接枝改性羧甲基纤维素对铜离子的吸附研究

将离子型单体丙烯酸(AA)及非离子型单体丙烯酰胺(AM)接枝在羧甲基纤维素(CMC)上,通过协同作用提高材料的吸水性及吸水速率,并研究了其对铜离子的吸附性能.通过傅里叶红外(FTIR)对材料分析表明,从及AM成功接枝在CMC上;对吸附物进行了表面分析,扫描电镜图(SEM)显示吸附物表面有大量颗粒状物质,X射线能谱(XPS)证实材料表面吸附了铜离子;在浓度为10mmol/L的铜离子溶液中,CMC-g-P(AA-co-AM)材料的吸附容量为20.30mmol/g.     

蚕丝辐射接枝丙烯腈

以氯化锌水溶液为溶剂 ,用钴 60γ射线引发蚕丝均相溶液接枝丙烯腈 .研究了辐射吸收剂量、剂量率、铜离子浓度、蚕丝浓度和单体浓度及“后效应”对单体转化率、接枝率、接枝效率、接枝链分子量的影响 ;研究发现初始接枝效率主要取决于 [S]丝/ ( [S]丝 +[M]单) ,接枝效率随吸收剂量增加而增加 ;铜离子的存在使接枝链分子量下降 ,而对接枝率和接枝效率影响不大 ;用IR、TGA、DTA等多种方法对接枝物进行了表征 ,表明蚕丝接枝上聚丙烯腈后 ,其热学性能有较大提高 .     

双硫腙改性的聚(二甲基丙烯酸乙二醇酯-甲基丙烯酸羟乙酯)微球的制备及其对铜离子的吸附研究

用悬浮聚合法由二甲基丙烯酸乙二醇酯(EGDMA)和甲基丙烯酸羟乙酯(HEMA)共聚制备得到聚(二甲基丙烯酸乙二醇酯-甲基丙烯酸羟乙酯)(PHEMA)微球,考察了NaOH浓度、反应时间等对用双硫腙进行PHEMA改性反应的影响以及铜离子水溶液浓度(5～500mg/L)、pH(2.0～6.5)、吸附时间等对改性后的微球对铜离子吸附性能影响的因素.改性的PHEMA微球对铜离子的最大吸附量为65.6mg铜离子/g双硫腙;而且,吸附有铜离子的改性PHEMA微球用0.1mol/L的硝酸的解吸率可达到90%以上,经过3次吸附-解吸循环后,解吸率仍基本不变,这表明双硫腙改性的PHEMA微球可以多次反复使用,具有良好的应用前景.     

聚四氟乙烯纤维辐照接枝制备弱酸性离子交换剂及其对Cu~(2+)的吸附

以聚四氟乙烯纤维为基体通过6 0 Co辐射引发与丙烯酸接枝制备弱酸性阳离子交换纤维 .产物功能基含量为 3 0 6mmol g,在pH =5时该纤维达到对Cu2 + 的最大动态吸附量为 10 7 4 8mg g.使用不同浓度HCl对饱和吸附铜的接枝纤维进行洗脱 ,证实该纤维对铜离子具有优异的解吸性能     

二步法聚丙烯/丙烯酸表面接枝聚合研究

研究了二步法聚丙烯膜表面的丙烯酸接枝反应 .实验发现 ,以醋酐为溶剂的反应体系所得接枝率明显好于以水为溶剂的体系 ;接枝率随光敏剂浓度、单体浓度增大而增加 ;提高反应温度 ,可使接枝率明显增大 ;接枝后的聚丙烯膜表面亲水性可明显改善 .并用红外光谱证实了丙烯酸在聚丙烯膜表面的接枝 .     

尼龙—6／丙烯酸接枝膜的结构与性能

应用ＩＲ确定了尼龙－６与丙烯酸接枝反应的接枝点位于尼龙大分子酰胺键的Ｎ原子上，用Ｘ射线衍射研究了接枝膜的结晶状况，探讨了接枝率对接枝膜的电阻、离子交换容量、强度等性能的影响．     

一种咔唑类衍生物的合成及其探针性能研究

用两步简便方法合成了基于咔唑基的荧光探针2,6-二(9-乙基咔唑-3氨甲基)-4-叔丁基苯酚,并对其光谱性能和离子选择性进行了研究.结果表明:在pH=7.4的体系中,该化合物对铜离子具有较强的选择性,铜离子的出现使得该探针在438nm处的荧光猝灭,且猝灭程度和铜离子浓度之间呈现良好的线性关系.     

具有高离子识别能力的镉离子表面印迹材料的制备及其离子识别机理的研究

采用氨基-过硫酸盐氧化还原引发体系, 先实现了甲基丙烯酸羟乙酯(HEMA)在微米级硅胶微粒表面的引发接枝聚合, 制得高接枝度的接枝微粒PHEMA/SiO₂. 然后使接枝大分子PHEMA的侧羟基与5-氯-8-羟基喹啉(CHQ)发生亲核取代反应, 将8-羟基喹啉(HQ)基团键合在接枝大分子侧链, 使接枝大分子PHEMA实现8-羟基喹啉功能化转变, 制得表面含有高密度HQ基团的功能接枝微粒HQ-PHEMA/SiO₂, 考察研究了功能微粒HQ-PHEMA/SiO₂对Cd²⁺离子的强螯合吸附作用. 在此基础上, 采用本课题组建立的新的分子表面印迹技术, 以Cd²⁺离子为模板离子, 二氯乙醚为交联剂, 对接枝在硅胶表面的功能大分子链HQ-PHEMA进行了离子印迹, 制备了Cd²⁺离子表面印迹材料IIP-HQP/SiO₂, 深入考察研究了其离子识别与结合特性. 实验结果表明, 该离子表面印迹材料对Cd²⁺离子具有特异的识别选择性与优良的结合亲和性, 相对于Cu²⁺和Pb²⁺两种对比离子, 印迹材料IIP-HQP/SiO₂对Cd²⁺离子的识别选择性系数分别高达25.52和22.91, 显示出超高的离子识别能力.     

含季铵基离子交换纤维的制备研究

以辐射接枝丙烯酸(AA)后的聚丙烯(PP)无纺布(PP-g-AA)为基材,采用紫外引发的方法接枝甲基丙烯酰氧乙基三甲基氯化铵(DMC),建立了一种制备阴离子交换纤维的新方法,得到了PP-g-AA-DMC纤维.研究了丙烯酸接枝率、DMC浓度、溶剂种类、光照时间,浸泡时间等因素对DMC接枝率的影响,结果表明,DMC的接枝率随着丙烯酸接枝率、DMC浓度、光照时间和纤维浸泡时间的增加而增大.接枝前后纤维的红外光谱分析表明,DMC被成功接枝在PP-g-AA基材上.吸附性能测定结果表明,纤维对水中以阴阳离子存在的金属铬均具有较好的吸附性能.     

UV辐照接枝制备酚酞基聚芳醚酮纳滤膜——链转移剂的作用

酚酞基聚芳醚酮(PEK-C)超滤膜的表面通过紫外辐照接枝丙烯酸(AA)可以制备对II价盐有很好截留率的亲水性纳滤膜. FTIR-ATR、表面接触角、SEM和AFM的研究结果表明, 在接枝单体溶液中加入异丙醇(i-PrOH)作为链转移剂并不影响AA在PEK-C超滤膜表面的接枝反应. 得到的改性膜同样具有优良的纳滤性能. 与不加i-PrOH的AA改性膜相比, 新合成的膜有较高的滤出液通量, 该膜对盐离子的截留率虽有所降低, 但可以通过增加接枝反应时间和辐照光源的强度来提高. i-PrOH的浓度对膜的分离性能的影响很大, 在低浓度时, 改性膜对离子的截留率会有所下降, 继续提高i-PrOH的浓度, 膜的截留率不再变化而滤出液通量会有成倍的增加, 表明链转移剂的存在可能会提高膜的接枝密度, 增加膜的表面电荷, 使膜对离子的截留率保持不变.     

Polymerization of methyl methacrylate with cupric laurate–benzoin system as initiator

The polymerization of methyl methacrylate initiated by cupric laurate in combination with benzoin has been investigated in carbon tetrachloride medium at 60°C. The rate of polymerization was found to be proportional to the square root of both cupric ion and benzoin concentrations, and to the 1.5th power of the monomer concentration. Spectral studies indicated that there is a complex formation between cupric ion and the monomer methyl methacrylate. A reaction scheme, based on initial formation of the complex and its subsequent reaction with benzoin to produce the free radicals responsible for initiation has been postulated to explain the observed results.     

Dimethylaniline (DMA)–Cu2+ ion system-induced graft polymerization of methyl methacrylate on viscose

Graft polymerization of methyl methacrylate on viscose fibers induced by the DMA–Cu²⁺ ion system was investigated under different conditions. Variables studied include concentration of DMA, Cu²⁺ ion, and MMA, reaction time, and temperature. There are optimal concentrations of DMA and Cu²⁺; below or above these concentrations lower grafting occured. Within 4 hr reaction time, the grafting reaction showed an initial fast rate followed by a slower one at 80°C. At 70°C, on the other hand, the graft yield increased in proportion to the increase in reaction time. Increasing the monomer concentration did not have a significant effect on the graft yield during the first 45 min of reaction. Beyond this, the effect of monomer concentration was marked.     

Graft copolymerization of methacrylic acid and acrylamide onto acrylonitrile-butadiene-styrene terpolymer by photoinduced hydroperoxide

Graft copolymerization of methacrylic acid (MAA) or acrylamide (AM) from an aqueous solution onto acrylonitrile-butadiene-styrene terpolymer (ABS) was initiated by the thermal decomposition of polymeric hydroperoxides, which are formed upon UV irradiationof ABS, which contains anthracene. Diffusion of anthracene at room temperature from a methanolic solution into ABS was affected by the acrylonitrile content ofABS.The graft yield was independent on the concentration of anthracene in the wide range of 0.03 X 10^-3 to 14.29 X 10^?3 mol/L in ABS. The graft polymerization reaction does not occur below 100°C.The effect of other variables, such as time of irradiation, intensity of UV, reaction time, and concentration of monomer in aqueous solution, on the amount of monomer grafted to ABS were also investigated.The contact angle significantly decreases upon grafting, indicating that the graft layer is on the surface of the polymer. © 1995 John Wiley & Sons, Inc.     

Cupric sulfate–hydrazine system as an initiator of vinyl polymerization. II. Polymerization of methyl methacrylate in aqueous solution in the absence of oxygen

The cupric sulfate–hydrazine system has been used to initiate the aqueous solution polymerization of methyl methacrylate at pH 9.25 in the absence of oxygen. There is no decomposition of hydrazine on the surface of the reduced cupric hydroxide until a flocculant precipitate is formed (cupric sulfate concentration of about 10^?3 mole/1). Below this concentration, the initiating reaction occurs solely in solution, the rate of polymerization decreasing when the reaction mixture becomes depleted in cupric ions. When a suitable surface area of the precipitated polymer is attained, adsorption and decomposition of hydrazine occurs on its surface, causing further initiation of polymerization.     

Grafting Vinyl Monomers onto Wool Fibers. VII. Graft Copolymerization of Methyl Methacrylate onto Wool Using Peroxydiphosphate-Thiourea Redox System

Graft copolymerization of methyl methacrylate onto wool was investigated in aqueous solution using the potassium peroxy-diphosphate-thiourea redox system as the initiator. The rate of grafting was determined by varying the monomer, peroxydi-phosphate ion, temperature, and solvent. The graft yield increases with increasing peroxydiphosphate ion up to 80 × 10^?-⁴ mol/L, and with further increase of peroxydiphosphate ion the graft yield decreases. The graft yield increases with increasing monomer concentration. The percentage of grafting decreases with increasing thiourea concentration. The rate of grafting increases with an increase of temperature. The effect of acid and water-soluble solvent and certain salts on graft yield has been investigated and a suitable rate expression has been derived.     

Functionalized Cellulosic Fibers for Removal of Toxic Metal Ions From Contaminated Water

Functionalization of cellulosic okra fibers was carried out by graft copolymerization of acrylamide in the presence of ascorbic acid and hydrogen peroxide as redox initiator in aqueous medium. Different reaction parameters such as time, temperature, initiator concentration, and monomer concentration were optimized to obtain the maximum graft yield. The graft copolymerized fibers were characterized by FT-IR, TGA, and X-ray diffraction techniques. Further, chemically modified fibers were used for removal of Zn²⁺ and Cd²⁺ toxic metal ions from contaminated water. The effect of pH, contact time, and metal ion concentration was studied in batch mode experiments. The kinetics of adsorption were studied using pseudo-first and pseudo-second-order kinetic models. The adsorption isotherm was studied using Langmuir and Freundlich isotherm models. The Langmuir model was found to fit the equilibrium data well.     

Comparative Spectrophotometrc Analysis of Rifampicin by Chelate Formation and Charge-Transfer Complexation

Abstract

Simple, rapid, and accurate spectrophotometrc procedures for the determination of the antibiotic rifampicin, in capsules, are presented. A chelate formation of the antibiotic with cupric ion and charge-transfer complexation with halogenated quinones are carried out. Linear correlations between absorbance and concentration over the range of 40-100 μg ml^?1 were computed. The reaction pathways were proposed. The utility of copper chelate as a stability indicating procedure as well as a method to determine rifampicin In spiked urine samples is demonstrated.     

A Mechanistic Study of the Effects of Antioxidants on the Formation of Malondialdehyde‐Like Products in the Reaction of Hydroxyl Radicals with Deoxyribose

The reactions of ^.OH radicals with deoxyribose, DR, form five different DR^. radicals, only one of which is transformed into malondialdehyde (MDA)‐like products. The radiolytic yield of the MDA‐like products increases with the increase in the DR concentration indicating that some of the initially formed “unproductive” radicals react with DR to form the “productive” radicals. The yield of the MDA‐like products also increases with the dose rate delivered to the solution suggesting that the formation of the MDA‐like products involves the reaction of the “productive” radicals with a radical. The addition of ascorbate, AH^?, to the solution decreases the yield of the MDA‐like products as expected from the relative rates of the reaction of DR and AH^? with ^.OH radicals. On the other hand the addition of the exogenous thiol, N‐acetylcysteine (NAC), to the solutions decreases the yield of the MDA‐like products considerably more than expected from the rate constants of the reaction with ^.OH radicals. The addition of the endogenous thiol, glutathione (GSH), to the solutions affects the yield of the MDA‐like products at low concentration less than expected and at “high” concentrations more than expected from the rate constant of the reaction. Addition of low concentration of AH^? to solutions containing GSH increases considerably its antioxidant activity whereas addition of small concentrations of AH^? to solutions containing NAC has no effect on its antioxidant activity. The results point out that the DR^. radicals react differently with NAC and GSH and that the GS^. and NAC^. radicals react differently with DR, the GS^. radical being considerably more active than the NAC^. radical. Thus it has to be concluded that the relative activity of antioxidants depends also on the rate constants of many secondary reactions and on the concentrations of all the solutes present in the system.     

Photoinitiated free radical polymerization of vinyl compounds in aqueous solution

A new method for the photochemical initiation of polymerization of vinyl compounds in aqueous solution is described. The photochemically active species is an ion pair complex of the formula Fe³⁺X⁻(X⁻ = OH⁻, CI⁻, N⁻₃, etc.). The light absorption by the ion pair leads to an electron transfer causing reduction of the cation and oxidation of the anion to an atom or free radical X. The latter leads to the initiation of polymerization in accordance with X + CH₂CHR→XCH₂ CHR . The kinetics of the reaction were studied by the measurement of: (a) ferrous ion formed (colorimetrically), (b) monomer disappearance (by titration and by weighting the polymer), (c) the chain length of the polymer (in the case of methyl methacrylate). The dependence of the quantum yield on the light intensity, light absorption fraction, and the concentration of vinyl monomer and ferrous ion added initially was investigated. A complete mechanism, both with regard to the formation of free radicals and the polymerization reaction, was put forward involving: (1) light absorption, (2) a primary dark back reaction, (3) dissociation of the primary product, (4) a secondary dark back reaction, (5) initiation of polymerization by free radicals, (6) propagation of polymerization, and (7) termination by recombination of active polymer endings. The mechanism was verified by the experimental results and some constant ratios were estimated quantitatively.     

尼龙66与甲基丙烯酸甲酯接枝共聚合的研究——DMA/硫酸铜引发体系

烯类单体与聚酰胺(尼龙)纤维接枝共聚合已有报道.Varma等人研究了Ce4+引发丙烯腈、丙烯酰胺分别与尼龙纤维的接枝共聚反应。Lenka发表了用P2O48-引发甲基丙烯酸甲酯(MMA)与尼龙6纤维接枝共聚合的研究结果.Nayak等人报道了用乙酰丙酮锰为引发剂使MMA与尼龙6接枝共聚合.本文以二甲基苯胺(DMA)/硫酸铜为引发体系,用MMA接枝尼龙66纤维丝,研究了Cu2+浓度等因素对该接枝共聚反应的影响.