氧化还原引发接枝—填充聚合制备pH响应型分离膜

由全反射红外光谱和场发射电子显微镜证实,利用氧化还原可成功地引发甲基丙烯酸在酚酞型聚醚砜膜表面的接枝聚合.继而,接枝膜在不同pH下的水通量测定实验表明.该接枝膜膜孔径的变化具有着显著、快速、可逆的pH响应性.     

Studies on elastic hydrogel membrane. I. Effect of preparation conditions on the membrane performance

The properties and the permeation characteristics of poly(vinyl alcohol) hydrogel membranes were investigated. The membranes have excellent elasticity and showed reversible compaction by operating pressure. The membrane performance was also changed reversibly by pressure, and was held stable at ambient temperature for more than 12 months. The hydrogel membrane was stable against temperature up to 40°C, and was melted down at 70°C. Rejection increased with operating pressure. In the case of 1% (w/w) aqueous solution of poly(ethylene glycol) whose degree of polymerization is 400, the rejection increased from 30 to 85% by changing operating pressure from 5 kg/cm² to 60 kg/cm². These results suggested the possibility for the pressure controlled fractionation of molecular weight.     

Application of GPC to Studies of the Viscose Process. I. Evaluation of the Method

Abstract

This is the first part in a series of papers describing the application of GPC to studies of the viscose process. In this part the procedures used are described. For these studies THF solutions of nitrocellulose were used. Modifications were made to the standard nitration procedures, resulting in improved efficiency. The importance of sampling homogeneity was studied and precision was-obtained. In addition, a computer program to handle the data was developed.     

Studies on the mechanism of ZSM-5 formation

The nucleation of (Al-free) zeolite precursor gels was studied using X-ray diffraction,²⁹Si FT-NMR, and ion exchange. Results suggest that in ZSM-5 nucleation, the channel intersections are first formed. These clathrate-like units, each containing essentially one TPA⁺ cation, are initially randomly connected, but progressively anneal with rearrangement under the influence of OH^– ions to form the ZSM-5 framework.     

Supercritical carbon dioxide extraction in membrane formation by thermally induced phase separation

In this study, a novel and environmentally friendly extracting method, supercritical carbon dioxide (SC‐CO₂) extraction, was investigated in the thermally induced phase separation (TIPS) process for making microporous membranes. In the SC‐CO₂ extraction, the effects of extraction time, pressure, and temperature on the extraction fraction, membrane morphology, and membrane performance were investigated. It was concluded that with extraction conditions of 18 MPa, 35°C and 2 h, the porous membrane had the highest extraction fraction. There was a close relationship between membrane performance and the extraction conditions of SC‐CO₂, and it is possible to tailor membrane performance through the choice of extraction conditions. Compared with traditional solvent extraction, a dry membrane treated by SC‐CO₂ extraction has much less shrinkage and greater water permeability, whereas the degree of crystallization of a membrane extracted by SC‐CO₂ is slightly greater than that extracted by ethanol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1632–1639, 2007     

Influences of different preparation variables on polymeric membrane formation via nonsolvent induced phase separation

This work presents a comparative study on the formation of polyethersulfone ultrafiltration membranes via nonsolvent-induced phase separation (NIPS) in two different solvent systems. N-methyl-2-pyrrolidone was chosen as conventional solvent and 2-pyrrolidone as a greener alternative. The overall objective was to obtain a mechanistic clarification of the membrane formation process in dependence of the most important controlling parameters. By performing different series of experiments, it was possible to determine the differences between the two solvents regarding the effects of variations in nonsolvent additives, polymer concentration, and precipitation conditions. It was found that a raising concentration of several nonsolvents, the increase of the polymer concentration and changes in the precipitation conditions can suppress the formation of macrovoids, regardless of the applied solvent. In contrast, differences were observed with regard to the performance of the membrane prototypes. This study improves the understanding of membrane formation via NIPS and identifies the effects of different variables. It shows that the choice of the solvent is essential for the dominating formation mechanisms and therefore for the resulting membrane features. It also proves that green solvents can substitute hazardous solvents if the influencing variables are well-understood in order to control them for obtaining desired membrane properties. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48852.     

Polymersome formation mechanism and formation rate in stirred‐tank reactors

Uniform polymersomes (polymer vesicles) made of poly(2‐methyloxazoline)₁₅‐b‐poly(dimethylsiloxane)₆₈‐b‐poly(2‐methyloxazoline)₁₅ (PMOXA15–PDMS68–PMOXA15) can be formed in miniaturized‐stirred tank reactors by the aid of a recently published process. In this study, the occurring self‐assembly mechanism was elucidated by using transmission electron microscopy. Subsequent to the initial formation of small spherical micelles and the following fusion to worm‐like micelles, two simultaneously occurring pathways, describing the transformation of further intermediate structures to the desired vesicles, were found. The resulting particle increase was followed by dynamic light scattering. Thus, the vesicle formation rate was judged by the linear increase of the particle diameter over time. While temperature showed no influence, higher initial polymer concentrations and lower final solvent concentrations accelerated the polymersome formation. Besides, the process was crucially dependent on the agitation speed. While spherical micelles did not transform into polymersomes when no stirring or too slow stirring is applied, the self‐assembly process was accelerated by increasing the agitation speed. Uniform polymeric vesicles can be formed under vigorous stirring in stirred‐tank reactors in short process times. In this study, the underlying mechanisms of vesicle formation were elucidated, showing that the polymer forms small micellar structures before undergoing two separate pathways to form the desired vesicular structures. The formation rate of the polymer vesicles was mainly dependent on the agitation speed but also on the polymer and solvent concentrations, highlighting the need for controlled formation conditions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46077.     

Surface morphology and nodule formation mechanism of cellulose acetate membranes by atomic force microscopy

By the use of atomic force microscopy (AFM), formation mechanism of nodular structure in cellulose acetate membranes was systematically investigated. Elementary factors affecting the nodule formation were delineated on the basis of both kinetic and thermodynamic considerations. It was shown that (1) the exact nature of nodular structure is thermodynamic equilibrium glassy state; nodular structure will vanish in the rubbery state; (2) the thermodynamic factor affecting nodule formation is the membrane formation temperature; with the membrane formation temperature decreasing, more chain segments are able to form nodular structures; (3) nodule formation is dependent on the segment rearrangement; variation of the solvent environment is the major kinetic factor affecting the segment rearrangement and nodule formation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1328–1335, 2003     

Elaboration of a membrane with bipolar behaviour using the semi-interpenetrating polymer networks technique

The semi-interpenetrating polymer network technique was applied for the elaboration of three ion-exchange membranes. Poly(vinyl alcohol) (PVA) was chosen as polymer matrix. Commercial poly(styrene sulfonate) (PSSNa) was used as anionic polyelectrolyte (Pe). Poly(N-ethyl-4-vinylpyridinium bromide) (PEVPBr) and poly(vinylpyridinium chloride) (PVPCl) were synthesised and characterised in order to use them as cationic Pe. Membranes were obtained by mixing PVA and Pe solutions, followed by solvent evaporation and crosslinking with gaseous 1,2-dibromoethane. The influence of the crosslinking conditions on the sample properties was studied.Various processes were used to elaborate the bipolar membranes (BMs). The most interesting result was obtained by sticking together a wet PVA/PEVPBr membrane on a wet PVA/PSSNa membrane using a PVA/PSSH (acidic form of PSSNa) solution as glue and by crosslinking the junction by heat treatment. Current-voltage experiments were performed on the BMs. Bipolar behaviour was observed when a water dissociation catalyst was introduced in the PVA/PEVPBr layer.     

Preparation of polysulfone hollow fiber affinity membrane modified with mercapto and its recovery properties. I. Synthesis and preparation of hollow fiber matrix membrane

Several kinds of chloromethyl polysulfones (CMPSF) with different chlorinity and reactive groups were synthesized by Friedel‐Crafts reaction, which could be utilized as reactively matrix membrane materials. The CMPSF hollow matrix membranes were prepared with phase inversion by utilization of the CMPSF/additive/DMAC casting solution and CMPSF as membrane materials. The rheological behavior of CMPSF/additives/DMAC spinning casting solution was studied. The experimental results showed that the spinning casting solution was a pseudoplastic fluid, the apparent viscosity of the spinning casting solution decreased with the increase of shearing rate, and the viscous flow activity energy of the spinning casting solution was inclined to unchange at high shearing rate. The effects of composition of spinning casting solution and process parameters of dry–wet spinning on the structure of CMPSF hollow fiber matrix membrane were investigated. The pore size, porosity, and water flux of membrane decreased with the increase of additive content, bore liquid, and dry spinning distance. With the increase of extrusion volume outflow, the external diameter, wall thickness, and porosity of the hollow fiber matrix membrane increased, but the pore size and water flux of the membrane decreased. It was also found that the effects of internal coagulant composition and external coagulant composition on the structure of CMPSF hollow fiber matrix membrane were different. The experimental results showed that thermal drawing could increase the mechanical properties of CMPSF hollow fiber matrix membrane and decrease the pore size, porosity, and water flux of the CMPSF hollow fiber matrix membrane, and the thermal treatment could increase the homogeneity and stability of the structure of the CMPSF hollow fiber matrix membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 758–771, 2006     

低碳烯烃异构化/芳构化反应机理研究进展

简述了分子筛催化剂上低碳烯烃异构化的单分子机理、双分子机理、假单分子机理及环状过渡态机理, 指出单分子机理和双分子机理更为大多数研究者所接受, 在低碳烯烃的异构化过程中单分子机理和双分子机理同时存在, 单分子机理是烯烃异构化的主要途径, 而双分子机理主要生成副产物。介绍了分子筛催化剂上低碳烯烃芳构化反应机理的研究进展, 指出低碳烯烃的芳构化是一个混合聚合的过程。另外, 介绍了低碳烯烃在金属改性的分子筛催化剂上的芳构化机理研究进展, 指出金属的引入导致了新的反应路径, 能有效提高烯烃的转化率和芳烃的选择性。     

Investigation of membrane preparation condition effect on the PSD and porosity of the membranes using a novel image processing technique

A totally computerized image processing program package is developed to analyze the SEM images of membrane surface and cross‐section. Pore size distribution and porosity of the fabricated membranes are determined using the proposed image processing procedure. Furthermore, effect of coagulation bath temperature on the morphology and mechanical properties (such as tensile strength, strain break, tensile energy absorbent, and tensile stiffness) of Polysulfone (PSf) membranes are investigated. The results reveal that the mechanical properties are higher when N‐methyl‐2‐pyrrolidone (NMP) is used as solvent. Also, an increase in the coagulation bath temperature caused a monotonous increase in the mean pore size value of Dimethylformamide (DMF)‐based membranes. However, mean pore size curve has a maximum when NMP is used as solvent. Also, porosity of the fabricated membranes increased when coagulation bath temperature increased. For the NMP‐base membranes, pore's diameter was in the range of 0–5 μm. However, DMF‐based membranes have pore size value of smaller than 1 μm when the precipitation medium is kept at 8°C. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39899.     

Studies of performances by the interchanging of the sequence of the photomodified layer in the thin film composite (TFC) membrane

UV‐initiated photomodification by a hydrophilic functional moiety (i.e., acrylic acid) was performed in and on a polypiperazineamide thin‐film composite membrane. The sequence of the bilayers (i.e., acrylic acid and polypiperazineamide) was altered on a polysulfone membrane. The size exclusion order through the membranes was Atrazine > Simazine > 2,4,6‐Trichlorophenol > 2,4‐Dichlorophenol according to the molecular size, which was calculated by the quantum mechanical approach. Apart from the molecular size, the polarity and hydrophobicity of the molecules also influenced the separation. The performance of the membranes is based on size exclusion. The membrane with an inner layer of acrylic acid showed more blocking effect than the membrane with the same layer on the top of polypiperazineamide membrane and the unmodified polypiperazineamide membrane. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies on phase separation rate in porous polyimide membrane formation by immersion precipitation

Phase separation rate during porous membrane formation by immersion precipitation was investigated by light scattering in a polyimide/N‐Methylpyrrolidone (NMP)/water system. In the light scattering measurement, plots of scattered intensity against scattered angle showed maxima in all cases, which indicated that phase separation occurred by a spinodal decomposition (SD). Characteristic properties of the early stage of SD, such as an apparent diffusion coefficient D_app and an interphase periodic distance Λ, were obtained. The growth process of Λ was also followed by light scattering. The growth rate had the same tendency as D_app when water content in the nonsolvent bath and the polymer concentration in the cast solution were changed. The pore size of the final membrane increased with decreasing water content, which was opposite to the tendency of Λ growth rate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 292–296, 2003     

Studies on cellulose acetate–polysulfone ultrafiltration membranes: I. Effect of polymer composition

Ultrafiltration techniques have particular advantages for simultaneous purification, concentration and fractionation of macromolecules. Studies are presented on novel ultrafiltration membranes, based on cellulose acetate and polysulfone blends, for the separation of proteins and heavy metal ions. The effects of polymer composition on pure water flux, water content, molecular weight cut‐off and hydraulic resistance are discussed. Scanning electron microscopy images of the membranes show the presence of segregated individual domains of cellulose acetate and polysulfone. The molecular weight cut‐off obtained from the protein separation studies is also presented. Applications of these membranes for separating metal ions from aqueous streams are discussed. Copyright © 2005 Society of Chemical Industry     

纳滤技术在矿冶领域的应用研究进展

纳滤具有传统处理方法不具备的低能耗、高截留率、较好选择性等优点,可望在国民经济各个领域得到广泛应用。介绍了纳滤技术在矿井水、矿山浸出液、矿山废水以及铅锌、钼、钨等冶炼废水处理中的情况。肯定了纳滤技术的应用效果,指出了现行纳滤技术在实际应用中可能存在的问题、不足与解决方法,同时展望了纳滤技术发展趋势。     

Studies on the mechanism of the hydrogen electrode reaction by means of deuterium tracer—I. the reaction route

The reaction route of the hydrogen electrode reaction on Ni, Rh, Au, and Pt at the reversible potential was investigated through the exchange reaction between deuterium and light water. Various reaction routes involving hydrogen adatom H(a) and adsorbed hydrogen molecule-ion H⁺₂(a) as the reaction intermediates were considered. In order to single out the correct reaction route, these routes were examined, without assuming a priori the existence of a single rate-determining step, for satisfactory interpretation of the isotopic composition of the hydrogen gas during the exchange reaction. It is concluded that the reaction route consists of two consecutive steps,

and

, where B represents H₂O or OH^?.     

膜分离技术在油田含油污水处理中的应用研究进展

介绍了膜分离技术及其优点,有机膜、无机膜和复合膜在油田含油污水处理中的应用研究进展;分析了膜处理含油污水过程中的破乳机理、影响含油污水处理效果的各种因素、产生膜污染的原因及其控制措施;探讨了膜分离技术的研究方向和发展前景.最后指出,深入研究分离膜的分离过程和机理,探索合适的清洗周期,研究合适的清洗剂和清洗工艺,明确分离膜的预处理指标要求,合理安排工艺流程,开发新型膜及膜组件是膜分离技术在油田含油污水处理中应重点解决的问题.     

Phase separation mechanism during membrane formation by dry‐cast process

Phase separation mechanisms during the membrane formation by dry‐cast process were investigated by light scattering in the cellulose acetate/dimethylformamide (DMF)/2‐methyl‐2,4‐pentanediol system. Phase separation occurred by spinodal decomposition (SD) when paths of the composition changes due to the evaporation of DMF were close to the critical point in the phase diagram. Characteristic properties of the early stage of SD such as an apparent diffusion coefficient and an interface periodic distance were obtained from the Cahn theory. Phase separation occurred by nucleation and growth (NG) when paths of the composition changes were far from the critical point. SEM observation confirmed that the membrane formed by the SD mechanism had interconnected structure, whereas that by the NG mechanism had the closed cell porous structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 776–782, 2000     

Phase‐inversion applications beyond membrane formation. I. Lithography films

Polymeric films cast from a polymer solution can develop a bulk porosity, if the conditions are favorable for phase inversion (PI), a physical chemical process based on fluid–fluid demixing of which there are two known major variants: wet and dry PI. As the formation of polymeric coatings often involves a polymeric solution or gel precursor, dry or wet PI phenomena may affect the structure formation of the final solvent‐free coating. In this article we identify the situations under which lithographic films can develop a PI structure and focus on solid polymer layers undergoing postcasting wet processing. Examples are provided from the wet processing of a fractionated epoxy novolac resin currently used in lithographic patterning. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2145–2157, 2000