Chloride-sulphate exchange on anion resins — kinetic investigation,IX. Direct,isotopic and reverse exchange

Experimental kinetics of direct, isotopic and reverse Cl^?/SO⁼₄ exchange on different anion resins are presented.At very low concentration (C = 6 × 10^?3 N) extremely high resin selectivity toward sulphates occurs (separation factors ranging from 52 to 589). Consequently chemical interaction of interdiffusing species within the resin seems to influence the rate determining step, exception made for isotopic exchange. Application of model equations from Nernst-Planck and SN₂ rate theories is discussed.     

Chloride/sulfate exchange on anion resins. Kinetic investigations. II. Particle diffusion rates

The exchange rates for the chloride to sulfate conversion on several anion resins, when particle diffusion is the rate determining step, have been measured, using the stirrer-reactor technique and infinite solution volume conditions. The interdiffusion coefficients resulted to be variable, depending mainly on the conversion degree of the resin. Two approaches have been used to calculate the exchange rates. The first one, based on the simpler rate laws for isotopic exchanges, allowed the exchange kinetics to be anticipated by the aid of a semiempirical equation for the interdiffusion coefficient.According to the second procedure, the single ion diffusion coefficients, calculated as limiting values of the (apparent) interdiffusion coefficients, and the more rigorous Nernst-Planck model for ion exchange processes were applied. Both approaches showed a satisfactory agreement between calculated and experimental kinetics.     

Chloride-sulphate exchange on anion resins,kinetic investigations. VI. Differential exchange rates in diluted systems

The kinetics of the SO₄ uptake by 6 × 10^-3N Na₂SO₄ solution of some typical anion resins in Cl form have been followed differentially, i.e. with complete conversion progressively occurring in about five steps. Like for the integral exchange the kinetics for the differential conversions agree with a rate equation previously developed for systems with reactions accompanying exchange. The accordingly determined differential rate parameters increase regularly with the conversion degree, and the integral value seems to be determined by the final rate. The sulfate selectivity also arises during the conversion, while no appreciable differences in water fluxes have been associated with ionic modification of the resins.     

Chloride/sulfate exchange on anion resins. Kinetic investigations. Chemical control in selective exchanges

Rate determinations for the Cl^-/SO⁼₄ exchange on anion resins in very diluted systems (1 ÷ 6 × 10^-3N), where resin selectivities for the divalent ion are drastically raised by the electroselectivity effect, show convincing evidence that the chemical reaction rate on fixed charges controls the overall process kinetics. Activation energies, in particular, (up to 16.83 kcal/eq) are definitely out of the range for usual diffusion-controlled kinetics.A spherically-symmetrical diffusion model with a billiard-ball-like mechanism of site-to-site jumping of ions inside the resin is suggested.     

Chlorine exchange resins,effects of resin formulation on exchange properties

Chlorine exchange resins prepared from urea, melamine and formaldehyde in various ratios and under various conditions were found to vary widely in physical structure, diffusion coefficients and capacity to absorb chlorine. Resins prepared by relatively intensive heating of the methylol syrup, or by condensation at relatively high pH, about 5, or by condensation at low temperature appeared to undergo some phase separation resulting in an opaque white resin with a macroreticular structure. Such resins had good physical stability. The opaque, porous, macroreticular resins generally had higher effective diffusion coefficients, but lower chlorine absorption capacity, than the relatively uniform translucent resins. An increase in the water content of the resin from 50 to 65% resulted in an increase in the effective diffusion coefficient (D?) by a factor of 3, and a small increase in chlorine capacity. D? was a maximum when the pH of the chlorinating solution was about 3, suggesting that HOCl is the diffusing species. The production of these resins in bead form by suspension polymerization is described.     

Adsorption of streptomycin on ion exchange resins: Equilibrium and kinetic studies

Equilibrium and kinetic studies of streptomycin adsorption from aqueous solutions of streptomycin sulphate were carried out using four weakly acidic ion exchange resins: Indion 236 [Ion Exchange (India) Ltd], Amberlite IRC-50 (Rohm and Haas Co, USA), KB-2 and KB4-P2 (both Russian resins), initially in the sodium form. The maximum amounts of streptomycin taken up by the exchangers were about 1640, 1560, 2050 1400 mg g^?1 dry resin (sodium form), respectively. The rate of adsorption of the antibiotic was highest with the ion-exchanger KB-2, and lowest with KB4-P2. The initial diffusivity values calculated for the four exchangers at a temperature of 9°C were 2.87 × 10^?8, 1.87 × 10^?8, 3.42 × 10^?8 and 0.468 × 10^?8 cm² s^?1, respectively.     

4种触须式强碱性阴离子交换树脂的制备及其对曙红Y的吸附性能

以不同的大分子多糖为骨架材料,通过三步反应以触须式引入季铵基团,从而制得4种具有高通量的强碱性阴离子交换树脂:淀粉基树脂、微晶纤维素基树脂、纤维素微球基树脂及琼脂糖微球基树脂.研究树脂对曙红Y的吸附,探讨了时间、溶液pH值和染料初始浓度对染料去除率的影响.结果表明,4种树脂在pH值为1～12范围内对染料的去除效果稳定;5min内4种树脂基本都达到了吸附平衡,其中琼脂糖微球基树脂按1g/L投放时,在2min内即可将200mg/L的曙红Y完全去除;通过拟合得知,4种树脂的吸附动力学符合拟一级动力学方程,等温线符合Freundlich等温线方程.这4种树脂尤其是琼脂糖微球基树脂在吸附速率及吸附量上均具有较大优势,但4种树脂的原料成本不一,可根据需求选用不同的树脂.     

Numerical investigation of the influence of the activity coefficient on barium sulphate crystallization

We investigate in this paper the influence of the value and computational method for the activity coefficient on the crystallization process of BaSO₄. We consider for this a mixing-controlled configuration based on a coaxial pipe mixer. The corresponding flow is turbulent and this problem is solved using numerical simulations until reaching steady-state conditions. The precipitation model has been coupled with the method of moments to describe the crystal population, taking the first four moments into account. All supplementary physical models and transport equations have been defined as User-Defined Functions and Scalars and compiled into a commercial Computational Fluid Dynamics code (here Fluent 6.1). The simulations have been performed for various inlet concentrations with different values and models for computing the activity coefficient in order to analyze its influence on the product quantity and on the crystal size distribution at the pipe outlet. The supersaturation ratio, containing the activity coefficient in its definition, is the driving force for the crystallization process. This is the reason why, as concluded from the present results, it is important to model correctly and accurately the activity coefficient in order to obtain reliable data, a point which has been often neglected in the literature. Even relatively small variations of this coefficient can considerably affect the results, in particular for fast reactions.     

Batch and column adsorption of perfluorooctane sulfonate on anion exchange resins and granular activated carbon

Perfluorooctane sulfonate (PFOS) has been detected widely in the natural water matrix and is persistent, bioaccumulative, and toxic. To prevent the adverse effects of PFOS contamination on human health and the environment, effective removal techniques are needed. Adsorption is considered an effective technique for PFOS removal. In this study, five anion exchange resins and granular activated carbon (GAC) were examined to evaluate their performance for the removal of PFOS in both batch and column experiments. Experimental adsorption data for all of the adsorbents exhibited a high correlation with the Freundlich isotherm (R² = 0.95 – 0.98). Most of the anion exchange resins demonstrated a higher adsorption capacity than the GAC. PFA300 had the highest adsorption capacity (455 mg/g). Continuous adsorption of PFOS was performed in column experiments using the same adsorbents that had been used in the batch experiments. The experimental breakthrough curves were set at C/C₀ = 0.1. PFA300 showed the longest operation time before reaching the breakthrough point. The Yoon and Nelson model was used to predict the half‐saturation time of the anion exchange resins. Moreover, the anion exchange resins exhibited high recovery of PFOS by an organic solvent. Continuous PFOS adsorption on a column can be achieved using anion exchange resins for water/wastewater treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39782.     

Hydrothermal effects on the physico-chemical properties of pure and glass fiber reinforced polyester and vinylester resins

The effect of aging by immersion in water at 60°C on polyester and vinylester resins, unreinforced and reinforced with glass fibers, was investigated. Changes in weight, glass transition temperature, secondary relaxations, and storage modulus, as well as loss modulus were measured, and the environmental effects on these parameters were assessed. Moreover, the chemical structure changes of the materials during aging were studied by the use of IR spectra. The evolution of the physico-chemical and the mechanical properties as a function of the aging time was established. The results indicate the importance of the matrix morphology, the structure regularity, the presence of the fibers on the water diffusion mechanisms, and the thermomechanical properties through gravimetric changes, DSC, DMA and IR experiments.     

Studies on selective adsorption resins. XXI. Preparation and properties of macroreticular chelating ion exchange resins containing phosphoric acid groups

Macroreticular cation exchange resins containing phosphoric acid groups (RGP) were prepared by the reaction of glycidyl methacrylate–divinylbenzene copolymer [or poly(glycidyl methacrylate)]beads (RG) with phosphoric acid or phosphorous oxychloride, and the adsorption behavior of metal ions on the RGP was investigated. The phosphorylation of the polymer beads could be effectively carried out by treatment of the polymer beads with 85% phosphoric acid at 80°C for 3 h. The RGP obtained from glycidyl methacrylate–divinylbenzene (2 mol %) copolymer beads showed high cation exchange capacity, salt splitting capacity, and adsorption capacity for Cu²⁺, Zn²⁺, Cd²⁺, Ca²⁺, and Ag⁺. On the other hand, the RGP obtained from poly(glycidyl methacrylate)beads had high adsorption capacity for Al³⁺, Fe³⁺, and UO₂²⁺. The RGP prepared by treating the RG with phosphoric acid had a higher selective adsorption for Li⁺ than for Na⁺.     

Anion exchange influence on the electrochemomechanical properties of polyaniline

The anion influence on the volume changes of polyaniline (PANI) thick films (∼200 μm) during redox switching was studied using voltammetric experiments with simultaneous microscopical observation. The area occupied by the polymer film in the microscope images was measured and used to compute the film volume and its variations. It is found that the electrolyte anion has a definite influence on the film volume changes. When a film equilibrated with perchloric acid is transferred to sulphuric acid, fully reduced and relaxed and afterwards subject to voltammetric cycling, a net volume increase is observed, spanning several potential cycles until a stationary profile is reached. This change is not reversed when the film is transferred back to perchloric medium, and in this electrolyte the response shows a faster evolution. Exchanges with hydrochloric acid show behaviour more similar to HClO₄. IR measurements show that anion exchange is complete before the voltammetric cycling is started, indicating that anion ingress/exchange alone is not the only cause for PANI volume changes. The results are interpreted in terms of polymer backbone conformational changes and polymer/anion interactions.     

壳聚糖/壳聚糖季铵盐交联共混阴离子交换膜的制备与性能研究

制备了一种新型阴离子交换膜——壳聚糖/壳聚糖季铵盐交联共混膜,并用FTIR对共混膜进行了初步表征;分析研究了不同交联度及配比对离子交换膜相关性能的影响;并运用测试膜电位的方法估算了离子的迁移数和选择透过度。研究表明,膜呈现较好的电化学性能,而膜的力学性能较差、含水量高、选择透过度稍低。HACC含量为25%,交联度为0.2%的共混膜干强与湿强分别为53.10 MPa和8.40 MPa,含水量66.4%,IEC为1.97 mmol/g,面电阻2.67Ω.cm2,离子迁移数为0.91,选择透过度为81.6%。     

PEI交联的PECH/nylon复合阴离子交换膜的制备及性能研究

聚环氧氯丙烷（PECH）是一种线性高分子聚合物,具有较好的稳定性和成膜性能,且以PECH为基体制备阴离子交换膜,可避免致癌物质如氯甲醚、双氯甲醚的使用,但存在机械强度差与吸水性较大等缺点。本研究采用聚乙烯亚胺（PEI）作为交联剂,通过其与PECH发生交联反应,在其内部形成网状结构限制PECH膜在水中的过度溶胀,从而增强膜的机械强度,同时引入尼龙网布（nylon）作为支撑材料进一步提高膜的力学性能,制备了QCPECH/nylon复合阴离子交换膜。研究结果表明,制备的P1膜在电渗析应用过程中的脱盐效率（94.8%）比商业膜（Neosepta AMX）的脱盐效率（92.4%）更高,由此可见,用PEI交联的PECH/nylon复合阴离子交换膜在电渗析脱盐中具有潜在的发展前景。     

Estimation of kinetic parameters associated with the curing of thermoset resins. Part I: Theoretical investigation

This is a two-part theoretical and experimental study on the estimation of kinetic parameters associated with the curing of a thermoset epoxy resin. In Part I, the estimation procedure is presented. This estimation procedure is based on a method referred to as the Box-Kanemasu method, which involves the minimization of a least squares function, and it represents a new application of this method. The kinetic parameters under consideration were the Arrhenius constants associated with two rate constants in a kinetic model used to describe the curing rate of an amine epoxy resin. The use of differential scanning calorimetry (DSC) and dielectric data assuming isothermal and dynamic experimental conditions was first investigated in a sensitivity study. It was determined that the degree of cure should be treated as the dependent variable and that data from isothermal experiments should be used. The estimation procedure was then used to estimate the Arrhenius constants from simulated degree of cure data with added errors. These results compared favorably with those found using a linear regression method.     

阴离子交换膜改性及抗污染性能研究进展

电渗析技术应用于工业废水脱盐时,废水中有机物及其它杂质组分等会造成膜污染,进而影响脱盐性能。电渗析膜污染防治对促进电渗析在工业废水处理中的应用有重要意义。相比于阳离子交换膜,阴离子交换膜更易形成有机污染,且更严重。阴离子交换膜污染主要由腐殖酸、牛血清蛋白、阴离子表面活性剂等有机物造成,污染过程主要受静电作用、亲和作用和几何因素的影响。膜改性提高阴离子交换膜的抗污染性能是电渗析膜污染防治的有效方法,目前已有许多有关膜改性提高阴离子交换膜抗污染性能的报道。膜改性方法主要有化学改性法、等离子体改性法、表面涂覆改性法、电沉积改性法、自聚合改性法及改进基膜结构法等。本工作对阴离子交换膜改性及抗污染性能的研究进展进行了综述,对不同改性方法的优缺点进行了分析和评价。这些改性方法能提高阴膜表面的负电荷密度和亲水性、降低膜表面粗糙度和基膜含水率等,因此可以改善阴离子交换膜的抗污染性能。然而,目前研究获得的改性阴离子交换膜仍存在修饰层不稳定、抗污染性能不理想和性能测试不系统等缺点,需进一步优化改性方法、改性工艺、组分修饰及性能测试等,以获得抗污染性能稳定且效果良好的改性阴离子交换膜。     

阴离子交换树脂对磺基水杨酸的吸附解吸性能

用阴离子交换树脂(D201)吸附的方法研究了磺基水杨酸的富集及回收。测定了溶液的pH值、温度、吸附时间等因素对吸附的影响,探讨了吸附的热力学和动力学特性。结果表明:D201树脂在pH=2—11时,吸附能力最好,等温吸附服从Freundlich经验式,吸附动力学符合Lagergren一级速率方程,颗粒内扩散是速率控制步骤之一,膜扩散也共同影响着吸附过程。在295—313 K条件下,磺基水杨酸吸附质量分数为380—420 mg/g的吸附焓变为-13.73—-8.422 kJ/mol,自由能变为-19.89—-21.45 kJ/mol,吸附熵变为20.88—41.62 J/(K.mol),吸附速率常数为0.025 3—0.056 5 min-1,吸附活化能为34.04 kJ/mol。315 K下用质量分数10%NaCl+2%NaOH溶液可定量洗脱,洗脱率达99%。     

Volatile fatty acid adsorption on anion exchange resins: kinetics and selective recovery of acetic acid

ABSTRACT

The removal of volatile fatty acids was examined through adsorption on anion exchange resins in batch systems. During the initial screening step, granular activated carbon and 11 anion exchange resins were tested and the resins Amberlite IRA-67 and Dowex optipore L-493 were chosen for further investigation. The adsorption kinetics and diffusion mechanism and adsorption isotherms of the two resins for VFA were evaluated. Based on the selective adsorption capacity of the resins, a sequential batch process was tested to achieve separation of acetic acid from the VFA mixture and selective recoveries > 85% acetic acid and ~ 75% propionic acid was achieved.     

Synthetic resins. XVIII. Chelation ion exchange properties of 2,4-dinitrophenylhydrazone of 4-hydroxy acetophenone–formaldehyde resins

A large number of copolymers were synthesized by condensing 2,4-dinitrophenyl hydrazone of 4-hydroxy acetophenone (4HA 2,4 DNPH) with substituted benzoic acids/phenols and formaldehyde in the presence of NaOH or HCl as catalyst. The resins were characterized by IR spectra. The decomposition temperature, solubility parameter, and viscositv of the polymers have been determined. The ion-exchange properties have been studied using the batch equilibrium method. The measurement of the distribution of a given metal ion between an aqueous solution and the resins has been performed. The investigation was carried out over a wide range of pH and varying the ionic strength of the medium. © 1992 John Wiley & Sons, Inc.     

Effect of proccessing on flow properties of some linear polyethylene resins

Changes in flow properties of polyethylene resins have often been observed during processing operations. Studies in this laboratory show that melt viscosity of polyethylene normally increases when the resin is heated in a compression mold at temperatures below 300°C. At the same time, the solution viscosity actually decreases in some cases. During extrusion, on the other hand, both melt viscosity and solution viscosity are shown to decrease. In addition, the logarithm of melt flow rate is seen to deviate markedly from the expected linear dependence on reciprocal of absolute temperature. The results suggest that both crosslinking and chain-scission reactions occur during processing, the former predominating at low or zero shear, the latter at high shear.