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Direct extraction of metals from solids with complexing agents in supercritical CO2(SC-CO2) has recently attracted interests in separation,purification,recovery,and analysis of metals.In the present study,the static/dynamic extraction of rare earth elements(Nd,Ce) from their oxides(Nd2O3,CeO2) with organophosphorus complexes with HNO3 and H2O in SC-CO2 was investigated.The static extraction efficiency of Nd from Nd2O3 with the tri-n-butylphosphate(TBP)-HNO3 complex could reach 95% under optimized experimental conditions.However,the static extraction efficiency of Nd from Nd2O3 with the trilkyl phosphine oxide(TRPO)-HNO3 complex was less than 10%,and the static extraction efficiency of Ce from CeO2 with the TBP-HNO3 complex was less than 1%.The dynamic extraction efficiency of Nd from Nd2O3 with the TBP-HNO3 complex could reach more than 97%.Effects of parameters were evaluated on the extraction efficiency to ascertain the optimum conditions.This study illustrated the extraction process using the TBP-HNO3 complex in SC-CO2 would be feasible for separation,purification,recovery,and analysis of some rare earth elements from various oxide mixtures.
Direct extraction of metals from solids with complexing agents in supercritical CO2 (SC-CO2) has attracted interests in separation, purification, recovery, and analysis of metals. The present study, the static / dynamic extraction of rare earth elements (Nd, Ce) from their oxides (Nd2O3, CeO2) with organophosphorus complexes with HNO3 and H2O in SC-CO2 was investigated. The static extraction efficiency of Nd from Nd2O3 with the tri-n-butylphosphate (TBP) optimized experimental conditions. However, the static extraction efficiency of Nd from Nd2O3 with the trilkyl phosphine oxide (TRPO) -HNO3 complex was less than 10%, and the static extraction efficiency of Ce from CeO2 with the TBP-HNO3 complex was less than 1 %. The dynamic extraction efficiency of Nd from Nd2O3 with the TBP-HNO3 complex could reach more than 97%. Effects of parameters were evaluated on the extraction efficiency to ascertain the optimum conditions. This study illustrated the extraction process using the TBP-HNO3 complex in SC-CO2 would be feasible for separation, purification, recovery, and analysis of some rare earth elements from various oxide mixtures.