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.     

Application of membrane processes in closing of water cycle in a textile dye-house

In this study, investigations were made to close water cycle in dye-houses. At the first stage, optimum operation conditions of a membrane nanofiltration were determined. Experiments were carried out for DL membranes (Osmonics, USA). The effect of temperature, pressure and pH was investigated. Investigations were performed for different types of real wastewater produced in a laboratory-scale Pyrotec S dyeing apparatus (Roaches) for various types of reactive dyes. An over 90% dye hold-up was obtained for all dye baths.At the final stage of the experiments, dyeing processes were carried out with the use of a filtrate from nanofiltration as water applied for dyeing, rinsing and washing after dyeing. In cooperation with the Technical University of Lodz, we have managed to apply biological degradation of the concentrate, carried out in two different reactor systems.     

Influence of dyes, salts and auxiliary chemicals on the nanofiltration of reactive dye baths: experimental observations and model verification

The aim of this study was to investigate the effects of dyes, salts and auxiliary chemicals in reactive dye baths on the separation performance of nanofiltration membranes. A reactive dye bath was simulated for this purpose with auxiliary chemicals. A DS5-type nanofiltration membrane was used in the experimental runs. Performance of the nanofiltration membrane was evaluated by measuring permeate flux, salt and color rejections in five steps. Reactive black 5, reactive orange 16, NaCl, NaOH, Na₂SO₄, acidic acid, mollan and slipper were used to prepare synthetic dye baths. Pressures in the range of 8 to 24 bars were applied, and flow velocity was kept constant at 0.74 m/s. NaCl rejection of 20% and color rejection of more than 95% were achieved throughout the experiments. Permeate quality was satisfactory enough to recycle these effluents in reactive dyeing. Acidification ofthe original synthetic dye bath solution with HCl and H₂S0₄ decreased the membrane fouling and also increased the NaCl recovery and color rejection. Besides, using HCI instead of H₂SO₄ increased these positive effects. The effects of auxiliary chemicals were determined by using salt rejection model parameters of α and k_D in the presence of an organic ion. There was a correlation among the results of experiments and the model. The model parameters (α and k_D were also calculated for all steps.     

Advances in Polymeric Nanofiltration Membrane: A Review

The nanofiltration membrane was first introduced during late 1980s possessing properties between reverse osmosis and ultrafiltration membrane. Nanofiltration membranes have been used for applications including food industry, pharmaceutical, wastewater treatment, and desalination. This review presents an inclusive outlook of recent research and advances in polymeric nanofiltration membrane technology. Various methods were reported for nanofiltration membrane preparation particularly through electron beam irradiation, UV/photografting, layer by layer, plasma treatment, interfacial polymerization, and nanoparticle incorporation. Nanofiltration membranes were reported to remove microorganisms, turbidity, dissolved salts, and hardness. Major problem in application is nanofiltration membrane fouling, thus efforts regarding fouling mitigation are discussed.     

膜技术在饮用水除砷中的应用研究进展

以低压驱动膜的微滤膜(MF)与超滤膜(UF),和高压驱动膜的反渗透膜(RO)与纳滤膜(NF)为主,分析了目前国内外膜技术在饮用水除砷方面的效果、影响因素、浓水处理、膜污染及其清洗等方面的应用研究和进展情况,同时对膜技术优缺点及其在除砷中的应用研究方向与前景做了展望.     

Peroxopolyoxometalate nanoparticles blended PES membrane with improved hydrophilicity,anti-fouling,permeability, and dye separation properties

Poly(ethersulfone) (PES) is one of the polymers most widely used for the fabrication of ultrafiltration or nanofiltration membranes in various applications, but its membrane suffers from fouling. In this study, preparation, characterization, and performance of PES nanocomposite membrane comprising peroxopolyoxometalate nanoparticles was studied to provide improved permeability and anti-fouling properties. The high oxygen ratio of the PW₄ nanoparticles could enhance the hydrophilicity of the membranes. The PW₄ nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction analyses. The mixed matrix membranes were fabricated using a non-solvent induced phase-separation method. The fabricated membranes were characterized using atomic force microscopy, attenuated total reflection, SEM, EDX mapping, total average porosity, thermogravimetric analyze, and water contact angle experiments. The dye flux and rejection, pure water permeability and anti-fouling properties of the membranes were investigated. All of the membranes blended by different contents of the PW₄ nanoparticles presented better performance compared to the unmodified membrane. The filtration performance of the membranes in reactive green 19 (RG19) and reactive yellow 160 (RY160) dye separation showed that all of the PW₄ blended membranes possessed dye rejection greater than 86% and 96% for RY160 and RG19, respectively. The reusability test using bovine serum albumin (BSA) protein and RG19 dye solutions in five cycle experiments presented good reproductivity of the PW₄ blended membranes. The PES membrane containing 1 wt% of PW₄ nanoparticles showed the highest flux recovery ratio (75%) as well as reduced irreversible fouling ratio (8%) through BSA protein filtration.     

Treatment of effluents from textile-rinsing operations by thermally stable nanofiltration membranes

Thermally stable nanofiltration membranes were used to recover hot water from rinsing effluents from acid and reactive dyeing operations. Two types of flat-sheet membranes, MPF-34 (MWCO 200) and MPF-36 (MWCO 1000), were tested at 60°C and 10 bar. Experiments carried out with the made-up feeds containing acid dye and acetic acid showed that both membranes were able to retain more than 99% of dye. MPF-36 suffered from substantial flux decline due to the dye and acid in the feeds but still provided higher fluxes than MPF-34. Furthermore, reactive dye rejection of MPF-36 was acceptable, ranging from 97 to 99.5%, while the fluxes, 105-140 1/m².h, were exceptionally high. MPF-36 was then further tested with the wastewater from industrial processes. The membrane could recover hot water by removing more than 98% of acid dye and 90% of reactive dyes. Despite severe fouling by acid dye, the membrane was still able to provide 40-50 1/m².h of permeate fluxes. For the reactive dye rinsing effluents, remarkably high fluxes of 120-1501/m2.h were obtained. Chemical cleaning of the used membrane with 0.2% wt. HNO₃ and subsequently 0.5% wt. NaOH recovered 80-100% of the flux.     

纳滤膜及其在水处理中的应用

纳滤膜具有筛分效应和电荷效应两个显著特性,能截留大分子量有机物和多价离子,而允许小分子有机物和单价离子通过。对于纳滤膜的分离机理,提出了非平衡热力学模型,电荷模型,静电排斥和立体位阻模型。根据纳滤膜特有的性质,介绍了其在水处理领域包括水的软化、脱除饮用水中有害物质、废水处理三个方面的应用,并分析了纳滤膜污染的机理以及防止措施。     

膜法绿色制糖技术研究进展

介绍了膜法绿色制糖技术在实验室、现场中试和示范工程方面的研究进展,对甘蔗压榨汁的澄清、脱色和浓缩提纯过程中的选膜研究进行了综述,分析比较了陶瓷膜和有机膜的优劣,重点介绍了膜浓缩液中残糖回收、膜污染机理及清洗策略,展望了膜法绿色制糖技术工业化亟需解决的问题.     

Interaction mechanisms associated with organic colloid fouling of ultrafiltration membrane in a drinking water treatment system

The Extended Derjaguin Landau Verwey Overbeek (XDLVO) approach was introduced to predict organic colloid fouling of membranes in an initial ultrafiltration (UF) phase. Two polymeric UF membranes, made of polyvinylchloride (PVC) and polyvinylidene fluoride (PVDF) respectively, were selected to investigate membrane fouling by filtering water samples with different organic colloid compositions. The experiment was performed to determine the fouling contributions of van der Waals (LW) interactions, electrostatic (EL) interactions, as well as double layer and short-range acid–base (AB) interactions, to the total interaction energy caused by organic colloids attaching to UF membrane surfaces. The results showed that LW interaction energy predominated when the distance between the membrane surface and organic colloid was > 5 nm, while AB accounted for a key contribution to total interaction energy over short distances (< 2.5 nm). The influence of EL interaction energy was ignored in the total interaction energy composition. The surface energy, among all characteristics of membrane material, was a dominant factor affecting membrane fouling. The experimental results of initial ultrafiltration of raw water from the actual water source were in accordance with the predictions based on XDLVO theory, indicating that it was a feasible option for predicting membrane fouling during the initial ultrafiltration phase.     

纳滤膜分离技术及其进展

纳滤技术是一种介于超滤和反渗透之间的新型分离技术。作者介绍了纳滤膜的特性及其独特的分离特点。高分子纳滤膜的几种主要制备方法的制备原理、制备要点,国内外纳滤膜在生产研究方面的进展,以及当前已商品化的几种主要的纳滤膜的材质。最后简单介绍了纳滤膜在水处理、食品、生化、医药、染料和化工等领域的应用进展,指出今后的发展将着重于传质机理、新的膜材料及集成工艺开发等方面。     

Flux,antifouling and separation characteristics enhancement of nanocomposite polyethersulfone mixed-matrix membrane by embedding synthesized hydrophilic adipate ferroxane nanoparticles

Polyethersulfone (PES) nanofiltration (NF) membranes were prepared by blending of synthesized hydrophilic adipate ferroxane nanoparticles (AFNPs) as a novel multifunctional nanofiller via the phase inversion method. The water contact angle measurement indicated the higher hydrophilicity of the NF membranes. The water flux of the membranes improved significantly after the addition of AFNPs, from 10.4 to 32.2 kg/m²h. Antifouling characteristics of AFNPs/PES membranes were improved by increased hydrophilicity and decreased membrane surface roughness. The 0.6 wt% AFNPs/PES membrane exhibited the highest FRR (96%) and the lowest irreversible fouling resistance (6%). The nanofiltration performance of the prepared membranes was evaluated by dye removal and salt retention. The results proved the high dye removal capability of modified membranes (98% rejection) compared with the unfilled PES membrane (89% rejection). The salt retention sequence for membrane with 0.2 wt% of nanoparticles was Na₂SO₄ (70%)>MgSO₄ (60%)>NaCl (18%).     

Nanofiltration flux, fouling and retention in filtering dilute model waters

Fouling of membranes decreases the applicability of the nanofiltration (NF) process, and thus a deeper understanding of membrane fouling is needed. Fouling and retention of different NF membranes by model feed waters was investigated in a laboratory-scale filtration unit. The model waters were composed so as to imitate the characteristics of chemically pre-treated surface water. No differences were seen in membrane flux declines when filtering feed waters containing the studied organic compounds of different characteristics. However, organic matter containing feed waters resulted in remarkably lower flux than the metal ions containing feed waters. An additional decrease in flux was seen when both organic matter and metal ions,especially silica, were present in the feed water. An increased feed water organics concentration increased the retention of organic matter, but the addition of metal ions to organics containing feed water caused a decrease in the retention of both organic matter and conductivity. The different behaviour is most probably caused by the differences in the fouling layers and foulant characteristics as well as by the electroneutrality effect. Generally, it is difficult to change feed water composition to non-fouling, but the operating pH can be used to some extent in optimising membrane performance.     

多孔纳米材料改性水处理超滤膜的研究进展

基于压力驱动的超滤膜面临渗透性和选择性的制衡及膜污染问题。多孔纳米材料是高性能超滤膜改性制备中一类重要的添加剂,是新型水处理功能膜的研究热点之一。多孔纳米材料的添加为膜提供了额外水通道,其可调的孔尺寸又为在膜内构建出具有高度选择性的纳米通道提供了潜在有利条件,进而突破膜渗透性和选择性的Trade-off效应。同时,亲水性多孔纳米材料的添加有利于提升膜的抗污染性能。本文综述了近年来多孔纳米材料对超滤膜的改性方法,总结了微孔沸石分子筛、介孔炭、介孔二氧化硅、金属有机骨架材料和共价有机骨架材料对超滤膜的改性研究进展,着重评价了不同改性材料对超滤膜在亲水性、渗透性、污染物截留和抗污染能力等方面的影响。最后对未来多孔纳米材料改性超滤膜的研究及应用的发展趋势进行了展望。     

Electrodialysis in an Integrated NF/ED Process for Water Recovery in the Leather Industry

Electrodialysis (ED) was assessed for integration in a nanofiltration NF/ED sequence for water reuse in the leather industry. Two ED feeds composed of different model solutions were used: Model Solution FED1, which is a surrogate of a nanofiltration permeate generated by the NF processing of a biologically treated leather effluent, and Model Solution FED2, which has the same salt concentration as FED1 but with an organic matter content that is approximately ten times higher. The electrodialysis experiments were carried out in a five-compartment bench cell using cationic and anionic membranes HDX 100 and HDX 200. The final product water, with a conductivity ranging from 3.28 to 3.67 mS cm^?1, can be reused as process water for beamhouse operations. With respect to chloride and COD parameters, the ED product water meets the requirements of process water, even for dyeing operations. An alkaline membrane cleaning process for fouling removal was also tested for the membranes using Model Solution FED2. The cleaned membranes were evaluated in terms of visual aspect, polarization curves, TGA, and SEM/EDS analysis. The results obtained with the cleaned membranes were very similar to those obtained with the new ones in ED experiments with Model Solution FED2.     

膜分离技术在垃圾渗滤液处理中的应用

垃圾渗滤液是一种重污染的有毒有机废水,对生态环境造成了严重的威胁。本文综述了垃圾渗滤液现有的膜处理技术,与传统处理工艺相比,膜技术具有低能高效等优点,是未来渗滤液处理技术的重要发展方向。由于垃圾渗滤液组成的复杂性,根据不同处理目的,微滤膜(MF)、超滤膜(UF)、纳滤膜(NF)和反渗透膜(RO)4种膜在垃圾渗滤液处理中都得到了一定的应用。总结发现,其中MF和UF对渗滤液的处理效果较差,一般作为渗滤液的预处理技术;NF和RO对渗滤液的处理效果较好,主要作为其深度处理技术。然而,膜污染阻碍了膜技术在渗滤液处理方面的发展与应用,为此可通过研究开发新型膜材料、有效的预处理技术和膜分离工艺优化等方面来防止膜污染的发生,以便膜技术在渗滤液及其他水处理方面得到更加广泛的应用。     

微细通道内CO2沸腾换热与干涸特性

CO₂作为一种天然制冷剂在微通道内应用具有很大的换热优势,然而由于微尺度效应及其物性,在低干度区容易发生干涸,严重影响换热效果。为研究微细通道内CO₂流动沸腾换热与干涸特性,搭建了相应实验装置,对内径分别为1mm、2mm、3mm以及内表面粗糙度为16μm的不锈钢管,在CO₂制冷剂热流密度2~34kW/m²、质量流率50~1350kg/(m²·s)、饱和温度-10~15℃下进行换热性能与干涸实验对比研究。结果表明:常规管径换热特性在微细通道内不再适用;热流密度的增加对于强化核态沸腾换热具有显著影响,高于临界热流密度(critical heat flux,CHF)则发生干涸;质量流率对于核态沸腾区换热系数的影响则较小;不同饱和温度时换热特性有所不同,高饱和温度下换热系数随其升高而提高,低饱和温度下则相反;干涸过程对总换热系数的影响占34%。研究结论为CO₂微通道换热器的研究开发提供理论依据。     

超滤和纳滤膜分离提取纳他霉素

为提高纳他霉素(natamycin)生产提取得率,减少溶剂使用,本文采用超滤、纳滤操作对工业生产的纳他霉索发酵液进行处理。实验结果表明:操作压力、操作时间及料液流速对超滤过程有很大影响。通过超滤可将蛋白质等大分子杂质去除,然后再用纳滤膜对超滤渗透液进行浓缩纯化,对纳滤工艺的操作条件如进料压力、料液pH、浓缩倍数等进行了研究。采用超滤、纳滤技术提取纳他霉素,其收率可达62.74%。     

金属有机骨架混合基质水处理分离膜研究进展

金属有机骨架（MOFs）晶体由无机金属离子和有机配体通过自组装合成,具有高的孔隙率和可调节的窗口尺寸,可使MOFs混合基质膜在水处理时同步获得高通量和高截留率,有望突破传统分离膜的渗透性和选择性之间此消彼长的trade-off效应。本文综述了MOFs的典型构造、影响MOFs混合基质膜性能的关键因素、MOFs混合基质膜的制备方法、MOFs颗粒改善混合基质膜水传输和溶质分离性能的原理以及MOFs混合基质膜在水处理微滤/超滤、纳滤/反渗透和正渗透领域的最新研究进展。最后总结了MOFs混合基质膜在水处理领域的未来发展亟待解决的关键问题,主要包括高性能、低成本膜的可控制备、膜结构和性能之间定量构效关系的深入探索以及如何拓宽其应用范围等,对加快MOFs混合基质膜的产业化进程具有指导意义。     

疏水性油水分离膜及其过程研究进展

油水分离是治理含油废水和含水油液的重要工业过程。本文概括了疏水性油水分离膜的类型与制备方法,包括常规分离膜和高度疏水/超亲油分离膜。前者为常规微滤、超滤及纳滤过程用膜;后者由构筑高度疏水（水滴接触角≥120°）表面方法得到,形式有金属网膜、纤维膜、滤纸、复合膜及不对称膜,其为制备耐污染的疏水性油水分离膜提供了新思路。指出了疏水性膜用于油水分离的过程原理及应用现状：含油废水除油中,疏水性膜可实现O/W乳液的破乳、粗粒化油滴、滤除油滴及吸附油分子几方面的功能;含水油液除水中,膜被用来截留水滴,可直接得到净化的油品。最后,指出了其过程规模化应用前尚需解决的重要问题,特别是高度疏水/超亲油分离膜的制备、相关过程研究的深入及其规模化试验等方面需着力加强。