Recent advances in nanofiltration,reverse osmosis membranes and their applications in biomedical separation field

In the face of human society’s great requirements for health industry, and the much stricter safety and quality standards in the biomedical industry, the demand for advanced membrane separation technologies continues to rapidly grow in the world. Nanofiltration(NF) and reverse osmosis(RO) as the highefficient, low energy consumption, and environmental friendly membrane separation techniques, show great promise in the application of biomedical separation field. The chemical compositions, microstr...     

Surface properties of Reverse osmosis membrane

The morphology and structure of the top surfaces of three commercially Reverse osmosis (RO) membranes (Vontron Eviro‐Tech) have been studied using SEM and AFM techniques. As a result, the unevenness of the surface of ULP21 membrane was the greatest and that of SW21 membrane was smooth. The more the roughness of the top surface of the RO membranes was, the larger the flux of the RO membranes was. Accordingly, the roughness of the top surface of RO membranes intensively affected on the performance of RO membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Reverse osmosis technology for water treatment: State of the art review

This paper presents a review of recent advances in reverse osmosis technology as related to the major issues of concern in this rapidly growing desalination method. These issues include membrane fouling studies and control techniques, membrane characterization methods as well as applications to different water types and constituents present in the feed water. A summary of the major advances in RO performance and mechanism modeling is also presented and available transport models are introduced. Moreover, the two important issues of RO brine discharge and energy costs and recovery methods are discussed. Finally, future research trends and needs relevant to RO are highlighted.     

Identification,Modelling, and Control of Continuous Reverse Osmosis Desalination System: A Review

Desalination is a separation process used to reduce the amount of dissolved salts in seawater or brackish water to a usable or potable level by distillation, multiple effect vapor compression, evaporation, or by membrane processes such as electro-dialysis reversal, nano-filtration, and reverse osmosis (RO). RO is the most widely used desalination process. Recent advances in RO technology have led to more efficient separation and now is the most cost-effective process to operate. The performance of the Reverse Osmosis process is dependent on the concentration of dissolved solids in the feed-water, feed-water pressure, and the membrane strength to withstand system pressure, membrane solute rejection, membrane fouling characteristics, and the required permeate solute concentration. RO is a promising tool that uses cellulose acetate (or) polyamide membrane and is widely chosen as the cost of production is reduced by the use of energy-efficient and process-control techniques. This article presents a review of literature survey of identification of parameters, dynamic modelling, and control of desalination system in the past twenty years by collecting more than 65 literatures.     

Grey water treatment and simultaneous surfactant recovery using UF and RO process

The membrane-based grey water treatment for grey water reuse and surfactant recovery is presented in this research paper. Grey water from washing machine discharges having turbidity and used surfactant was processed through the polymeric ultrafiltration (UF) membrane to remove the turbidity. The UF treated grey water is further purified by reverse osmosis (RO) membrane for surfactant recovery and water reuse. The surfactant trapped inside the RO spiral wound membrane module is recovered through various membrane physical regeneration techniques such as backwashing, simultaneous backwash–back-flush and ozone back-flush. Among this, backwash–back-flush is found to be effective process for surfactant recovery. The methodology for optimising surfactant recovery is captured by studying effect of various operating parameters such as feed detergent concentration, backwash pressure, backwash temperature and back-flush flow rate. By implementing optimal process conditions, the integrated UF and RO membrane process is able to produce 300 L of reusable pure water and 80 L of concentrated detergent solution and 20 L of turbid water while treating 400 L of grey water discharges. Maximum surfactant recovery of 82% is obtained while treating grey water which consists of 720 ppm of total dissolved solids (detergent) and 45 ppm of surfactant. The extent of UF and RO membrane fouling is determined by measuring the pure water flux before and after the grey water treatment. The membrane performance is found to be stable when membrane is regenerated by backwash–back-flush technique for RO and gravity backwash for UF membrane.     

反渗透膜污染及其清洗的研究

反渗透膜分离技术在水处理中的应用越来越广泛,膜污染也日益受到重视。就常见的膜污染情况进行研究,针对不同的污染情况提出了几种常用的清洗方式,并比较了几种清洗方式的优劣,重点揭示了化学清洗机理,为反渗透膜的清洗提供建议。     

反渗透膜元件及膜系统的数学模型

介绍了反渗透膜元件性能指标的差异,讨论了建立性能各异膜元件系统运行模型的必要性,给出了单支反渗透膜元件的运行数学模型,分析了并联及串联膜元件的运行数学模型,从而建立了各类膜系统结构的通用数学模型.     

饮用净水机中SPM与反渗透膜集成技术研究

随着R0反渗透膜技术的迅速发展,目前市场上销售的净水机中,RO（reverse osmosis）反渗透膜技术使用日益增多。为使反渗透装置能够长期稳定地运行,必须选择合适的给水预处理装置,保护好反渗透膜。该文将国产化的SPM（special powder material）作为反渗透预处理的主要材料,对比SPM与GAC、纤维滤膜、活性炭棒组合预处理效果,筛选出优化组合,同时分别考察了填料填充高度、SPM粒度及进水流速对预处理效果的影响。并分别与反渗透膜联用,选取优化的工艺条件,研究了饮用水净水机中SPM与反渗透膜组合技术的可行性及其净化效果。     

我国反渗透膜材料研究现状

反渗透膜分离技术以其特有的优点得到了越来越广泛的应用,近几十年来我国对反渗透膜材料的研究取得了较大发展.该文综述了我国反渗透膜材料研究现状,根据反渗透膜的研究及应用现状,提出了反渗透膜材料的未来发展趋势及我国下一步发展反渗透膜分离技术的看法.     

Magnetic resonance imaging and 3D simulation studies of biofilm accumulation and cleaning on reverse osmosis membranes

Reverse osmosis (RO) is one of the multiple pressure-driven membrane separation processes used primarily for the production of high purity water for various industries, including food processing. Biofilm growth in the spiral-wound membrane module, commonly referred to as biofouling, reduces the efficiency to produce water. Biofilm accumulation and removal using chemical cleaning on RO membranes were studied using magnetic resonance imaging (MRI) techniques. Additionally, a previously validated biofilm simulation model, which is based on a lattice Boltzmann platform, was modified to account for cleaning operations. The spatial and velocity MRI experimental results captured biofilm distribution and water flow within the fouled membrane modules and subsequent changes in the biofilm distribution and water flow due to cleaning. Cleaning was simulated by accounting for reductions in the biofilm cohesive strength in the numerical model. Qualitative and quantitative comparisons between the experimental and simulated images showed good agreement.     

废旧反渗透膜循环再利用研究现状与进展

随着反渗透（RO）技术在水处理领域的广泛应用,全球每年有数百万计的废旧RO膜组件作为垃圾被处理处置,由此造成了环境污染与资源浪费。本文首先综述了废旧RO膜可能的循环再利用方案和相关的应用案例,为了比较不同循环方式对环境的影响,概述了通过全生命周期分析（LCA）的方法评价不同循环利用方式的环境效益和物质投入的研究进展。文章指出研究结果表明：回收利用废旧RO膜是研究RO膜末端处理的方法之一,其中包括通过使用清洗后的RO膜作为新生RO膜直接再利用、通过化学转化为其他多孔膜材料再循环使用、通过清洗RO膜拆解回收RO膜。另外,LCA在膜工艺中的分析仍以评估使用过程为主,而缺少在膜设计、膜改造和膜回收等关键过程的分析研究。     

膜技术在水处理中的应用与发展

膜技术方法很多，应用面也很广，本文对反渗透，电渗析，超过滤，纳滤和微孔过滤等膜技术在国内水处理方面的应用概况作一综合介绍。     

复合膜反渗透装置微生物的污染及防治

反渗透膜分离以其优异的特点已成为最受欢迎的分离技术之一。在反渗透膜分离技术的实际应用过程中,膜污染问题是影响反渗透膜分离技术可靠性的决定性因素。本文概述了复合膜反渗透装置中微生物污染的机理、预防措施及其清洗方法。     

反渗透膜清洗剂的实验评价方法

添加阻垢剂是反渗透系统重要的预处理方法之一,但膜在运行中还是会被反渗透过程中沉淀出的不溶性物质所逐渐污染.为了克服污染,必须对膜进行的定期清洗.反渗透市场上每年都会推出新的清洗剂,如何评价这些反渗透清洗剂及销售商提供的清洗程序至关重要.文章提供一种快速、方便、可靠的膜清洗剂试验方法.     

反渗透膜元件的微分方程数学模型

在反渗透膜元件的理想结构模型基础上建立了反渗透膜元件运行的微分方程数学模型,在分析膜元件运行参数的基础上确认了微分方程的边界条件,从而使微分方程组具有惟一解。膜元件运行微分方程模型的建立为膜元件及膜系统运行精确模拟计算软件的编制提供了数学基础。     

循环水排污水回收处理中过滤工艺的选择

循环水由于含盐量较高,在对其排污水进行回收处理时一般采用反渗透除盐工艺。反渗透膜对于进水的洁净度要求较为严格,为此采用压力式过滤器加超滤的预处理工艺处理循环水排污水,对三种压力式过滤器和两种超滤膜的出水特性比较试验,试验表明,多介质过滤器加外压式中空纤维超滤膜的过滤工艺,其出水水质和运行稳定性均满足后续反渗透设备的要求。     

电厂反渗透系统膜污染防治与膜清洗的研究

考察了长期运行的电厂反渗透系统中导致膜污染的原因、膜污染的种类和膜的清洗方法。采用反渗透系统进水和浓水的水质分析数据,提出了判断膜污染原因及污染物组成。根据反渗透系统进水和浓水的水质分析数据,实验筛选了膜清洗剂配方。结果表明表面活性剂对无机、有机混合垢有明显的促溶作用,以0.05%Na-SDS＋0.1%NaOH＋1%Na4-EDTA为配方的清洗剂,其清洗无机、有机混合膜污染的效果良好。     

膜技术在饮用水深度处理中的应用

本文综合介绍了反渗透,电渗析,等攻在饮用水度处理中的应用 。     

Effects of aluminum sulfate and ferric chloride coagulant residuals on polyamide membrane performance

Pretreatment may constitute up to one-fourth of the total costs of a membrane desalting facility. By using preexisting conventional filtration plants for pretreatment, significant cost savings may be realized. However, coagulant residuals from the pretreatment process may negatively affect reverse osmosis (RO) membrane performance. Various RO membranes were tested at three different treatment plants in southern California, using either aluminum sulfate (alum) or ferric chloride coagulants and chloramines. Repeated testing using alum with multiple RO elements revealed rapid deterioration in specific flux (up to 60% over 100 h of operation), as well as progressive reductions in salt rejection (typically 3-4% over 500 h of operation). Microscopic analysis of the fouled membranes revealed that the foulants were primarily aluminum hydroxide and aluminum silicate materials. In contrast to the RO data for alum coagulation, which showed declining membrane flux, the specific flux data using ferric chloride and chloramines increased over time for all membranes. Salt rejection decreased significantly during testing of each membrane. These data suggest that the RO membranes were physically degrading over time. The RO membranes may have been degraded by residual iron catalyzing a chlorine-amide reaction on the membrane surface, despite the fact that chlorine was present as chloramines.     

Effect of feed spacer arrangement on flow dynamics through spacer filled membranes

Operational issues arising from scaling and fouling of membranes are addressed by pre-treatment processes and alternative membrane or membrane secondary structures. In the present work the flow patterns associated with fluids within the membrane module are investigated using Computational Fluid Dynamics (CFD) tools. The effects on flow patterns through a spacer filled Reverse Osmosis (RO) membrane with the secondary structure of the membranes (feed spacer filaments) at various angles with the inlet flow are analyzed. The presence of the feed spacers in membrane module appears to generate secondary flow patterns enhancing the prospects for self induced backwashing increasing the allowable operational time and membrane efficiency. The flow visualization in the present study is useful in understanding the complex flow patterns generated in spacer filled RO membrane modules and could possibly lead to developing a new RO membrane which is more efficient, economical and appears to be a practically viable solution to reduce costs associated with the maintenance of RO membranes.