基于碳纳米管-聚丙烯腈纤维支撑层的正渗透膜制备

在聚丙烯腈(PAN)溶液中加入功能化的多壁碳纳米管(f-MWCNTs),采用静电纺丝法制备纳米纤维多孔支撑层,在其表面通过界面聚合制备超薄聚酰胺截盐层,制得正渗透复合膜,考察了PAN浓度及碳纳米管添加量对膜结构性能的影响.结果表明,随PAN浓度增大,支撑层纤维直径增大,水通量降低,截盐率增大.含羧基和羟基的f-MWCNTs可增强膜的亲水性和机械强度,提高膜通量和截盐率.PAN浓度为12%(?)、f-MWCNTs浓度为1.44%(?)时,膜的机械强度可达10.55 MPa,与水的接触角为41.39°,机械强度和亲水性优于未添加碳纳米管的PAN正渗透膜(机械强度3.60 MPa,接触角为61.86°).以1 mol/L Na Cl为汲取液、去离子水为原料液,膜的水通量可达79.1 L/(m2·h),明显高于商用渗透膜CTA-NW和CTA-ES[8.8和18.4 L/(m2·h)],溶质反向通量仅为50.4 g/(m2·h).     

三乙酸纤维素正渗透膜的制备与性能

以三乙酸纤维素（CTA）为膜材料,1,4-二氧六环、丙酮为溶剂,甲醇、乳酸为添加剂,采用相转换法制备了三乙酸纤维素正渗透膜。研究了不同1,4-二氧六环/丙酮配比、添加剂乳酸含量、挥发时间、膜厚度、热处理温度条件下正渗透膜性能的变化规律。研究表明,当采用纯水为原料液,0.56mol/L CaCl2为汲取液时,优化制备的CTA正渗透膜的水通量达到14.10L/(m2?h),溶质反扩散量为0.031mol/(m2?h);采用0.1mol/L NaCl为原料液,4mol/L葡萄糖为汲取液时,优化制备的CTA正渗透膜的水通量保持在5L/(m2?h)以上,对NaCl的截留率大于99%。CTA正渗透膜相比于HTI膜,具有较高的亲水性、水通量、截留率,稳定性更好。     

壳寡糖汲取液的正渗透性能

以3种不同分子量的壳寡糖(COS)溶液为汲取液,研究了汲取液浓度与p H值、电导率、粘度和渗透压的关系,分析了不同分子量、壳寡糖浓度、膜活性层朝向时的水通量、反向溶质通量和截留率等因素的变化规律,讨论了其对纯水的回收率.结果表明,壳寡糖溶液具有较高的电导率和渗透压,可产生较高的水通量,正渗透膜的活性层朝向汲取液(AL-DS)模式时的水通量优于活性层朝向原料液(AL-FS)模式,但AL-DS模式下的反向溶质通量较AL-FS模式大;两种模式下膜的截留率均在99.9%以上,且AL-FS模式的截留率略高于AL-DS;COS汲取液对纯水的回收性能良好.     

正渗透—纳滤耦合处理苦咸水脱盐工艺

以2 000 mg/L氯化钠模拟苦咸水,采用二价无机盐作为汲取液,研究了正渗透淡化苦咸水时的水通量;通过软件计算和试验研究了不同组成汲取液的纳滤性能,并且设计了二级纳滤系统用于汲取液的回收。结果表明:相同浓度时硫酸镁汲取液正渗透水通量最低,而氯化镁汲取液水通量最高;相反在纳滤过程中,硫酸镁汲取液性能最佳,氯化镁最差;稀释硫酸钠汲取液浓度为30 g/L时,二级纳滤过程可以将汲取液浓缩至初始浓度(60 g/L),并制得浓度低于500 mg/L的产水。     

正渗透膜生物反应器膜过滤特性研究

以氯化钠为驱动溶质,采用正渗透膜生物反应器处理模拟生活污水,系统地考察了各因素对正渗透膜过滤性能的影响。结果表明,随着驱动液浓度增加,水通量和反向盐通量也随之增加;正渗透膜活性层朝向驱动液时(AL-DS)的水通量和反向盐通量较活性层朝向原料液(AL-FS)时大;水通量和反向盐通量与错流速率正相关,在错流速率较低时增加不明显;随着活性污泥浓度增加,水通量呈下降趋势,而反向盐通量呈上升趋势。     

三醋酸纤维素正渗透膜的制备与性能初步研究

以高分子物质三醋酸纤维素(CTA)作为膜材料主要成分,将其溶解于1,4-二氧六环溶剂中,加入致孔剂聚乙烯吡咯烷酮K30(PVP),加热搅拌形成均匀铸膜液采用相转化法制备正渗透膜。在温度为(20±1)℃,原溶液为去离子水,汲取液为2 mol/L氯化钠溶液的条件下测试膜的性能,研究了CTA和PVP含量及预蒸发时间3种因素对正渗透膜性能的影响。结果表明,在1,4-二氧六环和乳酸体积分别为170和13.2 mL下,当CTA和PVP的质量分别为23、4 g,预蒸发时间为60 s时,正渗透膜的性能最佳,水通量可达10.24 L/(m2·h),溶质反混通量为6.68 g/(m2·h)。     

壳聚糖季铵盐汲取液的正渗透性能研究

采用超声降解方法制备了3种不同相对分子质量的壳聚糖季铵盐(CTS-QTS),通过红外光谱和凝胶渗透色谱对降解产物进行了表征,分别研究了CTS-QTS水溶液作汲取液时,CTS-QTS含量与黏度、电导率、渗透压的关系,以及不同膜朝向和汲取液CTS-QTS含量时的水通量、反向溶质通量、截盐率和水回收率等的变化规律。结果表明,正渗透膜的活性层朝向汲取液(AL-DS)模式的水通量要高于活性层朝向原料液(AL-FS)模式,但AL-DS模式下的反向溶质通量大约是AL-FS模式的2倍;在2种模式下,膜的截盐率均在99.9%以上,且AL-FS模式的截盐率略高于AL-DS。CTS-QTS汲取液的水回收性能优良。CTS-QTS有望成为低能耗型绿色正渗透汲取剂。     

荷电中空纤维复合膜及其正渗透性能研究

以聚丙烯中空纤维微滤膜为底膜、羧甲基纤维素钠为功能材料、氯化铁为交联剂,采用溶液涂覆-交联工艺制备了表面荷电的中空纤维复合膜,将该中空纤维复合膜用于正渗透(FO)过程,研究了汲取液盐含量、原料液流速等对FO通量的影响。结果表明,制备的荷电中空纤维复合膜可用于FO过程,以蒸馏水为原料液、Na2SO4水溶液为汲取液,采用PRO模式进行FO试验,当原料液与汲取液体积流量均为15 mL/min、汲取液浓度为0.5 mol/L时,FO水通量为12.3 L/(m2.h),盐通量与水通量的比为1.42 g/L。     

正渗透膜净水试验研究

研究了正渗透(FO)过程中水通量和驱动溶质扩散规律,并以奎宁和腐殖酸作为模型有机物,研究FO膜对有机物的截留性能。结果表明,FO水通量与驱动液含量正相关,但由于内部浓差极化的影响并不呈正比例;温度越高所产生的水通量也越大,在温度11～36℃时水通量从4 L/(m2.h)上升至10 L/(m.h)。驱动溶质的反扩散量随运行时间的延长线性增加,由于唐南效应Na+的反扩散量大于2价阳离子。FO膜对奎宁和腐殖酸均有较好的截留效果。     

碳酸氢铵为汲取液正渗透海水淡化研究

正渗透技术因低能耗、低膜污染和高回收率等优点逐渐成为膜分离技术的研究热点。本文以碳酸氢铵溶液为汲取液、0.6mol/L氯化钠溶液为模拟海水进行了正渗透实验,研究了不同操作条件下正渗透水通量的变化规律和汲取液部分解吸-吸收过程中氨解吸率、氨吸收率以及解吸能耗的变化。结果表明,提高进料流量和汲取液浓度,正渗透过程水通量增加;提高吸收塔进料流量,氨吸收率增加,操作条件对氨解吸率影响较小;海水淡化正渗透系统能耗主要用于汲取液解吸过程,降低解吸塔进料浓度可以降低解吸过程的能量消耗。在优化的工艺条件下,正渗透过程水通量为13.6L/(m~2·h),汲取液回收利用率达到99%,海水淡化产水总溶解固体(TDS)不高于1000mg/L,系统吨水耗电量约为195kW·h。实验结果对正渗透过程的工业化应用具有指导意义。     

正渗透过程中汲取质反向渗透研究进展

正渗透(FO)作为一种浓度驱动的膜技术,因其膜污染轻、能耗低和回收率高等优点而逐渐成为膜技术领域的研究热点之一。汲取质的反向渗透是正渗透过程中不可忽视的现象,但其研究相对比较滞后。本文主要介绍了汲取质反渗模型的研究进展,分析了渗透压差、膜表面流速、膜结构与膜材料、温度、汲取质种类、膜取向、离子水力半径等因素对汲取质反向渗透的影响情况,并发现汲取质的反向渗透通量可由其浓度或汲取液渗透压的一元多项式表达。总体而言,FO模式的汲取质反渗模型经过不断发展已相对比较完善,而压力阻尼渗透(PRO)模式的反渗模型则缺陷较大,有待进一步研究;此外,关于汲取质反渗过程影响因素及其影响机制的研究对于汲取质、膜材料的选择与开发,以及正渗透过程的优化均具有重要的指导作用,因此会引起越来越多的关注。     

A trimethylamine–carbon dioxide draw solution for osmotic engines

This study evaluates the pressure retarded osmosis performance of TMA–CO₂ for potential use in osmotic heat engines. Power densities up to 18.6 W m^?2 were achievable at relatively low pressure (10 bar) using 5 M TMA–CO₂ draw solutions. Compared to NaCl control tests, the TMA–CO₂ exhibited 20% lower water flux due in large part to its larger molecular size and associated higher solution viscosity and lower diffusion coefficient. Compared to the ammonia‐carbon dioxide draw solution, water flux was comparable but reverse solute flux of TMA–CO₂ was nearly one order of magnitude lower. Larger solute size was found to create a performance tradeoff as reduced reverse solute flux improved water flux while higher viscosity and lower diffusion coefficient worsened water flux. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3369–3375, 2018     

操作条件对正渗透分离性能的影响

正渗透是以渗透压差为驱动力的新型膜分离过程。采用水流分布较佳的膜池结构,研究了膜朝向、流动方式对正渗透水通量性能的影响,结果表明PRO模式（当膜的活性层朝向驱动液时）的水通量明显高于FO模式（当膜的活性层朝向原料液时）,但其衰减程度较大;在溶液浓度差相同的条件下,逆流操作更利于水通量的提高。针对FO模式和逆流条件,探讨了溶液温度对水通量和反向盐通量的影响,结果表明：膜两侧溶液温度同步升高时,正渗透过程的水通量和反向盐通量均增加,且水通量的增加幅度大于反向盐通量;单侧增加溶液的温度时,驱动液侧温度升高对水通量性能的提升效果优于原料液侧。综合考虑过程能耗和系统性能,认为单独升高驱动液温度更具实用价值。     

正渗透过程中水与溶质的传递现象

正渗透是一种利用渗透原理的新兴膜技术,近年来在国内外受到了广泛的关注。解析该过程中溶剂水的传递和驱动溶质的反向传递对其发展和应用至为关键。首先开展了两种膜的取向下,正渗透过程中的水通量和溶质反向摩尔通量的实验研究。当驱动溶液在膜分离层侧时,水通量更高,而溶质反向摩尔通量更低,表明水的传递对溶质的反向传递有限制作用。而后分别考察了不同的单一溶质和二元混合溶质作为驱动溶质时,水和溶质的传递现象。当单一中性溶质或电解质作为驱动溶质时,水通量和溶质反向摩尔通量均随驱动溶液浓度的升高而增大;在相同操作条件下,驱动溶质的扩散系数越小,溶质反向摩尔通量越小;中性溶质与电解质混合溶液为驱动溶液时,溶质分子之间存在耦合传递效应。     

Lithium-based draw solute for forward osmosis to treat wastewater discharged from lithium-ion battery manufacturing

As draw solute is the core element of forward osmosis (FO) technology, here Li-Bet-Tf₂N synthesized from a customized ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf₂N]) and Li₂CO₃ recovered from lithium-ion battery (LIB) wastes is proposed as a novel draw solute to treat Li⁺-containing wastewater from LIB manufacturing through FO filtration. Having high dissociation ability and an extended structure, Li-Bet-Tf₂N generates a sufficiently high osmotic pressure to drive the FO filtration efficiently along with insignificant reverse solute diffusion. Li-Bet-Tf₂N produces a water flux of 21.3 L·(m²·h)⁻¹ at 1.0 mol∙L^–1 against deionized water, surpassing conventional NaCl and MgCl₂ draw solutes with a higher water recovery efficiency and a smaller solute loss. Li-Bet-Tf₂N induces a more stable and higher water permeation flux with a 10.0% water flux decline than NaCl and MgCl₂ for which the water fluxes decline 16.7% and 16.4%, respectively, during the treatment of 2000 mg∙L^–1 Li⁺-containing wastewater for 12 h. More remarkably, unlike other draw solutes which require intensive energy input and complicated processes in recycling, Li-Bet-Tf₂N is easily separated from water via solvent extraction. Reproducible results are achieved with the recycled Li-Bet-Tf₂N. Li-Bet-Tf₂N thus demonstrates a novel class of draw solute with great potentials to treat wastewater economically.     

Synthesis and application of ethylenediamine tetrapropionic salt as a novel draw solute for forward osmosis application

The development of suitable draw solutes for forward osmosis (FO) process is a big obstacle on the way of its real industrialization. In this work, a novel draw solute, ethylenediamine tetrapropionic (EDTP) acid (salt) is developed for FO application. The successful synthesis is confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and high resolution mass spectrum. By optimizing the pH of EDTP solution, its composition is varied, and therefore, its water solubility and osmotic pressure are effectively improved. The effects of EDTP concentration on the osmotic pressure and FO performance are also investigated. Its outstanding osmotic pressure and big molecular size result in a high water flux of 22.69 LMH and a low salt flux of 0.32 gMH with 0.8 M EDTP draw solution (water as the feed solution, pressure retarded osmosis mode). The good stability and easy recovery by nanofiltration of EDTP solution also demonstrate its great potential as the draw solute for future FO applications. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1309–1321, 2015     

具有三维聚酰胺脱盐网络结构的无纺布复合正渗透膜

利用间苯二胺（MPD）和均苯三甲酰氯（TMC）,直接在聚酯无纺布（NV）织物的多孔空间中进行界面聚合,形成大通量无纺布复合正渗透（NVC-FO）膜。NVC-FO膜在无纺布内部形成的多层次三维（3-D）聚酰胺结构,分布在30~50μm深的聚对苯二甲酸乙二醇酯支撑材料的内部。这种相对松散的有深度的3-D聚酰胺网络,不仅透水表面积大,而且可以避免薄层聚酰胺缺陷导致的高漏盐性,有较低的反向盐通量。进一步研究发现,在一定范围内降低单体质量分数（MPD 1%~0.01%,TMC 0.5%~0.005%）,可以形成更宽广的3-D聚酰胺网络结构,在保持较低的反向盐通量的同时得到更高的水通量。使用1mol/L NaCl作为汲取溶液,优化的NVC-FO膜水通量最高可以达到193.54L/(m²·h),反向盐通量为0.047mol/(m²·h)。采用加压正渗透实验,发现这些高通量NVC-FO膜的盐穿透破裂压力在200~1400Pa之间,而且证实了降低单体质量分数会导致膜的耐压性能显著降低。尽管NVC-FO膜的耐压性能有待提高,但是该研究有可能为构建高脱盐性能的FO膜提供一条新的思路。     

High performance forward osmosis cellulose acetate (CA) membrane modified by polyvinyl alcohol and polydopamine

Cellulose acetate (CA) is a low cost and readily available material widely used in forward osmosis (FO) membranes. However, the performance of pure CA membranes is not good enough in salt separation and the traditional modification methods are generally multistep and difficult to control. In this paper, we reported high performance cellulose acetate (CA) composite forward osmosis (FO) membranes modified with polyvinyl alcohol (PVA) and polydopamine (PDA). PVA was first cross-linked onto the surface of CA membranes, and then PDA was coated with a rapid deposition method. The membranes were characterized with respect to membrane chemistry (FTIR and XPS), surface properties comprising wettability (by water contact angle), and osmosis performance. The modified membrane coated by PVA and PDA shown better hydrophilicity and exhibited 16.72 LMH osmotic water flux and 0.14 mMH reverse solute flux with DI water as feed solution and 2.0 M NaCl as draw solution and active layer facing the feed solution. This simple and highly effective modification method makes it as an excellent candidate for further exploration for FO.     

正渗透膜生物反应器运行过程中溶质反渗对微生物群落的影响

以氯化钠为驱动溶质,采用正渗透膜生物反应器(forward osmosis membrane bioreactor, FOMBR)处理生活污水,考察其在运行过程中溶质反渗对系统内微生物群落造成的影响。稳定运行状态下的第7、14、20天的混合液污泥样品分别称为A1、A2、A3,并对微生物群落物种丰度、群落结构、聚类等进行了分析。结果表明：正渗透膜生物反应器运行20 d内水通量从9.5 L/(m²·h)下降到8.17 L/(m²·h),反向盐通量从29.52 g/(m²·h)增加到35.06 g/(m²·h)。整个运行过程中溶质反渗对微生物群落结构的变化有着一定的影响,3个样品共产生1496个OTUs,各样品间共享的OTUs不尽相同;溶质反渗对3种样品的微生物群落多样性、菌群丰度等影响较小。PCA分析中A2和A3两个样品距离更近,组成更相似,热图聚类分析再次验证A2与A3相似性更高;3个样品斜率较小且非常接近,并且A1和A3两个样品所含物种的丰富程度和均匀程度几乎一样;3个样品的活性污泥群落结构在门、纲、目分类水平上均具有较高的多样性,各分类水平上的菌群丰度存在一定的差异。