有机物分子尺度对纳滤膜污染的影响研究

以市政污水处理厂的MBR出水作为纳滤进水,从有机物分子尺度分布的微观角度分析进水中有机物分布特征与纳滤膜污染的相关性,研究含不同分子质量的有机物水样对纳滤膜通量衰减、脱盐率以及膜表面污染的影响规律.结果表明,随着进水中溶解性有机物分子质量的减小,膜比通量衰减幅度不断增加,特别是分子质量＜1 ku的溶解性有机物引起膜通量衰减幅度最大,连续运行28 h后膜比通量下降了85.2％.电镜扫描分析进一步表明,进水中分子质量＜1 ku的有机物是造成膜有机污染的主要成分.此外,水中有机物在纳滤膜表面的累积会使纳滤膜的脱盐率有所增加.当进水中有机物分子质量在1 ku以下时,纳滤膜的初始脱盐率在94％左右,经28h连续运行后脱盐率上升了3.5％ ～4％;进水中有机物分子质量在100 ku以下时,纳滤膜的初始脱盐率为91％ ～92％,经28 h连续运行后脱盐率上升4％ ～4.5％.     

纳滤膜处理受污染地下水的运行影响因素研究

以预处理、纳滤组合工艺处理受污染地下水,分析了操作压力、运行时间、水温及预处理等因素对终端纳滤膜运行性能的影响。研究表明,以活性炭为预处理的纳滤膜通量衰减速率最小,说明由有机物造成的纳滤膜污染作用明显大于铁、锰及硬度等引起的无机污染;当膜进水操作压力由0.3 MPa增至0.8 MPa时,膜通量由8.7 L/(m2.h)线性增至19.1 L/(m2.h),而离子截留率、硬度及碱度去除率却呈线性降低;对高锰酸盐指数的去除率随运行时间的增加而明显下降,在80 h内降幅达12.5%,而总硬度的去除率则随运行时间变化不明显;当水温在5~25℃变化时,随着温度的升高则膜通量增加,但对盐的截留率减小,对有机物的去除率没有显著影响,而对硬度的截留率在22℃以前变化不大,当温度>22℃后会有较大的下降。     

纳滤膜去除饮用水中Cr(Ⅵ)的应用研究

分别采用自制的芳香聚酰胺平板纳滤膜和某芳香聚酰胺平板纳滤膜商品处理模拟含铬饮用水,考察其处理效果及影响因素。结果表明:在Cr(Ⅵ)浓度为50～250μg/L、pH值为7左右、操作压力为0.5 MPa、温度为25℃的条件下,两种纳滤膜对Cr(Ⅵ)的截留效果均较好,出水Cr(Ⅵ)浓度均低于0.05 mg/L(GB 5749—2006的限值),且截留率均随Cr(Ⅵ)浓度的升高而下降,膜通量则基本不变;随着操作压力的增加,两种纳滤膜对Cr(Ⅵ)的截留率均呈上升趋势,膜通量也大幅增加;进水pH值越高,则纳滤膜对Cr(Ⅵ)的截留效果越好,但膜通量无明显变化。     

纳滤及反渗透系统脱除有机物的试验研究

通过小型系统对多类有机物进行的脱除率试验,分析了纳滤及反渗透系统对有机物脱除率受膜脱盐率、产水通量、给水温度、给水p H值、给水有机物浓度等运行条件的影响。表明了纳滤系统对解离型有机物和难解离型有机物的脱除率受给水温度的影响明显,受有机物浓度、产水通量等影响较小;对解离型有机物的脱除率受给水p H值影响较大。验证了反渗透系统对小分子量有机物的脱除率较低,而对大分子有机物的脱除率很高。     

纳滤膜深度处理抗生素制药废水的运行条件优化

以抗生素制药废水的二级生化出水为研究对象,采用DK纳滤膜对其进行深度处理。优化了操作压力、pH值、进水流量、温度等操作参数,并考察了增加活性炭预处理对产水水质及膜污染的影响。结果表明,操作压力为1 000 kPa、pH值为6. 0、进水流量为8. 0 L/min是纳滤的最佳操作条件,在此操作条件下,采用纳滤膜深度处理经活性炭预处理后的抗生素制药废水的二级生化出水,TOC基本降至零左右,色度降至零,脱盐率达到31. 51%,产水可回用于原厂生产过程。活性炭预处理可提高膜通量,改善产水水质,有效降低膜污染,运行216 h后,膜通量衰减率可由14. 87%降至10. 30%。     

两级反渗透系统中膜元件的优化组合

明确了二级系统给水p H值约为7.75时系统透盐率达到最低值;论证了对于不同透盐率水平元件,若将较低透盐率元件用于二级系统而较高透盐率元件用于一级系统则全系统透盐率较低;讨论了调换一、二级系统元件的方式即形成系统元件的优化组合,以使全系统产水水质相应提高的工艺措施。     

反渗透系统中的通量失衡现象与通量均衡工艺

指出了膜系统通量严重失衡的原因与危害,提出了膜元件透水压力的概念,分析了透水压力、给水盐量及给水温度与通量失衡之间的关系。描述了淡水背压、段间加压与分段配膜等三项常规通量均衡工艺以及元件位置优化、能回加压透平与梯级加压水泵等三项特殊通量均衡工艺,并较为全面地分析了反渗透系统中的通量失衡现象与各项通量均衡工艺。     

纳滤膜去除饮用水中无机离子的中试研究

采用纳滤作为主体工艺生产直饮水,考察了两组标准脱盐率不同的纳滤膜对各种无机离子的去除效果.结果表明,纳滤膜可以确保直饮水中总溶解性固体(TDS)、SO24-、F-的含量达到《饮用净水水质标准》的要求,同时纳滤膜对自来水中的NH4+、NO2-、Cl-等离子的去除效果良好;标准脱盐率高的纳滤膜对无机离子的去除率较高,反之则较低.综合考虑各种因素,建议直饮水工程中选用标准脱盐率为80%-85%的纳滤膜.     

反渗透系统中膜元件安装位置的优化排列

提出了反渗透系统中膜元件位置优化排列的概念;分析了膜元件的产水量、透盐率及膜压降三项指标的离散特性;明确了膜元件位置优化排列的数学方法;实例计算了离散特性膜元件优化排列的系统运行效果。     

纳滤膜在饮用水处理中操作压力的确定研究

将纳滤膜用于饮用水处理,考察了不同操作压力下膜通量和出水水质的变化。结果表明,膜通量随着操作压力的增大逐渐升高,脉冲压力和恒压条件所对应的膜平均通量分别为0.953和0.830 L/(m2.h)。操作压力为0.3~0.4 MPa时,纳滤膜对COD和总硬度的去除率最大。     

Factors influencing flux decline during nanofiltration of solutions containing dyes and salts

In this paper, factors influencing the flux decline of nanofiltration membranes for the treatment of dye bath wastewaters were investigated. Experiments were performed with synthetic wastewaters. Synthetic solutions were prepared in different dye and salt concentrations at laboratory conditions. Operating conditions including cross-flow velocity and pH were changed to observe the effects of interactions between NaCl, dyes and the membrane. Cake formation rate of dye molecules on membrane surface with time was investigated by using linearized forms of cake filtration equations. The results suggest that cake layer formation of dye molecules on membrane surface, especially at low salt concentrations was the principal cause of flux decline. Operating conditions had a strong influence on permeate flux. Effects of cross-flow velocity on permeate flux were more pronounced at low NaCl concentrations. Furthermore, the lowest permeate flux values were obtained at the alkaline conditions due to increased dye hydrophobicity at high pH values.     

rGO/ZIF-8改性聚酰胺纳滤膜的制备及分盐性能

为了改善纳滤膜的性能,用水热合成法制备了rGO/ZIF-8复合纳米材料,通过界面聚合法引入到纳滤膜的功能层中,制成新型改性聚酰胺复合纳滤膜,并研究了改性膜的表面形貌、结构及分盐性能。结果表明:改性膜的表面出现沟壑状聚酰胺簇突起,粗糙度有较大提升,负电性增强,接触角降至42.7°,亲水性能有所提高。改性膜对Na₂SO₄的截留率由原状膜的95.8%下降至85.6%,但纯水通量提升近一倍,达到39.2 L/(m²·h),且在连续48 h运行过程中性能稳定。由此可见,新型rGO/ZIF-8材料的引入虽然会导致截留率略有下降,但可以大幅提高改性纳滤膜的水通量。     

正渗透去除单宁酸的影响因素分析

以单宁酸溶液作为原料液、NaCl溶液作为汲取液,在不同的膜朝向、汲取液和原料液浓度、膜面流速、原料液温度、pH值条件下,研究正渗透膜对单宁酸的去除效果。结果表明,汲取液浓度越高、原料液浓度越低、原料液温度越高、错流流速越大、膜活性层朝向汲取液运行模式均有助于提高膜通量,盐通量与膜通量呈正相关;不同影响因素条件下,正渗透膜对单宁酸的截留率均在97%以上,而在膜活性层朝向原料液模式下运行,对单宁酸的截留率更高。     

关于纳滤膜法水处理技术的探讨

通过对纳滤膜法去除CODMn、有机物、消毒副产物、藻类、微生物、无机盐和重金属的研究,总结了纳滤膜法的特点和优点,归纳了纳滤膜技术应用中存在的问题,指出纳滤膜法是一种具有应用前景的水处理技术。     

New PVDF membranes: The effect of plasma surface modification on retention in nanofiltration of aqueous solution containing organic compounds

New nanofiltration membranes were prepared by non-solvent-induced phase inversion from a PVDF/DMF/water system. The effect of exposure time before coagulation on the membrane characteristics (morphology, thickness, overall porosity, tensile strength) was investigated. PVDF membrane prepared at a fixed exposure time of 45s (PF45) was further plasma surface modified (RF 13.56 MHz) (PF45psm), introducing amino groups on the membrane. The performances of PF45, PF45psm and of a commercial nanofiltration membrane (N30F) were tested in the removal of two dyes from aqueous solution, characterized by different charge and molecular weight (congo red and methylene blue). The observed rejections depended more on the charge of the compound than on their molecular weights and results were optimized for the plasma modified membrane (PF45psm) with respect to unmodified (PF45) and commercial N30F membranes. In particular, methylene blue was retained for 100% by PF45psm with a relative flux of 65% compared to 38% of rejection and 59% of relative flux observed for N30F.     

双膜法处理污水厂尾水效能分析与膜再生研究

为提高污水厂出水水质,寻求适合处理污水厂尾水滤膜的再生方法,采用超滤—纳滤双膜工艺,针对辽宁省本溪市某城市污水厂二级尾水开展深度处理研究。考察了进水流速、累积过滤水量(超滤进水流速为25 L/min,纳滤进水流速为4 L/min)对膜分离效果的影响,同时开展了超滤和纳滤膜再生方式及效果研究。结果表明:在考察范围内,超滤装置的分离性能受进水流速影响较小,主要与进水污染程度有关,对COD、TP、氨氮的平均去除率分别为48%、55%、27%。当纳滤单元进水流速为4 L/min时,双膜法对COD、TP、氨氮的平均去除率分别为87%、96%、68%。双膜法对COD、TP的去除率随着进水污染程度的减轻而降低,氨氮去除率受累积过滤水量的影响较小,这与原水污染程度有关。随着累积过滤水量的增加,膜分离性能呈减弱趋势。超滤膜轻微污染时采用物理清洗效果良好,严重污染时需采用化学清洗的方法。超滤有效延缓了纳滤膜污染,纳滤膜轻微污染时采用酸碱浸泡法再生效果良好。     

海洋环境对软质聚氨酯泡沫材料燃烧特性影响的实验研究

对常见软垫家具填充物软质聚氨酯泡沫(FPUF)的燃烧特性及其燃烧烟气中窒息性气体组分生成量的变化特性展开实验研究,并采用有效剂量分数FED模型对烟气毒性进行评价.结果表明:无论是在强制点火模式抑或是非强制点火模式中,不同盐湿度雾滴沉降作用下FPUF热释放速率(HRR)曲线的发展规律基本相似.FPUF的着火时间在无强制点...     

Removal of THMP by nanofiltration: Effects of interference parameters

An experimental investigation is conducted to evaluate the effects of interference parameters on the performance of nanofiltration for removal of trihalomethane precursors (THMPs). The influence of operating pressure, feed THMPs concentration, pH, presence of other ions (Ca²⁺ and Mg²⁺), and suspended solids on nanofiltration performance are determined. The effect of membrane precompaction is studied as well. Membrane performance for reversible and irreversible compaction is compared. Pretreated surface water from a pond is used as the feed water in the study to simulate the practical conditions in water treatment industries. Experimental results show that precompacted membrane has a higher rejection capacity. Higher pressure, feed THMP concentration, and suspended solids increase rejection. However, overall flux variation due to these parameters is found to be negligible. On the other hand presence of divalent ions reduce the rejection capacity. Generally rejection is found to be greater than 90% for a precompacted membrane, which turned out to be well suited for industrial scale application of nanofiltration for removal of THMPs.     

Effects of reverse osmosis isolation on reactivity of naturally occurring dissolved organic matter in physicochemical processes

A field reverse osmosis system was used to isolate dissolved organic matter (DOM) from two lacustrine and two riverine surface water sources. The rejection of DOM was on the order of 99% and did not vary significantly with pressure. A simple mass balance model using a single measured value of rejection predicted the concentration within the closed-loop isolation system. The effect of operating pressure and solution flux on mass recovery of DOM was evaluated in laboratory and field trials. Under controlled laboratory conditions, >99% of a lacustrine DOM could be accounted for. A fraction of the isolated DOM was not recoverable using hydrodynamic cleaning; however, this fraction was recovered by using a pH 10 NaOH wash solution. The mass recovered in the NaOH solution increased from <1% to >6% with increasing transmembrane pressures from 414 kPa (60 psi) to1000 kPa (145 psi), respectively. This is consistent with fouling that results from an increase in solution flux, and a decrease in tangential crossflow velocity. Under field conditions, mass balances were generally >95% and mass recovery was >90% in all cases. The effects of temperature on solution flux were consistent with changes in fluid viscosity; effects of temperature on membrane diffusivity or morphological properties were small. RO isolation under low pressure conditions designed to maximize DOM recovery had little effect on DOM reactivity evaluated in terms of nanofiltration membrane fouling, XAD-8 resin adsorption, activated carbon adsorption, competition with trichloroethylene for adsorption sites on activated carbon, and molecular weight distribution measured using size exclusion chromatography.     

Performance and Morphology Evaluation of Thin Film Composite Polyacrylonitrile/Polyamide Nanofiltration Membranes Considering the Reaction Time

Polyacrylonitrile/polyamide (PAN/PA) thin film composite nanofiltration membranes were manufactured by interfacial polymerization (IP) of trimesoylchloride reacting with piperazine, in the presence of triethylamine. The influence of IP reaction time up to 100 s on the membrane performance and structure was investigated considering flux, rejection, structural morphology and roughness of the membrane using permeation test, scanning electron microscopy, atomic force microscopy as well as fourier transform infrared spectroscopy. Structural evaluation of membranes revealed that the average PA surface pore size was reduced initially up to 60 s of reaction due to the crosslinking process and PA layer compaction increment, however, became larger at longer reaction times. The PA layer effective thickness grew up with IP time and became constant after 60 s. The best water flux and Na₂SO₄ salt rejection were obtained at 60 s of reaction, which were 100 m³/day and 87% at pressure of 13 barg. Variation trends of permeation and morphological results showed accordance that confirmed their accuracy. Comparison of the Na⁺ rejection value with the rejection of commercialized NF membrane of Dow Company (NF90–400/34i) showed acceptable result for membrane performance.