纳滤和电渗析对浓海水一二价离子的分离性能

采用纳滤及一价选择性离子交换膜电渗析2种方法对模拟浓海水进行分离浓缩,探索一、二价离子(Na~+/Mg~(2+),Cl~-/SO_4~(2-))的分离效果.实验表明,DL2540膜对二价离子的截留性能优于NF270膜,在2.1 MPa压力、浓侧流量为300 L/h的条件下,对Mg~(2+)和SO_4~(2-)的截留率分别达98.1%和80.5%,分离因子为2.5和40.0.一价离子选择性电渗析膜对阴离子Cl~-和SO_4~(2-)的分离效果明显好于阳离子Na~+和Mg~(2+),Na+回收率为90%时,选择性迁移比分别为18.4和2.9.纳滤和选择性电渗析对一、二价离子都有较好的分离效果,电渗析离子分离的同时可实现浓缩,而纳滤对一价离子几乎无浓缩效果.     

电渗析脱盐过程离子传递现象的数值模拟

建立了电渗析脱盐过程离子传递稳态模型，研究了离子电荷数、离子扩散系数和离子交换膜电导率对脱盐过程传质的影响，描述了离子浓度分布、电势分布和离子传递通量分布的变化情况。研究表明：相较于一价离子，二价离子在电渗析过程中膜两侧浓度差较小，跨膜电压降较高，各项传递通量较小；当离子扩散系数增大时，膜两侧浓度差减小，跨膜电压降升高，总传递通量和电迁移通量增大；当离子交换膜电导率增大时，膜两侧浓度差增大，跨膜电压降降低，各项传递通量均增大。     

m（SA-CS）双极膜在盐湖卤水离子分离中的应用

海藻酸钠经二价钙离子改性后作为阳膜层,用戊二醛改性壳聚糖制备了阴膜溶胶,将阴膜溶胶流延于阳膜层上,制备了Ca2＋-SA/戊二醛-CS双极膜m（SA-CS）BPM。测定了双极膜的红外光谱、热重分析和机械性能。将m（SA-CS）BPM应用于从盐湖卤水提取锂,二价离子的透过率均小于2%,而一价离子的透过率均大于20%。表明该双极膜能够有效分离卤水中的一价、二价金属离子。     

一/二价离子分离膜材料研究进展

一/二价离子分离膜在能源存储和转换、污染监测和控制、清洁工业过程等领域发挥重要作用。本文旨在回顾近年来一/二价离子分离膜材料的研究进展,重点综述聚合物膜、混合基质膜及金属有机骨架和二维材料等新型膜用于一/二价离子分离的研究现状,深入讨论界面聚合、层层组装、沉积、共混等不同制备方法对膜微结构和分离性能的影响,探讨一/二价离子分离膜面临的主要挑战和未来研究方向。     

导电聚合物改性阳离子交换膜提高一价离子选择性

对近年来导电聚合物改性阳离子交换膜的研究进行了综述和分析。导电电子聚合物与离子交换膜合成复合材料,在电渗析过程中增强离子的选择性。离子交换膜电渗析最重要的一个应用是从湿法冶金废酸液和电镀废水中回收强酸,这些过程的溶液通常含有多价金属离子,因此需要使用能优先选择透过一价阳离子的特定阳离子交换膜。而在电渗析法海水浓缩时,只有优先通过一价离子,阻止二价离子通过,才能有效提高脱盐率和电流效率,避免形成硫酸钙沉淀,以减轻膜污染和保证电渗析器长期稳定运行。显然,实现上述两个过程要求的一个有效途径是赋予阳离子交换膜一价离子选择性。因此,研究提高阳离子交换膜对阳离子间选择性的各种改性方法很重要。     

国产纳滤膜对无机盐截留性能的研究

通过对苦咸水中常见阳离子Mg~(2+)、Ca~(2+)、Na~+和阴离子HCO_3~-、SO_4~(2-)、Cl~-构成的单组分溶液以及双组分(同阴离子和同阳离子)混合溶液进行分离截留实验,研究对比国产纳滤膜NF1和VNF2对离子的截留性能以及同种电荷离子间的相互影响。结果表明,在单组分溶液中,荷负电膜NF1和VNF2对阳离子截留顺序相同为Mg~(2+) Ca~(2+)Na~+;对阴离子截留顺序则因电黏滞效应引起纳滤膜孔径变化的影响不同,对NF1为HCO-3~-SO_4~(2-)Cl~-,对VNF2为SO_4~(2-)HCO_3~-Cl~-。在混合溶液中,2价离子会阻碍单价离子的去除。在处理无机盐方面,VNF2膜的截留性能优于NF1膜,特别是单价离子;同种电荷离子之间相互影响不同,扩散系数差别越大,同种电荷离子间相互影响越大。     

无机盐对聚二甲基硅氧烷/陶瓷复合膜渗透汽化性能的影响

将渗透汽化应用于醇/水体系的分离,具有诸多显著的优势。然而,目前的研究大都基于二元体系,而实际的应用体系是多元的,还包含少量无机盐和糖类等,它们的存在对膜的性能具有一定的影响。本文研究了NaCl、KCl和MgCl2 3种无机盐的加入对聚二甲基硅氧烷 （PDMS）/陶瓷复合膜渗透汽化性能的影响。结果表明,在313 K,无机盐的加入使复合膜的分离因子和通量均有所提高。其中二价盐MgCl2对渗透汽化性能的影响最为显著,分离因子最大提高到醇/水体系的2.8倍。而一价盐NaCl和KCl的加入,使分离因子分别提高为醇/水体系的2.5倍和2.4倍。同时借助于Setschenow扩展方程计算了乙醇活度,对实验结果进行了初步的解释。     

填充床电渗析器制备纯水的研究

本文介绍了离子交换树脂在填充床电渗析器中的脱盐及电再生机理，实验研究了一价离子及二价离子在设备内的操作参数。一价离子与二价离子相比，树脂使用周期长，操作范围宽，对于一价离子，树脂可在低电压下（〈２５Ｖ）再生，在较高电压下（〉２５Ｖ），树脂内的一价离子及二价离子均可再生。操作电流应略大于极限电流，以保护产水质量。     

纳滤技术在油田调驱配聚中的应用进展

纳滤(Nanofilitration,NF)是一种新型分离技术,对二价离子具有高截留的特性,可分离大部分油田水中的二价离子,如Ca2+、Mg2+、Ba2+、CO32-、SO42-等成垢离子.用纳滤技术处理后的注入水配聚,可减少高价离子对聚合物凝胶的影响.介绍了纳滤处理油田采出水的原理,油田采出水特性,以及纳滤软化注入水...     

反渗透及其在工业废水处理中的应用(下)

(2)膜的透过特性:醋酸纤维膜对无机盐类的去除性(一价离子为90％以上,二价离子为95％以上),一般离子价愈大者愈容易分离,又对同离子价中水合离子半径愈大者愈容易去除。海水中溶存离子的非透过性顺序为Mg~(2+)>HCO_3~->Na~+>K~+>Cl~+>Br~-。对分子半径大于4.5(?)的分子,几乎能完全分离,有分子筛的作用。盐的透过度如表3。     

Fabrication of anti-fouling polyamide nanofiltration membrane by incorporating streptomycin as a novel co-monomer

Polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membrane has extremely broad application prospects in separation of monovalent/divalent inorganic salts mixed solution. However, membrane fouling is the main obstacle to the application of PA, TFC and NF membrane. Streptomycin (SM) is a hydrophilic antibiotic containing a large number of hydroxyl and amino groups. In this work, the NF membrane was prepared via interfacial polymerization (IP) between trimesoyl chloride (TMC) in the organicphaseand SM/piperazine (PIP) mixture in theaqueousphase. The NF membrane structure and performance were characterized in detail. The results showed that SM successfully participated in the IP. The negative charge and hydrophilicity of membrane surface were improved. The prepared membrane exhibited good anti-adhesion and anti-bacterial performance. Additionally, when the SM concentration was 2%, the prepared membrane exhibited the optimal permselectivity. The water permeance was 89.4 L·m^-2·h^-1·MPa^-1. The rejection of NaCl and Na₂SO₄ were 17.17% and 97.84%, respectively. The NaCl/Na₂SO₄ separation factor of the SM2-PIP/TMC membrane in 1000 mg·L^-1 NaCl and 1000 mg·L^-1 Na₂SO₄ mixed solution was 40, which was 3.3 times that of PIP/TMC membrane. It indicated that SM2-PIP/TMC demonstrated excellent monovalent/divalent salts separation performance. This work provided an easy and effective approach to preparing anti-fouling NF membrane while possessing superior monovalent/divalent salts separation performance.     

Removal of metal ions from an acidic leachate solution by nanofiltration membranes

This paper presents the feasibility of the application of two commercial nanofiltration (NF) membranes (Desal5 DK and NF-270) in the removal of metal ions from an acidic leachate solution generated from a contaminated soil using H₂SO₄ as a soil washing agent. The experimental results of soil washing indicated that H₂SO₄ is highly effective in removing metal ions from contaminated soil. Following this process, the treatment of this acidic solution by nanofiltration membranes showed good metal ion rejection (between 62% to 100%) where divalent ions were better rejected than monovalent ions. For characterization purposes, the membrane experiments were conducted using K₂SO₄ solutions at different pHs. Membrane performance criteria were evaluated according to membrane permeability and ionic retention in the tank and permeate, taking into account different operating conditions such as pressures, flow rate and pH. These results demonstrated the effectiveness and feasibility of the application of nanofiltration treatments in the cleaning-up of contaminated water residues generated during soil washing processes.     

Rejection of salt mixtures from high saline by nanofiltration membranes

Nanofiltration (NF) membranes have recently been employed as pretreatment unit operations in seawater desalination processes and as partial demineralization to seawater. The present paper investigates the performance of selected commercial NF membranes to reject salts of high concentrations at salinity levels representative of brackish and sea water. Two commercial nanofiltration membranes (NF90 and NF270) have been investigated in detail to study their performance in filtering aqueous solutions containing different salt mixtures in a cross-flow NF membrane process within the pressure range from 4 to 9 bar. Spiegler-Kedem model (SKM) was used to fit the experimental data of rejection with the permeate flux. The results showed that NF90 membrane was shown to have a distinct ability to reject both monovalent and divalent ions of all investigated mixtures with very reasonable values but with relatively low flux. This will make NF90 more suitable for the application in the pretreatment of desalination processes. On the other hand, NF270 can reject monovalent ions at relatively low values and divalent ions at reasonable values, but at very high permeate flux. The SKM model only fitted well the experimental data of divalent ions in salt mixture. Based on the evaluation of the overall performance of NF90 and NF270 membranes, their distinct ability to reject salts at high salinity from seawater is considered an advantage in the field of pretreatment of seawater feed to desalination units.     

Performance of Nanofiltration Membranes in the Treatment of Synthetic and Real Seawater

Abstract

Nanofiltration membranes (NF) are being employed in pretreatment unit operations in both thermal and membrane seawater desalination processes and as partial demineralization to seawater. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against seawater is presented in this paper. Two commercial nanofiltration membranes (NF90 and NF270) have been investigated in details to study their performance in filtering the salt mixture, synthetic and real seawater in a cross‐flow NF membrane process at a pressure range from 4 to 9 bars. The Spiegler‐Kedem model was used to fit the experimental data of rejection with the permeate flux in order to determine the fitting parameters of the reflection coefficient (σ) and the solute permeability (P_s). The results showed that the rejection increases with pressure for NF90 and slightly increases with pressure for NF270. Also, the NF90 membrane has shown to be able to reject both monovalent and divalent of all investigated mixtures and seawater with very reasonable values but at a relatively low flux. Moreover, it reduced the salinity of investigated seawater from 38 to 25.5 g/L using one stage of the NF membrane at 9 bars. This makes NF90 more suitable for the application in the pretreatment of desalination processes. On the other hand, NF270 can reject monovalent ions at relatively low values and divalent ions at reasonable values. It has also reduced the seawater salinity to 33.6 g/L, but at a very high permeate flux. The SKM model fitted the experimental data of divalent ions in salt mixture and seawater.     

利用纳滤膜分离精制饱和卤水的研究

针对饱和卤水直接制碱过程需要去除硫酸根、钙离子、镁离子（SO₄^2-、Ca²⁺、Mg²⁺）等杂质离子的问题,探索了利用纳滤膜分离精制饱和卤水新工艺。通过考察NF270、DL2540、ESNA1 3种类型纳滤膜的透过通量和离子截留率,确定了选用DL2540为实验用膜;分析了DL2540纳滤膜对离子的截留性能和对盐田饱和卤水的分离性能及其对饱和卤水精制的效果。结果表明,增加同离子浓度、降低压力有利于不同价态阳离子、阴离子间的分离,DL2540纳滤膜对盐田饱和卤水中SO₄^2-、Ca²⁺、Mg²⁺截留率分别达到95%以上、30%~50%、30%~70%,对Na⁺、Cl^-截留率均低于15%,进一步证明DL2540纳滤膜具有较好的稳定性和二价离子截留效果,在饱和卤水精制上展示出较好的应用前景。     

纳滤—电渗析处理纤维染色废水反渗透浓水研究

针对反渗透处理纤维染色废水过程中产生的高COD、高色度和高盐含量浓水,研究采用纳滤-电渗析集成技术对其进行脱色、一二价盐分离和盐浓缩中试。结果表明,纳滤膜NF5和NF4分别用于废水脱色和分盐,经过2级纳滤处理后废水色度降低至原水的1/1200,COD从原水的200 mg/L降低至小于100 mg/L,Cl^-和SO4^2-离子的质量浓度比从原水的3:2提高到21:1。电渗析可将纳滤膜NF4透过液中的总溶解盐浓缩至质量分数10%以上。盐浓缩液可重新用于染色,染色效果良好。表明该集成技术在纤维染色废水的深度处理上具备良好的工业化应用前景。     

高浓度含盐草甘膦溶液的纳滤分离实验研究

为了考察纳滤技术分离含高浓度单价盐的草甘膦溶液的可行性,采用商业化Desal-DK纳滤膜对含有高浓度NaCl的草甘膦溶液开展了分离实验研究和模拟计算。首先研究了物料浓度、跨膜压差等因素对NaCl和草甘膦的单组分溶液的体积通量及截留率的影响,并通过拟合SK（Spiegler-Kedem）方程计算得到了膜的特征参数;其次探究了Desal-DK纳滤膜对高浓度NaCl和不同浓度草甘膦混合溶液的分离效果,实验结果说明Desal-DK纳滤膜对NaCl呈现较高的透过性,而对草甘膦则呈现较高的截留性,从而能够有效实现草甘膦和NaCl的分离;最后通过对含有100 g/L NaCl和1 g/L草甘膦的混合溶液进行预浓缩-连续恒容渗滤过程的模拟计算,得到了较高浓度的草甘膦溶液和相对较纯的NaCl溶液,证明通过纳滤渗滤过程实现含草甘膦浓盐水的资源化利用是可行的。     

Preparation and characterization of high‐selectivity hollow fiber composite nanofiltration membrane by two‐way coating technique

A novel coating technique, named as two‐way coating (TWC), was explored to prepare hollow fiber composite (HFC) nanofiltration (NF) membrane through interfacial polymerization from piperazine (PIP) and trimesoyl chloride (TMC) on the lumen side of hollow fiber polysulfone ultrafiltration membrane with an effective membrane area of 0.4 m². The optimum preparation conditions were systematically investigated and obtained as follows: PIP 0.023 mol/L, TMC 0.0057 mol/L, air blowing rate 2.7 m/s for 30 min after aqueous coating, aqueous coating pressure 0.1 MPa, organic solution flowing rate 0.32 m/s, and heat treating time 3 min. The resultant HFC membrane showed a high selectivity of divalent ion and monovalent ion. Salt rejections of MgSO₄ and NaCl were 98.13 and 18.6% with the permeate flux of 32.6 and 40.2 L m^?2 h^?1 at 0.7 MPa, respectively. Field emission scanning electron microscopy images indicated that composite membrane prepared by TWC technique had a uniform active layer from the upper end to the bottom of the hollow fiber. And the salt rejection and permeate flux showed almost no difference between different membrane sections. Stability results suggested that good reproducibility could be obtained by TWC technique for the preparation of high‐performance HFC NF membrane. The resultant NF membrane showed a high removal rate of chemical oxygen demand and chroma of landfill leachate which were approximately 100%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41187.     

天然有机物对纳滤水处理工艺的影响

天然有机物（NOM）广泛存在于天然水体中,对纳滤处理过程产生较大影响。该文在介绍NOM的组成和物化性质的基础上,讨论了NOM对截留率和膜通量的影响,阐述了纳滤过程中NOM的亲、疏水性,浓差极化效应,静电排斥作用,氢键作用,二价离子络合等对纳滤过程的影响机理,对提高纳滤膜过滤性能有重要意义。     

耐溶剂纳滤膜的制备与应用研究进展

有机溶剂纳滤(organic solvent nanofiltration,OSN)是近年来快速发展起来的一项新型纳滤膜分离技术,具有广阔的应用前景。耐溶剂纳滤(solvent-resistant NF,SRNF)膜的制备是OSN技术发展的关键,也是目前的研究热点之一。本文侧重阐述了SRNF膜在制备及应用方面的进展,着重介绍了相转化法、界面聚合法、自组装法及有机-无机杂化法等SRNF膜制备方法。相转化法是目前国内外SRNF膜制备研究常用的方法,但该法所制备的膜皮层较厚,通量明显偏小;界面聚合法SRNF膜制备的相关研究目前较少,但由于其皮层非常薄,因此是SRNF膜制备发展的一大趋势;自组装膜有较好的耐溶剂性能;加入无机物可以提高耐有机溶剂性,有机-无机杂化法的膜制备是SRNF膜制备的趋势之一。同时简单介绍了SRNF膜的应用,并对未来SRNF膜研究的方向提出了建议。