouling membrane based on sodium alginate coated polyamide thin film composite for desalination of brackish water

Sodium alginate coated polyamide thin film composite (SA/PA-TFC) membranes were synthesized for the desalination of brackish water through reverse osmosis. Membranes were characterized by Fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, AFM, thermogravimetry, and universal testing machine for structural analysis, crystallinity, morphological, compositional, thermal, and mechanical properties, respectively. The effect of feed pressure on water flux and % salt rejection was quantified. Simulation results generated using the commercial process simulator PRO/II were in good agreement with the experimental data. Case studies using simulator were performed for brackish water with different salinity to optimize operating pressure based on product unit cost (PUC) by varying the feed pressure and membrane area. The calculated PUCs were found to be 0.9 and 0.3 $/m³ for corresponding feed total dissolved solids (TDS) concentrations of 5000 and 500 mg/L at an optimum pressure of 10 bar, to achieve a salt rejection of 98% using a membrane area of 335 m². We believe these membranes are a prospective solution for brackish water desalination.