Alumina powder with an exchange capacity of about 1 meq/100 g removed as much strontium as a montmorillonite sample with 91 meq/100 g capacity when tested in a simulated waste solution of 0.1M NaN0, containing 1.1 x M Sr(N03)2 and in a basic pH.Additions of orthophosphate to the simulated waste solution resulted in improved strontium removal by CaCO, powder. With 5000 p.p.m. of orthophosphate, 0.5 g of CaCO, removed over 99 per cent of the strontium from 50 cm3 of simulated waste adjusted to p H 9. Under the same test conditions, natural vermiculite showed improvement, but sodium-saturated vermiculite showed a reduction in strontium removal. By pretreating vermiculite with solutions of NaCl and NaC1-NaOH, this mineral's affinity for strontium was improved, and an increase from 35 to 85 per cent removal was obtained using a 0.5 g sorbent/50 ml solution ratio. From these slurry tests four possible mechanisms for removing strontium from radioactive wastes are suggested. These are: (1) ion exchange as an absorption process exemplified by vermiculite, clinoptilolite, and the clay minerals; (2) ion exchange as an adsorption process characterized by alumina and possibly variscite; (3) metasomatic replacement as characterized by the CaC0,-phosphate waste reaction; and (4) precipitation reactions as evidenced by natural vermiculite in contact with phosphated waste.
'The production and utilization of nuclear energy has expanded during the past ten years into a nation-wide, multipurpose industry with a capital investment of over six and a half billion dollars.
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