悬浮型光催化纳滤膜反应器处理H酸溶液工艺中操作压力变化的机理研究：机理分析

首次通过系列黑暗条件下的膜分离空白试验对悬浮型光催化纳滤膜反应器中耦合分离膜操作压力的变化机理进行研究。耦合工艺中分离膜操作压力的变化主要由目标污染底物及其光催化降解中间产物的吸附、堵塞污染形成,与目标污染底物光催化降解速率以及中间产物的组成及数量随时间变化的关系密切,因而耦合分离膜初始操作压力的大小对其后续变化过程及变化规律影响颇大。由于耦合分离膜循环液中悬浮态光催化剂颗粒对耦合分离膜及被吸附其上的污染物分子强烈的冲刷作用,使得耦合分离膜操作压力在连续运行一定时间后下降至初始压力以下0．20～0．50kPa。在任何操作压力条件下,悬浮态光催化剂溶液均不对耦合分离膜形成膜污染现象,这与其在水相中的絮凝聚合过程有关。     

耦合分离膜对悬浮型光催化纳滤膜反应器耦合工艺特性的影响研究

以阿特拉津(atrazine)模拟废水作为处理对象,采用3种不同种类和性质的纳滤膜与悬浮型光催化氧化过程进行耦合构成悬浮型光催化纳滤膜反应器的废水耦合处理工艺,比较耦合纳滤分离膜的种类和性质对光催化膜反应器处理atrazine模拟废水耦合工艺特性的影响.实验得出,由于对目标污染底物及主要光催化降解中间产物出色的选择性分离截留效果,将TS-60与光催化膜反应器进行耦合处理目标废水的处理效果最佳.     

悬浮型光催化纳滤膜反应器处理H酸废水光催化降解效率及反应动力学

分别采用悬浮型光催化反应器和悬浮型光催化纳滤膜反应器进行光催化降解H酸溶液试验。结果表明,后者比前者具有更好的光催化处理效果。在污染物初始质量浓度分别为50mg／L、100mg／L和150mg／L、p／p0≥0．7的反应条件下,悬浮型光催化反应器中污染物光催化降解过程分别遵循L-H-级、一级以及一级与0级耦合的反应动力学。而在悬浮型光催化纳滤膜反应器的耦合工艺中,光催化降解过程分别遵循L-H一级、一级与0级的耦合以及0级反应动力学模型。     

光催化-膜分离耦合技术的水处理应用研究进展

介绍光催化-膜分离耦合工艺,它是在传统光催化技术中粉末催化剂难分离回收和废水处理后水质不够理想的基础上进行研发的。总结了不同构型的光催化膜反应器的特点及其存在的局限性,并简述了新型光催化膜反应器工艺运行时需考虑的因素。分析表明悬浮型光催化膜反应器的光催化效率明显高于负载型光催化膜反应器;针对悬浮式光催化膜反应器面临的由压力驱动引起的高能量输入和膜污染问题,指出光催化与渗透气化或膜蒸馏联用工艺所具有的独特优势。认为光催化/膜分离耦合工艺在水处理领域具有重要前景,今后研究应集中在高活性光催化剂的开发、高抗氧化性和耐污染的膜制备及光催化膜反应器结构的优化上。     

光催化膜反应器在污废水处理中的应用研究进展

传统光催化氧化技术在催化剂应用形式方面存在诸多不可克服的制约因素,将光催化氧化技术与膜分离技术进行耦合可从不同角度较好解决此类难题;目前的光催化膜反应器主要有悬浮型、负载型和内嵌型光催化膜反应器3种;在全面论述各类光催化膜反应器的工艺特性的基础之上,针对当前光催化耦合分离膜在合理选择膜类型和膜孔径方面存在理论不足的现状,首次提出耦合分离膜在膜类型和膜孔径选择过程中所要遵循的理论原则、依据和一套可操作性极强的选择程序。     

悬浮型光催化-膜分离反应器研究进展

悬浮型光催化反应体系因比表面积大和传质快等优点而具有较高光催化效率,但催化剂的分离回收工艺复杂,提高了工业成本。利用膜分离技术与悬浮型反应器耦合,可较好的解决固液分离问题,提高工艺经济性,代表了悬浮型光催化反应器的发展方向。本文重点对国内悬浮型光催化-膜分离反应器的研究进展进行综述,展望了该技术的发展方向。     

纳滤膜脱盐性能及其在海水软化中应用的研究

选择了ESNA1型纳滤膜对NaCl、MgCl2、Na2SO4、MgSO4等4种无机单盐水溶液体系进行分离实验;考察操作压力和料液浓度等的变化对纳滤膜分离性能的影响及纳滤膜脱盐的稳定性,得到一些纳滤膜脱盐的规律;并对ESNA1膜在人工海水和海水软化脱盐中的应用作了初步探索.无机盐体系脱盐实验结果显示:随操作压力升高和料液浓度增大,ESNA1膜对4种盐溶液中的离子的截留率分别增大和减小,操作压力和料液浓度的变化对一价盐溶液的截留率影响较大,对二价盐溶液的截留率影响较小.人工海水和海水软化脱盐试验结果显示:ESNA1纳滤膜在实验过程中稳定性好,在较低的操作压力下膜通量也较高,且ESNA1纳滤膜对Ca2 、Mg2 、SO42-离子的截留率均＞90%,初步判断此种纳滤膜可用于海水软化预处理.     

糖-盐水溶液的纳滤膜分离特性

根据 NF- 45纳滤膜对糖和氯化钠的截留特性 ,选择其开展糖和盐单组分和混合体系的分离实验研究 ,考察了纳滤膜分离性能随着操作压力、循环流量及料液浓度的变化影响 ,讨论了葡萄糖 -氯化钠、蔗糖 -氯化钠混合体系中糖和盐的相互影响作用 ,运用 NF- 45纳滤膜在适宜的操作条件下 (如操作压力、料液浓度 )可实现糖和盐的较好分离     

不同纳滤膜在软化浓海水性能方面的研究

选用纳滤膜NF270、DK、DL对浓海水进行实验研究。考察了不同操作压力下3种纳滤膜的透过通量、截留性能和分离系数的变化,从而选出适宜软化浓海水体系的纳滤膜。     

纳滤膜脱除淡盐水中硫酸根离子的研究

通过实验室与现场试验，研究了进淡盐水浓度(Co)、进淡盐水不同温度、pH值、操作压力(△P)、流量和不同纳滤膜对纳滤膜分离的影响，可以得到纳滤膜适宜的操作条件：温度55％；流量2—4L／min；操作压力1．5MPa。实验结果表明：对氯碱工业离子膜电解系统淡盐水中硫酸根的脱除率大于80％，硫酸根含量小于1．5g／L，符合工业生产要求。经过二个月的现场试验论证，所选用的纳滤膜稳定性、耐温性、耐污染性等好；同时，由现场试验可知，离子膜系统淡盐水脱除硫酸根离子纳滤膜分离技术是可行的，从而建立了离子膜系统淡盐水脱除硫酸根离子纳滤膜分离性能评价体系。     

单通道陶瓷膜管低压透水性能实验分析

无机陶瓷膜作为多孔介质具有分离效率高、耐酸、耐碱等优点,被视为在海水淡化、废水处理、气体分离等领域的研究热点。采用Al₂O₃管式单通道陶瓷膜材料构建膜组件,以燃煤电厂自来水、烟气冷凝水、脱硫废水三种不同水质为例,开展低跨膜压差下的膜组件透水性能实验,研究了膜参数、跨膜压差及水体温度等因素对渗透通量、渗透水质的影响,并对引发膜污染的机理过程进行了探讨分析。实验结果表明：陶瓷膜管的结构参数是关键因素,如孔隙率、孔径及厚度等;低跨膜压差下的渗透通量随压力增大呈线性提高,并未发现浓差极化现象,水体温度变化通过改变黏度进而影响渗透通量,同时水质较差时会导致渗透通量降低;陶瓷膜管的孔径是影响渗透水质的核心要素,微滤与纳滤膜对改善悬浮物含量、浊度及色度效果明显,不同孔径对盐度、电导率影响不同;从SEM图可以看出,污染物在膜表面或膜内部发生的沉积、架桥等现象导致严重的膜污染。充分认识影响陶瓷膜管渗透特性的关键因素及污染物的作用机理,对提高无机陶瓷膜的应用前景具有重要意义。     

气液两相流强化卷式纳滤膜分离硫酸镁水溶液

气液两相流强化卷式纳滤膜分离实验是针对DK2540卷式纳滤膜,采用气液两相流强化分离技术,对硫酸镁溶液进行研究,较系统地研究了温度、料液浓度、过膜压力、料液流速、气体流速等因素在分离硫酸镁溶液时,对膜通量、截留率和膜通量增加率的影响,并总结了气液两相流强化效果。结果表明,气液两相流强化卷式纳滤膜分离有明显的效果。温度宜在30~40℃。料液浓度越大、过膜压力越小、气液比越大,气液两相流强化效果越明显。     

Separation of Liquiritin from Glycyrrhizic Acid in Licorice Root Extract by Nanofiltration Membrane

The aim of this work was to study the separation of liquiritin (LQ) from glycyrrhizic acid (GA), in licorice aqueous solutions using nanofiltration (NRT-7450) membrane. The LQ and GA components are the main active ingredients of licorice root extract with various pharmacological effects, The effects of transmembrane pressure, feed temperature, feed pH, and cross-flow velocity on permeate flux and recovery were determined. A lab scale cross-flow set up using flat-sheet configuration membrane was employed for all experiments. SEM micrographs showed the changes in the fouled surface during operating time. The applied transmembrane pressure, feed temperature, feed pH, and cross-flow velocity were varied from 4 to 10 bars, 30 to 40°C, 3 to 9, and 0.8 to 3.1 m s^?1 respectively. The obtained recoveries for GA and LQ varied between 0.65 to 1.86% and 16.89 to 41.65%, respectively. The optimum operating conditions for separation LQ from GA in licorice aqueous solutions using NRT-7450 nanofiltration membrane were 1.8 m s^?1cross-flow velocity, 8 bars transmembrane pressure, 40°C of feed temperature and pH 7.     

Molecularly imprinted organic solvent nanofiltration membranes – Revealing molecular recognition and solute rejection behaviour

A new class of organic solvent nanofiltration (OSN) membranes featuring molecular recognition sites has been fabricated by a phase inversion molecular imprinting technique. Polybenzimidazole (PBI) was employed as a functional polymer for molecular imprinting for the first time. Apart from acting as a functional polymer, PBI exhibits excellent chemical and solvent stability and can be used as a nanofiltration membrane, acting both as shape-specific adsorbent and size-exclusion membrane. The molecularly imprinted organic solvent nanofiltration (MI-OSN) membranes fabricated in this study showed both nanofiltration membrane performance, and excellent molecular recognition ability. The model system comprised roxithromycin pharmaceutical, 2-aminopyrimidine building block and N,N-dimethylaminopyridine catalyst, which are retained, adsorbed and permeated through the MI-OSN membrane, respectively. The effect of both dope solution concentration and applied pressure on the molecular recognition behaviour of MI-OSN membranes has been investigated by employing Sips and Freundlich adsorption isotherms, as well as examining the physical morphology of the membranes. The rate of adsorption was investigated, revealing that the adsorption follows second-order kinetics and is not limited by diffusion. The imprinted membrane exhibited fourfold higher flux whilst maintaining the same rejection performance in comparison to the control membrane. It is shown that increasing the transmembrane pressure across the MI-OSN membrane irreversibly suppresses the molecular recognition whilst maintaining the rejection and flux performance.     

Separating Cyanide from Coke Wastewater by Cross Flow Nanofiltration

Investigations on separation of cyanide from coke wastewater were carried out in a cross flow nanofiltration membrane module following microfiltration of real industrial wastewater. Different composite polyamide nanofiltration membranes were used in the system while studying their effectiveness in cyanide separation under different operating conditions. Transmembrane pressure, pH, and cross flow velocity exhibited strong influence on percentage removal of cyanide. 94% cyanide rejection with a permeate flux of 79 liters per hour at a transmembrane pressure of 13 kg/cm² and at a volumetric cross flow rate of 700 liters per hour was achieved. The membrane module with a composite membrane having high negative charge was successfully operated without any significant loss in flux even after 72 hours operation. These encouraging results show that microfiltration and nanofiltration with properly selected membranes in an appropriate module could lead to a practical solution to a longstanding problem of cyanide removal from industrial wastewater.     

A new combination of a membrane and a photocatalytic reactor for the depollution of turbid water

This paper describes the combination of a dialysis membrane and a photocatalytic reactor into an original membrane photoreactor (MPR) to mineralize organic compounds contained in artificial turbid waters which are obtained by using natural clay named bentonite. Various systems have been described in the literature, combining photocatalysis with pressure-driven membrane techniques, such as nanofiltration (NF) and ultrafiltration (UF), but these systems can lead to membrane fouling. Only the combination of photocatalysis and membrane distillation avoids this problem, but it needs energy to reach pervaporation phenomena. The MPR system presented here works at ambient temperature, with the membrane used as a barrier for particles and to extract the organic compounds from the turbid water without transmembrane pressure. Thus, we were able to separate the polluted turbid water from the photoreactor compartment and to separate TiO₂ continuously from the treated water. The photocatalytic reaction and dialysis were studied separately before the MPR process was developed. A model pollutant, 2,4-dihydroxybenzoic acid (2,4-DHBA), was mineralized from turbid waters by photocatalysis. By means of the membrane, the TiO₂ remained in the photoreactor compartment without filtration and bentonite was kept away from the photoreactor.A mathematical model, based on diffusion through the membrane, with zero-order reaction in the reactor, is in good agreement with the experimental data.     

Concentration of ethanolic extracts from Sideritis ssp. L. by nanofiltration: Comparison of dead-end and cross-flow modes

The present investigation considers the flux decline during concentration of ethanolic extracts from Sideritis ssp. L. by nanofiltration. Membranes Duramem with molecular weight cut-off (MWCO) 300 and 500 Da have been used. Two sets of nanofiltration experiments are performed: dead end filtration in a stirred cell and cross flow filtration in a 4 flat sheet membrane rig. Comparable fluxes and rejections are observed. The membrane behaviour with respect to the operation conditions: transmembrane pressure and feed concentration is studied. The effect of the latter is illustrated by experiments with different feed concentrations and permeate-to-feed ratios. The discussion is supported by rejections and mass balance calculations. In both modes flux decreased with concentration and the observed rejections remained constant. Better conditions for reduced flux decline and tendency to a steady value are obtained by cross-flow nanofiltration. Combined with the greater membrane area and feed volume used in these experiments, these results can be regarded as having potential for larger scale applications.     

陶瓷膜气升式纳滤装置过滤杆菌肽水溶液的研究

气升式纳滤装置是一种新型膜过滤装置,具有能耗低、过滤条件温和等优点,在生化产品的分离纯化中应用前景广泛。以杆菌肽水溶液为过滤体系,采用孔径为0.9 nm的TiO2陶瓷纳滤膜,系统考察了曝气量和跨膜压差对气升式纳滤装置过滤性能的影响。结果表明,曝气可有效提升通量和截留率;当跨膜压差为0.3 MPa时,曝气量由20 L h 1增大到100 L h 1,通量和截留率分别提升34.0%和14.5%,在曝气量100 L h 1时两者达到最大,进一步增大曝气量,通量和截留率开始下降;当跨膜压差为0.1、0.3、0.5 MPa时,对应的最优曝气量分别为60、100、140 L h 1。并通过模型计算,分析了不同操作条件下,气升式纳滤装置流体力学性质和能耗的变化情况。     

Selective Strontium Removal from a Sodium Nitrate Aqueous Medium by Nanofiltration - Complexation

Abstract

In aqueous medium, selective complexation increases the ionic separation by nanofiltration. The combination of nanofiltration and complexation can be applied to the nuclear effluents treatment. To separate radioelements from a sodium salt medium, poly(acrylic acid) is associated to the FILMTEC NF 70 membrane. Effects of transmembrane pressure, pH, ligand concentration and ionic strength on salts retention are described, and the complexation constants are estimated. Finally, to reach the objectives, a strontium two - stages concentration by nanofiltration - complexation with a control of retentate salinity is investigated in a nonactive solution case.