膜蒸馏脱盐中膜污染与膜润湿的研究进展

膜蒸馏作为一种脱盐的新兴技术受到广泛关注。然而,因为实际水质组分复杂,可能含有如表面活性剂、油类物质、易结垢盐和有机溶剂等污染物,导致一般疏水膜在长时间运行情况下极易发生膜污染或者膜润湿,最终造成膜通量或截留性能降低。本文首先简述了不同种类的膜污染和膜润湿的特点及形成原因,并分析了膜污染和膜润湿之间的区别和联系。对膜蒸馏过程中膜污染和膜润湿的监测和预测手段进行了简要介绍,最后针对膜蒸馏脱盐过程,重点介绍了近几年国内外预防膜污染和膜润湿的研究进展。研究者一般从污染物与疏水膜的相互作用力着手对疏水膜进行表面改性制备全疏膜和Janus复合膜,避免污染物在膜面的吸附以及抑制表面或孔道润湿。越来越多的研究人员采用致密亲水膜的渗透汽化脱盐来从根本上避免疏水膜带来的润湿。除此之外,对进料液进行预处理也能显著延迟膜的污染和润湿,如混凝/沉淀、膜过滤、煮沸、pH调控等,还可通过改变进料方式、辅助外加磁场等措施控制膜表面局部区域的流体力学状态,减少污染物的附着。适当的膜后处理措施也能恢复膜性能。最后,文章指出了解决膜蒸馏中膜污染和膜润湿的研究方向。     

陶瓷膜微滤凹凸棒土过程中膜污染的控制和再生

采用阻力系列模型分析了膜污染主要来自凹土在膜表面的沉积,通过Darcy定律过滤模型计算,确定过滤过程的阻力主要来自滤饼层阻力Rg,约占总阻力的85%。实验结果表明,单一的物理、化学清洗方法不能达到理想的清洗效果,采用化学方法和反冲技术相结合的清洗方法,可使膜的纯水通量恢复至新膜的89 %以上,且多次的清洗效果稳定。考察了反冲压力、反冲时间和反冲周期等因素对陶瓷膜微滤凹土浆液强化过程的影响,确定合适的反冲操作条件：反冲压力0. 5 MPa、时间10 s、周期20 min。反冲技术在陶瓷膜微滤过程的膜污染控制和再生环节上起了重要作用,并具有广阔的应用前景。     

Effects of surface force interactions on an NF/UF membrane

Appreciation of a membrane's surface chemistry and steric exclusion character is needed to truly understand and predict membrane performance for specific industrial separations. The interpreter of membrane characterization data must consider both factors in the assessment of separation potential. The test conditions employed will strongly influence the separation data outcome, as will inherent surface force interactions between the membrane and solution components. SEPA CF cell solute challenges and affinity chromatography methods are useful tools to characterize the pore size and surface character of ultrafiltration and nanofiltration membranes.

The characterization data presented demonstrate the separation potential of B-type membranes. For example, the combination of the B-type membrane surface charge and pore size affords economical separations of salts from organics. The anionic surface charge of B-type membranes also makes them competitive for high fouling applications. Dye concentration, paper pulp waste treatment and similar applications appear promising for B-type membranes where traditional membranes are not well suited.     

基于膜表面与界面作用的膜污染控制方法

膜污染控制是膜技术能否成功应用的关键因素之一。讨论了膜面粗糙度、亲水性和荷电性等性质对膜分离性能的影响,介绍了膜表面性质参数的表征方法,分析了颗粒污染物团聚、颗粒与胶体吸附、胶体大分子的变形等对膜污染形成的影响。最后对面向应用过程的陶瓷膜材料表面与界面控制方法进行了总结。膜污染的研究已从操作参数调节发展到表面与界面作用的控制,对提高膜分离性能,促进膜过程在更多领域的推广应用有重要意义。     

Adsorption properties of aromatic compounds on polyethylene as a membrane material

Membrane fouling is an important problem in microfiltration processes. Although the solute adsorption on the membrane is one of the factors inducing membrane fouling, its evaluation is difficult. In this study we have attempted this evaluation using liquid chromatography with polyethylene as the stationary phase. Polyethylene is a common material of a microfiltration membrane. Aromatic compounds were retained significantly by the polyethylene stationary phase, although small amount of solute loading to the column was allowed. The logarithm of the capacity factor (log k′) for aromatic compounds was linearly correlated with the logarithm of 1‐octanol/water partition coefficient (log K_o/w), and this indicated that the main controlling factor for the adsorption is the hydrophobic interaction. We also found that alkyl substituents and the nonplanarity of the molecular structures exerted negative effects for the adsorption. Moreover, evaluation of partition coefficient based on the surface area of the stationary phase revealed that polyethylene could adsorb aromatic compounds as much as 15 to 90 times more than octadecylsilane. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1037–1043, 1999     

反渗透/纳滤膜剖检分析与膜污染诊断研究进展

反渗透（RO）/纳滤（NF）膜元件在长期运行过程中会不可避免地发生膜污染,当产水水质无法满足应用指标时,就需要对膜元件进行更换。膜剖检分析是研究和确定膜污染最直观有效的方法,通过膜剖检分析及膜污染诊断可以为膜元件的日常维护、膜系统运行优化和膜性能修复提供有效依据。但是,目前对于膜剖检分析的实践及膜污染诊断研究还不系统、不全面。本文针对RO/NF膜剖检分析及膜污染诊断相关研究,介绍了膜元件剖检分析流程和各类膜污染分析方法,分析了实际应用中存在的问题,并根据膜剖检分析的意义和价值,重点综述了膜污染成分诊断、膜污染分布情况诊断、不同应用场景膜污染情况对比和不同膜材料的污染情况对比研究进展,以期为膜污染机制研究、膜污染预防控制和膜系统运行改善提供参考。     

阴离子交换膜改性及抗污染性能研究进展

电渗析技术应用于工业废水脱盐时,废水中有机物及其它杂质组分等会造成膜污染,进而影响脱盐性能。电渗析膜污染防治对促进电渗析在工业废水处理中的应用有重要意义。相比于阳离子交换膜,阴离子交换膜更易形成有机污染,且更严重。阴离子交换膜污染主要由腐殖酸、牛血清蛋白、阴离子表面活性剂等有机物造成,污染过程主要受静电作用、亲和作用和几何因素的影响。膜改性提高阴离子交换膜的抗污染性能是电渗析膜污染防治的有效方法,目前已有许多有关膜改性提高阴离子交换膜抗污染性能的报道。膜改性方法主要有化学改性法、等离子体改性法、表面涂覆改性法、电沉积改性法、自聚合改性法及改进基膜结构法等。本工作对阴离子交换膜改性及抗污染性能的研究进展进行了综述,对不同改性方法的优缺点进行了分析和评价。这些改性方法能提高阴膜表面的负电荷密度和亲水性、降低膜表面粗糙度和基膜含水率等,因此可以改善阴离子交换膜的抗污染性能。然而,目前研究获得的改性阴离子交换膜仍存在修饰层不稳定、抗污染性能不理想和性能测试不系统等缺点,需进一步优化改性方法、改性工艺、组分修饰及性能测试等,以获得抗污染性能稳定且效果良好的改性阴离子交换膜。     

Study of humic acid adsorption on nanofiltration membranes by contact angle measurements

Membrane fouling is a major problem, which extent depends on the respective natures of the solute and membrane material. Membrane surface characterization under different fouling conditions may help in understanding the fouling mechanism. Such characterization was performed for the case of humic substances filtered on two nanofiltration membranes, using special contact angles measurements. The measured contact angles allowed the calculation of polar and non-polar contributions to the surface energy of dry, hydrated and fouled membranes. The results reveal significant differences in the two membrane behaviours and information about the way that fouling material may be adsorbed on membrane surface.     

RO membrane solute rejection behavior at the initial stage ofcolloidal fouling

This study investigated the rejection of salt and inert organic compounds by reverse osmosis membranes during the initial stage of colloidal fouling. Results of laboratory-scale experiments showed that colloidal fouling caused a marked decrease in flux, salt rejection and rejection of organics with molecular weight (MW) smaller than about 100 g/mol. Removal of neutrally charged organics was mainly by size or steric exclusion. Rejection of xylose, which has MW >100 g/mol, was not affected much by colloidal fouling. The decrease in salt and low MW organic rejections during the initial stage of colloidal fouling was attributed to cake-enhanced concentration polarization, whereby the colloidal cake layer hindered back diffusion of solutes from the membrane surface to the bulk solution, resulting in higher solute concentration gradient across the membrane. At higher channel wall shear rate, the rates of colloidal deposition, flux decline, decrease in salt rejection, and decrease in low MW organic rejection were lower.     

膜生物反应器中污泥特性对膜污染的影响研究

膜生物反应器(MBR)是膜技术与污水生物技术的组合工艺，与传统污水处理工艺相比具有许多优点，但膜污染目前仍是限制MBR广泛应用的突出问题。有效的膜污染防治技术，可以增加膜通量，增强系统稳定性，减少系统维护和运行费用。在膜过滤过程中，污泥混合液的特性对于膜污染具有重要作用。近年来围绕污泥特性对膜污染的防治问题取得了许多研究成果，膜污染的数学模型研究也得到了很大发展。     

Surface modification of polypropylene membrane by low‐temperature plasma treatment

Microporous polypropylene membranes were low temperature plasma treated with acrylic acid and allylamine. Parameters of plasma treatment were examined and optimized for the enhancement of membrane performance properties. Excess power damaged the membrane surface and excess monomer flow rate increased the reactor pressure to interfere with the glow discharge. Longer plasma treatment time resulted in even more plasma coating and micropore blocking. The contact angle with water decreased and wettabilities increased with the increase of plasma treatment time. Deposition of the plasma polymer on the membrane surface was confirmed by FTIR/ATR spectra of the treated surface. In determining the flux, the hydrophilicity of the surface played a role as important as that of the micropore size. Adequate plasma treatment could enhance both water flux and solute removal efficiency. Results from the BSA (bovine serum albumin) solution test confirmed that fouling was greatly reduced after the plasma treatment. The BSA solution flux through the plasma‐treated membranes depended on pH, whereas pH variation had no serious effects on the untreated membrane. Modification of the surface charge by the plasma treatment should exert a substantial influence on the adsorption and removal of BSA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1555–1566, 2001     

Polymer adsorption on multicomponent surfaces with relevance to membrane fouling

Block copolymer thin films that include low surface energy domains are analyzed as a possible way to overcome the problem of membrane fouling by proteins and other natural organic matter. A model is presented that accounts for both fouling due to chemical interactions between the solute and surface and due to convective deposition. Guidelines for the formation of novel membranes with improved fouling-resistant properties are suggested based on comparison of the relative permeate flux decline due to fouling on different model copolymer membranes. In general, it is observed that copolymer films having small and dispersed polymer blocks that interact unfavorably with the fouling species show an overall decrease in fouling and increase in permeate flux compared with the homopolymer films.     

Green and feasible fabrication of loose nanofiltration membrane with high efficiency for fractionation of dye/NaCl mixture by taking advantage of membrane fouling

Loose nanofiltration membrane emerges as required recently, since it is hard for conventional nanofiltration membrane to fractionate mixture of dyes and salts in textile wastewater treatment. However, the polymeric membranes unavoidably suffer from membrane fouling, which was caused by the adsorption of organic pollutants (like dyes). Normally, the dye fouling layer will shrink membrane pore size, thus resulting in flux decline and rejection increase. It is thought that membrane fouling may be a double-edged sword and can be an advantage if properly utilized. Thereby, loose nanofiltration membranes were constructed here by a green yet effective method to fractionate dyes/salt mixture by taking advantage of membrane fouling without using poisonous ingredients. A commercially available polyacrylonitrile (PAN) ultrafiltration membrane with high permeability was chosen as the substrate, and dyes were used to contaminate PAN substrate and formed a stable barrier layer when adsorption of dyes reached dynamic equilibrium. The resultant PAN-direct red 80 (DR80) composite membranes displayed superior permeability (~128.4 L m⁻² h⁻¹) and high rejection (~99.9%) to DR80 solutions at 0.4 MPa. Moreover, PAN-DR80 membranes allowed fast fractionation of dyes/sodium chloride (NaCl) mixture, which maintained a negligible dye loss and a low NaCl rejection (~12.4%) with high flux of 113.6 L m⁻² h⁻¹ at 0.4 MPa. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47438.     

Sulfonated polyethersulfone by heterogeneous method and its membrane performances

Polyethersulfone was sulfonated by heterogeneous method with chlorosulfonic acid. Ion exchange capacity was controlled to 0.68 meq/g to reduce fouling. Sulfonation was confirmed by Fourier transform infrared spectroscopy and ¹H‐nuclear magnetic resonance. Polyethersulfone and sulfonated polyethersulfone ultrafiltration membranes were prepared successively by the typical phase inversion method. Membrane performance of sulfonated polyethersulfone was compared with that of polyethersulfone. In the preparation of ultrafiltration membranes, the effect of the addition of dichloromethane and poly(vinyl pyrrolidone) in a casting solution was investigated on the membrane performance. It was observed that the addition of dichloromethane increased the solute rejection rate. By changing the ratio between polymer and poly(vinyl pyrrolidone), membrane performance could be controlled. Negatively charged sulfonated polyethersulfone could reduce fouling at higher or lower pH than isoelectric point of protein bovine serum albumin. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2046–2055, 1999     

膜法制备乳状液研究进展

膜法制乳是靠膜两侧的压差使分散相通过微孔膜,以小液滴的形式分散在连续相中而形成乳状液的方法。与转-定体系、高压均化等传统方法相比,该法液滴尺寸均一、节能、剪应力小,可应用于化妆品、食品、医药等领域,其中一些应用已经工业化。液滴从膜孔中形成和分离依赖于各种过程参数(如过膜压差、膜表面连续相的剪切应力)、膜材料和结构。很多实验研究集中在膜乳化过程参数的影响上,膜乳化过程的机理尚需进一步完善。     

Characterization of cation‐exchange membrane fouling during bipolar membrane electrodialysis of monosodium glutamate isoelectric supernatant

BACKGROUND: A novel procedure that involved regeneration and recycling of ammonia and sulfuric acid from monosodium glutamate isoelectric supernatant with bipolar membrane electrodialysis (BMED) was proposed. As the performance of the membranes deteriorated during the batch runs, fouling of the cation‐exchange membrane (CEM) in contact with the base cell was studied. RESULTS: During ten consecutive batches of BMED, some operating parameters deteriorated gradually. Using scanning electron microscopy observations, fouling deposits were found on the CEM surface on the base cell side. Using Fourier transform infrared spectroscopy and reversed‐phase high‐performance liquid chromatography (RP‐HPLC), the organic fouling fraction of the CEM foulants was found to contain eight amino acids. Using X‐ray energy‐dispersive analysis, the mineral fouling fraction was shown to be mainly O and Ca elements, and a little Mg. Using X‐ray diffraction, the inorganic foulant was identified as CaCO₃, mainly in the form of calcite and a little aragonite. CONCLUSION: The CEM was subject to membrane fouling consisting of an organic fouling fraction and a mineral fraction. The organic fraction occurred as ions with some positive charges from the isoelectric supernatant and probably existed in the form of amino acids or their peptides. The mineral fraction was mainly CaCO₃ calcite and aragonite, and probably a little amorphous Ca and Mg hydroxides. Copyright © 2011 Society of Chemical Industry     

往复旋转管式陶瓷膜超滤脱脂奶水溶液的研究

往复旋转管式陶瓷膜过滤系统通过膜组件往复旋转在膜表面反复产生高剪切率,达到减缓膜污染的效果。在相同操作条件下,与单向旋转过滤和死端过滤相比较,往复旋转过滤具有更好的减缓膜污染的作用。本实验利用往复旋转膜过滤装置超滤脱脂奶水溶液,考察了各种参数对该膜系统过滤特性的影响。实验结果表明,料液浓度增大,膜通量减小;过高的操作压差将会抑制膜通量增加;旋转速度增大,膜表面剪切强化作用增强,膜通量相应增大;膜稳态通量随往复旋转周期增大呈现先增大后减小的趋势。当料液速度达到膜组件转速时,瞬时反方向旋转膜组件,膜表面产生最大的剪切率,膜稳态通量也达到最大值。能耗分析表明,往复旋转过滤较单向旋转过滤单位通量能耗低。     

Modified polyether-sulfone membrane: a mini review

Polyethersulfone has been widely used as a promising material in medical applications and waste-treatment membranes since it provides excellent mechanical and thermal properties. Hydrophobicity of polyethersulfone is considered one main disadvantage of using this material because hydrophobic surface causes biofouling effects to the membrane which is always thought to be a serious limitation to the use of polyethersulfone in membrane technology. Chemical modification to the material is a promising solution to this problem. More specifically surface modification is an excellent technique to introduce hydrophilic properties and functional groups to the polyethersulfone membrane surface. This review covers chemical modifications of the polyethersulfone and covers different methods used to enhance the hydrophilicity of polyethersulfone membrane. In particular, the addition of amino functional groups to polyethersulfone is used as a fundamental method either to introduce hydrophilic properties or introduce nanomaterials to the surface of polyethersulfone membrane. This work reviews also previous research reports explored the use of amino functionalized polyethersulfone with different nanomaterials to induce biological activity and reduce fouling effects of the fabricated membrane.     

Evaluation of membrane fouling and flux decline related with mass transport in nanofiltration of tartrazine solution

BACKGROUND: This work was carried out to investigate and analyze the interrelated dynamics of mass transport, membrane fouling and flux decline during nanofiltration of tartrazine. A combined application including pore diffusion transport model and a material balance approach was used to model an experimental flux data obtained from different values of pH (3, 5, 7 and 10), feed‐dye concentration (25, 100 and 400 mg L^?1), and transmembrane pressure (1200, 1800 and 2400 kPa). RESULTS: Almost 100% dye solution removal and a permeate flux of 135 L m^?2 h^?1 were obtained for 25 mg L^?1 and 1200 kPa at pH 10. At pH 10, lower membrane fouling was obtained due to the increase of electrostatic repulsion between anionic dye molecules and the more negatively charged membrane surface. Flux decline and membrane fouling increased together with transmembrane pressure and dye concentration. Fouling was found to be directly related to proportional‐permeation coefficient (k_O′) of dye which was identified as the solute passing into the permeate with respect to the amount transported into the membrane from the feed. CONCLUSIONS: For a decrease of pH (10 to 3) and transmembrane pressure (2400 to 1200 kPa) or an increase of feed‐dye concentration (25 to 400 mg L^?1), fewer dye molecules passed into the permeate with respect to the amount transported into the membrane from the feed. This situation depended mainly on the combined influences of the gel layer and fouling in the membrane. Copyright © 2010 Society of Chemical Industry     

膜生物反应器中膜污染控制技术的研究进展

膜污染是膜生物反应器(MBR)运行的必然结果,是MBR大面积推广的严重阻碍,因此研究膜污染控制技术具有重要意义。从膜污染发生前的预防和膜污染发生后的清洗2个方面,论述了常见的各种膜污染控制手段,综述了膜污染控制技术的研究现状与进展。其中膜污染的预防手段主要有膜(膜组件)固有性质的改进、操作条件的优化以及混合液性状的调控3类,而膜污染的清洗手段按是否使用药剂可分为物理清洗和化学清洗2类。综合考察MBR运行中的膜污染状况,采用合理的方法对膜污染进行控制,能够有效延长膜的使用寿命,提高MBR的实用性能。