共价有机框架膜的制备及其在海水淡化和水处理领域的研究进展

日益严重的水资源短缺和水资源污染问题是全球面临的挑战,大力发展海水淡化和水处理技术是缓解该问题的有效途径.近年来,能耗低、环境友好的膜分离技术被广泛用于海水淡化和水处理领域.共价有机框架（Covalent organic framework,COF）膜因其具有大小可控、化学性质可调的孔道,成为潜在的高性能膜分离材料.本综述详细介绍了COF膜合成方法学的研究进展,概述了COF膜在海水淡化和水处理领域的研究,并展望了其在海水淡化和水处理领域的前景和面临的挑战.     

高回收率膜法苦咸水淡化工艺的应用研究进展

膜法苦咸水淡化过程中,符合环境保护要求的浓排水处理方法成本高昂,所以只有当回收率达到较高值时,在实际运行中才具有经济可行性。目前,在不加剧膜污染的条件下进一步提高苦咸水淡化系统回收率的方法已成为该领域研究热点。本文详细综述了高回收率膜法苦咸水淡化工艺的应用研究进展,包括基于反渗透、纳滤、正渗透、膜蒸馏、电渗析和电容去离子化淡化工艺过程,以及这些过程面临的热点问题,并对此提出了建议。     

NEWS

膜分离技术在污水处理、中水回用、水质净化、海水淡化、血液透析和生物制药等领域得到了广泛应用。然而,膜在运行过程中出现的膜污染问题严重限制了该技术的发展。膜污染不仅会引起膜通量和分离性能下降,影响膜的长期稳定运行,而且污染后膜的清洗和更换也大大提高了运行成本。为了深入     

基于离子浓差极化的立体式海水淡化微流控器件研究

海水淡化是解决人类淡水资源匮乏的一个重要途径。现有的海水淡化技术存在设备体积大、海水淡化成本高等问题。本研究采用聚二甲基硅氧烷( PDMS)制备了基于离子浓差极化原理的海水淡化器件,采用盐溶液模拟海水,进行盐离子和水分子分离的研究。研究了不同的外加电压、盐溶液在通道中的流动速度、盐溶液通道深度和Nafion纳米通道的深度等实验条件和结构参数对微流控器件分离盐离子和水分子的影响。对微流控器件的结构参数进行了优化。实验结果表明,采用外加电压为25 V、盐溶液流速为4μL/min、盐溶液通道深宽比为1：20、Nafion纳米通道深度为450~500μm的微流控器件进行盐溶液分离,除盐率可达到99%。研究结果对于开发新型高效、低能耗的海水淡化器件有重要的指导意义。     

全自动蒸馏前处理-ID/GC-ICP-MS测定海水中痕量甲基汞

建立了基于自动蒸馏前处理,气相色谱-电感耦合等离子质谱联用(GC-ICP-MS),同位素稀释法(ID)测定海水中痕量甲基汞的分析方法。结果表明,自动蒸馏仪在45 min内即可完成海水样品的蒸馏,采用Br Cl溶液能有效消除蒸馏管路中甲基汞的残留,降低实验空白;同位素稀释剂的添加量对甲基汞的测定结果无明显影响,样品中总汞质量浓度低于1. 0μg·L~(-1)时,因操作产生的甲基汞量可忽略不计。海水中甲基汞的加标回收率为98. 2%~122%,天然海水及加标海水中甲基汞的相对标准偏差(RSD)分别为16%和5. 4%,方法检出限为0. 009 ng·L~(-1)。以大连湾表层海水为实际样品,测得水样中甲基汞的质量浓度的平均值为(0. 103±0. 036) ng·L~(-1),方法可满足近岸海水中痕量甲基汞的分析要求。     

海水淡化原理及方法综述

介绍了海水淡化的原理和多级闪蒸、反渗透2种常用的海水淡化方法,并且简要回顾了我国海水淡化的研究和技术应用情况。     

亲水膜的表面改性及在膜蒸馏中的应用

膜的微孔性和疏水性是水溶液膜蒸馏的两个基本条件,迄今人们均采用疏水性高分子材料制成疏水微孔膜用于膜蒸馏研究。本文采用辐照接枝聚合和等离子体表面聚合的方法,将亲水的醋酸纤维素微孔膜和硝酸纤维素微孔膜表面疏水化改性,成功地用于膜蒸馏研究,大大扩展了疏水微孔膜的材料来源。实验结果表明,亲水膜表面改性得到的疏水膜,其膜蒸馏性能不低于疏水材料制成的膜,尤其是等离子体聚合法可以实现多种特殊单体在多孔的材料表面聚合,成为制备高性能疏水微孔膜的有效手段,为膜蒸馏的深入发展和实用化创造了有利条件。     

应用于膜蒸馏过程的F26微孔膜的初步研究

以N-甲基吡咯酮作为溶剂 ,丙酮为溶胀剂 ,聚乙二醇 4 0 0为添加剂利用相转换法制备出偏氟乙烯 六氟丙烯共聚物 (F2 6 )的疏水微孔膜并且应用在膜蒸馏过程中 .研究了丙酮以及N 甲基吡咯酮 丙酮体系对膜参数以及结构的影响 .通过SEM观察了膜的微观结构 ,发现用N 甲基吡咯酮 丙酮体系制得的微孔膜兼具指状孔和海绵状孔结构 .无添加剂条件下制得的F2 6膜其对蒸馏水的接触角比相同条件下制备的PVDF膜大 .在用相转换法制备的F2 6和PVDF的疏水膜中 ,选择具有适当孔径结构的微孔膜用于膜蒸馏实验 ,F2 6膜的膜蒸馏系数比PVDF膜来得大 ,相同操作条件下的膜蒸馏通量也比PVDF膜高 .     

水蒸汽蒸馏实验的改进

水蒸汽蒸馏实验的改进付湘林谭俊杰（湖南农业大学有机教研室长沙４１０１２８）水蒸汽蒸馏实验是大学中重要的有机化学实验之一。在传统的水蒸汽蒸馏装置中，水蒸汽发生器与冷凝管部分是通过双孔塞与反应容器圆底烧瓶相连结的；或者水蒸汽发生器部分通过单孔塞与反应容器...     

海水中溶解态硝酸盐的氮同位素分析的预处理方法

建立了一套适合海水中溶解态硝酸盐的氮同位素分析的预处理方法.以蒸馏为基础,先去除海水样品中的NO-2-N和NH+4-N,然后加入达氏合金将海水样品中的NO-3-N还原为NH+4-N,并通过蒸馏富集,馏出液用沸石吸附后,经过滤等步骤,送入同位素质谱仪检测15N.研究了预处理过程中的蒸馏条件、盐度影响、沸石吸附效率以及大体积水样预处理方法的改进等.结果表明,每300 mL水样中加入0.5 g达氏合金在强碱性条件下蒸馏30 min,氮回收率平均可达(104.9±4.2)%(n=6);当盐度从0%增加至0.5%时,同位素分馏程度迅速减小盐度再增大时(1%～3.5%),同位素分馏变化不明显.沸石对铵氮的平均吸附率较高,约为(95.96±1.08)%(n=6);处理大体积水样时多次蒸馏并改进了馏出液的收集方式,实验效果较好.应用此方法对长江口海域水样进行了分析,结果表明,这一方法可以应用于海水中溶解态硝酸盐的氮同位素分析,为海水中溶解态氮的来源问题及循环机理研究等提供了有效信息.     

基于海水淡化的正渗透膜分离技术的发展

近年来,水资源危机日益加重。在海水淡化技术中,与反渗透分离技术相比,正渗透分离技术作为一种低能耗、绿色的解决方案,具有明显优势,在国际上得到了广泛的重视,是膜分离技术的研究热点之一。本文从正渗透膜材料结构与性能关系的角度,对膜材料的最新进展进行了综述,同时分析了汲取液的常见类型,并简述了正渗透分离技术的新应用,展望了其未来的发展前景。     

Biofouling Potential Reductions Using a Membrane Hybrid System as a Pre-treatment to Seawater Reverse Osmosis

Biofouling on reverse osmosis (RO) membranes is the most serious problem which affects desalination process efficiency and increases operation cost. The biofouling cannot be effectively removed by the conventional pre-treatment traditionally used in desalination plants. Hybrid membrane systems coupling the adsorption and/or coagulation with low-pressure membranes can be a sustainable pre-treatment in reducing membrane fouling and at the same time improving the feed water quality to the seawater reverse osmosis. The addition of powder activated carbon (PAC) of 1.5 g/L into submerged membrane system could help to remove significant amount of both hydrophobic compounds (81.4%) and hydrophilic compounds (73.3%). When this submerged membrane adsorption hybrid system (SMAHS) was combined with FeCl(3) coagulation of 0.5 mg of Fe(3+)/L, dissolved organic carbon removal efficiency was excellent even with lower dose of PAC (0.5 g/L). Detailed microbial studies conducted with the SMAHS and the submerged membrane coagulation-adsorption hybrid system (SMCAHS) showed that these hybrid systems can significantly remove the total bacteria which contain also live cells. As a result, microbial adenosine triphosphate (ATP) as well as total ATP concentrations in treated seawater and foulants was considerably decreased. The bacteria number in feed water prior to RO reduced from 5.10E(+06) cells/mL to 3.10E(+03) cells/mL and 9.30E(+03) cells/mL after SMAHS and SMCAHS were applied as pre-treatment, respectively. These led to a significant reduction of assimilable organic carbon (AOC) by 10.1 μg/L acetate-C when SMCAHS was used as a pre-treatment after 45-h RO operation. In this study, AOC method was modified to measure the growth of bacteria in seawater by using the Pseudomonas P.60 strain.     

Three-dimensional porous photo-thermal fiber felt with salt-resistant property for high efficient solar distillation

The urgent need for fresh water resource is a public issue facing the world. Solar distillation for seawater desalination is a promising freshwater production method. Interfacial solar evaporation systems based on 2D photo-thermal membranes have been widely studied, but salt pollution is one of the main challenges for solar distillation. In order to solve this problem, a hydrophilic three-dimensional (3D) porous photo-thermal fiber felt (PFF) was obtained by one-step method, through a simple polydopamine (PDA) coating method with hydrophobic graphite felt as a substrate. The PFF had a good evaporation rate of 1.48 kg m^?2 h^-1 and its corresponding light-vapor conversion efficiency reached 87.4%. In addition, the PFF exhibited an excellent salt-resistant ability when applied to photo-thermal evaporation of high-salinity seawater with 10 wt% NaCl, owing to its intrinsic 3D macroporous structure for the migration circulation of salt ions. The development of the PFF offers a new route for the exploration of salt-resistant photo-thermal materials and is promising for the practical application of solar distillation.     

Experimental study of desalination using direct contact membrane distillation: a new approach to flux enhancement

New membrane distillation configurations and a new membrane module were investigated to improve water desalination. The performances of three hydrophobic microporous membranes were evaluated under vacuum enhanced direct contact membrane distillation (DCMD) with a turbulent flow regime and with a feed water temperature of only 40 °C. The new configurations provide reduced temperature polarization effects due to better mixing and increased mass transport of water due to higher permeability through the membrane and due to a total pressure gradient across the membrane. Comparison with previously reported results in the literature reveals that mass transport of water vapors is substantially improved with the new approach. The performance of the new configuration was investigated with both NaCl and synthetic sea salt feed solutions. Salt rejection was greater than 99.9% in almost all cases. Salt concentrations in the feed stream had only a minor effect on water flux. The economic aspects of the enhanced DCMD process are briefly discussed and comparisons are made with the reverse osmosis (RO) process for desalination.     

Deep desalination of water by evaporation through polymeric membranes

Transport properties and structural features of a number of already known and new types of polymeric membranes in desalination of aqueous salt solutions by membrane distillation and pervaporation were studied. The possibility of obtaining distilled water in a single stage by pervaporation from dilute or concentrated aqueous salt solutions was examined for the example of membranes fabricated from celluloses of varied origin (wood, cotton, bacterial).     

磺化纤维素纳米纤维多孔膜支撑的高通量纳滤膜的制备及脱盐性能

以细菌纤维素为原材料, 先后通过NaIO₄和NaHSO₃氧化还原反应制备了表面部分磺酸化的细菌纤维素(SBC)纳米纤维. 利用SBC纳米纤维多孔膜替代传统的超滤膜作为支撑底膜, 结合界面聚合反应调控制得复合纳滤膜, 并对其纳滤性能进行研究. 结果表明, 制备得到了对Na₂SO₄和MgSO₄具有高截留率(>96%)和超高分离通量(>320 L·m ^-2·h ^-1·MPa ^-1)的新型纳滤膜.     

Reverse Osmosis Membranes for Seawater Desalination State-of-the-Art

Abstract

The field of membrane technology has developed very rapidly during the last three decades. In this study, the major technical and commercial developments that took place in the field of reverse osmosis membranes as applied to seawater desalination are investigated. A brief historical review for each membrane type is also presented.     

Theoretical modeling and experimental analysis of direct contact membrane distillation

A two-dimensional mathematical model was theoretically developed to predict the temperature polarization profile of direct contact membrane distillation (DCMD) processes. A concurrent flat-plate device was designed to verify the theoretical prediction of pure water productivity on saline water desalination. The numerical results from the temperature polarization profile were obtained using the finite difference technique to reduce the two-dimensional partial differential equations into an ordinary differential equations system. The resultant simultaneous linear equations system was solved with the fourth-order Runge-Kutta method. The results show theoretical prediction agreement with the measured values from the experimental runs. A combination of the Knudsen flow and Poiseuille flow models in the present mathematical formulation for membrane coefficient estimation was used to establish theoretical agreement. The influence of the inlet saline water temperature and volumetric flow rate on the pure water productivity as well as the hydraulic dissipated energy are also delineated.