Abstract
Mud Hills clinoptilolite has been used in an effluent treatment plant (SIXEP) at the Sellafield nuclear reprocessing site. This material has been used to remove 134/137Cs and 90Sr successfully from effluents for 3 decades. Samples of the zeolite have been tested in column experiments to determine their ability to remove radioactive Cs+ and Sr2+ ions under increasing concentrations of competing ions, Ca2+, Mg2+, Na+ and K+. These ions caused increased elution of Cs+ and Sr2+. Ca2+, Mg2+ and K+ were more effective competitors than Na+. For Na+, it was found that if concentration was reduced, then column performance recovered rapidly.
Highlights
Ion exchange provides a reliable and cost-effective method for removing radioactive C s+ and Sr2+ from liquid wastes, provided that the ionic strength is relatively low [1]
The unusual ability of clinoptilolite to scavenge Sr from aqueous nuclear wastes has been an obvious bonus to the nuclear industry and has led to speculation that it exists as a speciated monovalent cation [25, 26], such as [SrHCO3]+
The column experiments have shown that clinoptilolite can be effective in removing Cs+ and Sr2+ ions from aqueous solutions that are simulants of the feed to the site ion exchange effluent plant (SIXEP) plant
Summary
Ion exchange provides a reliable and cost-effective method for removing radioactive C s+ and Sr2+ from liquid wastes, provided that the ionic strength is relatively low [1]. Clinoptilolite, a naturally occurring zeolite, can exchange Cs+ and Sr2+ radioisotopes selectively from aqueous solutions in the presence of other common cations, Na+ [3, 4]. For the clinoptilolite used at Sellafield, 1 mol of Sr2+ and 20 mol of Cs+ may be selectively extracted in the presence of 7.5 × 105 mol of Na+, 6.5 × 103 mol of Mg2+ and 5 × 103 mol of Ca2+ [5]. As an aluminosilicate, it is compatible with encapsulation for long-term storage and subsequent disposal [7]. It can be used in particle sizes appropriate for columns, and most clinoptilolites are stable under
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