Preparation, characterization and effect of annealing on performance of cellulose acetate/sulfonated polysulfone and cellulose acetate/epoxy resin blend ultrafiltration membranes

Polymeric membranes based on cellulose acetate (CA)--sulfonated polysulfone blends at three different polymer compositions were prepared by solution blending and phase inversion technique, characterized and subjected to annealing at 70, 80 and 90 °C. The permeate water flux, separation of bovine serum albumin and its flux by the blend membranes before and after thermal treatment, have been compared and discussed. Similarly, CA and epoxy resin (diglycidyl ether of bisphenol-A) were blended in various compositions, in the presence and in the absence of polyethyleneglycol 600 as non-solvent additive, using N,N^′-dimethylformamide as solvent, and used for preparing ultraflltration membranes by phase inversion technique. The polymer blend composition, additive concentration, casting and gelation conditions were optimized. Blend membranes were characterized in terms of compaction, pure water flux, water content and membrane resistance. The effects of polymer blend composition and additive concentration on the above parameters were determined and the results are discussed.     

XPS STUDIES ON SURFACE MODIFIED POLY [1-(TRIMETHYLSILYL)-1-PROPYNE] MEMBRANES Ⅱ SURFACE MODIFICATION BY BROMINE VAPOR*

Surface modification of poly [1-(trimethylsilyl)-1-propyne] (PTMSP) membranes bybromine vapor has been studied. It is shown that Br/C atomic ratio at the surfaces increased withthe time of bromination until about 60 min, then it reached a plateau. The results of XPS and IRstudies indicated that the addition of bromine to double bonds and the replacement of H on CH_3 bybromine had taken place so that a new peak at 286.0 eV (C--Br)in C_(1s) spectra and some newbands, e. g. at 1220 and 580cm~(-1) in IR spectra were formed. The fact,t Po_2, permeability ofoxygen, decreased and α_(O_2/N_2), separation factor of oxygen relative to nitrogen, increased withbromination time, shows that surface modification of PTMSP by bromine may be an efficient approach to prepare PTMSP membranes used for practical gas separations.     

Long-term study of an intermittent air sparged MBR for synthetic wastewater treatment

Membrane bioreactors (MBR) combine biological processes with membrane filtration. Advantages of MBR in municipal wastewater treatment include high effluent quality and reduced space requirements. Steady operation of membrane plants requires careful management of membrane fouling. Even though it might be impossible to prevent, fouling can be limited by techniques such as gas sparging. The injection of gas bubbles increases the shear stress and removes fouling material from the membrane surface. Most cited literature on air sparging refers to short-term experiments, often times in bench scale. The aim of this study was therefore long-term investigations in pilot plant scale of a 70 L reactor fed with glucose-based synthetic wastewater. The main focus was on enhancing permeate flux by air sparging. The results showed that using air sparging significantly increased the permeate flux was doubled even over several weeks. The findings were interpreted using the dimensionless fouling and shear stress number. The fouling resistance was found to decrease significantly with air injection ratios between 0.4 and 0.5. When air sparging was applied after a period without air sparging, the shear stress number doubled. This increase in shear led to a reduction of the fouling number by approximately 30%. During several weeks air sparging only a slow fouling number increase was. In contrast to that after air sparging was ceased, an exponential increase of the fouling number was observed.     

Carotenoid incorporation into microsomes: yields, stability and membrane dynamics

The carotenoids beta-carotene (BC), lycopene (LYC), lutein (LUT), zeaxanthin (ZEA), canthaxanthin (CTX) and astaxanthin (ASTA) have been incorporated into pig liver microsomes. Effective incorporation concentrations in the range of about 1-6 nmol/mg microsomal protein were obtained. A stability test at room temperature revealed that after 3 h BC and LYC had decayed totally whereas, gradually, CTX (46%), LUT (21%), ASTA (17%) and ZEA (5%) decayed. Biophysical parameters of the microsomal membrane were changed hardly by the incorporation of carotenoids. A small rigidification may occur. Membrane anisotropy seems to offer only a small tolerance for incorporation of carotenoids and seems to limit the achievable incorporation concentrations of the carotenoids into microsomes. Microsomes instead of liposomes should be preferred as a membrane model to study mutual effects of carotenoids and membrane dynamics.     

原位合成分子筛膜毛细管色谱柱的研制

吸附型多孔层毛细管柱既耐高温又对气体及烃类异构体有选择性，同时又具有毛细管色谱快速、高效等优点，是解决难分离组分的重要柱型．常用作气一固吸附色谱固定相的有强极性的硅、中极性的氧化铝、非极性的碳质及特殊吸附作用的分子筛．其中分子筛以其独特的吸附作用，在永久性气体和烃类碳数族组成分析中有重要地位．Pruecell和Soulages[1，2]等制备了涂渍型5A和13X型分子筛的毛细管柱，对低碳烃类化合物显示了良好的分离能力，分析柱温较填充柱降低约100℃．邹乃忠等[3～5]也先后制备了分子筛层的毛细管柱用来作直馏汽油的分析．由于通…     

不同分子筛载体对CO加氢产物分布的影响

研究了几种小孔分子筛ＺＳＭ－５，ＨＹ，ＮａＹ及β担载ＺｒＯ２对Ｃ加氢反应的催化作用，并就产物的分布情况与担载ＺｒＯ２的硅铝中孔分子筛进行了对比研究。其中中孔分子筛分别用季铵盐和一级胺为模板剂，在水热条件和常温常压下合成；并用ＢＥＴ，ＸＲＤ，ＳＥＭ等手段表征了它们的孔道和骨架结构。另外，考察了碱金属Ｋ＾２＋，Ｎａ＾２＋对催化剂催化性能的影响。     

Electrokinetic characterization of a microporous non-commercial polysulfone membrane: phenomenological coefficients and transport parameters

Electrical and electrokinetic phenomena (electrical resistance, streaming potential and membrane potential) in a porous polysulfone membrane was studied in the framework of the linear thermodynamics of irreversible processes and the phenomenological coefficients were determined for different concentrations of NaCl and MgCl₂ solutions (10⁻³M<5×10⁻²M). From experimental values, other characteristic membrane parameters such as the concentration of fixed charge in the membrane (=−3×10⁻³M), the ionic transport numbers and permeabilities through the membrane (t(Na⁺)=0.392 and t(Mg⁺²)=0.363; P(Na⁺)=3.5×l0⁻⁸m/sec and P(Mg⁺²)=2.9×10⁻⁸m/sec) were also obtained. Membrane surface-electrolyte solution interface was characterized by zeta potential values. The effect of both salt concentration and pH on zeta potential results was also studied.     

Optimization of tetramethoxysilane-derived sol gel entrapment protocol stabilizes highly active chlorophyllase

Entrapment of membrane proteins is a challenging task compared to that involving soluble proteins. Chlorophyllase, a membrane protein, was successfully entrapped in tetramethoxysilane-derived sol-gel. Pre-gel sol typically consists of an aqueous suspension of chlorophyllase, precursors including tetramethoxysilane and/or methytrimethoxysilane, and sodium fluoride as catalyst. To obtain a highly active entrapped enzyme preparation, the effects of various immobilization parameters, including the chemical compositions of pre-gel sol (water/silane ratio, precursor type and proportions, enzyme loading, sodium fluoride concentration), and sol-gel process parameters (aging and drying time and approach) have been investigated. Chlorophyllase demonstrated the highest activity in gel derived from a pre-gel sol with water/silane ratio of 30 and enzyme loading of 0.257 mg_protein/g_gel, and showed moderately lower activity in organically modified sol-gel than that in hydrophilic sol-gel. The effects of water/silane ratio and precursor combinations on the activity of entrapped chlorophyllase were also studied by examining the pore morphology of gel via nitrogen adsorption-desorption. Longer aging time leads to an entrapped chlorophyllase preparation with higher activity. Chlorophyllase preparation demonstrated negligible activity after air-drying for 12 h while lyophilized chlorophyllase preparation demonstrated 8, 4 and 4 times higher activity than air-dried, vacuum-dried and solvent-dried preparations. Chlorophyllase demonstrated 30% higher activity in the improved sol-gel protocol than that from a non-optimized sol-gel protocol developed in a previous study.     

On the modification of solid adsorbents with volatile organics II. The role of the layer adsorbed

Summary This paper presents a continuation of our research dedicated to solid-adsorbent surface modification with what are commonly regarded as volatile and easily eluted organic compounds. Two porous adsorbents were used: natural zeolite (clinoptilolite) and alumina, while the adsorbates employed were n-hepatane and benzene. The results show that a simple injection of volatile adsorbate greatly alters the solid surface adsorption properties. The consequences of volatile modifier application are discussed on the grounds of adsorption isotherms determined at 313K. Possible implications to the tailor made adsorbents are outlined as well.Part I, J. Chromatogr.442, 105 (1988)     

Interactions of dicarboxylic porphyrins with membranes in relation to their ionization state

The interactions of dicarboxylic porphyrins with membrane systems are discussed with particular emphasis on the effect of the charge of the porphyrin and the nature of the side-chains. The incorporation of hematoporphyrin or related dicarboxylic porphyrins within small unilamellar vesicles as membrane models is favored by a decrease of the pH in the range of physiological pH values. This effect might play an important role in the retention of porphyrins by tumors, which are more acidic than normal tissues. Kinetics studies also show that the partition of the porphyrin between the lipidic bilayer and the aqueous phase is governed by its release rate rather than by its incorporation rate.