PTFE平板微孔膜用于渗透蒸馏浓缩茶多酚的研究

采用"挤出-压延-拉伸"法,通过改变纵向拉伸倍数,制备出平均孔径为0.25～0.80μm,孔隙率为46.9%～78.3%的4种疏水PTFE平板微孔膜。制备得到的PTFE平板微孔膜具有"纤维-结点"的网状微孔结构。随着纵向拉伸倍数的增加,微孔膜结构中的结点变小,纤维变细,孔径和孔隙率增大,孔隙分布更均匀。分别以茶多酚水溶液和CaCl2溶液为进料液和渗透液,进行渗透蒸馏浓缩实验。研究了膜孔径、渗透液和进料液的浓度、流速等对渗透通量和截留率的影响。结果表明,增大PTFE平板微孔膜孔径、提高渗透液的浓度以及进料液和渗透液的流速可提高渗透通量。整个实验过程中,4种PTFE平板微孔膜对茶多酚的截留率均能保持在99.9%以上,且不受操作条件的影响。     

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。     

新型中空纤维空气隙式膜蒸馏用于海水淡化

利用自制的添加隔热管状隔网并呈螺旋缠绕结构编排的中空纤维膜组件进行了空气隙式膜蒸馏(AGMD)海水淡化过程性能研究, 实验以模拟标准海水(质量分数3.5%, 总溶解性固体含量35000 mg·L^-1)为热料液进水, 考察了热料液进水温度、热料液流量、冷凝液进水温度和冷凝液流量对膜通量、造水比和热效率的影响。结果表明, 随着热料液进水温度增加, 膜通量、造水比和热效率均增加;冷凝液进水温度增加, 膜通量下降而造水比和热效率增加;热料液流量增加, 膜通量上升而造水比和热效率明显下降;冷凝液进水流量对膜蒸馏过程性能影响较小。实验过程中产水TDS始终保持在3.0 mg·L^-1以下, 相应的离子去除率高于99.99%, 膜通量、造水比和热效率最高可分别达5.87 L·m^-2·h^-1、5.37和0.943。研究表明, 引入清洁能源取代传统电加热驱动热源将进一步突出膜蒸馏技术的实际应用潜力。     

真空膜蒸馏海水淡化过程的强化研究

采用气液两相流技术对管状炭膜真空膜蒸馏模拟海水淡化过程进行强化研究。纯水物系和NaC l水溶液的气液两相流强化实验中,相比未通气体时通量分别增加了29%~35%和16%~66%。气体流量、渗透侧真空度和膜组件放置方式对两相流膜蒸馏过程通量的影响结果表明:气液体积流量之比在(1~2)∶1时两相流强化效果最佳;通量随着渗透侧真空度的增大而增大,且气液两相流操作在较小真空度时通量增加的幅度大于较大真空度时;膜组件的放置方式对通量影响较大,相对于水平放置时,膜管竖直放置时的通量较大,最大可达水平放置时的131%左右。     

利用多效膜蒸馏技术浓缩硫酸和磷酸水溶液

利用自制中空纤维气隙式多效膜蒸馏组件进行了多效膜蒸馏过程浓缩稀硫酸和磷酸溶液的研究, 考察了膜入口温度、料液进口浓度和料液流量对渗透通量和造水比的影响。结果表明,膜入口温度升高时渗透通量和造水比增加;料液流量增加,渗透通量增加,而造水比随之降低;料液酸浓度增加,渗透通量和造水比均随之下降,且硫酸的影响更为显著。实验过程中渗透通量和造水比最高可达5.3 L/(m²·h)和11.5。在适当的操作条件下,该过程可将质量分数(下同)为2%的稀硫酸或稀磷酸溶液浓缩至40%以上,且渗透液最大的电导率仍小于200 μS/cm。以10%的硫酸溶液为料液,利用2个不同的膜组件进行了持续30 d的多效膜蒸馏过程稳定性实验研究,实验期间所用膜组件操作性能没有明显下降,没有观察到膜渗漏现象。     

鼓气减压膜蒸馏过程研究

设计了新型鼓气减压膜蒸馏(AVMD)过程,在原水进入疏水膜组件前鼓入低压压缩空气,形成气液混合流进入疏水膜组件,在疏水膜组件的产汽出口外接负压系统,构成AVMD系统.采用疏水性聚偏氟乙烯中空纤维微孔膜,以自来水为测试液,研究了鼓气强度、进料温度、流速、冷侧真空度对AVMD过程性能的影响,考察了AVMD对不同NaCl含量溶液的分离性能.结果表明,随着鼓气量、进料液温度、流速,真空度的提高,AVMD过程通量有明显的增加,而产水电导率始终低于0.3 mS·m~(-1).当进料液温度70℃,冷侧真空度85 kPa,进料流速1.33 m·s~(-1)时,AVMD过程膜通量可高达45 kg·m~(-2)·h~(-1),而相同实验条件下减压膜蒸馏(VMD)过程的通量约为30 kg·m~(-2)·h~(-1).     

苯酚的膜蒸馏及结晶回收处理研究

采用中空纤维蒸馏技术研究了含酚废水的膜蒸馏处理及结晶回收，考察了料液相的温度、酸度、流速、吸收液浓度以及结晶回收苯酚等因素对苯酚膜蒸馏及结晶过程的影响。结果表明：以2％的NaOH溶液为吸收液时，膜蒸馏通量与料液相流速率有苯酚的浓度成正比，而当料液pH低于2．5及温度高于40℃的条件下，膜蒸馏通量几乎不受上述两因素的影响。以浓度为5000μg/mL的苯酚溶液为料液，经膜蒸馏处理可降至50μg/mL。采用CO2气流处理NoOH吸收液，即可得到结晶苯酚。     

吸收膜蒸馏淡化海水研究

针对吸收膜蒸馏(OD)系统的进料液和吸收液的温度非常接近甚至相同,其传质过程无相变热损失,有可能实现能耗较低的膜蒸馏过程这一设想,尝试开展OD法海水淡化研究。以葡萄糖水溶液为吸收液,考察了温度、料液及吸收液流速、吸收液含量等参数对OD过程的影响。结果表明,随温度的升高,膜通量增大明显;随吸收液和料液流速的增大,膜通量增大,且料液浓缩倍数较小、含量较低时,吸收液流速相对料液流速,对通量的影响更大,反之,料液浓缩倍数较大、含量较高时,料液流速的影响更大;随着吸收液含量的增大,膜通量也相应增大。试验过程中未发生疏水膜的亲水化渗漏现象。     

膜结晶处理高浓度Na+、Mg2+//Cl——H2O溶液的结晶调控

利用真空膜蒸馏-结晶耦合技术处理多元高盐废水(Na⁺、Mg²⁺//Cl^--H₂O),回收纯水和高品质NaCl晶体产品,考察不同操作温度和不同无机盐离子浓度对膜蒸馏性能和NaCl晶体产品性质调控作用。结果表明随着温度升高导致饱和蒸气压增大,增大了跨膜压差,膜的渗透通量逐渐升高;随着溶液中Mg²⁺浓度的逐渐升高,膜的渗透通量呈下降的趋势,主要是由于水的质量分数下降和溶液黏度增加;膜蒸馏过程中,通过对比实验,分析了疏水微孔膜表面在膜蒸馏操作条件下表面晶体颗粒沉积的程度,证实了使用的中空纤维膜性能稳定,重复使用20次后仍能保持稳定通量;操作温度为65℃时,不同离子浓度的饱和原料液(MgCl₂质量占NaCl和MgCl₂总质量的0%、5.0%和10.0%)得到NaCl晶体产品平均粒径分别为91.04、91.38和122.56 μm,粒度分布的变异系数C.V.值分别为28.78、30.63和36.77,粒径分布集中,表面相貌平整,呈完美的立方体形态,没有团聚现象;同时,膜蒸馏得到的水纯度较高,电导率均小于5 μS?m^-1,采用选择性溶剂乙醇洗涤后的NaCl晶体产品纯度均大于98.15%。综上,通过膜蒸馏过程中渗透通量和膜界面的有效调控,在适宜的操作温度和较低的Mg²⁺含量下,膜蒸馏结晶过程从多元高盐废水(Na⁺、Mg²⁺//Cl^--H₂O)控制分离获得纯度较高、表面形貌完好、粒度均一的NaCl晶体产品。这一研究将为综合治理多元无机高盐废水,实现废水的近零排放和无机盐资源回用开拓新的思路。     

气隙式膜蒸馏NaCl溶液的两相流强化

以膜蒸馏海水淡化为研究背景,采用气液两相流技术,对疏水改性管状陶瓷膜进行气隙式膜蒸馏模拟海水(NaCl溶液)强化实验研究。研究结果表明,在膜管内通入气体形成两相流后,去离子水和NaCl溶液的强化传质效率分别达到30.36%和28.57%。两相流过程强化影响因素的实验分别考察了料液温度、料液浓度和气体流量对渗透通量的影响,结果表明:在实验范围内,渗透通量随料液温度的升高而显著增大,且相比未通气体时增加了12%~44%;料液浓度增大导致渗透通量减小;气体的通入使得渗透通量增大,但当气体流量超过40L/h后,渗透通量却呈现缓慢下降的趋势;在体积气含率为0.5时的两相流强化效果最好,高速摄像仪拍摄到的现象很好地解释了该实验结果。研究结果将为进一步探究膜蒸馏强化过程的研究奠定基础。     

平板式超声对污染聚偏氟乙烯中空纤维超滤膜清洗

Polyvinylidenefluoride （PVDF） hollow fiber ultrafiltration membrane is frequently employed in water treatment. However, the fouling of ultrafiltration membranes affects the economic effectiveness of such process significantly. The ultrasound generated by flat plate transducer （UFPT） was used to clean the polluted PVDF ultrafiltration membrane with 2 g·L^-1 of citric acid aqueous solution in our study. The effects of UFPT intensity on the membrane surface were studied. The new membrane was easy to be polluted by the saturated CaCl2 solution. A synergistic effect of UFPT and 2 g·L^-1 citric acid aqueous solution could remove the foul of the membrane, and its flux could be recovered about 81%. The flux recovery of old membrane polluted was increased to 73.2% after 7 h soaking in citric acid aqueous solution, but its flux recovery without soaking was only increased to 56.2%.     

无机陶瓷膜处理印染废水的研究

研究了无机陶瓷膜处理印染废水过程,考察了膜孔径,操作条件对处理效果的影响及清洗剂和清洗时间对清洗效果的影响。结果表明:选用200nm的Al2O3膜管处理染料废水效果较好,合适的操作条件为:膜面流速4.2m/s,操作压力0.2MPa,温度30℃,此时渗透通量为129.64L/m2·h,CODCr的截留率达65%以上,色度去除率达90%以上。选择0.5mol/L硝酸溶液为清洗剂,清洗20min后,通量恢复为原来的81%以上。     

纳米SiO2/SDBS复合强化超滤处理含镉废水的影响因素

以纳米SiO2同阴离子表面活性剂十二烷基苯磺酸钠（SDBS）复合的胶束强化超滤处理含镉废水。考察了粉体加入、pH值、粉体浓度对超滤的影响。结果表明,纳米SiO2加入后,膜通量提高了25%,Cd2+截留率有所提高,渗透液中SDBS的浓度在一定条件下有所降低。膜通量、SDBS及Cd2+的截留率随pH值的变化而变化,三者随纳米SiO2加入量的增大而降低。另外,膜阻力主要为膜面吸附和膜孔堵塞阻力。     

Applicability of nanofiltration for the advanced treatment of landfill leachate

Landfill leachates are generated from municipal solid waste landfills under the action of water percolating through the landfilled waste. A treatment system using a combined membrane engineering process was developed to effectively treat the landfill leachate in the Dahanzhuang sanitary landfill (Tianjin, China). The process combines a membrane bioreactor (MBR) and nanofiltration (NF) technology to treat the leachate. The results indicate that the NF system, including the hollow‐fiber NF membrane, is an appropriate advanced treatment alternative for landfill leachates. This system provided good removal of chemical oxygen demand and color. The membrane flux renewal reached over 96% after washing with 0.01 mol/L HCl. As a result, the effluent water quality met effluent discharge standards (GB16889‐2008). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

减压膜蒸馏法稀碱液浓缩过程研究

以聚偏氟乙烯疏水膜为材料,采用减压膜蒸馏技术在较高真空度下浓缩硫化钠溶液,研究了各种条件对膜通量的影响.结果表明,当进料温度80℃、真空度为80kPa、流速为0.99m·s~(-1)时,质量分数4.6%的硫化钠溶液VMD膜通量为23.7 kg·m~(-2)·h~(-1);连续运行时,将稀碱液浓缩5倍后,膜通量仍维持在10.6kg·m~2·h~(-1),用稀盐酸清洗后膜通量恢复到初始值的95.6%;浓缩过程产水电导维持在10μS·cm~(-1)以下,脱盐率大于99.99%.     

有机硅烷改性ZSM-5/BPPO非对称膜制备及其渗透汽化性能

以硅烷改性ZSM-5分子筛为填充剂,采用沉浸凝胶相转化法制备了ZSM-5/BPPO非对称膜. 结果表明,分子筛在BPPO膜中分散均匀,填充分子筛后膜表面粗糙度增大、疏水性增强. 以低浓度乙醇-水体系为研究对象,考察了分子筛填充量、进料液浓度及进料液温度对ZSM-5/BPPO膜渗透汽化分离性能的影响. 结果表明,随乙醇浓度增大,ZSM-5/BPPO膜的分离因子减小,渗透通量增大;随进料液温度升高,ZSM-5/BPPO膜的分离因子及渗透通量均增大;在60℃、分子筛填充量为0.3%(w)时,ZSM-5/BPPO膜对5%(w)乙醇-水体系的分离因子高达18.49,渗透通量为529.69 g/(m2×h). ZSM-5/BPPO膜对不同醇-水体系的分离结果表明,醇类分子量越大,膜分离性能越好.     

减压膜蒸馏浓缩硫酸钠溶液的实验研究

采用减压膜蒸馏技术在较低真空度下浓缩Na2SO4水溶液，研究了真空度、料液温度、料液流速以及料液浓度对膜通量与截留率的影响。结果表明，随着膜下游真空度增加，膜通量增大；料液温度显著影响膜通量；随着料液浓度增加，膜通量严重衰减；实验条件下聚丙烯中空纤维膜表现出很好的疏水性，Na2SO4的截留率接近100%。     

Anti-fouling characteristic of carbon nanotubes hollow fiber membranes by filtering natural organic pollutants

Membrane fouling is a universal problem for conventional membrane filtration that usually causes a deterioration in membrane performance. We used electro-assisted carbon nanotubes hollow fiber membranes (CNTs-HFMs) to investigate the anti-fouling properties using natural organic pollutants. Benefiting from the electro-assistance, the permeation flux of humic acid solution using CNTs-HFMs was 190.20 L/(m²·h·bar), which was about 1.5- and 4.4-times higher than those of CNTs-HFMs without electro-assistance and traditional polyvinylidene fluoride hollow-fiber membranes (PVDF-HFMs). And the permeation fluxes of bovine serum albumin, sodium alginate and supernatant of anaerobic bioreactor also presented similar results. The average COD removal rate of CNTs-HFMs (66.8%) at ?1.0 V was higher than that of CNTs-HFMs without electro-assistance and PVDF-HFMs, which can be attributed to the formation of electrostatic repulsive force. It could reduce the deposition of pollutants on membrane surface under electroassistance.     

Influence of flocculant polyacrylamide on concentration of titanium white waste acid by direct contact membrane distillation

Effort has been made to investigate the concentration of titanium white waste acid (TWWA) by direct contact membrane distillation (DCMD) and the focus is the influence of polyacrylamide (PAM) on membrane wetting and fouling. It was found that the presence of PAM in feed reduced membrane flux and retarded wetting development, even though its level in feed of H₂SO₄ solution was only 0.0002 wt%. The difference between the tests using pure water and neat PAM aqueous solution, respectively, as feed also indicated the above effect registered with PAM. AFM results showed that the addition of PAM in feed solution changed the membrane shell surface morphology. However, conclusive proof of the PAM existence in membrane cross-section and inner surface was not obtained, probably due to its low concentration in feed solution. Two approaches were tried to recover membrane flux. In comparison with operation w/o any treatment, HCl solution rinsing did not lead to obvious improvement in membrane flux recovery, while rinsing combined with gas purge has clearly delayed the degradation in acid concentration factor. Nevertheless, even the latter could not ensure long term stability. High tortuosity and low hydrophobicity of the membranes used were suggested as underlying causes and should be addressed in the future.