A Compatible Membrane Process for Separation and Concentration of Pediocin PA-1 from Fermentation Broth

This work describes an effective combined ultrafiltration (UF)-nanofiltration (NF) membrane process for the separation and concentration of pediocin PA-1 from fermentation broth. Three polysulfone (PS) membranes with MWCOs of 5, 10, and 30 kDa were tested for ultrafiltration effectiveness. The 10 kDa membrane was selected because it displayed high permeability, good pediocin PA-1 recovery and reduced fouling. When the volume concentration factor (VCF) of UF reached 2.5, continuous diafiltration (DF) was carried out. The optimal diafiltration factor (DFF) was 1. The permeate obtained from UF was then concentrated by NF. When the VCF of NF reached 4.5, pediocin PA-1 recovery loss was only 10.5%. This two-stage membrane process improved the loading solutions by 4.5-fold, allowing up to 71.6% recovery of pediocin PA-1. After the membrane process, the NF retentate could be concentrated and subjected to preparative chromatography to obtain purified pediocin PA-1, or it could be dried to obtain a rich pediocin PA-1 preservative.     

膜技术分离纯化低聚半乳糖

用截留相对分子质量(以下简称分子量)1000的GE超滤膜对低聚半乳糖溶液进行分离纯化。结果表明,溶液的透过通量及ΔR(低聚糖与葡萄糖和乳糖之间的截留率差)随着温度的升高而增加;各种糖组分的表观截留率和分离选择性随透过通量的增加而增加,ΔR随透过通量的增加而降低,三者最终都趋于平缓,并且其变化趋势不受原料浓度的影响。当透过通量为20～40L/(m2.h)时,可达到膜的最佳分离效果。在最佳条件下对低聚糖原料进行连续渗滤,当累积透过体积为原料体积的3倍时,低聚糖的质量分数由36.4%提高到57.8%(1.59倍),收率为70.2%。     

用活性炭吸附强化超滤过程脱除废水中染料的研究(英文)

In this study, orange G dye was efficiently removed from aqueous solution by ultrafiltration (UF) mem-brane separation enhanced with activated carbon adsorption. The powdered activated carbon (PAC) was deposited onto the UF membrane surface, forming an intact filter cake. The enhanced UF process simultaneously exploited the high water permeation flux of porous membrane and the high adsorption ability of PAC toward dye molecules. The influencing factors on the dye removal were investigated. The results indicated that with sufficient PAC incor-poration, the formation of intact PAC filtration cake led to nearly complete rejection for dye solution under opti-mized dye concentration and operation pressure, without large sacrificing the permeation flux of the filtration process. Typically, the dye rejection ratio increased from 43.6% for single UF without adsorption to nearly 100% for the en-hanced UF process, achieving long time continuous treatment with water permeation flux of 47 L·m 2·h 1. The pre-sent study demonstrated that adsorption enhanced UF may be a feasible method for the dye wastewater treatment.     

微纳米气泡对超滤膜过滤腐植酸污染影响研究

为有效解决超滤过程中因有机物堵塞膜孔导致的膜污染和渗透通量下降问题，提出在对腐植酸（HA）溶液超滤传输及反洗过程中引入微纳米气泡水处理工艺，以强化超滤过程，实验研究了微纳米气泡对超滤膜渗透通量和截留效率的影响以及膜污染去除效果。结果表明在纯水和HA溶液中鼓入微纳米气泡后其归一化通量增大到1.1~1.3，截留效率提高了2.5%~22.0%，微纳米气泡水清洗和反洗后膜通量恢复分别高于纯水21%和25%。     

水溶性荧光染料溶液脱盐浓缩的纳滤实验研究

选用NTR7450和NF270两种纳滤膜对水溶性工业荧光染料原液进行分离，选择出透过通量大、除盐效果好和染料截留率高的纳滤膜，并对该染料溶液进行了脱盐和浓缩的间歇渗滤过程研究：在温度25℃和压力1.0MPa下，膜对染料截留率达到100％，最终料液中NaCl浓度从0.214mol／L降到0.0025mol／L,料液被浓缩了2．6倍。说明纳滤膜的间歇渗滤操作过程能够实现染料溶液的脱盐浓缩。     

Optimization of backflushing conditions for ceramic ultrafiltration membrane of disperse dye solutions

In the ultrafiltration (UF) of disperse dye solutions using ceramic membrane, backflushing is necessary to minimize the formation of fouling by disperse dye, and to enhance the permeate flux. In this work, the effects of backflushing on the ultrafiltration performance and decolorization were investigated. In the optimum backflushing condition, the permeate flux increased slightly and the filtration performance was stable during filtration process.     

Ultrafiltration behavior in the treatment of agro-industry effluent: Pilot scale studies

This pilot-scale study deals with highly polluting agro-industry's wastewater, palm oil mill effluent (POME). Ceramic ultrafiltration membrane was applied to treat this effluent. UF separation behavior of POME is reported. The effects of transmembrane pressure and crossflow velocity on permeate flux, limiting flux and percentage rejection for suspended solids and dissolved organic matters were investigated. The limiting flux obtained was further applied to determine critical flux and deposit resistance, R_c, using the possible theoretical link of critical flux and limiting flux. The verified values of critical flux are useful in the operation of ultrafiltration to minimized membrane fouling; thus, longer lifespan of the membrane can be expected. Both transmembrane pressure and crossflow velocity show their significant effects to the permeate flux, whereas only the crossflow velocity influences the rejection of dissolved organic matters in terms of COD and BOD.     

膜分离技术在低分子量生物产品分离纯化中的应用

介绍了膜分离技术在低分子量生产产品分离纯化中的应用。以压力差为推动力的膜分离技术包括微滤、超滤、纳滤、反渗透等，其分离性能通常由透过通量和截留率表征，而操作模式则分为浓缩和渗滤两种。本文将低分子量生物产品划分为氨基酸和多肽、抗生素、乳酸及低聚糖等，综述了膜分离技术在上述产品的回收、分离、纯化和浓缩过程中的研究与应用进展。     

Application of ultrafiltration hybrid membrane processes for reuse of secondary effluent

This study evaluates the factors affecting pretreatment conditions for hybrid UF membrane processes for reuse of secondary effluent from the sewage treatment plant. The experimental results obtained from the ultrafiltration (UF) membrane process showed that the particles of the size range between 0.2 and 1.2 μm caused a significant impact on membrane fouling in all cases even with or without the coagulation process. As pretreatment of UF membrane process, the coagulation significantly improved the permeate flux. Optimal flux improvement was seen at an alum dose of 50 mg/L. In addition, it was found that the permeate flux was least declined under the coagulation condition of charge neutralization (pH 5.0). Also, the powdered activated carbon (PAC) adsorption enhanced the permeate flux. Application of the direct filtration as a pretreatment of UF membrane process was also very effective in reducing the UF membrane fouling.     

纳滤膜在染料工业脱盐浓缩中的应用

对CA50(醋酸纤维素)纳滤膜的盐截留率和染料截留率进行了考察,并将CA50纳滤膜应用于染料工业脱盐浓缩,考察了膜污染现象,对综合效益进行了分析。结果表明,CA50纳滤膜的盐截留率较低,对染料则有很高的截留率：将CA50纳滤膜应用于黄染料工业生产中,使主体染料的纯度提高20％,对黑染料膜分离过程进行优化,当盐浓度保持在5％时能获得最佳的脱盐效果;膜分离蓝色染料一段时间后,会造成膜污染,引起膜污染的物质主要是油污、无机物、有机物和染料分子,通过适当的预处理和清洗可以保持膜通量和防止膜污染：采用膜分离工艺使染料工业在经济、环境和社会效益得到提高．     

Constrained optimization of cellulose acetate membrane using two-level factorial design

This work presents a method, the SUMT algorithm, to optimize the performance of the cellulose acetate (CA) membrane by maximizing the permeate flux subject to an equality constraint of salt rejection and a pair of inequality constraints for each variable. Three variables, i.e., (1) the concentration of formamide in the casting solution, (2) the time of evaporation of the membrane prior to gelling, and (3) the annealing temperature of the membrane, were selected for this optimization study. Experiments based on the two-level factorial design were conducted for the determination of regression equations for both premeate flux and salt rejection. At a level of 97.00% rejection of a 0.5% sodium chloride solution at 600 psig, the maximum permeate flux of the CA membrane was predicted to be 14.52 gallons per day per sq. ft (gfd). This was later confirmed by experiments. The effects of the casting variables on membrane performance concluded in this study were consistent with those reported by other researchers.     

Direct filtration of Procion dye bath wastewaters by nanofiltration membranes: flux and removal characteristics

The treatment and reuse of industrial wastewaters by membrane processes has become more attractive in the last few years due to constraints on water usage. The aim of this study was to investigate the direct filtration of reactive dye house wastewaters by nanofiltration membranes based on permeate flux, and sodium chloride and colour removal. Experiments were performed using both synthetic and industrial dye bath wastewaters with the fluxes of the industrial dye bath wastewaters lower than those of the synthetic solutions. The effects of operating conditions such as pressure and pH were assessed. Studies with DS5 DK type (polysulfone–polyamide) membranes showed that nanofiltration membranes are suitable for direct treatment of wastewaters and the permeate quality was appropriate for reuse in the dyeing process. Pre‐treatment and neutralisation were important for recovery of large amounts of salt and water from the permeate stream. Neutralisation of the solution with HCl rather than H₂SO₄ gave a better permeate from the point of view of the reuse. The highest permeate flux and colour removal and the lowest salt removal were achieved with the HCl neutralisation. Copyright © 2003 Society of Chemical Industry     

Poly(vinylidene fluoride-co-hexafluoro propylene) membranes prepared via thermally induced phase separation and application in direct contact membrane distillation

A non-toxic and environmentally safe diluent, acetyl tributyl citrate, was employed to prepare poly(vinylidene fluoride)-co-hexafluoropropylene membranes via thermally induced phase separation. Effects of the polymer concentration on the phase diagram, membrane morphology, hydrophobicity, pore size, porosity and mechanical properties (tensile stress and elongation at break) were investigated. The results showed that the pore size and porosity tended to decrease with increasing polymer concentration, whereas the contact angle, liquid entry pressure and mechanical properties showed the opposite trend. In direct contact membrane distillation operation with 3.5 wt-% sodium chloride solution as the feed solution, the prepared membranes performed high salt rejection (>99.9%). Furthermore, the prepared membranes retained excellent performance in long-term stability tests regarding the permeate flux and salt rejection.     

聚丙烯中空纤维膜的应用与清洗方法

采用聚丙烯中空纤维微孔膜的减压膜蒸馏技术对氯化钠、氯化钙和硫酸镁等盐溶液进行脱盐处理，考察了料液温度、料液流量、料液浓度和冷测真空度对膜的渗透通量和去除率的影响。实验表明：随着真空度及料液流量、温度的提高，膜的渗透通量有增加的趋势。在相同条件下处理不同的盐溶液，膜的渗透通量相差不大，膜的去除率达到99％以上。使用0．5mol／L盐酸以及0．05mol／L EDTA清洗被污染的膜效果最明显，可迅速有效地将附着在中空纤维膜上的无机污染物去除，使膜渗透通量得到基本恢复。     

Study of drinking water treatment by ultrafiltration of surface water and its application to China

In China, many water supplies depend on conventional water treatment. Due to unfit soil and water conservationin some regions of China, conventional water treatment has showed some defects for the poor quality of water resource. In addition, advances in membrane technology and increasing requirements on water quality have stimulated ultrafiltration (UF) for water treatment. In this research, OF test apparatus was set up to produce drinking water from raw water of the Binxian Reservoir (China). The performance of UF membranes was investigated. There was a linear relationship between membrane resistance and accumulated permeate water. Using coagulation before OF increased permeate flux and retarded membrane flux decline. Surprisingly, membrane permeate flux in a coagulation/UF process was higher than that in coagulation-sand filtration-UF process with raw water of medium turbidity. OF treatment provided effective turbidity removal. Iron, manganese and aluminum were removed completely. The UF membrane also perfectly removed all coliform bacteria. The reduction of total organic carbon was satisfactory. The treated water quality complied with China's drinking water guidelines. The Ames test showed that the mutagenic activities of membrane permeate water was negative.     

The reuse of reactive dye liquors using charged ultrafiltration membrane technology

A closed-loop recycle system using a charged ultrafiltration membrane to decolourise reactive dye effluents from a textile yarn and fabric dyeing process is described. The economics of the process depend on the value of the electrolyte ($5 to $10 per M³). Conventional reactive dyeing technology was examined and modified to facilitate dye liquor reuse. The performance of the membrane was examined in terms of electrolyte rejection, colour rejection and permeate flux under varying conditions of solution pH, ionic strength and operating pressure.     

Manipulating the separation performance of nanofiltration membranes by coating thickness of organic phase during interfacial polymerization

Nanofiltration (NF) membranes have excellent separation capabilities and selective performance, and are widely applied in the field of concentration and separation of salt and inorganic salt mixtures. In this article, NF membranes with a higher comprehensive performance were fabricated using a thinner coated organic phase during interfacial polymerization, which greatly reduced the rejection of sodium chloride and significantly improved the water flux without reducing the rejection of magnesium sulfate. Structure comparison found that thinner polyamide separation layer resulted in the higher crosslinking degree, smaller particle, and relatively rough surface. Based on these analyses, we hypothesized that thermodynamically efficiency in the system varies with the coating thickness. Finally, the mechanism of the influence of the coating thickness of organic phase during heat treatment on the interfacial polymerization process and membrane structure was discussed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48284.     

High frequency excitation and vibration studies on hyperfiltration membranes

In an effort to increase the freshwater production rate, possible effects of high-frequency vibrations (both acoustically and electrically induced) on the hyperfiltration (reverse osmosis) process have been reexamined comprehensively. Cellulose-acetate membranes were used, both as customarily prepared by the Loeb-Sourirajan process, and with added magnetic and non-magnetic iron oxide powders. Flow and salt rejection were measured with sodium chloride feeds, without and with iron hydroxide or calcium sulfate membrane fouling. Flow and rejection were found substantially independent of the applied vibrations over the frequency and power ranges applied. The one exception was ultrasonic vibration on a depressurized, fouled membrane, which showed an advantageous cleaning effect (hyperfiltrate flux increased after the treatment), confirming previous observations.     

Direct Contact Membrane Distillation Applied to Colored Reactive or Disperse Dye Solutions

The influence of dye class and chromogen groups of dyeing wastewaters composed by reactive or disperse dyes with different colors on direct contact membrane distillation (DCMD) was investigated. The state‐of‐the‐art shows that disperse dyes and different dye colors are not studied in DCMD and the application of DCMD for dyeing wastewater treatment is limited to a few publications. High color rejection was obtained and water was recovered at the permeate side for feed solutions containing reactive or disperse dye. Influence of chromogen groups (colors) was not observed, whereas the class dye was decisive for the process performance. Reactive dyes showed higher mean permeate flux due to the repulsion between their anionic groups and the negative surface of the membrane. Partial wetting of larger pores allowed the passage of small disperse dye molecules, reducing color rejection.     

Treatment of a textile effluent: application of a combination method involving adsorption and nanofiltration

A combination of adsorption and nanofiltration (NF) was adopted for the treatment of a textile dyehouse effluent containing a mixture of two reactive dyes. The effluent stream was first treated in a batch adsorption process with sawdust as an adsorbent to reduce the dye concentration of the effluent by about 83% for Dye 1 and 93% for Dye 2. The effluent from the adsorption unit was passed through an NF unit for the removal of the remaining small amount of dyes and to recover the associated chemicals (mainly salt) in the effluent stream. The dyes remaining after this step were less than 1 ppm. The percentage removal of COD was greater than 99%, and the salt recovery was on the order of 90%. Equilibrium studies were carried out with synthetic solutions of the dyes (both single component as well as two-component systems) at room temperature. The adsorption rates were studied in detail using varying amounts of the adsorbent. NF of the effluent was performed in a cross-flow system using a 400 molecular weight cut-off membrane. A detailed study was carried out to observe the effect of the process parameters, namely applied pressure and bulk velocity on the process outputs such as dye rejection, COD removal, permeate flux and salt recovery. Finally, direct NF of the effluent (with the original high concentration) was undertaken, and the performance of the process was compared with the combination method. The permeate flux for the proposed combined method was found to be about twice that for the direct NF method. The dye rejection improved significantly compared to adsorption.