导热增强型PVDF膜及其膜冷凝过程强化

为了增强PVDF膜的导热性能,将导热性能优异的短多壁碳纳米管(SMWCNTs)与PVDF共混制成疏水多孔膜.当SMWCNTs质量分数为0.2%时,PVDF膜的疏水性和机械性能都得到了明显提升,其导热性能从0.0686 W/(m·K)提升到0.0771 W/(m·K),在膜冷凝应用中的回收率和流量分别达到了17.39%和0.85 kg/(m^2·h),提高了膜冷凝过程的效率.

超滤对血橙果汁中抗氧化成分及总抗氧化能力的影响

采用管式聚偏氟乙烯(PVDF)超滤膜,探讨了超滤对血橙果汁中抗氧化成分及总抗氧化能力的影响。结果表明,其对维生素C和花青素类成分的保存率约为85%左右,对几种酚酸和类黄酮组分(除槲皮素外)的保存率均在90%以上。同未杀菌的血橙原汁相比,巴氏杀菌汁的总抗氧化能力(TAA)损失率为23%,而超滤澄清汁仅为10%左右,主要与维生素C和花青素含量损失有关。

管式聚偏氟乙烯超滤膜澄清血橙汁的应用研究

采用管式聚偏氟乙烯 (PVDF)超滤膜对血橙汁进行超滤澄清处理。超滤后的果汁澄清透明 ,透光率达到 96 %以上 ,维生素C保存率高 ,并较好地保持了原汁色泽与风味 ;同时还探讨了不同操作条件对膜透过速率的影响 ,测定了超滤前后血橙汁中抗氧化成分及抗氧化能力的变化。

Insight into fouling behavior of poly(vinylidene fluoride)(PVDF)hollow fiber membranes caused by dextran with different pore size distributions

Membrane fouling is the key problem that occurs in membrane process for water treatment. However, how membrane microstructure influences the fouling behavior is still not clear. In this study, fouling behavior caused by dextran was deeply and systematically investigated by employing four poly(vinylidene fluoride)(PVDF)membranes with different pore sizes, ranging from 24 to 94 nm. The extent of fouling by dextran was accurately characterized by pore reduction, flux decline, and the change of critical flux. The result shows that membrane with the smallest pore size of 24 nm experienced the smallest fouling rate and the lowest fouling extent. As the membrane pore size increased, the critical flux ranges were 105-114, 63-73, 38-44 and 34-43 L·m^(-2)·h^(-1),respectively. The critical flux and fouling resistances indicated that the fouling propensity increases with the increase of membrane pore size. Two pilot membrane modules with mean pore size of 25 nm and 60 nm were applied in membrane filtration of surface water treatment. The results showed that serious irreversible membrane fouling occurred on the membrane with pore size of 60 nm at the permeate flux of40.5 L·m^(-2)·h^(-1).On the other hand, membrane with pore size of 25 nm exhibited much better anti-fouling performance when permeate flux was set to 40.5,48 and 60 L·m^(-2)·h^(-1).

Membrane Engineering for Green Process Engineering

绿色过程工程是实现工业可持续发展的一个重要途径。基于过程强化原则,它涉及新设备和新过程方法,期望能够给化学及其他生产领域和过程领域带来根本进步,比如降低生产成本、减小设备尺寸、降低能耗、减少废物产生及改进远程控制、信息流控制和过程弹性等。膜技术为过程强化原则做出了很大的贡献,在过去这些年,其潜力获得了广泛的认可。本文综合分析了膜技术在水处理、能源生产和天然材料提取等工业领域的应用和前景,重点强调了创新膜集成单元的协同使用存在的机遇,介绍了集成膜系统在海水淡化与原材料生产耦合工艺中的一个应用案例。本文将说明膜工程在实现"零排放""原材料全利用"和"低能耗"等目标中的作用。

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 0.45μm)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 0.22μm membrane coated by 5%(mass)PFPE),the highest MD flux29.08 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.

Heterogeneous Photooxidation of Phenol by Catalytic Membranes

In this work the heterogenization in polymeric membranes of decatungstate,a photocatalyst for oxidation reactions,was reported.Solid state characterization techniques confirmed that the catalyst structure was preserved within the polymeric membranes.The catalytic membranes were successfully applied in the aerobic photo-oxidation of phenol,one of the main organic pollutants in wastewater,providing stable and recyclable photocatalytic systems.The dependence of the phenol degradation rate by the catalyst loading and transmembrane pressure was shown.By comparison with homogeneous reaction,the catalyst heterogenized in membrane appears to be more efficient concerning the rate of phenol photodegradation and mineralization.

催化膜和催化膜反应器:整合的高效和环保催化过程(英文)

The design of new heterogeneous photooxygenation systems able to employ visible light,oxygen,mild temperatures,and solvent with a low environmental impact has been investigated. In particular,the heterogenization of decatungstate (W10O4-32),a polyoxometalate with photocatalytic activity in oxidation reactions,has been carried out in polymeric membranes of polyvinylidenefluoride. The polymeric catalytic membranes prepared by phase inversion technique have been successfully applied in the aerobic mineralization of phenol in water,which was used as an example of organic pollutant. In order to evaluate the effect of the polymeric environment on the overall catalyst behavior,we have also heterogenized the decatungstate (opportunely functionalized) in perfluorinated membrane made of Hyflon. The photocatalytic composite membranes are characterized by different and tuneable properties depending on the nature of the polymeric micro-environment,in which the catalyst is confined. Moreover,the selective separation function of the membrane results in enhanced performance in comparison with homogeneous reactions.

Surface Modification of PEEK-WC Membranes by Wet Phase Inversion for Ni(II) Adsorption

This work focuses on the preparation and characterization of flat sheet membrane based on modified polyether ether keetone (PEEK-WC). Additives, such as dibutyl phatalate (DBP) and diethyl hexyl phosphoric acid (DEHPA), were used to investigate their effect on membranes properties which are prepared by immersion precipitation. For that, several techniques were used to characterize membranes like thermal analyses, scanning electron microscopy and microanalyses. SEM pictures show versatile structures of the membranes from dense to porous membranes characterized by a sponge and finger like structure. Moreover, microanalyses of both surfaces, bottom and top surfaces show an aggregation of DEHPA at the top surface of the membrane. However, by adding dibutylphtalate, a well dispersion of the extractant was observed. Initially, micro-porous membranes were used in supported liquid membranes experiments for Ni(II) metal ions transports using diethyl hexyl phosphoric acid (DEHPA) as carrier. The extraction efficiency was very low about 28%, but enhanced by adding xylene to the organic phase. However, the modified membranes (with additives) by DBP and DEHPA were used on solid liquid extraction of Ni(II). The results show that by adding the plasticizer and the extractant, the efficiency of the system reached 63%.

A review on membrane distillation in process engineering: design and exergy equations, materials and wetting problems

One of the problems that most afflicts humanity is the lack of clean water.Water stress,which is the pressure on the quantity and quality of water resources,exists in many places throughout the World.Desalination represents a valid solution to the scarcity of fresh water and several technologies are already well applied and successful(such as reverse osmosis),producing about 100 million m^(3)·d^(-1) of fresh water.Further advances in the field of desalination can be provided by innovative processes such as membrane distillation.The latter is of particular interest for the treatment of waste currents from conventional desalination processes(for example the retentate of reverse osmosis)as it allows to desalt highly concentrated currents as it is not limited by concentration polarization phenomena.New perspectives have enhanced research activities and allowed a deeper understanding of mass and heat transport phenomena,membrane wetting,polarization phenomena and have encouraged the use of materials particularly suitable for membrane distillation applications.This work summarizes recent developments in the field of membrane distillation,studies for module length optimization,commercial membrane modules developed,recent patents and advancement of membrane material.

Imprinted membranes for sustainable separation processes

The rapid industrial growth and the necessity of recovering and recycling raw materials increased the interest in the production of highly selective and efficient separation tools.In this perspective,a relevant input was given by the membrane-based technology and the production of imprinted membranes,which possess specific recognition properties at molecular and ionic level,offers the possibility of developing sustainable and green processes.Furthermore,the integration of imprinted membranes with traditional or membrane-based approaches is a promising strategy in the logic of process intensification,which means the combination of different operations in a single apparatus.This work discusses the concept and separation mechanisms of imprinted membranes.Furthermore,it presents an overview of their application in organic solvent nanofiltration,for the removal of toxic agents and recovery solvent,as well as valuable compounds.The recent advances in water treatment,such as pesticide removal and recovery of metal ions,are also discussed.Finally,potential applications of imprinted membranes in hybrid processes are highlighted,and a look into the future of membrane separations for water treatment and recovery of critical raw materials is offered.