The affinity of cholera toxin for Ni2+ ion

Cholera toxin (CT) was shown to bind to immobilized Ni2+ ion. The affinityof CT for the complex required the presence of the Ni2+ ion, since CT wasunable to bind in its absence. Binding was mediated by the B-subunit (CTB)as both CT and CTB bound to the resin, but not the A- subunit (CTA).Binding was reversible in the presence of imidazole and suggested that theaffinity of CT for the Ni2+ ion was mediated by His residues. Theheat-labile enterotoxin of Escherichia coli (LT), which is closely relatedto CT, was unable to bind to the Ni2+ ion. Comparison of amino acidsequences revealed the presence of three His residues in CT (positions 13,57 and 94), but only one in LT (position 57). To confirm that the residuesat positions 13 and 94 of CTB were responsible for the binding, they werechanged to residues found in LTB. Changing His13-->Arg completelyabrogated the ability of CTB to bind to Ni2+ ion. In contrast, the mutationof His 94-->Asn reduced, but did not abrogate, the ability of CTB tobind to Ni2+ ion. Based on calculated interatomic distances, it is unlikelythat His13 and His94 are part of the same complex. There appear to be twoseparate binding sites, with the principal site involving His13 and a muchweaker site involving His94. This latter site can only participate inbinding if the complex involving His13 has formed.     

改性聚丙烯腈纤维膜处理铅离子废水的研究

采用静电纺丝法制得改性聚丙烯腈纳米纤维膜,处理高铅含量废水,考察了铅离子初始浓度、pH、反应温度、反应时间对吸附效果的影响。结果表明,吸附在2 h时基本达到平衡,其吸附容量随着初始浓度的增加而增大,随着pH的增加而增大,随着温度的升高而增大。在最佳吸附条件(C_0=100 mg/L、pH=5、50℃、2 h)下,吸附容量达137 mg/g。吸附过程符合Langmiur等温吸附模型,吸附动力学符合准一级吸附模型和准二级吸附模型。这种吸附剂为处理高铅含量废水提供了有效途径,也为静电纺丝法应用到污水处理中提供了新方法。     

Preparation of polysulfone hollow fiber affinity membrane modified with mercapto and its recovery properties. II. Preparation of PSF‐SH hollow fiber affinity membrane for recovery of Hg2+

A high qualified polysulfone hollow fiber affinity membrane modified with mercapto as chelating groups was prepared by phase inversion technology using chlormethyl polysulfone (CMPSF) as membrane matrix materials, through the reaction between thiourea and CMPSF hollow fiber matrix membrane to afford the methyl isothiourium polysulfone and was then alkaline hydrolyzed. The adsorption isotherms of the hollow fiber affinity membrane chromatography for Hg²⁺ were determined, and the effects of mobile phase conditions and the operating parameters on removal performance of the hollow fiber affinity membrane chromatography for Hg²⁺ were also investigated. The experimental results showed that adsorption isotherms of Hg²⁺ could be described by the Langmuir isotherm. Addition of NaCl into feed solution for the increase of ionic strength was harmful for the removal of Hg²⁺. The recovery of Hg²⁺ decreased at low pH and the optimum range of pH was from 5.0 to 7.0. The feed concentration had a remote effect on recovery of Hg²⁺ at the specified loading amount of Hg²⁺, and the Hg²⁺ could be removed from different concentration feed solution by the hollow fiber affinity membrane chromatography. The increase of feed flow rate led to slight decrease of recovery of Hg²⁺ at the specified loading amount of Hg²⁺. The hollow fiber affinity membrane chromatography could be operated at height feed flow rate and a large scale removal of Hg²⁺ could be realized. With the increase of load amount, Hg²⁺ recovery decreased, but the saturation degree of hollow fiber affinity membrane chromatography increased. According to required recovery of Hg²⁺ and the saturation degree of membrane chromatography, the optimum loading amount of Hg²⁺ should be selected in the actual removal of Hg²⁺. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4795–4803, 2006     

Recovery of CO2 from flue gas using an electrochemical membrane

A novel process has been designed for the economic production of very pure carbon dioxide from flue gas. Using a molten carbonate fuel cell stack as an electrically-driven membrane concentrator, a portion of the carbon dioxide in the flue gas, along with some oxygen, is emitted as a product stream. The oxygen is recycled to enrich the flue gas entering the concentrator. Preliminary economics appear favorable, with carbon dioxide produced at $21 per ton, this product is, however, in a binary mixture with oxygen and must be separated for final use, this mixture is suitable for standard means of separation. The cost is sensitive to the cost of electricity and the installed cost of the fuel-cell stack, as can be seen in Table 1. The projected cost, however, is significantly below the typical $70 per ton sales price for carbon dioxide, so that the process could be viable at higher electricity and equipment charges.     

碳气凝胶改性全氟磺酸质子交换膜的性能

利用苯酚-甲醛体系的碳气凝胶对全氟磺酸质子交换膜进行改性,考察了碳气凝胶粒径以及添加量对改性效果的影响,并将其应用于电吸附脱盐过程分析了其脱盐效果。结果表明,采用平均粒径为9.76 nm,比表面积为590 m²/g且质量分数为2%添加量的中孔碳气凝胶改性后的全氟磺酸质子交换膜在含水率、保水率、溶胀度以及导电性方面性能优异,并且应用于电吸附脱盐过程效果明显。     

远程氩等离子体改性膜固定化脲酶的研究

利用远程Ar等离子体技术引发聚四氟乙烯(PTFE)膜表面接枝丙烯酸,并以此膜为脲酶的固定化载体。研究结果表明:在放电压力20 Pa、放电功率100 W、放电时间100 s的等离子体处理条件和接枝温度70℃、接枝时间50 h、单体体积分数26%的接枝条件下,PTFE膜表面丙烯酸接枝量为131.7μg/cm2;固定化脲酶接枝密度随PTFE膜接枝丙烯酸(AA)量的增加几乎呈线性上升,固定化酶活性开始随PTFE膜接枝AA量的增加而增加,随后趋于平缓增加。同时评价了固定化酶膜的稳定性,并对接枝膜和固定化酶膜的结构进行了表征。     

Fabrication of polyetherimide microporous membrane using supercritical CO2 technology and its application for affinity membrane matrix

Polyetherimide (PEI) microporous membranes with uniform cellular structure, high porosity, and narrow pore size distribution were formed by supercritical CO₂ (ScCO₂) phase inversion method, and the membrane was modified to be a matrix for the preparation of affinity membrane due to its low solvent residue and appropriate porous structure. The effects of ScCO₂ temperature and pressure on the morphology and pure water flux of the membrane were investigated. The membrane prepared at 24 MPa and 45 °C with a large mean cell diameter of 6.0 μm, high porosity of 73%, narrow pore size distribution and a pure water flux of 56 L/(m² h bar) was coated with chitosan to improve its hydrophilicity and coupled with Cibacron Blue F3GA (CB) as a special ligand to form an affinity membrane (PEI-coated chitosan-CB membrane). The PEI-coated chitosan-CB membrane showed a high adsorption capacity of 33.9 mg/g membrane to bovine serum albumin and was higher than most of affinity membranes. Moreover, the tensile strength of PEI-coated chitosan-CB membrane was 11.58 MPa and was much higher than those of affinity membranes. This work demonstrates that ScCO₂ phase inversion method is a potential method to prepare an affinity matrix.     

Adsorption of Pb2+ and Pd2+ on polyethylene membrane with amino group modified by radiation‐induced graft copolymerization

Six chelating hollow fiber membranes were prepared by radiation‐induced grafting of glycidyl methacrylate onto a polyethylene hollow fiber membrane and its subsequent amination. The adsorption characteristics of Pb²⁺ and Pd²⁺ for the chelating hollow fiber membranes were presented when the solution of Pb²⁺ and Pd²⁺ permeates across the chelating membrane, respectively. The degree of grafting for glycidyl methacrylate increases with increasing monomer concentration, reaction temperature, and preirradiation dose. The adsorption of Pd²⁺ by chelating hollow fiber membranes modified with five kinds of amines was in the following order: diethylene triamine > hexamethyl diamine > ethylene diamine > dimethyl amine > trimethyl amine. The chelating hollow fiber membrane modified with iminodiacetic acid adsorbed Pb²⁺ ions much more than Pd²⁺. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 643–650, 1999     

硅胶改性壳聚糖膜的制备及其对Cu2+的吸附性能

重金属是水体中十分严重的生态环境污染之一,而壳聚糖具有较强的重金属吸附能力。采用硅胶粒子浸出法制备出大孔壳聚糖膜,并且研究了其对重金属Cu²⁺的吸附性能。发现3.0 g壳聚糖溶于10%（质量分数）的乙酸溶液中,加入3.0 g硅胶再经过戊二醛交联后制备出大孔壳聚糖膜的吸附能力较好。在40 mL、400 mg/L的CuSO₄溶液中,加入0.4 g制备好的壳聚糖膜,经过25 h后,壳聚糖膜呈蓝色,用紫脲酸铵指示反应为紫色,吸附率为93%。说明壳聚糖膜对Cu²⁺具有良好的吸附能力,吸附过后膜很容易从溶液中取出,克服了传统的吸附剂在溶液中固液分离困难的问题。     

应用离子交换膜通过电化学氧化合成氯甲苯

以钛网为阳极,镍网为阴极,饱和的NaCl溶液为阳极电解质,应用离子交换膜通过阳极氧化甲苯的方法合成氯甲苯。讨论了阳极电解质质量分数、电流密度、电解液温度、反应时间等反应条件的选择。结果表明：在反应温度25 ℃,阳极、阴极电解液分别为25％NaCl和10％NaOH溶液,电流密度为10～15 A/dm2条件下电解,并在4.5 h左右结束反应,氯甲苯的产率最高,可达55.5％,电流效率为51.5％。     

纳米SnO_2-TiO_2改性双极膜的制备及表征

将纳米SnO2-TiO2复合半导体材料添加到壳聚糖（CS）阴离子交换膜中,制备了PVA-CMC/nano-SnO2-TiO2-CS双极膜（CMC羧甲基纤维素钠,PVA聚乙烯醇）,并用扫描电镜、接触角测定仪等对其进行了表征。研究表明,添加纳米SnO2-TiO2可提高双极膜的亲水性和机械性能。在高压汞灯照射下,纳米SnO2-TiO2复合半导体材料较纳米SnO2或纳米TiO2单一半导体材料具有更强的光催化双极膜中间界面层水解离能力,从而大大降低双极膜的膜阻抗和膜电阻压降（即IR降）。     

Preparation of cellulosic ion exchange fiber using an ionic liquid as reaction reagent and medium

A cellulosic ion exchange fiber (CIEF) was prepared by using room‐temperature ionic liquid 1‐(3‐chloro‐2‐hydroxypropyl)‐3‐methylimidazolium chloride as reaction reagent and medium. The results showed the degree of substitution of the CIEF was up to 0.78. The product was characterized by Fourier transform infrared spectrometry, thermogravimetric analysis, scanning electronic microscope. The thermal stability of the CIEF was over 200°C. The adsorption experiments of CIEF for Cr(VI) were performed. The adsorption capacity of CIEF for Cr(VI) was found to be 196.1 mg g^?1 at 30°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Study on preparation of heterogeneous polysulfone affinity filter membrane and its sorption properties for Hg2+

High quality heterogeneous polysulfone affinity flat filter membranes having chelating groups were prepared by phase separation by the use of blends of chelating resin and polysulfone as membrane materials, N,N‐dimethylacetamide as the solvent, and water as the extraction solvent. The effects of blending ratio, chelating resin grain size, and temperature of casting solution on the structure of affinity membranes were investigated. The sorption process of an affinity filter membrane for Hg²⁺, adsorbed under various chelating conditions such as chelating resin grain size, pH value, and the concentration of the metallic ion solution, was also studied. The results revealed that the greatest chelating capacity of an affinity filter membrane for Hg²⁺ was 1050 μg/cm² per membrane under appropriate conditions, and the sorption isotherms of Hg²⁺could be expressed by the Freundlich sorption model. Dynamic chelating experiments indicated that the Hg²⁺ could be extracted with the affinity filter membrane and reextracted under acidic conditions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 908–915, 2003     

Preparation and recovery of polysulfone affinity membrane with mercapto as chelating group for Hg2+ cations

Highly qualified homogeneous poly(benzylsulfone) plate affinity membrane with mercapto group (PSF‐SH) was prepared successively through reactions between chloromethyl polysulfone matrix membrane and thiourea, and then alkalic hydrolysis. The mercapto‐functionalized polysulfone affinity membrane was utilized for the adsorption of Hg²⁺ cations through the coordination of the mercapto group and Hg²⁺ cations, in which the effects of the morphological and the structure of the affinity membrane on the chelating properties were investigated. The chelating conditions, including concentration of Hg²⁺, and temperature and pH of the introductory solution had significant influence on the chelating capacity of PSF‐SH affinity membrane. The highest static and dynamic chelating capacity of PSF‐SH plate membrane for Hg²⁺ cations were 398 and 403 μg/cm² per membrane, respectively, which demonstrated that the resultant polymer membrane was a highly efficient affinity chromatography for Hg²⁺. The affinity membrane containing mercapto group can be conveniently recovered by dilute hydrochloric acid for coordination of Hg²⁺ cations, which would have wide application for the treatment of waste water containing heavy metal cations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2514–2522, 2007     

A study of graft polymerization of methacrylic acid to polycaproamide using a reversible redox system containing CU2+ ions

Graft polymerization of methacrylic acid to polycaproamide, initiated by the K₂S₂O₈? Na₂S₂O₃? Cu²⁺ reversible redox system, has been studied. Kinetic characteristics of graft polymerization have been investigated in a wide concentration range of every component of the initiating system. Cu²⁺ ions have been found to catalyze graft polymerization in the 1.0 · 10^?5?1.2 · 10^?4M concentration range, whereas at concentrations higher than 1.2 · 10^?4M, Cu²⁺ ions are involved in the kinetic chain termination. A mechanism of graft polymerization is proposed. © 1993 John Wiley & Sons, Inc.     

Adsorption of Co2+ and Cs1+ by polyethylene membrane with iminodiacetic acid and sulfonic acid modified by radiation‐induced graft copolymerization

Two modified hollow fiber membranes, the chelating hollow fiber membrane with iminodiacetic acid and the cation‐exchange hollow fiber membrane with sulfonic acid group ( SO₃H), were prepared by radiation‐induced grafting of glycidyl methacrylate onto polyethylene hollow fiber membrane and its subsequent iminodiacetation and sulfonation. The adsorption characteristics of Co²⁺ and Cs¹⁺ for the 2 hollow fiber membranes were examined when the solutions of Co²⁺ and Cs¹⁺ permeate across the 2 membranes, respectively. Without regard to the chelating membrane with iminodiacetic acid group and the cation‐exchange membrane with sulfonic acid group ( SO₃H), 2 membranes were observed to adsorb Co²⁺ higher than Cs¹⁺. The adsorption curves of Co²⁺ by IDA group‐chelating fiber membrane in the presence of Na¹⁺ and Ca²⁺ showed that the chelating hollow was found to have a very high selectivity for Co²⁺, even though there is a high concentration of Na¹⁺ and Ca²⁺ in the inlet solution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 999–1006, 1999     

Ligand-directed immobilization of proteins through an esterase 2 fusion tag studied by atomic force microscopy

Atomically flat mica surfaces were chemically modified with an alkyl trifluoromethyl ketone, a covalent inhibitor of esterase 2 from Alicyclobacillus acidocaldarius, which served as a tag for ligand-directed immobilization of esterase-linked proteins. Purified NADH oxidase from Thermus thermophilus and human exportin-t from cell lysates were anchored on the modified surfaces. The immobilization effectiveness of the proteins was studied by atomic force microscopy (AFM). It was shown that ligand-esterase interaction allowed specific attachment of exportin-t and resulted in high-resolution images and coverage patterns that were comparable with immobilized purified protein. Moreover, the biological functionality of immobilized human exportin-t in forming a quaternary complex with tRNA and the GTPase Ran-GTP, and the dimension changes before and after complex formation were also determined by AFM.     

Separation of phenol from aqueous solution by membrane pervaporation using modified polyurethaneurea membranes

Hydroxy‐terminated polybutadiene‐based porous and nonporous polyurethaneurea membranes were prepared and used to study the phenol separation efficiency from dilute aqueous solution. The porosity was developed by incorporation of lithium chloride in polymer matrix with subsequent leaching of the same in hot water. The porous membrane showed higher phenol flux over that of nonporous membrane. Permeate containing about 97 wt % phenol was obtained from feed containing 7 wt % phenol, when pervaporation was carried out with porous polyurethaneurea membrane at 75°C. The activation energies for diffusion, permeation, and pervaporation were calculated from Arrhenius plots. From the activation energy values, it was observed that the pervaporation process became easier with increased phenol concentration in the feed and porosity of the membrane used. The membrane boundary resistance was observed to decrease with increase in temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1857–1865, 2006     

Recovery of Co2+ Ions from Aqueous Solutions by Froth Flotation

ABSTRACT

The recovery of Co(II) ions from aqueous solutions under acidic conditions (pH 5) was investigated in flotation columns with inside diameters of 4.0 and 8.0 cm. Three surfactants, dodecylamine, cetyl pyridinium chloride, and sodium dodecyl sulfate, were used as collectors. Sodium dodecyl sulfate was found to be the most efficient; all three, however, produced hydrated froths, leading to rather low recoveries and separation efficiencies. The volumetric gas flow rate was found to affect the process in relation to the amount of surfactant added and the column diameter. The scale-up of the column should be done in terms of the same superficial gas velocity in order to maintain similar levels of metal ion recovery.     

Electrochemical detection of copper ion using a modified copolythiophene electrode

This paper studies the detection of copper ions by using an iminodiacetatic acid (IDA) modified conducting copolymer electrode. The copolymer film comprising 3-methyl thiophene (3MT) and 3-thiophene acetic acid (3TA) was chosen as the selective metal cation sensing electrode. The carboxylic group of the copolymer was modified to produce IDA group for metal ion capture. The modified electrode was used for the electrochemical analysis of trace copper ions by square wave voltammetry (SWV) technique. The electrode was found to be highly selective to Cu²⁺ in the range of 0.1-10 μM. The modified electrode offered an excellent way, with a high stability and reusability, for selective determination of Cu²⁺ in a solution of mixed metal ions.