海藻酸钠-醋酸纤维素复合薄膜的制备及除湿性能测试

为提高膜式全热交换器的除湿效率,以海藻酸钠为表面活性层,醋酸纤维素膜为支撑层,氯化锂为亲水添加剂制备了一种新型除湿复合膜。测试了复合膜的水蒸气透过量和水溶性,对薄膜结构进行表征及分析了应用复合膜的全热交换器的传质系数。研究结果表明:复合膜的水蒸气透过量随氯化锂含量增加而高达4.42×10~(-5)g·m~(-2)·s~(-1)·Pa~(-1),是无氯化锂复合膜的1.56倍,商用纸膜的2.63倍。表面活性层水溶性介于18.29%~28.55%之间,具有一定的防水耐水性。热重曲线表明通入55℃干燥空气复合膜可实现再生,红外光谱图显示出海藻酸钠为复合膜引进大量亲水性羟基。最后,将复合膜应用到全热交换器中,并与商用纸膜换热器在传质系数上进行了分析比较。     

空气除湿用抗菌透湿复合膜的制备

为提高膜式全热交换器的除湿性能并使膜具备抗菌性能,以Li Cl为亲水添加剂,Ag NO3为抗菌剂,添加到聚乙烯醇（PVA）水溶液中制成铸膜液,以聚丙烯（PP）膜为支撑层,制备了一种抗菌透湿复合膜。搭建了薄膜透湿性测量平台,测试了复合膜的水蒸气透过量,对复合膜的抗菌性进行了检测。结果表明,复合膜的水蒸气透过量随Li Cl含量的增加而增加,Li Cl含量为5%的复合膜是不含Li Cl复合膜的1.79倍,是商用纸膜的2.67倍。加入Ag NO3后薄膜的透湿性没有明显变化,抗菌实验结果显示,复合膜对表皮葡萄球菌、大肠杆菌有抗菌作用,对表皮葡萄球菌的抗菌作用更强。     

基于亲水/憎水复合膜的全热交换器换热换湿性能[

膜全热交换器由于可以同时回收空调排风中的潜热和显热而受到重视。研究了基于PVAL/PVDF复合透湿膜的全热交换器的透热透湿性能，实验测定了新风与排风之间的显热交换能力和水蒸气交换能力，并建立了基于亲水/憎水复合膜的逆流膜全热交换器传热传质计算模型，实验与理论结果吻合较好。结果表明，该复合膜全热交换器的总传热系数为20～35 W·m-2·℃-1，总传质系数为（1.5～3.5）×10-3 m·s-1。     

海藻酸钠/CNC/山梨酸钾复合膜的制备及性能研究

以海藻酸钠为基材,纤维素纳米晶(CNC)为增强增韧剂,以山梨酸钾为防腐保鲜剂,采用流延法制备海藻酸钠/CNC/山梨酸钾复合膜。研究CNC、山梨酸钾的加入对海藻酸钠膜光学性能、力学性能、水蒸气阻隔性能等的影响。结果表明：随着CNC含量的增加,复合膜的透光率先增加后降低;添加山梨酸钾后,复合膜的透光率逐渐下降。CNC的加入使复合膜的拉伸强度和断裂伸长率均先提高后降低,水蒸气阻隔性能先降低后升高。随着山梨酸钾的添加,复合膜的拉伸强度逐渐降低,断裂伸长率先降低后增加,水蒸气阻隔性能先升高后降低。当CNC含量为5%、山梨酸钾含量为3%,复合膜的拉伸强度为120.78 MPa,断裂伸长率为4.38%,水蒸气透过系数为7.62×10^-13 g·cm/(cm²·s·Pa),与纯海藻酸钠膜相比,分别提高了21.66%、27.33%和17.59%,复合膜综合性能最佳。     

木薯氧化淀粉/海藻酸钠复合膜的制备及性能

利用海藻酸钠(SA)和氧化改性木薯淀粉(OS)为成膜基材,添加增塑剂甘油和改性剂硬脂酸;采用流延法制备一种新型复合膜。探究氧化淀粉氧化度、淀粉与海藻酸钠比例、甘油含量和硬脂酸添加量对复合膜拉伸强度、断裂伸长率、吸光性和水蒸汽透过率的影响,以复合膜综合性能评分为响应值,淀粉与海藻酸钠比例、甘油含量、硬脂酸添加量为自变量,利用响应面法对配方进行优化,并建立了二次多项式回归模型。结果表明,氧化淀粉∶海藻酸钠为6︰4、甘油添加量23%、硬脂酸添加量1.8%,复合膜性能指标综合分为74.0,此时复合膜的拉伸强度为(8.319±1.058)MPa,断裂伸长率为(67.063±4.891)%,吸光度为(1.333±0.026),水蒸气透过系数为(0.375±0.020)g·mm/(m~2·h·kg)。     

香芹酚/海藻酸钠生物复合膜的制备及表征

为了提高海藻酸钠膜的包装性能，本文采用溶剂浇铸法制备了不同含量香芹酚/海藻酸钠生物复合膜，通过SEM、XRD和FTIR对复合膜的微观结构进行了表征，并对其物理、化学、抑菌和保鲜性能进行了考察。结果表明：添加香芹酚增加了香芹酚/海藻酸钠生物复合膜的粗糙度，膜中海藻酸盐和香芹酚的分子间发生静电和氢键作用。复合膜的热稳定性随香芹酚 含量增加呈现先增强后降低的趋势，其中香芹酚体积分数为0.8%时，香芹酚/海藻酸钠复合膜的综合性能最优，水溶性为90.48%，透明度为0.23 mm-1，水蒸气透过速率为0.17 g/(d•cm2)，拉伸强度为72.24 MPa，断裂伸长率为83.41%，对丰孢木霉菌(Trichoderma sp.)的抑制效率为65.79%。香芹酚/海藻酸钠复合膜能有效保持采后双孢蘑菇的品质，延长其货架期。     

燃煤电厂湿烟气的除湿特性

燃煤电厂湿法脱硫后排放的烟气中含有大量水蒸气,造成大量水资源的浪费,溶液除湿工艺是水分回收技术之一。通过绝热型管式降膜除湿试验台,采用价格低廉的CaCl₂溶液为除湿剂,探究了湿烟气状态下溶液浓度、溶液温度、传质面积及进口温度对除湿性能的影响,试验得到了CaCl₂溶液除湿过程的传质系数,溶液除湿效率远高于清水冷凝除湿,为烟气除湿工艺的选择和性能预测提供了参考。     

香芹酚/海藻酸钠生物复合膜的制备及性能

为了提高海藻酸钠膜的包装性能,采用溶剂浇铸法制备了添加不同含量香芹酚的海藻酸钠生物复合膜,通过SEM、XRD和FTIR对复合膜的微观结构进行了表征,并对其物理、化学、抑菌和保鲜性能进行了考察。结果表明:添加香芹酚增加了香芹酚/海藻酸钠生物复合膜的粗糙度,膜中海藻酸盐和香芹酚的分子间发生静电和氢键作用。复合膜的热稳定性随香芹酚含量增加呈现先增强后降低的趋势,其中,香芹酚体积分数为0.8%时,香芹酚/海藻酸钠复合膜的综合性能最优,水溶性为90.48%,透明度为0.23mm~(–1),水蒸气透过速率为0.17g/(d·cm~2),拉伸强度为72.24 MPa,断裂伸长率为83.41%,对丰孢木霉菌(Trichoderma sp.)的抑菌率为65.79%。香芹酚/海藻酸钠复合膜能有效保持采后双孢蘑菇的品质,延长其货架期。     

硅橡胶复合膜用于含酚水溶液渗透萃取传质过程

以苯酚为模型污染物,以氢氧化钠溶液为萃取液,利用平板复合膜［聚二甲基硅氧烷（PDMS）/聚偏氟乙烯（PVDF）］构造渗透萃取体系,系统地研究了该体系渗透萃取含酚水溶液的传质过程与特性。探讨了料液与萃取液的浓度及流量、运行温度等操作条件及活性层厚度对渗透萃取传质性能的影响。结果表明,pH>13时,总传质系数K_ov不随萃取液流量及浓度变化而变化;苯酚的液膜传质系数kf与膜面流动Reynolds数Re^0.46呈正比,传质通量与温度符合Arrhenius方程。在苯酚初始浓度5.0～15.0 g•L^-1范围内,K_ov为定值。活性皮层厚度为4、6、8 μm的膜扩散传质系数分别为15.0×10^-7、9.9×10^-7及7.5×10^-7m•s^-1（323.2 K）,较均质膜提高了2～4倍。苯酚在复合膜中的传质仍属膜阻控制的传质。     

纳米SiO_x对壳聚糖膜透氧透湿可调性的研究

为了探究纳米SiOx对壳聚糖复合膜透氧和透湿的影响,采用共混法制备了不同纳米SiOx添加量的壳聚糖复合膜,并用红外(IR)和透射电镜(TEM)对复合膜的结构进行表征,同时考察复合膜中不同添加量的纳米SiOx对猕猴桃呼吸强度和失重率的影响。结果表明,当纳米SiOx添加量分别为0.01、0.03、0.05 g·(100 mL)-1时,纳米SiOx/壳聚糖复合膜的O2透过系数分别为32.61、24.89、31.48 mg·cm-2·d-1,水蒸气透过系数分别为91.68、73.62、85.35 mg·cm-2·d-1。特别是当纳米SiOx添加量为0.03 g·(100 mL)-1时,纳米SiOx/壳聚糖复合膜的O2透过系数及水蒸气透过系数达到最低,分别较壳聚糖单膜降低了34.40%和22.85%,猕猴桃呼吸高峰延迟了7 d。实验结果证实通过控制纳米SiOx的添加量,可以调节复合膜的透氧量和透水量,并能有效抑制采后呼吸,提高猕猴桃的保鲜效果。     

电纺及疏水改性制备CA/SiNPs-FAS超疏水复合膜及膜蒸馏脱盐研究

以1-甲基-2-吡咯烷酮/丙酮为混合溶剂,无纺布为支撑层,采用静电纺丝技术与溶胶-凝胶方法,制备了醋酸纤维素/二氧化硅复合纳米纤维膜,并将其浸渍于全氟烷基硅烷/正己烷分散液中进行疏水化改性。利用场发射扫描电子显微镜、红外光谱仪、孔径分析仪、接触角测量仪器等表征了改性前后复合膜表面形貌、官能团变化、孔径分布及润湿性等膜性能参数并将其应用于连续性直接接触式膜蒸馏盐浓缩过程。结果表明,静电纺丝复合膜呈三维空间网状结构,且利用正硅酸乙酯生成的纳米二氧化硅颗粒内陷于醋酸纤维素纤维内部形成微米-纳米梯级分布。经全氟烷基硅烷修饰后,红外特征峰明显,复合膜水接触角最高可达156°,且对质量分数为5%的十二烷基硫酸钠液滴也同时展示出优良的抗润湿性能（接触角125°）。以60℃、35 g·L^-1的NaCl溶液为进料液进行持续性直接接触式膜蒸馏脱盐实验,当渗透温度为20℃时,各复合膜盐截留率均能达到99.99%以上,其中,CA/SiNPs-FAS膜通量可稳定在11.2 kg·（m²·h）^-1。     

聚乙烯醇-SiO2/聚酯无纺布膜的制备及性能研究

采用聚酯无纺布(PET)作为支撑层,利用相转换法在PET表面制备聚乙烯醇(PVA)或PVA-SiO₂活性层,得到了PVA/PET复合膜与PVA-SiO₂/PET复合膜。考察了2种复合膜的过滤性能和污染行为。结果表明,PVA中加入质量分数4%纳米SiO₂颗粒,复合膜的接触角降至33.1o,亲水性显著增强,而膜孔径减小至3.1 nm,降低了85.5%,PVA/PET超滤膜转变为PVA-SiO₂/PET纳滤膜(0.6 L/(m²·h))。PVA-SiO₂/PET复合纳滤膜对海藻酸钠的抗污染性能较强。纳米SiO₂对复合膜的污染机制无明显影响,模拟污染物对复合膜的污染机制以标准堵塞为主。     

明胶涂覆于亲水化改性的支撑层上以提高复合膜的结构稳定性和渗透蒸发性能简

The interfacial compatibility of composite membrane is an important factor to its structural stability, andseparation performance. In this study, poly （ether sulfone） （PES） support layer was first hydrophilically modified with poly（vinyl alcohol） （PVA） via surface segregation during the phase inversion process. Gelatin （GE） was then cast on the PVA-modified PES support layer as the active layer followed by crosslinking to fabricate composite membranes for ethanol dehydration. The enrichment of PVA on the surface of support layer improved interfacial compatibility of the as-prepared GE/PVA-PES composite membrane. The water contact angle measurement and X-ray photoelectron spectroscopy （XPS） data confirmed the surface segregation of PVA with a surface coverage density of -80%. T-peel test showed that the maxima/force to separate the support layer and the active layer was enhanced by 3 times compared with the GE/PES membrane. The effects of PVA content in the support layer, crosslinking of GE active layer and operating parameters on the pervaporative dehydration performance were investigated. The operational stability of the composite membrane was tested by immersing the membrane in ethanol aqueous solution for a period of time. Stable pervaporation performance for dehydration of 90% ethanol solution was obtained for GE/PVA-PES membrane with a separation factor of -60 and a permeation flux of -1910 g.m^-2.h1 without peeling over 28 days immersion.     

聚偏氟乙烯/聚二甲基硅氧烷渗透气化膜在丁醇分离中的应用

通过相转化法制备PVDF多孔支撑膜,在其上涂覆致密的PDMS分离层制备得到PVDF/PDMS复合膜,用于丁醇的分离纯化。以丁醇水溶液为原料液,流速为1.6 L·min^-1,丁醇浓度为15 g·L^-1,温度为37℃时, PVDF/PDMS复合膜的总通量为158.2 g·m^-2·h^-1,分离因子为17.3。向丁醇水溶液中按丁醇：丙酮：乙醇比例为6：3：1添加丙酮和乙醇模拟发酵液,PVDF/PDMS复合膜的总通量升高到189.5 g·m^-2·h^-1,分离因子降低到14.8。进一步考察了以丙酮-丁醇-乙醇（ABE）发酵液为原料液的渗透气化膜分离性能,发酵液中不存在菌体时,PVDF/PDMS复合膜的总通量和分离因子分别为120.2 g·m^-2·h^-1和19.7,而菌体存在时,复合膜的总通量和分离因子分别为122.1 g·m^-2·h^-1和16.7。与PDMS均质膜相比,PVDF/PDMS复合膜在丁醇分离过程中的分离性能有了显著的提升, 具有潜在的应用价值。     

含有MCM-41分子筛的混合基质复合膜用于CO2分离

为了提高CO₂分离膜的性能,将接枝了氨基的MCM-41分子筛(MCM-NH₂)添加到聚乙烯基胺(PVAm)水溶液中配制涂膜液,并将PVAm-MCM-NH₂涂膜液涂覆到聚砜(PSf)超滤膜上制备PVAm-MCM-NH₂/PSf混合基质复合膜。复合膜分离层较薄,有利于CO₂渗透速率的提高。接枝的胺基提高了分子筛与聚合物的相容性和膜内胺基含量,有利于膜渗透选择性能的提高。使用CO₂/N₂混合气(15% CO₂ + 85% N₂,体积分数)考察了不同MCM-NH₂添加量的PVAm-MCM-NH₂/PSf膜的渗透选择性能。当涂膜液中m_MCM-NH2/m_PVAm为0.2、湿涂层厚度为50 μm,测试温度为22℃ 、进料气压力为0.11 MPa时,膜的CO₂渗透速率可达4.66×10^-7 mol·m^-2·s^-1·Pa^-1,CO₂/N₂分离因子可达150。较高的CO₂/N₂分离性能表明PVAm-MCM-NH₂/PSf膜在烟道气碳捕集领域具有良好的应用前景。此外,考察了湿涂层厚度、热处理、添加小分子胺等条件对膜渗透选择性能的影响。     

Reducing active layer thickness of polyamide composite membranes using a covalent organic framework interlayer in interfacial polymerization

Polyamide(PA)-based thin-film composite membranes exhibit enormous potential in water purification, owing to their facile fabrication, decent performance and desirable stability. However, the thick PA active layer with high transport resistance from the conventional interfacial polymerization hampers their applications. The controllable fabrication of a thin PA active layer is essential for high separation efficiency but still challenging. Herein,a covalent organic framework TpPa-1 interlayer was firstly deposited on a polyethersulfone(PES) substrate to reduce the thickness of PA active layer in interfacial polymerization. The abundant pores of TpPa-1 increase the local concentration of amine monomers by adsorbing piperazine molecules, while hydrogen bonds between hydrophilic groups of TpPa-1 and piperazine molecules slow down their diffusion rate. Arising from those synergetic effects, the PA active layer is effectively reduced from 200 nm to 120 nm. By optimizing TpPa-1 interlayer and PA active layer, the water flux of resultant membranes can reach 171.35 L·m~(-2)·h~(-1)·MPa~(-1), which increased by 125.4% compared with PA/PES membranes, while the rejection rates of sodium sulfate and dyes solution remained more than 90% and 99%, respectively. Our strategy may stimulate rational design of ultrathin PA-based nanofiltration membranes with high performances.     

Ti/Zr复合纳滤膜的制备及其性能

通过聚合溶胶路线制备出稳定的Ti/Zr(摩尔比=1:1)复合溶胶。采用浸浆法,在平均孔径为5～6 nm的片状a-Al₂O₃/g-Al₂O₃载体上制备出完整无缺陷的Ti/Zr复合纳滤膜。详细考察了焙烧温度对Ti/Zr粉体的影响,并考察了Ti/Zr复合纳滤膜的性能。结果表明:在较高烧成温度下(500℃),Ti/Zr粉体依然呈无定形态且保持微孔结构。在400℃烧成温度下制备出孔径为1.49 nm的Ti/Zr复合纳滤膜,该膜的截留分子量(MWCO)为880,纯水通量为4.3 L·m^-2·h^-1·MPa^-1。在pH=6,压力0.8 MPa的条件下,该膜对0.005 mol·L^-1的MgCl₂、CaCl₂的截留率分别为85%和78%。     

Preparation and characterization of PVA/SA composite nanofiltration membranes

Nanofiltration (NF) composite membranes based on poly(vinyl alcohol) (PVA) and sodium alginate (SA) were prepared by coating PVA/SA (95/5 in wt %) mixture solutions on microporous polysulfone (PSF) supports. For the formation of a defect free thin active layer on a support, the PSF support was multi‐coated with a dilute PVA/SA blend solution. The PVA/SA active layer formed was crosslinked at room temperature by using an acetone solution containing glutaraldehyde as a crosslinking agent. The prepared composite membranes were characterized with a scanning electron microscopy (SEM), a Fourier transform infrared spectroscopy (FTIR), an electrokinetic analyzer (EKA) and permeation tests: The thicknesses of the active layers were about 0.25 μm and 0.01 μm depending on the preparation conditions. The crosslinking reaction of the active layers were completed in less than three minutes via the formation of acetal linkage. The surface of the PVA/SA composite membrane was found to be anionic. The permeation properties of the composite membrane were as follows: 1.3 m³/m² day of flux and > 95% of rejection at 200 psi for 1000 ppm PEG600 solution. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 347–354, 2000     

Primary study of novel poly(acrylic sodium)/poly(ether sulfone) composite ultrafiltration membranes (I) the preparation of composite membrane

The poly(acrylic sodium) (PAS)/poly(ether sulfone) (PES) composite ultrafiltration membranes were prepared by coating PAS membrane solution on PES support membrane. The effects of substrate membrane, the composition of PAS solution such as PAS concentration, the choice of the solvent and the additive, and the thickness of PAS active layer on the performance of the composite membranes were extensively investigated. The experimental results have indicated the optimal PAS/PES composite membranes, containing a PES substrate with MWCO of 70,000, together with a PAS top layer having a thickness of about 20 μm, were tested at room temperature and under the pressure of 0.6 MPa with the mass concentration of 0.005 g/L poly(ethylene glycol) (PEG) (Mw = 1000 g/mol) solution, a flux of 32.6 L/(m² h) and a rejection of 92.2% were obtained, which are superior to those of the common commercial membranes reported.     

Innovative hydrophobic/hydrophilic perfluoropolyether (PFPE)/polyvinylidene fluoride (PVDF) composite membrane for vacuum membrane distillation

Though membrane distillation (MD) has gained more and more attention in the field of desalination, the wetting phenomenon was still a non-negligible problem. In this work, a method combined dip-coating and UV in situ polymerization for preparing hydrophobic/hydrophilic perfluoropolyether (PFPE)/polyvinylidene fluoride composite membranes. This composite membrane consisted of a top thin hydrophobic coating layer and hydrophilic substrate membrane. In terms of anti-wetting properties, contact angle and liquid entry pressure of all composite membranes (except for those based on 0.45 μm) exceeded 160° and 0.3 MPa, respectively. In particular, the desalination performance was tested in vacuum membrane distillation tests by feeding 3.5% (mass) saline solution (NaCl) at 60 ℃. The composite membranes with larger support pore size and lower PFPE content had higher membrane distillation flux. And for stability tests (testing the 0.22 μm membrane coated by 5% (mass) PFPE), the highest MD flux 29.08 kg·m^-2·h^-1 and stable salt rejection (over 99.99%) during the period. Except that, the effects of coating material concentration and pore sizes of substrate membrane were also investigated for surface morphology and topography, porosity, mechanical strength and pore size characteristics. This work provided a simple and effective alternative to prepare excellent hydrophobic composite membranes for MD applications.