Modification of PES Membrane: Reduction of Biofouling and Improved Flux Recovery

A 0.22 µm polyethersulfone microfiltration membrane was modified using acrylic acid irradiated with UV light. The degree of grafting (DG) was confirmed by FTIR spectroscopy, which varied from 21 to 568 µg/cm² for differing irradiation times and initial monomer concentrations. The contact angle of the modified membranes was at least 10° less than the unmodified PES membrane. Modification filled the pores with copolymer, and decreased the permeability of the membrane. However, following the filtration of E. coli, and membrane cleaning, the flux recovery was 100% for the modified membranes and only 50% for the unmodified membranes. Thus, the modification helped in showing reversible biofouling and higher flux recovery.     

Experimental Determination of Mass Transfer at the Active Surface of a Membrane Pervaporation Cell

This work is dedicated to an experimental study of overall mass transfer at the bottom of a rectangular cavity subjected to forced convective flow at its mouth. Mass transfer coefficients have been measured using an electrochemical method for different aspect ratios, H/h, between the depth of the cavity to the height of the upstream channel, range between 0.5 and 1.67. Reynolds number, based on the hydraulic diameter of the upstream duct, has been varied from 1 to 3000 and Schmidt number between 1010 and 8400. Overall mass transfer at the bottom edge of the cavity is found to increase with both Reynolds and Schmidt numbers and to decrease with the aspect ratio, H/h. General correlations taking into account these different parameters have been established in order to predict mass transfer at the bottom of the cavity. This work is the first part of a global investigation of a pervaporation membrane separation cell involving mass transfer in liquid phase at one side of the membrane surface, followed by a transfer of the species across the membrane and finally vaporization on the downstream side of the membrane occurs.     

Effect of Surface Roughness on Retention of Reverse Osmosis Membranes

The performances of two commercially available Thin Film Composite reverse osmosis membranes i.e. TFC-ULP and TFC-SR2 from Fluid Systems were studied. For the TFC-ULP membrane low water flux (around 7 lit/m²·h) and high ion retention (around 70%) were obtained. However the TFC-SR2 membrane showed much higher flux (90 lit/m²·h) and much lower retention (around 15%).Unlike the common membranes, TFC-ULP and TFC-SR2 membranes are composed of three layers. The skin layers of both membranes are made from polyvinyl alcohol and the two support layers are made from poly aryl sulfur ether and polyester. However contradictory behaviors of the membranes cannot be explained by the characteristics of materials used for membrane preparation and/or membrane morphology.Scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that the TFC-ULP membrane possesses a rough surface while the TFC-SR2 membrane predominantly has a smooth surface. Contradictory membrane performances may be due to higher trapping of the ions on the rough surface of TFC-ULP membrane resulting in higher retention. The deposition causes higher resistance against the flow leading to lower flux. The smooth surface of the TFC-SR2 membrane has less ability to trap the ions resulting in lower retention, lower resistance against the flow and therefore higher flux.     

Surface properties of Reverse osmosis membrane

The morphology and structure of the top surfaces of three commercially Reverse osmosis (RO) membranes (Vontron Eviro‐Tech) have been studied using SEM and AFM techniques. As a result, the unevenness of the surface of ULP21 membrane was the greatest and that of SW21 membrane was smooth. The more the roughness of the top surface of the RO membranes was, the larger the flux of the RO membranes was. Accordingly, the roughness of the top surface of RO membranes intensively affected on the performance of RO membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

天然矿石粉表面的氟烷烃处理对其表面疏水性的影响

表征了几种天然矿石粉粉末压实样品的疏水性,探索了氟碳表面处理剂对碳酸钙表面浸润性和表面能的影响。粉末表面的氟烷烃使材料与水的接触角增大,表面能各分量下降。     

表面疏水化热塑性淀粉材料的性能

用含有异氰酸酯基的预聚体对热塑性淀粉材料（TPS）表面进行了疏水化处理。研究了除层与TPS表面的反应性、涂层的疏水性能以及力学性能。红外光谱（IR）分析结果表明，预聚体与基体TPS之间进行了反应,为反应性涂层；TDI／蓖麻油体系涂层样品表面的疏水性能与TPS相比有很大的改善，而TDI／PEG涂层样品表面的疏水性差；另外，涂层对材料起到一定的增强作用。     

PVDF中空纤维膜的制备及冷拉伸处理对其性能的影响

用干-湿纺丝法制备聚偏氟乙烯(PVDF)中空纤维膜,用万能拉力仪进行冷拉伸处理,分别拉伸0.9、1.2、1.5、1.8倍.研究拉伸前后的中空纤维膜的纯水通量、牛血清白蛋白(BSA)通量衰减、孔隙率等基本性能,用电镜观察膜的表面形貌,用万能拉力仪测试膜的力学性能,用红外光谱仪分析膜内的晶体结构.结果显示,拉伸会影响中空纤维膜的基本性能及表面形貌.拉伸1.8倍为最佳拉伸倍数,此法可简易制得性能良好的高通量微孔膜.     

插入式超声对酵母细胞膜通透性影响的研究

本论文选择生产1,6-二磷酸果糖(FDP)的酵母细胞为研究对象,采用紫外分光光度计测定超声处理后酵母细胞内核酸和蛋白质透出细胞膜的情况,使用次甲基蓝对超声处理后的细胞进行染色,用血球计数,测试经超声处理后细胞的生存能力,及通过测定胞外FDP的浓度变化,反映细胞膜通透性的变化。结果表明,插入式超声对细胞的通透性及细胞的存活率都有很大影响,而脉冲超声的间隙时间对核酸、蛋白质及细胞活性影响不是很大,但对FDP的渗出率有较大影响。     

型腔气体反压对微孔发泡泡孔结构与制品表面质量的影响

设计型腔气体反压辅助微孔发泡注塑(GCP-MIM)成型系统、模具及周边设备,利用这一套系统以聚丙烯(PP)材料为研究对象,研究GCP-MIM工艺对注塑PP试样泡孔结构与表面质量的影响.结果表明,随着气体反压持续时间的延长和气体反压压力的增加,试样泡孔尺寸变小,泡孔密度升高,其中反压持续时间从5 s延长到20 s过程中,...     

Surface modification of nanofibrillated cellulose films by atmospheric pressure dielectric barrier discharge

A dielectric barrier discharge in a gas mixture of tetrafluoromethane (CF₄) and O₂ was used for tailoring the surface properties of nanofibrillated cellulose (NFC) films. The surface chemical composition of plasma-modified NFC was characterized by means of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, while surface morphology was illustrated by atomic force microscopy. Wettability was characterized through the static sessile drop method. The adhesion between NFC and polylactide (PLA) laminated films was tested by the double cantilever beam technique. As a result of atmospheric pressure plasma treatment, the water contact angle of NFC films increased and the values were comparable with those of PLA films. On the other hand, surface chemical characterization revealed inhomogeneity of the plasma treatment and limited improvement in adhesion between NFC and PLA films. Further research in this direction is required in order to enhance the uniformity of the plasma treatment results.     

固体材料性质对生物垢形成的影响

从固体材料表面性质入手 ,探讨了材料的表面粗糙度、表面自由能、界面能以及材料与生物垢之间的界面能对生物垢形成的影响。实验结果表明 :在 0 2 9～ 1 82 μm内 ,材料的表面粗糙度越大越有利于生物垢的形成 ;在 11 7～ 38 3mN/m内 ,材料的表面自由能和固 -液界面能与生物垢形成之间没有简单、直接的关系 ;在 1 3～ 18 0mN/m内 ,固体材料与生物垢之间的界面能对生物垢的形成存在一个极大值 ,此时的界面能约为 3 4mN/m。     

Filtering surface water with a polyurethane-based hollow fiber membrane: effects of operating pressure on membrane fouling

Membrane fouling seriously restricts applications of membrane technology. A novel strategy was ap-plied in this study to retard membrane fouling by changing operating pressure with the pressure responsibility membrane. A polyurethane-based hollow fiber membrane was used to treat surface water for evaluating the effect of operating pressure on membrane fouling. Some bench-scale tests in dead-end mode were carried out. In the experi-ments without backwashing, as operating pressure increased, severe membrane fouling occurred on membrane sur-face, while the permeate quality was improved obviously, which is considered to be due to shrinkage deformation. The total resistance, irreversible resistance and reversible resistance under different backwash pressures were de-termined in filtration/backwashing test. With the increase of backwash pressure, the total resistance decreased, and more importantly, the irreversible resistance also decreased, which implies that small particles deposited inside membrane pores and cake layers on membrane surface are effectively removed. Similar results could be obtained in mass balance tests. The results of the present study indicate that the application of pressure responsibility membrane in surface water treatment may be an effective strategy for reducing membrane fouling.     

Effect of Cu+2 Doping on the Nano-Scale Surface Roughness of Polyacrylamide Thin Replicas

High sensitive non-contact tapping mode atomic force microscopy has been used to study the effect of Cu⁺² doping on the nano-scale surface roughness of polyacrylamide replicas. The study was carried out by determining the root mean square roughness of the polymer surface as a function of doping concentration on glass substrates. Results show that doping with Cu⁺² leads to the formation of multi-scale features that increase in size and number with the doping concentration, which results in increasing the surface roughness.     

Surface Modification of Nanoporous Poly(ϵ-caprolactone) Membrane with Poly(ethylene glycol) to Prevent Biofouling: Part I. Effects of Plasma Power and Treatment Time

Biofouling, a result of protein adsorption and cell adhesion on a surface, is detrimental to membrane performance. The objective of this study is to modify the polycaprolactone (PCL) membrane surface with poly(ethylene glycol) (PEG) to prevent fibroblast adhesion. To achieve this goal, oxygen plasma and PEG(400)-monoacrylate were used to graft the PEG onto the membrane surface through covalent bonding. Various plasma treatment conditions were investigated to optimize the PEG-grafting quality and to achieve minimum fibroblast adhesion. After the treatment, the water contact angle decreased significantly. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectra indicated that PEG was successfully grafted onto the PCL membrane with the appearance of the PEG characteristic peaks. X-ray photoelectron spectroscopy (XPS) revealed that different plasma powers and treatment times changed the surface composition of membranes. To evaluate the applicability of this new strategy for the prevention of biofouling, NIH 3T3 fibroblast was used as a model biofoulant. Cell adhesion and morphology studies indicate that either lower plasma power or shorter treatment time is able to improve resistance to the cell adhesion. This simple and efficient method can be applied to inhibit biofouling on the membrane surface.     

Surface Morphology and Properties of Rigid Poly(γ-benzyl L-glutamate) Membrane Modified by Flexible Poly(Vinyl Chloride)

Rigid poly(γ-benzyl L-glutamate)/flexible poly(vinyl chloride) (PBLG/PVC) blend membranes were prepared by casting the polymer blend solution in dichloroethane. Structure and morphologies of the PBLG/PVC blend membranes were investigated by Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PBLG/PVC blend membranes were studied by differential scanning calorimetry (DSC), tensile tests, and other physical methods. It was found that the introduction of PVC could exert marked effects on the morphology and the properties of PBLG membrane.     

Effect of Support Material Properties on Dynamic Membrane Filtration Performance

A dynamic membrane is defined as a cake layer which forms on a support material, for example, filter cloth or mesh when the liquid to be filtered includes suspended particles. Formation of an effective dynamic cake layer is highly related with the retention of particles on the support material surface. Therefore, support material properties are considered to be of prime importance in the performance of dynamic membrane treatment systems. This study investigates the effect of support material properties including pore size and structure of the material on dynamic membrane formation and performance. In this concept, a comparative evaluation was made between support materials which have different yarn types. The results showed that high total suspended solids removal efficiency (>98%) could be achieved by using dynamic membrane filtration technology. Mono-monofilament and staple filter cloths were determined as the most appropriate materials in terms of the critical fluxes which were 9.2 L/m² · h and 17–19 L/m² · h for mono-mono filament and staple materials, respectively. However, considering the results of more long-term experiments, mono-monofilament filter cloth was found more suitable for cake layer accumulation. Therefore, we postulate that mono-monofilament cloth can be used in dynamic membrane filtration systems as an alternative to traditional membranes in anaerobic membrane bioreactors.     

聚丙烯腈超滤膜氩低温等离子体表面改性的研究

运用氩低温等离子体技术,对聚丙烯腈超滤膜进行表面改性。考察聚丙烯腈超滤膜随等离子体放电条件（放电功率、反应腔气压）变化的规律,测定改性前后膜透水率和截留率的变化情况,评价改性效果。     

钢材表面处理检查

防腐蚀涂料涂装的基础工作是表面处理,包括结构缺陷修正、除油、打磨、喷射抛丸清理等多种方法。介绍了表面处理过程中质量检查的内容和方法,以及相关的标准规范等。