耐污染聚酰胺复合纳滤膜的制备及性能

以哌嗪(PIP)和均苯三甲酰氯(TMC)为反应单体,以聚乙烯醇(PVA)为添加剂,通过界面聚合法在聚砜超滤基膜上制备了复合纳滤膜,主要研究了PVA、PIP、TMC单体浓度、热处理条件对复合膜性能的影响,并通过扫描电子显微镜(SEM)、原子力显微镜(AFM)对复合纳滤膜结构和形貌进行表征。研究表明,PVA能够提高膜通量,增强膜亲水性,提高膜表面光滑度。最佳制膜条件是:PIP浓度为3.0 g/L,TMC浓度为1.0 g/L,PVA浓度为0.54 g/L,界面聚合时间为1 min,热处理温度为50℃,热处理时间10 min。制备的纳滤膜在处理Na2SO4、MgSO4、NaCl和MgCl2等4种盐溶液时,其截留性能与陶氏NF-270和星达NFX膜相近,而在深度处理造纸脱墨废水时,也表现出良好的分离性能和耐污染性能。     

Preparation and separation properties of polyamide nanofiltration membrane

Utilizing an interfacial polymerization technique for the preparation of a polymeric composite nanofiltration membrane, both high permeation flux of water and high salt rejection can be achieved. Synthesis conditions, such as concentration of monomer, reaction time, and swelling agent, significantly affected the separation performance of composite membranes. The composite polyamide membrane had a permeation rate of ～2–5 gallon/ft²/day (gfd) and a salt rejection rate of ～94–99% when 2000 ppm aqueous salt solution was fed at 200 psi and 25°C. Also, a higher performance nanofiltration membrane could be prepared by suitably swelling the support matrix in the period of polymerization. The results of various feed concentrations showed that permeate flux decreased with increasing salt concentration in the feed solution. This result may be due to concentration polarization on the surface of polyamide membranes. The separation performance of polyamide membranes showed an almost independent relationship with operation pressure until it was up to 200 psi. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1112–1118, 2002     

聚乙烯醇微球抗污染动态膜的制备及性能

采用静电自组装和过滤预涂技术将表面富含羟基、具有强亲水性和电负性的聚乙烯醇微球(polyvinyl alcohol micro-sphere, PVA-MS)与工业滤布基膜相结合,分别制备无滤饼标准型和完全堵塞型PVA-MS动态膜。对膜的表征和性能的对比研究表明, PVA-MS组成的动态膜结构能明显改善基膜的亲水性、负电性。自组装PVA-MS动态膜的有效过滤孔径为2.1 μm, 清水阻力为1.02×10¹⁰ m^-1, 对基膜的截留性能基本没有提高, 预涂PVA-MS动态膜的有效过滤孔径为0.4 μm, 清水阻力为1.07×10¹¹ m^-1, 对浊度为21.34 NTU和TOC为18.3 mg•L^-1的上清液过滤出水为0.23 NTU和9.4 mg•L^-1, 分别提高基膜截留效果20%和30%。动态膜不可逆污染的去除性能研究表明, 自组装PVA-MS动态膜在化学清洗后能保持大部分PVA-MS的存在,预涂PVA-MS动态膜利用物理反冲洗可完全去除不可逆膜污染,再预涂后即再生。     

Fouling studies of a polyamide nanofiltration membrane by selected natural organic matter: an analytical approach

The present study compares the fouling properties of two selected and well-characterized hydrophobic (denoted HPOA) and hydrophilic (denoted TPIA) natural organic matters (NOM) fractions with a commercial polyamide (PA) nanofiltration (NF) membrane (denoted NF-55). Analytical tools such as elemental analyses using microanalyses, specific UV absorbance, solid-state cross-polarization magic angle spinning (CPMAS) ¹³C-NMR, high pressure size exclusion (HPSEC) chromatography, HPLC system and acid/base titration for characterizing NOM fractions and contact angle, hydraulic permeability, streaming potential (SP) and observed rejection of a NaCl aqueous solution to evaluate the affinity of the PA material with both selected NOM fractions isolated from the Blavet river (Britany region, France). The PA material was found to be more sensitive to hydrophobic NOM adsorption leading to irreversible fouling with drastic modifications of the initial physico-chemical properties of the membrane: (a) increase of its hydrophobicity; (b) decrease of its hydraulic permeability associated with a decrease in its pore size and consequently (c) increase the observed rejection of salty solutions. The higher decrease in the performances of this PA NF membrane is observed for the more hydrophobic foulant, HPOA. At the same time a displacement of the isolectric point (IEP) of the membrane material was observed from 4.5 for the clean membrane (KCl 10⁻⁴ mol.L⁻¹) to 3.4 after HPOA sorption. At a lower pH range than the IEP, the effects of cations and H⁺ on the charge properties of the membranes increases near the shear plane, yielding more positive SP values. For the hydrophilic TPIA foulant no displacement of the IEP was observed. Then the results of SP experiments conducted through the membrane with a homemade apparatus has indicated that HPOA is more retained inside the pores as compared to the TPIA that was mainly sorbed at the surface of the membrane. Furthermore the membranes acidic-basis properties were amplified after foulants deposit in comparison to the cleaned membrane where a dominant specific sorption of monovalents and divalents ions occurred.     

DK2540型工业纳滤膜处理微蚀废液的研究

为了循环利用深圳某电路板厂的微蚀刻废液,首先研究了利用铜粉还原去除废液中的氧化性物质,然后通过用DK2540型工业高脱盐纳滤膜处理,浓缩废液中的铜,回收其中的酸.实验结果为在室温下,桨搅拌速率为300 r/min,投料比n（Cu）∶n（Na2S2O8）=1.2,反应时间70 min时,对过硫酸钠有最高去除率89.37％.在压力4 MPa,进料流量770 L/h时,Cu2＋有最高截留率90.22％,H＋有最高透过率75.68％.对于ρ（铜）=1.55 g/L的废液,可以浓缩ρ（铜）=20 g/L,原液体积减少95％以上.实验表明利用膜法可以实现微蚀废液的循环利用.     

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.     

Retention of mineral salts by a polyamide nanofiltration membrane

Retention measurements with single salt solutions (KCl, K₂SO₄, MgSO₄ and MgCl₂) were carried out with an AFC 30 organic membrane. The membrane showed high retentions for K₂SO₄ and MgSO₄ solutions and moderate ones for MgCl₂ and KCl solutions. The effective pore radius and the effective thickness to the porosity ratio of the membrane were determined from the limiting retention of glucose and permeability measurements, respectively. The Donnan Steric Pore Model (DSPM), based on the extended Nernst-Planck equation and a modified Donnan equilibrium accounting for steric effects, was used to characterize the membrane in terms of effective membrane volume charge. It appears that the membrane is positively charged in presence of MgCl₂ and MgSO₄ solutions and negatively charged for KCl and K₂SO₄ solutions. This was attributed to ionic adsorption at the interface membrane/solution.     

新型复合纳滤膜研究进展

纳滤膜因操作压力低、通量高、具有分离选择性以及运行成本较低等优势引起越来越多的关注,目前已在苦咸水脱盐、污水治理和海水淡化等领域发挥着重要作用。界面聚合作为常见的制备聚酰胺纳滤膜的方法,其聚合反应进程的调控可以有效地调节纳滤膜的微观结构,进而对其分离性能产生重要影响。本文从复合纳滤膜的结构入手,总结了当前常用的提升纳滤膜性能的改性方法,包括优化分离选择层、构建中间层、调整底膜结构三个方面,讨论了界面聚合过程反应单体、添加剂种类、制备条件等对分离层结构和分离性能的影响,并分析了底膜的孔径、孔隙率、亲疏水性等理化性质对复合膜性能的影响以及不同类型中间层的优缺点。在此基础上,总结了当前业界内亟待解决的问题,并对纳滤膜的未来发展趋势进行了展望。     

Influence of membrane support structure on the efficiency of an iron-modified silica nanofiltration membrane

Inorganic membranes are generally created by depositing a thin film separation (membrane) layer atop a supporting structure in order to provide for the physical durability of the membrane. The separation layer thickness and morphology are normally evaluated to determine their contribution to fluid flow resistance across the membrane. The supporting structure is often ignored, yet can affect the quality of the membrane formed and significantly influence the global efficiency of the membrane module. In this paper, three different support structures are compared and evaluated with respect to the efficiency (rejection and flux) of an iron-modified silica separation layer. The main difference in the supports was the nominal pore size of the surface responsible for facilitating the membrane layer. The pore sizes of the supports investigated were 5, 10, and 20 nm in diameter. It was hypothesized that the largest pore size support would produce a higher water flux. However, this support did not provide an adequate surface for the deposition of a high quality membrane layer. The formation of an intact membrane layer was successfully achieved using the other two support structures. From the results obtained from salt rejection and flux data of these two functional membrane modules, the influence of the support structure on the overall efficiency of the membrane module was assessed. The 10 nm support structure produced a water flux that was 1.6 times greater than that of the 5 nm pore size support, without sacrificing the rejection of the electrolytes studied.     

Effect of coating and surface modification on water and organic solvent nanofiltration using ceramic hollow fiber membrane

Nanofiltration ceramic hollow fiber membranes were developed to simplify the manufacturing process and improve water and organic solvent permeation performance. The alumina hollow fiber support was prepared by a phase-inversion/sintering method, and a γ-Al₂O₃ sol was coated thereon as a selective layer. Polyvinyl alcohol and ethanol were used as the drying control chemical additive in the coating solution, so that a coating layer could be formed without defects in only one coating step. The coating layer thickness could be adjusted to 0.6–2 μm depending on the coating drawing speed. A sintering temperature of 350 °C was selected to provide both reasonable water permeability (6.91 LMH/bar) and rejection (a molecular weight cutoff of 1000 Da or less) and to form a stable γ-Al₂O₃ phase. In the case of a membrane that was surface-modified with (3-chloropropyl)-trimethoxysilane, the permeability of toluene and hexane was 2.3 and 4.3 LMH/bar, respectively. The newly developed ceramic membrane showed excellent permeability and separation properties, as well as potential effectiveness for organic solvent nanofiltration applications.     

Preparation and performance of novel thermal stable composite nanofiltration membrane

The novel thermal stable composite nanofiltration membranes were prepared through the interfacial polymerization of piperazine and trimesoyl chloride on the poly (phthalazinone ether) ultrafiltration substrate. The effects of polymerization and testing conditions on membrane performance were studied. The surface morphologies of the substrate and the composite membranes were observed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). The separation properties of membranes for dyes and salts were tested. The composite membranes show good thermal stability. The rejection for Na2SO4 was kept over 96%, while the flux reached 400 L·m⁻²·h⁻¹ when it was tested at 1.0 MPa and 80°C. When tested at 1.0 MPa and 60°C, the rejection of the composite membrane for dyes was kept at high level, and the flux reached 180–210 L·m⁻²·h⁻¹, while the rejection for NaCl was lower than 20%. __________ Translated from the Journal of Functional Materials, 2007, 38(12): 2025–2027, 2031 [译自: 功能材料]     

Gradient nanoporous phenolics as substrates for high-flux nanofiltration membranes by layer-by-layer assembly of polyelectrolytes

Thin film composite(TFC) membranes represent a highly promising platform for efficient nanofiltration(NF)processes. However, the improvement in permeance is impeded by the substrates with low permeances. Herein,highly permeable gradient phenolic membranes with tight selectivity are used as substrates to prepare TFC membranes with high permeances by the layer-by-layer assembly method. The negatively charged phenolic substrates are alternately assembled with polycation polyethylenimine(PEI) and polyanion poly(acrylic acid)(PAA)as a result of electrostatic interactions, forming thin and compact PEI/PAA layers tightly attached to the substrate surface. Benefiting from the high permeances and tight surface pores of the gradient nanoporous structures of the substrates, the produced PEI/PAA membranes exhibit a permeance up to 506 L? m~(-2)?h~(-1)?MPa~(-1), which is ～2–10 times higher than that of other membranes with similar rejections. The PEI/PAA membranes are capable of retaining N 96.1% of negatively charged dyes following the mechanism of electrostatic repulsion. We demonstrate that the membranes can also separate positively and neutrally charged dyes from water via other mechanisms.This work opens a new avenue for the design and preparation of high-flux NF membranes, which is also applicable to enhance the permeance of other TFC membranes.     

Fabrication of novel polyethersulfone based nanofiltration membrane by embedding polyaniline-co-graphene oxide nanoplates

Mixed matrix polyethersulfone (PES) based nanofiltration membrane was prepared through phase inversion method by using of polyvinylpyrrolidone (PVP) as pore former and N, N dimethylacetamide (DMAc) as solvent. Polyaniline-co-graphene oxide nanoplates (PANI/GO) were utilized as additive in membrane fabrication. The PANI/GO nanoplates were prepared by polymerization of aniline in the presence of graphene oxide nanoplates. FTIR analysis, scanning electron microscopy (SEM), scanning optical microscopy (SOM), 3D images surface analysis, water contact angle, water content tests, tensile strength tests, porosity tests, salt rejection and flux tests were used in membrane characterization. FT-IR results verified formation of PANI on graphene oxide nanoplates. SOM images showed uniform particles distribution for the mixed matrix membranes. SEM images also showed formation of wide pores for the modified membranes. Water flux showed constant trend nearly by use of PANI/GO in the casting solution. Opposite trend was found for the membrane surface hydrophilicity. Salt rejection was enhanced sharply by utilizing of PANI/GO. The membrane’s tensile strength was improved by increase of PANI/GO concentration. The water content was increased initially by use of PANI/GO nanoplates up to 0.05%wt into the casting solution and then decreased. Membrane porosity was also enhanced by using of PANI/GO nanoplates. Modified membrane containing 0.5%wt PANI/GO nanoplates showed more appropriate antifouling characteristic compared to others.     

Fabrication of polyamide thin film nanocomposite reverse osmosis membrane incorporated with a novel graphite-based carbon material for desalination

The properties of polyamide (PA) thin film composite (TFC) membranes are affected by many variables, especially the additives in the process of interfacial polymerization that play an important role in the properties of membranes. In this study, a new type graphite carbon was added into organic phase containing trimesoyl chloride for interfacial polymerization with aqueous phase containing m-phenylenediamine to prepare modified polyamide thin film nanocomposite (TFN) membranes for reverse osmosis (RO) adhibition. Polysulfone ultrafiltration membranes were used as the carrier of the interfacial polymerization. The concentration of graphite carbon was selected from 0.002 to 0.01 wt%. The polyamide nanocomposite membrane prepared with the concentration of 0.004 wt% graphite carbon showed the best RO desalination performance, which the water flux of this TFN membrane is over 2.3 times as much as pristine TFC membrane, and the salt rejection is over 99%. This article provides a well-performing polyamide thin film nanocomposite membrane modified by a new-type carbon nanoparticles consequently.     

Development of a chlorine‐resistant polyamide nanofiltration membrane and its field‐test results

For the development of chlorine‐resistant nanofiltration membranes, a thin‐film‐composite membrane was prepared by the interfacial polymerization of N‐phenylethylenediamine and 1,3,5‐benzenetricarbonyl trichloride on a microporous polysulfone support substrate. The polymerization on the substrate surface was confirmed by Fourier transform infrared measurements, and membrane surface properties such as the roughness and ζ potential were characterized. Rejections of NaCl and isopropyl alcohol of the prepared membrane were 95 and 50%, respectively. The membrane showed much higher chlorine resistance than a commercial polyamide membrane when the membranes were immersed in an aqueous NaOCl solution. A field test was carried out with a spiral‐type membrane module. Tap water was treated by this module for more than 70 days under the condition of continuous NaOCl injection. The prepared membrane module was quite stable, and no distinguished change in the rejection and flux was recognized. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

磺化聚醚砜/纳米TiO2复合超滤膜制备及其抗污染机理

Membrane fouling is one of the major obstacles for reaching a high flux over a prolonged period of ultrafiltration (UF) process. In this study, a sulfonated-polyethersulfone (SPES)/nano-TiO2 composite UF membrane with good anti-fouling performance was fabricated by phase inversion and self-assembly methods. The TiO2 nanoparticle self-assembly on the SPES membrane surface was confirmed by X-ray photoelectron spectroscopy (XPS) and FT-IR spectrometer. The morphology and hydrophilicity were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle goniometer, respectively. The anti-fouling mechanism of composite UF membrane was discussed through the analysis of the micro-structure and component of UF membrane surface. The results showed that the TiO2 content and the micro-structure of the composite UF membrane surface had great influence on the separation and anti-fouling performance.     

Ionic liquid-induced deep grafting of polyelectrolyte to reform polyamide layer for antifouling nanofiltration membrane

Surface grafting has been widely used to tune hydrophilicity and chargeability of nanofiltration membranes for reducing membrane fouling potential. However, surface grafting typically leads to a significant pore narrowing and resultant permeability loss, and monocharged surface still struggles to resist mixed foulants with different charges. Herein, ionic liquid (IL)-ethanol (EtOH) solution containing polyethyleneimine (PEI) is used to rearrange the nascent polyamide layer. The high affinity of IL to the PA layer and the low diffusion steric hindrance of EtOH contribute to the polyamide swelling and PEI deep grafting, during which the “self-regulation” effect (larger pores would be filled with more PEI molecules) narrows the pore size distribution and enhances hydrophilicity. The nearly charge-neutral and smooth separation layer shows impressive antifouling capacity to hydrophobic macromolecules and mixed charged molecules, along with long-term operating stability for real wastewater treatment. This study emphasizes the importance of solvent properties on the membrane grafting behavior.     

新型纳滤膜回收含镍废水的工业研究

介绍了新型纳滤膜处理高浓度电镀工业含镍废水的应用研究.在操作压力2.2 MPa,进料流量1 800 L/h的条件下,纳滤过程可将镍封漂洗水浓缩至20 000 mg/L以上,平均膜通量大于40 L/(h·m2);Ni2+、有机添加剂及硼酸的平均截留率分别大于99%、90%和35%,微孔剂则被完全截留.60 d工业运行结果表明,浓缩液和透过液分别回用于光亮镍电镀槽及镍封漂洗槽,满足电镀生产要求;单批次操作后用清水循环5 min以及运行5 d后用2%柠檬酸溶液循环30 min,能够有效解决膜面污染问题,达到工业化生产的要求,具有显著的社会效益与经济效应.     

Effect of operating conditions in removal of arsenic from water by nanofiltration membrane

The removal of arsenic from synthetic waters and surface water by nanofiltration (NF) membrane was investigated. In synthetic solutions, arsenic rejection experiments included variation of arsenic retentate concentration, transmembrane pressure, crossflow velocity and temperature. Arsenic rejection increased with arsenic retentate concentration. Arsenic was removed 93-99% from synthetic feed waters containing between 100 and 382 μg/L as V, resulting in permeate arsenic concentrations of about 5 μg/L. Under studied conditions, arsenic rejection was independent of transmembrane pressure, crossflow velocity and temperature. In surface water, the mean rejection of As V was 95% while the rejection of sulfate was 97%. The co-occurrence of dissolved inorganics does not significantly influence arsenic rejection. The mean concentration of As in collected permeated was 8 μg/L. The mean rejection of TDS, total hardness and conductivity were 75, 88 and 75% respectively.