脉冲响应技术在离子交换色谱中的应用

离子交换色谱法或脉冲响应技术提供了一个快速且经济的取代直接实验(TheConventional batch experiment)的方法,以建立平衡等温线,进而确定平衡常数.在低浓度溶液中,用脉冲响应技术估算的平衡常数 K 与直接实验法确定的这些参数有很好的一致性.     

乙醛酸及其钠盐、钙盐的制备和分离

本文介绍了在少量浓盐酸及亚硝酸钠存在下,用硝酸氧化20％乙二醛制备乙醛酸及其钠盐、钙盐的方法。乙醛酸产率为75—80％。用氢氧化钙粉末将反应混合液调节在不同的pH范围内,草酸钙(pH1.0～1.5)和乙醛酸钙(pH2.5～3.0)便接近定量析出。再先后用氫型和钠型离子交换树脂处理乙醛酸钙,可分别制得较纯的乙醛酸溶液和乙醛酸钠固体。该制备和分离方法具有简便、经济和得率较高的优点。     

Mathematical simulation and calculation of the continuous countercurrent process of ion-exchange extraction of strontium from strongly mineralized solutions

The program Countercurrent is developed for the simulation of a continuous ionexchange extraction of strontium from strongly mineralized NaCl and CaCl₂ solutions using a KB-4 carboxylic cation-exchanger in the countercurrent columns. The program allows one to calculate the conditions of Ca and Sr separation depending on the mode of operation at the sorption and regeneration stages, the residual Sr content on the overloaded sorbent, and the Sr separation on incompletely regenerated KB-4. It also makes it possible to find the optimal separation conditions. The program Countercurrent can be also used to simulate other ion-exchange processes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1034–1037, June, 1993.     

离子交换法提取谷氨酸的研究

本文就离子交换法提取谷氨酸树脂的筛选，不同树脂对发酵液中谷氨酸静态吸附性能及其影响因素进行了系统地研究．旨在探索离子交换法提取谷氨酸的最佳工艺条件和开发新的离子交换树脂．     

Thermal properties,induction period,interfacial energy and nucleation parameters of solution grown benzophenone

The kinetic parameters (reaction order, n, activation energy, E, pre-exponential factor, A, constant rate, k) for the dehydration step due to elimination of osmotic water and hydrogen-bounded water with the carboxylic groups, and for the anhydrifying step owing to the dehydration of two neighboring (-COOH) groups, were determined under non-isothermal conditions for some carboxylic resins with acrylic-divinylbenzene (DVB) matrix. The kinetic parameters were evaluated by means of isoconversional methods from (TG/DTG) thermal analysis data. The results show a dependence of the apparent kinetic parameters on the cross-linking degree, granulation, gel/macroporous matrix nature, exchange capacity and heating rate.     

Thermodynamic and magnetic resonance studies on the hydration of polymers: I. Interactions of water in a synthetic cation-exchange resin

Measurements of NMR spin-lattice relaxation times T ₁ were performed for sorbed H₂O and D₂O in a sulfonated ion-exchange resin at varying degrees of hydration with alkaline cations as counter ions. From the sorption isotherms at three different temperatures the partial molar enthalpies and entropies of sorption show a minimum for all alkaline cations at water concentrations of n 0.8, i.e., there are 0.8 water molecules per –SO ₃ ^– group. The first water molecules sorbed in the ion-exchange resin matrix are characterized by anisotrtopic rotational diffusion processes with correlation times of the order of ₁ 50 ns and ₂ 30 ps, respectively. This indicates that they are located in the electrostatic field between the corresponding ion pair. Although these two correlation times are very similar at a given temperature for all alkaline cations studied in the present investigation, the existence of a second spin-lattice relaxation time for sorbed H₂O at n=0.8 indicates that for Cs about 50% of the sorbed water diffuses between locations in the resin. This fraction decreases with ionic radii and with falling temperatures. For Li the amount is less than 20%.     

Determination of total,leachable and mobile boron in sedimentary rocks by ICP-AES

An ion exchange batch technique is described, which allows to determine the amount of mobile boron in geological material. Boron selective ion exchange resin IRA-743 (0.5 g, effective size 0.45 mm) was slurried together with 5 g sample (grain size smaller than 0.04 mm) at 70 °C in aqueous solution. After separating resin and suspension by sieving, elution was done in columns with 3N HCl. Boron was determined in the eluates by ICP-AES. Possible corrections for the iron interferences on the boron emission lines are discussed. The mobile boron content in the investigated shallow marine sedimentary rocks ranged between 5 and 10% of the total. It must be assumed that most of the boron in the shales is fixed in the lattice of the minerals.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Chromium(III, VI) speciation analysis with preconcentration on a maleic acid-functionalized XAD sorbent

Chromium may exist in environmental waters as Cr(III) and Cr(IV), the latter being the toxic and carcinogenic form. Since atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry can only yield information on total Cr concentration, a polymer resin bearing O,O-donor chelating groups such as the maleic acid-functionalized XAD(CO)CHCHCOOH resin was synthesized to selectively retain Cr(III) at pH 4.0-5.5. The dynamic breakthrough capacity of the resin for Cr(III) at pH 5.0 was 7.52 mg g⁻¹, and the preconcentration factor extended to 250-300. Chromium(III) in the presence of 250-fold Cr(VI)—which was not retained—could be effectively preconcentrated on the NH₄⁺-form of the resin and determined by AAS or diphenylcarbazide (DPC) spectrophotometry. When Cr(VI) was reduced to Cr(III) with Na₂SO₃ solution brought to pH 1 by the addition of 1 M H₂SO₄, and preconcentrated on the resin, total Cr could be determined. The developed method was validated with a blended coal sample CRM-1632. Since the adsorption behavior as a function of pH of possible interferent metal ions, e.g. Ni(II), Co(II), Cu(II), Cd(II), Zn(II), Pb(II) and Fe(III), was similar to that of Cr(III), selective elution of Cr(III) from the resin was realized using a mixture of 1 wt.% H₂O₂+1 M NH₃. The eluate containing Cr as chromate could be directly analyzed by diphenyl carbazide spectrophotometry without any adverse effect from the common interferents of this method, i.e. Fe(III), Cu(II) Hg(II), VO₃⁻, MoO₄²⁻ and WO₄²⁻. Various synthetic waste solutions typical of electroplating bath effluents containing Cr, Cu, Ni, Zn, Na, Ca, cyanide (and chemical oxidation demand (COD), achieved by glucose addition) were subjected to pretreatment procedures such as hypochlorite oxidation (of cyanide) and catalytic oxidation (of COD) with peroxodisulfate. Chromium determination gave satisfactory results. The combined column preconcentration—selective elution—diphenylcarbazide spectrophotometric determination was also successfully applied to the determination of Cr in artificial and real seawater.     

CdS/MS(M=Ag,Pb,Cu,Zn)半导体纳米复合结构的制备

利用金属硫化物在水溶液中溶度积的差异和通过水热及超声波等辅助方式,利用离子置换法与共沉淀法,对CdS纳米棒上金属离子(Cd²⁺)的部分置换而对纳米微粒进行侵蚀或包覆,形成镶嵌式点缀结构或完全包覆层的异质核-壳结构CdS/MS(M=Ag⁺,Cu²⁺,Pb²⁺,Zn²⁺)。使用XRD和TEM对所得样品进行了表征。