Preparation of the Ion Exchanger

The preparation of the ion-exchange resin has a large impact on the success of an ion-exchange separation. The commercial resin is rarely ready to use straight from the bottle. 

This experiment describes the preparation of liquid ion-exchange electrodes for Gk and Ga +. The liquid ion-exchange solutions are incorporated into PVG membranes and fixed to the end of glass tubing. The internal solutions are either NaGl or GaGk, and a Ag/AgGl reference electrode is situated in the internal solution. 

A cationic molybdenum sulfide cluster [Mo3S4(H20)9] " with incomplete cubane-type structure and a cationic nickel-molybdenum mixed sulfide cluster [Mo3NiS4Cl(H20)9p " with complete cubane-type structure were introduced into zeolites NaY, HUSY and KL by ion exchange. Stoichiometry of the ion exchange was well established by elemental analyses. The UV-visible spectra and EXAFS analysis data exhibited that the structure of the molybdenum cluster remained virtually intact after ion exchange. MoNi/NaY catalyst prepared using the molybdenum-nickel sulfide cluster was found to be active and selective for benzothiophene hydrodesulfurization. 

Na-ZSM-5(a molar SiOz/AlaOa ratio=23.8) provided by Tosoh Corp. was used. ln(4wt%)/H-ZSM-5 and lr(1wt%)/H-ZSM-5 catalysts were prepared by the ion exchange method using NH4-ZSM-5 derived from the Na-ZSM-5 with aqueous solutions of ln(NOs)3 at 368 K for 8 h and lrCI(NH3)sCl2 at room temperature for 24 h, respectively. Addition of precious metals, 1wt% platinum and iridium to ln/H-ZSM-5 was carried out by impregnating the ln/NH4-ZSM-5 in aqueous solutions of Pt(NH3)4Cl2 and lrCI(NH3)5Cl2, respectively. The catalysts were calcined at 813 K for 3 h. 

Pt/H-MCM-22 catalysts for methane combustion have been prepared by ion-exchange of a highly crystalline H-MCM-22 zeolite using [Pt(NH3)4](N03)2. The activation procedure of the catalyst precursor has been optimized and all steps monitored by HRTEM, SEM and FTIR of CO adsorbed. The preliminary decomposition/calcination of the ion exchanged sample is very crucial in that influence the final properties of platinum active species. 

The above difficulties are removed in the new version of the liquid membrane, which employs a polymeric film with the ion-exchanger solution functioning as a plasticizer. Then it is much easier to prepare a membrane without leaks and using only a minute amount of the ion-exchanger solution. When the membrane ceases to function, it is simply replaced. For a survey of those electrodes see [109,111,112,113, 180] they are generally termed solvent-polymeric membranes [180] or polyvinyl chloride-matrix membranes [112]. 

Likewise, in the preparation of many ion-exchange resins, suitable functional groups are introduced by secondary reactions of macromolecular substances (that are generally crosslinked see Sect. 5.2). In this context the utilization of crosslinked polystyrene resins or poly(acrylamide) gel in the solid-phase synthesis of polypeptides (Merrifield technique) or even oligonucleotides should be mentioned. After complete preparation of the desired products they are cleaved from the crosslinked substrate and can be isolated. 

GjFNa and C,oSNa are the same as used in the previous works (5). The water used for preparing solutions was obtained from distillation of the ion-exchange water pretreated with potassium permanganate. Surface tension of the water (30 Cl was 71.A mNm- (the literature value is 71.18 mNm (11)). 

The overall yield is essentially 100 by any of the preparation methods, but the physical characteristics of the ion exchangers are dependent on preparation conditions. For example, sodium titanate prepared by Eqs. la and lb with hydrolysis in one liter of water per mole of Ti(OC3H7)4 has a bulk density of 0.U5 g/cm3 and a specific surface area of lO-UO m /g. The same material prepared by Eqs. la and lb and hydrolyzed in a solution of 100 ml of water in 1000 ml of acetone for each mole of Ti(OC2H7)4 has a bulk density of 0.35 g/cm3 and a specific surface area of 200-UOO m /g. In all cases, the materials consist of agglomerates of 50-100 A particles with the degree of aggregation of the particles determining both the bulk density and surface area. 

Copper modified NbMCM-41 and A1MCM-41 sieves were prepared in three ways i) by the cation exchange with copper acetate solution, ii) by the impregnation with Cu(NC>3)2, and tii) by the incorporation of Cu2+ during the synthesis. In the case of the ion exchange, the obtained samples, after filtration, were calcined at 673 K for 4 h. 

Preparation of Derivatization Reagents. 535 Derivatization of the Ion-Exchange Cleaned. . . 535 Physiological Fluid... 

The preparation of ammonium ion exchanged Y zeolites has long been known to be a precursor step in the preparation of H Y zeolites. The former materials have been characterized by thermo-gravimetric experiments, while the latter zeolites that contain the H atoms as hydroxyl groups have been intensively examined by infrared spectroscopy (1 .2 A systematic description of the... 

Continuous electrodeionization is widely used today for the preparation of high-quality deionized water for the preparation of ultrapure water in the electronic industry or in analytical laboratories. The process is described in some detail in the patent literature and company brochures [29]. There are also some variations of the basic design as far as the distribution of the ion-exchange resin is concerned. In some cases the diluate cell is filled with a mixed bed ion-exchange resin, in other cases the cation- and anion-exchange resins are placed in series in the cell. More recently, bipolar membranes are also being used in the process. 

Several precolumn derivatization techniques are available for those who wish to trade extra sample preparation time for the expense and maintenance of post column pumps and reactors. The more popular derivatives are dansyl-(32), OPA-(33), PTH-(34) and PITC-(35) amino acids. There are problems and limitations with some of these systems, however, analysis time is only 15-25 min. compared to 90-240 min. of the ion-exchange post column systems. 

Lunsford and coworkers (26) have prepared a Ru(bpy)32 complex in zeolite Y and studied the quenching of oxygen and water. The emission bands of the ion-exchanged zeolite resemble those of aqueous solutions. Diffuse reflectance spectroscopy and ESCA measurements were also made in the characterization of these samples. 

Composition of the liquid products was determined by gas chromatography, using a 100m capillary column with squalane. gas products were analyzed over vaseline oil. The catalysts were prepared by the Ion exchange of the sodium form of zeolite Y with metal cations (3). 

The final operation in the preparation of an ion exchanger is equilibration of the exchanger with the appropriate counterions. The actual... 

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