Supercritical Fluid Dissolution and Extraction of Trivalent Metal Cations from Different Matrices

Studies on the recovery of trivalent metal ions such as Nd3+Eu3+ (taken as homologs of Am(III)) from solid oxide (Nd2O3), Thorium concentrate (obtained from Monazite ore processing), tissue paper/surgical gloves (rubber), and plant samples have been carried out by supercritical fluid extraction (SFE) using supercritical CO2 and ethanol/nitric acid. N,N,N',N'-tetraoctyl diglycolamide (TODGA) was used as the extractant in these studies. The results showed that the recovery of Nd increased with TODGA concentration from 50% (no TODGA) to 70% (10% TODGA) at 3 M HNO3 in ethanol. However, the extraction of Nd at 1 M HNO3 was invariant with 1-3% (v/v) TODGA concentration (73 +/- 4%). Interestingly, REEs recovery from Th concentrate was similar to 60% even without TODGA using ethanol/3 M HNO3 mixture. On the other hand, quantitative recovery of Eu-152,Eu-154 from tissue paper and surgical gloves sample could be achieved using 3 M HNO3/ethanol mixture. This suggested that it would be possible to decontaminate the contaminated laboratory waste papers using SFE technique.