Effect of Surface Roughness on Retention of Reverse Osmosis Membranes

The performances of two commercially available Thin Film Composite reverse osmosis membranes i.e. TFC-ULP and TFC-SR2 from Fluid Systems were studied. For the TFC-ULP membrane low water flux (around 7 lit/m²·h) and high ion retention (around 70%) were obtained. However the TFC-SR2 membrane showed much higher flux (90 lit/m²·h) and much lower retention (around 15%).Unlike the common membranes, TFC-ULP and TFC-SR2 membranes are composed of three layers. The skin layers of both membranes are made from polyvinyl alcohol and the two support layers are made from poly aryl sulfur ether and polyester. However contradictory behaviors of the membranes cannot be explained by the characteristics of materials used for membrane preparation and/or membrane morphology.Scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that the TFC-ULP membrane possesses a rough surface while the TFC-SR2 membrane predominantly has a smooth surface. Contradictory membrane performances may be due to higher trapping of the ions on the rough surface of TFC-ULP membrane resulting in higher retention. The deposition causes higher resistance against the flow leading to lower flux. The smooth surface of the TFC-SR2 membrane has less ability to trap the ions resulting in lower retention, lower resistance against the flow and therefore higher flux.     

Studies on Permeation,Rejection, and Transport of Aqueous Poly(ethylene Glycol) Solutions using Ultrafiltration Membranes

Abstract

The permeate flux and retention of aqueous solutions of poly(ethylene glycols) (PEG) with different molecular weights ranging from 4000 to 35,000 Da have been investigated using various compositions such as 100/0, 90/10, 80/20, and 70/30 wt% of cellulose acetate (CA)/sulfonated poly(etheretherketone) (SPEEK) ultrafiltration blend membranes. The factors affecting the rejection rate and permeate flux such as molecular weight of PEGs, concentration of the solute, composition of the membranes, and transmembrane pressures have been studied. It is seen that the increase in the concentration of PEG results in the decreased permeate flux and increased rejection for increasing CA content in the membranes. A similar observation in the flux and rejection was made for increasing the molecular weight of PEGs. Further, the mass transfer, diffusion, and true retention coefficients of the solute have been studied with different operating variables like molecular weight and concentration of PEGs. An increase in the molecular weight of PEGs results in the decrease of mass transfer and diffusion coefficients and increase of the true retention coefficient. A reverse trend is observed with increasing concentrations of PEG.     

NMP/GTA配比对CDA反渗透膜结构与性能影响

以二乙酸纤维素(CDA)为成膜基质,一定比例的N-甲基吡咯烷酮(NMP)/三乙酸甘油酯(GTA)为稀释剂,聚乙二醇400(PEG400)为致孔剂,采用复合相分离法来制备CDA平板膜,考察了NMP/GTA配比对CDA平板膜结构与性能的影响。实验结果表明,随着稀释剂中GTA含量的增加,膜横断面大的指状孔数目先减少后增加,小蜂窝孔的孔径增加;水通量总体呈下降趋势,与此同时脱盐率(Na Cl)上升后趋于平缓;膜表面的水接触角增大,意味着膜的亲水性随GTA含量的增加而下降;随着NMP/GTA配比的减小,CDA平板膜的拉伸强度先增大后降低。该CDA平板膜可作为后续热处理和交联的基膜。     

Effect of Temperature on the Physico-Chemical Properties of a Room Temperature Ionic Liquid (1-Methyl-3-pentylimidazolium Hexafluorophosphate) with Polyethylene Glycol Oligomer

A systematic study of the effect of composition on the thermo-physical properties of the binary mixtures of 1-methyl-3-pentyl imidazolium hexafluorophosphate [MPI][PF(6)] with poly(ethylene glycol) (PEG) [M(w) = 400] is presented. The excess molar volume, refractive index deviation, viscosity deviation, and surface tension deviation values were calculated from these experimental density, ρ, refractive index, n, viscosity, η, and surface tension, γ, over the whole concentration range, respectively. The excess molar volumes are negative and continue to become increasingly negative with increasing temperature; whereas the viscosity and surface tension deviation are negative and become less negative with increasing temperature. The surface thermodynamic functions, such as surface entropy, enthalpy, as well as standard molar entropy, Parachor, and molar enthalpy of vaporization for pure ionic liquid, have been derived from the temperature dependence of the surface tension values.     

Effect of Cyclic Changes in Temperature and Pressure on Permeation Properties of Composite Polyamide Seawater Reverse Osmosis Membranes

The effects of cyclic changes in feed water temperature and pressure on permeate flux, solute rejection, and compaction in spiral wound composite polyamide seawater reverse osmosis membranes were examined with pure water and 4% NaCl solutions. A membrane permeability hysteresis or memory effect due to the up and down temperature and pressure sequences was only seen with the saline water studies. However, the observed changes appeared to be reversible and were consistent with the Spiegler-Kedem/ Film Theory and the Kimura-Sourirajan Analysis/ Film Theory models. The overall results suggest that the net effect on permeance and solute rejection is the consequence of several interactions with feed/operating temperatures affecting membrane porosity and water/solute cluster size, and transmembrane pressure influencing membrane compaction.     

聚偏氟乙烯膜的亲水性改性研究进展

疏水性聚合物膜的亲水性改性是当前分离膜研究的热点之一。从膜表面亲水改性和膜材料亲水性改性的角度出发,综述了聚偏氟乙烯(PVDF)分离膜的各种改性方法的特点及改性效果,分析了其亲水改性机理,指出膜材料共混改性是今后发展的主要方向。     

Nd(NO_3)_3对Ni-Fe合金镀液及镀层性能的影响

研究了Nd(NO_3)_3对Ni-Fe合金镀液的阴极极化及Ni-Fe合金镀层的耐蚀性、硬度、高温抗氧化性和表面形貌的影响。结果表明:Nd(NO_3)_3可以增大Ni-Fe合金镀液的阴极极化,改善Ni-Fe合金镀层的结构,提高Ni-Fe合金镀层的耐蚀性、硬度和高温抗氧化性。     

Chemical Modification of Chitosan-Filled Polypropylene (PP) Composites: The Effect of 3-Aminopropyltriethoxysilane on Mechanical and Thermal Properties

Chitosan was used as filler in polypropylene (PP) polymer. In order to improve compatibility between chitosan and PP, chitosan was chemically modified with 3-aminopropyltriethoxysilane (3-APE). The results show that the increasing of filler content decreased tensile strength and elongation at break, but increased Young's modulus of composites. The treated composites exhibit higher tensile strength and Young's modulus, but lower elongation at break compared untreated composites. The addition of 3-APE has improved thermal properties such as thermal stability and crystallinity of treated composites. SEM study of the tensile fracture surface of treated composites shows better interfacial interaction and adhesion between the chitosan-PP matrix.     

Effect of Solvent on Physico-Chemical Properties and Antibacterial Activity of Chitosan Membranes

Chitosan is widely used in various applications such as pharmaceutical, medical, wastewater treatment (WWTR), and antibacterial. Modifying chitosan's properties is still attractive in scientific and industrial research. The acid solvation effect on the antibacterial activity (ABA) and physico-chemical properties of chitosan membranes synthesized via the solution casting-solvent evaporation technique was investigated. Various acids such as acetic, ascorbic, citric, glycolic, maleic, oxalic, and tartaric acid were used as chitosan solvents and membrane properties were characterized by Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) in order to study chemical interaction between the acid solvent and the shift of carbonyl and amine groups. Thermogravimetric analysis (TGA), static swelling, membrane thickness, and tensile strength experiments also characterized the membranes’ physical, chemical, and thermal properties. Further, the effect of acid solvation on the ABA of chitosan membranes for WWTR was interrogated with Escherichia coli and acetic acid solvated chitosan membrane exhibited highest ABA (99%).     

增塑剂聚乙二醇(300)对大豆分离蛋白/玻纤复合材料性能的影响

采用大豆分离蛋白和玻纤作原料,并用聚乙二醇(300)进行增塑,采用传统的热压成型方法来制备大豆分离蛋白/玻纤复合材料。加入10份聚乙二醇(300),SPI/GF复合材料拉伸强度和吸水率降低,断裂伸长率和流动性则呈明显升高。     

多孔壳聚糖膜的制备表征及其吸附性能研究

以琼胶固体颗粒为致孔剂,通过热致相转移法制备了的多孔壳聚糖膜,并通过FT-IR和SEM对其进行了表征,也考察了其对有机染料二甲苯蓝FF的吸附性能。结果表明,以琼胶作为制孔剂可以制备出性能良好的多孔壳聚糖膜,在吸附有机染料方面,多孔壳聚糖膜PCS-2对二甲苯蓝FF的吸附量是壳聚糖膜的1.3倍。另外,作为对比,本文也制备和表征了琼胶-壳聚糖共混薄膜。     

Effect of Poly(vinyl pyrrolidone) on Antifouling Properties of Asymmetric Poly(ethylene‐co‐vinyl alcohol) Membranes

Poly(ethylene‐co‐vinyl alcohol)/poly(vinyl pyrrolidone) (EVAL/PVP) blend membranes with antifouling properties were prepared by nonsolvent induced phase separation. Residual PVP in the sample was calculated by infrared spectroscopic data and confirmed by thermogravimetric analysis. The effect of residual PVP on hydrophilicity and permeation characteristics of the membranes was evaluated. Porosity and equilibrium water content of the membranes were influenced by the addition of PVP. The effect of protein fouling on flux using bovine serum albumin as a model system was studied in detail. The residual PVP content could enhance the antifouling property of the membrane. All membranes proved to have sufficient mechanical strength to withstand pressure‐driven filtrations.     

Surface Modification of Poly(3-hydroxybutyrate) (PHB) by Photografting and Its Properties Evaluation

Photografting reaction of poly(ethylene glycol) (PEG) onto poly(3-hydroxybutyrate) (PHB) by UV-irradiation was successfully conducted. The surface properties of PHB grafting copolymers such as hydrophilicity, enzymatic biodegradation and mechanical properties were investigated. The grafting copolymers showed better hydrophilic property and faster biodegradation rate than that of blank PHB in an enzymatic environmental medium, at the same time, its bulk properties such as mechanical properties were also improved in the certain content of grafting PEG. Varying the PEG grafting content, a series of copolymer with different biodegradation rate, which could fit the future application, can be attained. These photografting copolymers may be useful in some field, such as control-release delivery and tissue engineering, etc.     

Shape Memory and Physical Properties of Composites of Polyethylene Oxide/Poly(Propylene Glycol)-Block-Poly(Ethylene Glycol)-Block-Poly(Propylene Glycol)/2,4-Toluene Diisocyanate,Polypyrrole, and Modified MWCNT

Structural variation and its influence on morphology, mechanical, thermal, and electrical conductivity properties of polyethylene oxide/poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol)/2,4-toluene diisocyanate/polypyrrole (PEO/P(P-E-P)G/TDI/PPy) blends and nanocomposites with varying PPy content were reported. The chemical and fundamental linkages were confirmed by FTIR. SEM micrographs demonstrated homogeneous PEO/P(P-E-P)G/TDI/PPy blend formation and globular morphology for nanocomposites. The mechanical and DSC parameters were found to increase systematically with increasing PPy content in blend films. While for nanocomposites, better results were observed for 0.1% PPy content. Maximum electrical conductivity and good shape recovery of 94% was obtained for the nanocomposite with 1% PPy content.     

四氢呋喃均聚醚聚氨酯弹性体(PTMG-PU)影响环境性能的因素

介绍了四氢呋喃聚醚(PTMG)聚氨酯弹性体的性能。讨论了其化学结构对PU弹性体环境性能的影响。环境性能包括耐热性能、耐水性能、低温性能、耐介质性能、耐紫外线性能、耐磨性能、内生热、疲劳性、透明性、回弹性、导电性能等。     

Effect of fiber surface morphology on the hydrophilicity modification of cold plasma‐treated polypropylene nonwoven fabrics

Cold oxygen plasma was employed to give hydrophilicity modification to polypropylene (PP) nonwoven fabric (NWF). It was found that, after plasma treatment, PP NWF made from fibers with smooth surfaces can only keep its hydrophilicity for a short time and then shows a quick hydrophobic recovery at room temperature. However, this hydrophilic property can last for a long time in the case of the PP NWF made from fibers with rough surfaces. To prove the contribution of the rough surface to the long‐term hydrophilicity, this PP NWF was treated in an organic solvent to smooth the fiber surface. The hydrophilic feature of this PP NWF no longer lasts for a long time after the same plasma treatment. This observation strongly supports our opinion that the fiber surface morphology of PP NWF is a critical factor for long‐term hydrophilicity improvement after plasma treatment, which gives a positive solution to overcoming the aging effect of hydrophilicity modification often found in this technique. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Chitosan from Muga silkworms (Antheraea assamensis) and its influence on thermal degradation behavior of poly(lactic acid) based biocomposite films

The research work is focused on extraction of chitin from Muga silkworms (MS) and its conversion into chitosan by chemical treatment process. The extracted amount of chitin and chitosan from MS were obtained ～8 wt % and ～7 wt %, respectively. Potentiometric titrations, conductometric titrations, elemental analysis, ¹H‐NMR and FTIR analyses were employed to calculate the degree of deacetylation of chitosan (extracted at 80 ºC after 10 h) and found as 77% ± 2, 81% ± 1.8, 82% ± 2.4, 97.77% ± 0.3, and 82% ± 1.8, respectively. The deacetylation process of chitin showed pseudo‐first order reaction kinetics and activation energy was estimated as ～15.5 kJ/mole. The extracted chitosan (at 80 ºC after 10 h) showed higher crystallinity and improved thermal stability with respect to chitosan extracted from other marine sources. Subsequently, poly(lactic acid) (PLA) and extracted chitosan dispersed biocomposite films were prepared by solution casting method. Significant dispersion of chitosan (extracted at 80 ºC after 10 h) micro‐particles were observed in biocomposite films using FESEM analysis. Due to chitosan interaction with PLA, significant reduction in thermal degradation and activation energy was observed during nonisothermal degradation scan of such films using Flynn‐Wall‐Ozawa and Kissinger‐Akahira‐Sunose models. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43710.     

Increasing solvent polarity and addition of salts promote β‐phase poly(vinylidene fluoride) formation

This article investigates the effects of solvent polarity and salt addition on β‐phase poly(vinylidene fluoride) (PVDF) formation. Films were solvent cast in aprotic solvents of varying polarities with or without salt addition. Characterization was done by Fourier transformed infra‐red spectroscopy, differential scanning calorimetry, and scanning electron microscopy. Decreasing fractions of β‐phase PVDF was observed with increasing drying temperature when less polar solvents were used. The most polar solvent (hexamethylphosphoramide) consistently produced films with at least 90.0% β‐phase PVDF within the crystalline regions. Melting temperatures increased in correlation to absolute proportions of β‐phase PVDF. Salt addition increased the formation of β‐phase PVDF by 30%, with salts of higher valencies and smaller ionic radii resulting in more significant increases. Taken collectively, using solvents of higher polarities and addition of salts with high cationic valencies and small ionic radii will maximize β‐phase formation in solvent cast PVDF films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013