A NOVEL METHOD FOR FABRICATING COMPOSITE MOSAIC MEMBRANE WITH UNIQUE NF SELECTIVITY

A novel method of fabricating composite mosaic membranes was studied on the basis of interracial polymerization （IP） by coating a thin selective layer onto the surface of a micro-porous hollow-fiber membrane, in which, 2,5-diaminobenzene sulfonic acid was used as one monomer of the IP reaction, and a mixture of trimesoyl chloride （TMCI） and 4-（chloromethyl） benzoyl chloride as the other monomer. Through the IP reaction a thin selective layer with negatively charged groups could be first formed on the polyethersulfone （PES） support membrane. Then trimethylamine solution was introduced to modify the IP layer through a quaternization reaction. Thus the selective layer of this composite membrane contained both negatively charged and positively charged groups to perform the mosaic functionality. Characterization of the composite mosaic membranes was carried out through permeation experiments using different inorganic salts and dyes. The experimental results showed that the membranes could permeate both mono- and bi-valent inorganic salts, but reject larger organic molecules. Such a mosaic membrane is potentially useful for the separation of salts from water-soluble organics, especially in dye and textile industries.     

Heme-protein active site models via self-assembly in water

[structure: see text] Water-soluble models of heme-protein active sites are obtained via the self-assembly of cationic porphyrins 1 and tetrasulfonato calix[4]arene 2 (K(1.2)() = 10(5) M(-)(1)). Selective binding of ligands either outside or inside the cavity of assemblies 1.2 via coordination to the zinc center has been observed. Small ligands such as 4-methylpyridine and 1-methylimidazole are encapsulated, while the bulkier caffeine is bound outside. Assemblies Co-1.2, in which the Zn porphyrin moiety has been replaced by a Co(II) porphyrin, can act as O(2) carriers.     

Optical vs. direct sorption and swelling measurements for the study of stiff-chain polymer-penetrant interactions

This work involves interferometric ‘optical thickness’ and refractive index measurements performed in an optical thickness meter (OTM), on supported cellulose acetate (CA) films equilibrated with various activities of methylene chloride (MC) vapor. The relevant equilibrium sorption and volume swelling isotherms were determined by application of the Claussius-Mossotti equation on the assumption that these films swell unidimensionally along the thickness direction, and were compared with corresponding direct equilibrium sorption (weight gain), elongation and thickness dilation measurements on similar free films performed in a vacuum sorption/swelling apparatus (VSA) and complemented with refractive index data. Combined elongation and thickness dilation data from the VSA showed that free glass-cast CA films exhibit pronounced swelling anisotropy. The said anisotropy, although it cannot be completely eliminated, by conditioning at high degrees of swelling, does not appear to affect the extent of volume swelling significantly, thus permitting quantitative comparison of sorption and swelling isotherms determined by the VSA and the OTM. Such comparison showed satisfactory agreement between these two sets of results up to an MC uptake of ca. 0.4 gMC/cm³ of dry CA corresponding to a degree of swelling of ca. 0.2. Increasing discrepancies are observed at higher MC concentrations, which are attributable to breakdown of the assumption used that the supported films swell unidimensionally along the thickness direction. The present CA-MC volume swelling data exhibit the negative deviation from volume additivity on mixing typical glassy polymers.     

树脂填充EVAL纤维吸附剂的制备及其吸附性能表征

采用具有亲水性的乙烯-乙烯醇共聚物(EVAL)作为纤维吸附剂基质材料,粉末型Lewatit阳离子交换树脂CNP80ws为功能材料,采用可控相分离方法,制备了不同表面形态结构的树脂填充EVAL吸附剂.当使用外部液体调控相分离过程时,在纤维的表面形成了粗糙的开孔结构,并且随树脂的填充量提高纤维表面的粗糙度与开孔度有所提高.研究结果表明:树脂填充EVAL纤维吸附剂具有较大的吸附容量与较高的脱附率,其吸附容量不低于53.9mg BSA/g吸附剂(树脂填充量50%).     

CATIONIC POLYMERIC SURFACTANTS

An influence of polyvinyl alcohol molecular weight and acetate groups, present in the macromolecule, on adsorption and electrochemical properties of the TiO₂–polymer solution interface was studied. Calculated thickness of adsorption layers of PVA, on the surface of the oxide, allowed assume that acetate groups may have meaningful influence on the polymer chain conformation at the interface. Structure of macromolecules at titania–polymer solution interface was compared with that of bulk of solution. Obtained data allow determine the changes of the size and shape of polymer coils in the system. The results of experiments let us conclude main factors, responsible for observed zeta potential and surface charge changes of TiO₂. It was proved that change of the ion structure of Stern layer, depends on molecular weight and number of acetate groups (degree of hydrolysis) of PVA macromolecule. Possible mechanism of zeta potential changes was proposed as a function of pH of the solution and molecular weight of the polymer.     

Micro-fabricated metal nozzle plates used for water-in-oil and oil-in-water emulsification

In this paper the fabrication and use of micro-structured metal nozzle plates as emulsification devices is investigated and discussed. These structured metal nozzle plates were fabricated via two distinct routes. Laser ablation, performed with a femtosecond laser, was used to drill micrometer-sized holes into stainless steel and aluminum foils. Also a conventional steel mesh with an average pore size of 2.4 μm fabricated by weaving and roll compaction of micrometer-sized steel wires was investigated. The perforated metal nozzle plates were used for oil-in-water and after hydrophobization with alkylchlorosilanes for water-in-oil emulsification as well. In both cases, two types of drop formation processes were observed. The first one is the shear-induced drop formation well known for cross-flow membrane emulsification. The second is the spontaneous drop formation known from microchannel emulsification.     

A microfluidic membrane chip for in situ fouling characterization

A new method for non-invasive in situ monitoring of a microfiltration process is described. In microfiltration systems, local information on the deposition characteristics can be used to determine the cake behavior during a filtration run. Typically, non-invasive methods of fouling study are restricted to specialized membranes, or require highly complex systems. This study employs the use of synthetic embedded channel membranes, with channels separated by a porous structure (active membrane). The characteristics of the active membrane have been analyzed. Deposition on the membrane surface can be observed and monitored optically across the width of the feed channel. This can be used to observe the liquid hydrodynamics in the channel as well as the local cake properties in time. In dead end filtration, it has been observed that with 6 μm particles, the cake initially deposits towards the end of the membrane. However, as filtration continues, the deposition changes with more local deposition towards the channel entrance, leading to a more homogeneous cake layer.     

Fouling behavior of microstructured hollow fiber membranes in dead-end filtrations: critical flux determination and NMR imaging of particle deposition

The fouling behavior of microstructured hollow fibers was investigated in constant flux filtrations of colloidal silica and sodium alginate. It was observed that the fouling resistance increases faster with structured fibers than with round fibers. Reversibility of structured fibers' fouling was similar during silica filtrations and better in sodium alginate filtrations when compared with round fibers. The deposition of two different silica sols on the membranes was observed by NMR imaging. The sols had different particle size and solution ionic strength and showed different deposition behaviors. For the smaller particle-sized sol in deionized solution (Ludox-TMA), there was more deposition within the grooves of the structured fibers and much less on the fins. For the alkali-stabilized sol Bindzil 9950, which had larger particles, the deposition was homogeneous across the surface of the structured fiber, and the thickness of the deposit was similar to that on the round fiber. This difference between the deposition behavior of the two sols is explained by differences in the back diffusion, which creates concentration polarization layers with different resistances. The Ludox sol formed a thick polarization layer with very low resistance. The Bindzil sol formed a slightly thinner polarization layer; however, its resistance was much higher, of similar magnitude as the intrinsic membrane resistance. This high resistance of the polarization layer during the Bindzil sol filtration is considered to lead to quick flow regulation toward equalizing the resistance along the fiber surface. The Ludox particles were trapped at the bottom of the grooves as a result of reduced back diffusion. The fouling behavior in sodium alginate filtrations was explained by considering the size-dependent deposition within the broad alginate size distribution. The better reversibility of fouling in the structured fibers is thought to be the result of a looser deposit within the grooves, which is more easily removed than a compressed deposit on the round fibers.