Processing ion exchange

For plutonium in the tri- and tetravalent state, when hydrolysis would dominate the solution chemistry, most sorption phenomena in geologic systems can be looked upon largely as physical adsorption processes. Ion exchange processes, as defined above, would be... 

Hydrophilic interaction liquid chromatography (HILIC) can handle the matrix effects nonvolatiles, which may reduce the evaporation of volatile ions during the electrospray process. Ion-exchange methods that require the use of salts could otherwise interfere with MS. 

Ion exchange is similar to adsorption, since mass transfer from a fluid to a solid phase is common in both processes, i.e. they are basically diffusion processes. Ion exchange is also a sorption process, but ions are the sorbed species in contrast to adsorption, where electrically neutral species are sorbed (Noble and Terry, 2004 Perry and Green, 1999). It is generally accepted that adsorption and ion exchange can be grouped together as sorption for a unified treatment in practical applications. 

The separation of ionic species can occur by many processes ion exchange, ion suppression or ion pairing (see Fig. 4.9). Because the latter two processes occur in HPLC, only the first process will be described here in detail. 

We have already seen in Section 2.2 how the transport of both anions and cations is a vital part of biochemistry. We will examine supramolecular models of biological ion channels in detail in Chapter 12 but here we focus on some simple ion transport systems (ionophores) relevant to simultaneous anion and cation binding. Because of the need to maintain overall and local charge neutrality during any transport process the transport of individual ions across a biological or artificial membrane never occurs in isolation. There are two kinds of primary transport processes. Ion exchange or antiport, occurs when chemically different ions of like charge such as Na+ and K+ are simultaneously transported in... 

Screening strategy Precipitation and coagulation Membrane processes Ion exchange Electrochemical Adsorption... 

Some syrups are ion-exchanged at this point in the process. Ion exchange is essential in the production of certain types of sweeteners, such as high fructose syrups. Not only does ion exchange improve the color and color stability of the syrup by... 

N= neutralization IX=ion exchange IR=ion retardation IXN = two step process ion exchange to acid or base form followed by neutralization with appropriate base of acid of salt. Example (Step 1) resin-Q+NaOH—>resin-OH (IX) (Step 2) resin-OH + H-formate----> resin-formate + H OOl). 

Fe a-montmorillonites (Fe,Na-Mont) were prepared from natural Na-montmorillonite (Na-Mont) (Bentolite H, SCP Laport) by ion-exchange in iron chloride solution containing the same amount of iron as in e synthesis of Keggin ion applied in the pillaring process. Ion-exchange was performed at 353 K for 8 hours followed by washing the sample free of chloride. Finally, the solid material was separated by centrifogation and dried at room temperature. 

A wet process is also utilized for the production of uranium(IV) fluoride, namely the EXCER process (Ion Exchange Conversion Electrolytic Reduction). In this process the ion exchange- or extraction-purified uranium(VI) solution is either electrolytically or chemically reduced to uranium(IV), which is precipitated with hydrofluoric acid as uranium(IV) fluoride hydrate (UF4 O.75H2O). This is subsequently dehydrated at 400 to 450°C. 

A.G. Winger, Sorption Processes, membrane processes - ion exchange, Eng. Progr., 1957, 53, 606 W.W. Schlutz, E.W. Neuvar, J.I. Carroll and R.E. Bums, Electrodialytic conversion of uranyl nitrate to uranic fluoride salts, Ind. Eng. Chem., 1958, 50, 1768. 

Kale powder (Bowen) Ag Mo Hg Au Cr Co Se Fe Zn Wrap sample in filter paper, combust in O, rediss. in HF [DA] Irradiate in reactor 15 h, chemically process, ion exchange, count [SEP/CONC-RNAA] [DA-SEP/ CONC-RNAA] Van den Winkel etal. (1967)... 

Ion-pair HPLC mode is a superposition of two competitive processes ion-exchange and reversed-phase. Component retention is strongly dependent on the type of ionpairing agent, its concentration, and most of all, on the history of the used column. The virgin reversed-phase (RP) column does show the hydrophobic selectivity in the ion-pair mode. However, with time, the adsorbent surface can become covered with a dense layer of adsorbed surfactant. This may irreversibly transform the RP column into an ion-exchange one. 

From the literature it is well known that this etherification reaction requires an acidic catalyst. In industrial processes ion-exchange resins with sulfonic acid groups are in use. The structure of this cross-linked resin is depicted in Fig. 8.6 To have a catalyst that can compete with the existing materials we decided to prepare a catalyst that also contains sulfonic acid groups. To compile the requirements for the new catalyst, kinetic data for MTBE synthesis [11, 17] and information on chemical [18] and mechanical [19] stability of ion-exchange resins under the reac-... 

Insight, coupled fluxes in cellular and process scale membrane processes, ion exchange, and living systems... 

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