Solid-state ion exchange in zeolites: Part IV. Evidence for contact-induced ion exchange between hydrated NaY zeolite and metal chlorides

Results obtained by solid-state ²³Na MAS n.m.r. spectroscopy, X-ray diffractometry, and i.r. spectroscopy show that contact-induced ion exchange occurs at ambient temperature in mechanical mixtures of, for example, LiCl, KCl, BeCl₂, or CaCl₂, and hydrated NaY zeolite.     

Solid-state ion exchange in zeolites: Part 6. SystemLaCl3/NaY zeolite

La,NaY zeolite (I) is prepared by contact-induced ion exchange between solid LaCl₃·7 H₂O and NaY zeolite powder. La,NaY (I) is investigated by X-ray diffraction,²⁷AIMAS n.m.r.,²⁹SiMAS n.m.r.,²³NaMAS n.m.r., and i.r. spectroscopy after various treatments. Results are compared with those obtained employing a conventionally exchanged La,NaY sample (76). It is shown that the behavior of La,NaY zeolites obtained via either route are very similar except for a somewhat lower thermal stability of the La,NaY (I) after heat-treatment at high temperature (850 K), treatment with water, and repeated high-temperature treatment. The catalytic performance of La,NaY (I) and La,Nay (74) is almost identical when tested for acid-catalyzed selective disproportionation of ethylbenzene.     

The electrochemical investigation of salts partition with ion exchange membranes

The regenaration of acid and base from the solutions containing metallic salts was achieved by salt splitting method (SSM) using not only anion-exchange membranes (AEM) but also cation-exchange membrane (CEM). In these experiments, while the ion exchange membrane was anion-exchange membrane, acid solutions were used as an anolyte and different salts of potassium were used as a catholyte. In addition to these experiments, while the ion exchange membrane was cation-exchange membrane, base solutions were used as a catholyte and different salts of potassium were used as an anolyte. The effects of current density, initial concentrations of anolyte and catholyte solutions, the type of salt solution and the type of the ion-exchange membranes on the recovery ratio of bases and acids were investigated. The results of the experiments were investigated with the Statistical Package for Social Sciences (SPSS) program. The obtained results show that this technique can be used not only for recovering the acid and base wastes of industry but also for removing the impurities in order to obtain pure acids and bases in laboratory conditions.     

离子交换树脂膜在土壤植物营养研究中的应用

阐述了离子交换树脂膜的工作原理及其发展变迁的三个阶段；详细综述了９０年代以来国内外应用离子交换树脂（膜）在土壤、植物营养科学领域中的研究和应用进展；最后对该技术的应用前景及其进一步发展存在的问题进行了简述。     

新型通用离子交换膜的研究与实践

基于离子交换膜的电膜技术,由于其独特的离子传递特性,可以进行离子物系的分离分级,在清洁生产、节能减排、环境保护、能量转换等方面有着广泛的应用前景。然而,目前国内相关均相离子膜产品尚处于起步阶段,以日本为首的国家对我国进行相关技术封锁和价格垄断。正是基于这样的产业背景和现实意义,开发出新型的均相离子膜制备路线尤为重要。本课题组提出了一种简单而通用的侧链型离子化芳香族聚合物的合成方法,即“离子单体聚酰基化”均相离子交换膜制备路线,并通过ATRP法来设计离子交换膜的主链憎水、侧链亲水的接枝结构,通过对接枝密度和接枝长度进行调节,实现对膜性能的调控,以满足不同的应用过程对膜性能的要求。此种均相离子交换膜的制备工艺及产业化生产攻关,可以打破以日本为首的国家对我国离子膜产品的技术封锁,实现具有我国自主知识产权的离子膜技术的产业化。制备条件温和、制备工艺简单、快捷,而且整个过程没有传统方法中常用的季铵化或磺化步骤,有效地简化工艺和降低环境污染,可用于扩散渗析、普通电渗析以及双极膜电渗析过程对高性能离子交换膜材料的需求。该系列离子交换膜在特种废水处理、有机酸生产、氨基酸分离纯化、重金属废水处理等诸多领域得到了广泛的使用,均取得了较为满意的使用效果。     

The role of the co-ion in chelating ion exchange processes

Batch equilibration studies with unbuffered salt solutions have revealed that the metal ion sorbed by chelating exchange resins is accompanied by a co-ion which is labile and therefore easily eluted by buffer solutions. The predominant species sorbed is the 1:1 complex such as RCuCl, but there are significant contributions by 1:2 complexing of the metal due to the random nature of the resin. The inability of the sulphate ion to span two metal chelation sites has led to the conclusion that the co-ion, in such systems, is not retained within the matrix simply to effect electrical neutrality but is located at the metal sorption site. Column operation with a chelating ion exchanger and copper chloride in a sorption, washing and desorption cycle has confirmed the results of the batch equilibration studies. The presence in the resin of all sorbed species MR_n to RM-X_n−1, each with its own stability constant, is suggested as the main reason why chelating ion exchange is less selective than the solvent extraction process using the same chelating ligand.     

Determination of nitrate concentration in soil via photoacoustic spectroscopy analysis of ion exchange membranes

Numerous works have demonstrated that ion exchange membranes can be used for accurate determination of the availability of nitrate and other key nutrients in soils. After letting the ion exchange membrane interact with the soil for a known period of time, the membrane is typically immersed in a strong reagent to desorb the ions and the resulting solution is analyzed by standard chemical methods. The present study shows that mid-infrared photoacoustic spectroscopy can be used to estimate directly the amount of nitrate sorbed onto such membranes and could replace advantageously the standard chemical analysis. The study was conducted with two commercially available membranes, and in both cases the average determination error achieved with a simple partial least squares model was approximately 1.6-1.8 microeq, which under the specific experimental conditions corresponds to approximately 4.5-5.0 mg[N]/kg[dry soil]. Such errors are about 30% larger than those reported in a previous study in which the membrane was analyzed by transmittance spectroscopy. However, the present method is suitable for a much wider range of membranes, such as those commonly used for water treatment and that are too thick for transmittance measurements. For such membranes, photoacoustic spectroscopy is a very cheap and rapid alternative to standard chemical analysis.     

Role of metal ion incorporation in ion exchange resin on the selectivity of fluoride

Indion FR 10 resin has sulphonic acid functional group (H(+) form) possesses appreciable defluoridation capacity (DC) and its DC has been enhanced by chemical modification into Na(+) and Al(3+) forms by loading respective metal ions in H(+) form of resin. The DCs of Na(+) and Al(3+) forms were found to be 445 and 478 mg F(-)/kg, respectively, whereas the DC of H(+) form is 265 mg F(-)/kg at 10 mg/L initial fluoride concentration. The nature and morphology of sorbents are characterized using FTIR and SEM analysis. The fluoride sorption was explained using the Freundlich, Langmuir and Redlich-Peterson isotherms and kinetic models. The calculated thermodynamic parameters such as DeltaG degrees, DeltaH degrees, DeltaS degrees and sticking probability (S(*)) explains the nature of sorption. Comparison was also made by the elution capacity of these resins in order to select a cost effective material. A field trial was carried out to test the suitability of the resins with fluoride water collected from a nearby fluoride-endemic area.     

Specific ion effects on the properties of cationic Gemini surfactant monolayers

The effects of some anions of the Hofmeister series and different divalent cations of alkaline earth metals on the properties of Langmuir monolayers of the cationic Gemini surfactant ethyl-bis (dimethyl octadecylammonium bromide) have been investigated. Surface pressure and potential isotherms at the air-water interface were obtained on aqueous subphases containing sodium salts with several anions of the Hofmeister series (Cl⁻, NO₃⁻, Br⁻, I⁻, ClO₄⁻, and SCN⁻). The influence of the investigated anions on the monolayer properties can be ordered according to the Hofmeister series with a change in the order between bromide and nitrate anions. On the other hand, for a given anion, the cation of the salt also influences the surface properties of the Langmuir films. The monolayers can be transferred onto mica by the Langmuir-Blodgett technique and then the Langmuir-Blodgett films were characterized by atomic force microscopy (AFM). The AFM images show that the molecules become more closely packed and nearly vertical to the surface when anions screen the electric charge of the surfactant molecules.     

Experimental investigation of selective localisation by decomposition of the time reversal operator and subspace-based technique

The approaches of the active time reversal (TR) selective localisation based on the decomposition of the time reversal operator (DORT) and the TR multiple signal classification (MUSIC) location are presented. The waveguide experiment describes in detail the procedure of active TR location and shows that (i) the extended target could have multiple distinguishable eigenstates, unlike point-like targets in which one target corresponds to one eigenstate; (ii) the selective location can be achieved by means of the standard TR location in the presence of the suspended and bottom objects; (iii) compared with the standard TR location, TR MUSIC location based on signal subspaces performs better in locating non-resolved targets and has lower sidelobe levels to locate the extended target. Finally, the approach of acquiring the TR operator via array probing by weighting Hadamard?Walsh functions (to produce orthogonal beams) is discussed. The experimental result shows that the ambiguity surfaces of the standard TR location and the TR MUSIC location are greatly improved with this approach.     

热活化温度对坡缕石结构及饱和离子交换吸附量的影响

采用X射线衍射(XRD)、Fourier红外吸收光谱(FT-IR)、扫描电子显微镜(SEM)分析了热活化坡缕石晶体结构及显微形貌,并采用zeta(ζ)电位分析仪、比表面积分析仪及原子吸收光谱仪(AAS)测定了热活化坡缕石的zeta电位、比表面积及饱和Cu2+交换吸附量。结果表明热活化温度对坡缕石zeta电位无显著影响。当热活化温度低于250℃时,坡缕石脱出吸附水及部分配位水,比表面积显著增大,但晶体结构无明显变化;热活化温度为350～650℃时,坡缕石将脱出配位水和结构水,并发生"折叠作用",使得坡缕石表面活性中心增加,至750℃时晶体结构完全破坏,而比表面积则随热活化温度的升高依次降低。坡缕石饱和Cu2+交换吸附量仅与热活化温度密切相关,当热活化温度为450℃时,坡缕石饱和Cu2+交换吸附量最大。     

Acidity of modified Y zeolites: Effect of nonskeletal Al,formed by hydrothermal treatment,dealumination with SiCl4, and cationic exchange with Al

The acidity of modified Y zeolites was studied using adsorption and thermal desorption of pyridine (i.r.s. technique). It was found that at least some nonskeletal Al species always take part in the compensation of lattice charge, thus affecting the number of skeletal hydroxyls. Oxidic clusters prevailing on hydrothermally treated zeolites yield a much lower fraction of strong Al electron-accepting sites than of cationic species, which are typical for AIHY and are also formed in a considerable amount in zeolites dealuminated with SiCl₄. Both types of nonskeletal Al species decrease the Brönsted acid strength of the zeolite. The activity of modified zeolites in the oligomerization of ethylene is discussed taking into account the action of Al electron-accepting sites.