Preparation of NOx modified PMMA-EGDM composite membrane for the recovery of chromium (VI)

A non-interpenetrating cross-linked poly (methyl methacrylate-ethylene glycol dimethacrylate) copolymer ultrafiltration membrane on a microporous ceramic support has been prepared from the monomers in two stages. The polymer membranes thus obtained have been nitrated using NO_x (a mixture of NO and NO₂) by the gas phase reaction at 80 °C. Separation experiments on the chromium (VI) salt solution have been carried out using unmodified (giving 68% rejection per pass) and nitrated membranes (giving as much as 67% rejection per pass). For nitrated membranes, the water flux and the solute flux increased with time of nitration about hundred folds because of the increase in the hydrophilicity as well as the pore size.     

A comparison of liquid–liquid porosimetry equations for evaluation of pore size distribution

This paper reviews and numerically tests many of the methods for the determination of pore size distribution of liquid membranes by liquid–liquid porosimetry. The flux through membranes was defined for flow of two immiscible liquids when drops or a liquid jet is formed, as well as the case when the interface is forced out by sufficient pressure. Several methods from literature for the determination of pore size distribution, some variations of these, and one new method are presented with a consistent theoretical basis. Using numerical tests it was found that all methods were very sensitive to measurement noise as low as ±0.1%, and that some form of data smoothing, such as a smoothing spline, was required to obtain a satisfactory distribution. The effects of elastic and permanent membrane compression were tested and a method was proposed to reduce the resulting error. A method based on the ratio of flux liquids with and without a liquid–liquid interface was recommended as it was less sensitive to the effects of compression in some cases and it provides a check when compression is not repeatable.     

HPLC of phenylthiocarbamyol labelled uridine-diphosphate-hexosamine

Summary The biochemical functions of uridine-diphosphate-amino-sugar conjugates are largely unknown. As a first step to investigate their biological roles in glycolysis of higher organisms, bovine heart muscle, which metabolizes large quantities of glycogen, was assayed for uridine-diphosphate-hexosamine. A low molecular mass ultrafiltrate was prepared from the methanolsoluble fraction of a beef heart homogenate, and the fraction was further purified using anion-exchange and reverse-phase HPLC. Samples were analyzed by two HPLC methods; anion-exchange in borate buffer and reverse-phase ion-pair chromatography. One newly established technique employing phenylthiocarbamoyl labelled uridine-diphosphate-hexosamine also was used selectively to separate uridine-diphosphate-hexosamine from other uridine-diphosphate-sugars. Hydrolysate of purified sample was classified further according to molecular structure. As a result, phenylthiocarbamoyl labelled HPLC is suitable and easy for the detection of uridine-diphosphate-hexosamine and its derivatives.     

新型抑菌Cu2+固载超滤膜的制备及性能表征

将聚乙烯亚胺(PEI)通过静电作用自组装于聚丙烯腈(PAN)多孔基膜表面,形成高分子聚电解质层;进一步通过浸泡法和动态电沉积法,将Cu2+固载于高分子聚电解质层上,制备出新型Cu2+固载超滤膜.研究结果表明,Cu2+固载超滤膜的PEI层和Cu2+均具有较高稳定性;该分离膜对腐植酸的截留率高达99.0%,且具有优良的抑菌性能,抑菌率高达85.7%.此外,相对于静态浸泡法,动态电沉积法是一种更有效的Cu2+固载手段,不仅大幅缩短了固载时间,还显著提高了Cu2+固载率.     

CELLULOSE ACETATE AND EPOXY RESIN BLEND ULTRAFILTRATION MEMBRANES: REPARATION,CHARACTERIZATION, AND APPLICATION

ABSTRACT

Membranes based on cellulose acetate used in ultrafiltration applications lack good, chemical, mechanical and thermal resistance. In order to prepare membranes with improved properties, modification of cellulose acetate with epoxy resin through solution blending was attempted. In the present work, the membrane casting solutions with different polymer blend compositions of cellulose acetate and diglycidyl ether of bisphenol-A (DGEBA) were prepared at 30±2°C. The maximum percent compatibility of the two polymers, cellulose acetate and diglycidyl ether of bisphenol-A, was estimated to be 60/40%. Ultrafiltration blend membranes based on various blend compositions were prepared, characterized in terms of compaction, pure water flux, water content, membrane hydraulic resistance and molecular weight cut-off. The application of these membranes, in rejection of proteins of various molecular weights, are discussed.     

PVDF膜改性方法研究进展

本文介绍了目前国内外聚偏氟乙烯(PVDF)超滤膜改性中常用的膜表面改性方法和膜材料改性方法。PVDF膜表面改性主要通过膜表面的物理改性、磺化改性、表面接枝改性、光化学改性、低温等离子体改性等方法来实现;而PVDF膜材料的改性主要是通过PVDF与亲水性高分子材料或小分子无机粒子的共混以及膜材料本体的化学改性来实现。改性PVDF膜的亲水性增强,使水通量增加,提高了机械性能,改善了抗污染性,增加了膜的使用寿命。     

Polyphenylsulfone/multiwalled carbon nanotubes mixed ultrafiltration membranes: Fabrication,characterization and removal of heavy metals Pb2+, Hg2+, and Cd2+ from aqueous solutions

Polyphenylsulfone/multiwalled carbon nanotubes/polyvinylpyrrolidone/1-methyl-2-pyrrolidone mixed matrix ultrafiltration flat-sheet membranes were fabricated via phase inversion process to inspect the heavy metals separation efficacy from aqueous media. Fabricated membranes cross-sectional morphological changes and the topographical alterations were assessed with Scanning electron microscopy (SEM) and atomic force microscopy (AFM). Particularly, MWCNTs assisted membranes exhibited better permeability ability as well as heavy metal removal enactment than virgin membrane. The dead-end filter unit was engaged in current research to examine the permeability and heavy metal removal competence of membranes. With the continuous enhancement of MWCNTs wt% in a polymer matrix, significant enhancement was observed with pure water flux study, from 41.69 L/m² h to >185 L/m² h as well as with the heavy metals separation study. Added additive MWCNTs can impact the pore sizes in membranes. The heavy metal separation results achieved, the membrane with 0.3 wt% of MWCNTs (PCNT-3) exhibited >98%, >76% and >72% for Pb²⁺, Hg²⁺ and Cd²⁺ ions, respectively. Overall, MWCNTs introduced PPSU membranes exposed best outcomes with heavy metals contained wastewater treatment.     

Analysis of concentration polarization phenomenon in ultrafiltration under turbulent flow conditions

An ultrafiltration data set previously reported by Gekas and Olund is used to test three concentration polarization models. The data consist of testing eight ultrafiltration membranes representing different polymer materials and molecular weight cut-offs with 0.5 wt% Dextran T10 at 25°C and 0.5 MPa under turbulent flow conditions. The tested concentration polarization models include the modified film theory model, the original film theory model and the Sherwood correlation model. The Chilton-Colburn analogy is the common foundation of the these models.     

Hollow fiber ultrafiltration: The concept of partial backwashing

In dead-end hollow fiber filtration with humic acid solutions, we observed that the humic material accumulates in the final part of the fiber. We proved the hypothesis that backwashing of the last part of the fiber is sufficient to operate the filtration process in a sustainable manner. This strategy works very well for feed solutions that result in either local accumulation of the material at the end of the fiber, or that form a well-defined concentration polarization layer that does not lead to deposition. When deposition throughout the whole module occurs, the proposed cleaning strategy is unsuccessful. This overall deposition occurs when a force balance over the particle, results in net transport to the membrane surface over the entire length of the module. We simulated such conditions by the addition of calcium to the feed solutions. The latter results in large aggregates carried towards the whole membrane area by convective water flow, and an increased interaction between the aggregates and the membrane.     

Treatment of silk production wastewaters by membrane processes for sericin recovery

Sericin protein, although a valuable resource for many industries including cosmetics, pharmaceutical and biomedical, has been discarded as a waste in silk industry, causing environmental pollution. This paper describes determination of a membrane-based process for sericin recovery from cocoon cooking wastewaters (CCW) that will enable value-added utilization of waste sericin. The iso-electric point (pI) of sericin was found as 5–6, whose MW was distributed as 180–200, 70–80, 30–40 and 10–25 kDa. Prior to membrane filtration, sericin was separated from other impurities via centrifugation (CFG) followed by microfiltration (MF) in the pre-treatment stage, which also helped minimize post membrane fouling. Ultrafiltration (UF) and nanofiltration (NF) were adopted at a pH equal to pI of sericin. UF achieved partial recovery of sericin polypeptides at 37–60%, which was attributed to increased transmission of uncharged sericin polypeptides at their pI. On the other hand, NF achieved sericin recovery as high as 94–95%, containing all MW fractions. Severe flux decline was the major problem due to protein–membrane interactions and high sericin concentrations, where concentration polarization mainly had a dominant effect. Although flux declines were as high as 58–88% in UF and 70–75% in NF, flux recovery by at least 83% was achieved by chemical cleaning using NaOH and free chlorine.