Use of complexones solutions in liquid carbon dioxide for cleaning of materials contaminated with heavy and radioactive metals

In this paper liquid carbon dioxide (pressure 50-70 atm) was used for decontamination. The performed experiments on removal of cobalt, nickel, uranium and americium nitrates and carbonates by different solutions have shown that the solutions of such complexing agents as hexafluoroacetylacetone (HFA), tributylphosphate (TBP), di-2-ethylhexylphosphoric acid (D2EHPA) in liquid CO2 can be used for purification of pulps, metals, paper and fabrics. Liquid CO2 is high viscosity of the medium and hence low diffusion coefficients and long duration of the processes. It is known that 20 minutes are sufficient to attain equilibrium in supercritical CO2 medium on metal removal by HFA solutions. During the experiments it was established that with the use of liquid CO2 the keeping time should be increased to 40 min, which is acceptable from the standpoint of technical feasibility of decontamination processes in these solutions. Experiments on really contaminated samples of pulps, metals and fabrics have confirmed that the decontamination coefficients of 30-100 can be easily obtained by 2-3 fold material treatment operations. The secondary waste volume therewith is less by a factor of 20-200 than that of traditional techniques. (authors)