Inorganic exchange materials

The use of ion exchange resins and natural or synthetic inorganic exchange materials in the nuclear industry is well documented ( ). In the waste solidification application, the titanates or niobates offer no unique sorption properties. They do, however, provide a relatively high overall sorption capacity for a variety of nuclides in materials which can be converted into a stable ceramic host for the sorbed ions. After the sorption process, the column bed must be consolidated to reduce surface area. The project emphasis was directed toward a stable waste form and a considerable effort was devoted to producing and characterizing a highly dense form with favorable physical, chemical and thermal properties (l ). 

A.T. Howe, in A. Clearfield, Ed., Inorganic Exchange Materials, CRC Press, Boca Raton, FL, 1982. 

PhenoHc-based resins have almost disappeared. A few other resin types are available commercially but have not made a significant impact. Inorganic materials retain importance in a number of areas where synthetic organic ion-exchange resins are not normally used. Only the latter are discussed here. This article places emphasis on the styrenic and acryHc resins that are made as small beads. Other forms of synthetic ion-exchange materials such as membranes, papers, fibers (qv), foams (qv), and Hquid extractants are not included (see Extraction, liquid-liquid Membrane technology Paper.). 

A process that employs a powdered inorganic ion exchanger in a slurry has also been proposed [7]. This process appears rather cumbersome and messy since the ion-exchange materials must be repeatedly filtered and re-pulped over each cycle This process will also be expensive to operate, since the ion exchanger must be regenerated with NaOH. 

Ion removal by solids could involve more phenomena, as for example in inorganic natural materials where ion uptake is attributed to ion exchange and adsorption processes or even to internal precipitation mechanisms (Inglezakis et al., 2004). 

The preparation, composition, structure and leaching characteristics of a crystalline, ceramic radioactive waste form have been discussed, and where applicable, compared with vitrified waste forms. The inorganic ion exchange materials used such as sodium titanate were prepared from the corresponding metal alkoxide. The alkoxides were reacted in methanol with a base containing the desired exchangeable cation and the final powder form was produced by hydrolysis in an acetone-water mixture followed by vacuum drying the precipitate at ambient temperature. 

The baseline solidification process involves contacting an inorganic titanate ion exchange material with liquid waste in a... 

C. B. Amphlett, Inorganic Ion Exchange Materials , Elsevier, Amsterdam, 1964. 

Sorbent or ion-exchange material Type of water Temperature (°C) Initial pH Inorganic arsenic species Initial arsenic concentration (mg L-1) Batch sorbent dosage (sorbent/ batch solution) or column Initial surface area (m2g-1) of sorbent or ion-exchange material Maximum removal capacity (mg As g 1 sorbent or ion-exchange material) References... 

Sorbent or ion-exchange material Type of water Temperature Initial pH (°C) Inorganic arsenic species... 

Both organic and inorganic polymer materials have been used as solid supports of indicator dyes in the development of optical sensors for (bio)chemical species. It is known that the choice of solid support and immobilization procedure have significant effects on the performance of the optical sensors (optodes) in terms of selectivity, sensitivity, dynamic range, calibration, response time and (photo)stability. Immobilization of dyes is, therefore, an essential step in the fabrication of many optical chemical sensors and biosensors. Typically, the indicator molecules have been immobilized in polymer matrices (films or beads) via adsorption, entrapment, ion exchange or covalent binding procedures. 

Palmer, D. A. Meyer, R. E., "Adsorption of Technetium on Selected Inorganic Ion-Exchange Materials and on a Range of Naturally Occurring Minerals under Oxic Conditions," J. Inorg. Nucl, Chem. 1981, 43, 2979. 

S3> Meloni, S., A. Brandone, and V. Maxia Chromium Separation by Inorganic Exchangers in Activation Analysis of Biological Materials. The 1968 International Conference Modern Trends in Activation Analysis, Gaithersburg, Maryland, October 7—11, 1968, Paper 52. 

Clearfield A. In Inorganic Ion-Exchange Materials Clearfield, A., Ed. CRC Press Boca Raton, FL 1982. 

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