Conversion of neodymium oxide with N2O4 into nitrate followed by supercritical fluid extraction of nitrate

Supercritical Extraction of Lanthanide Tributyl Phosphate Complexes: Current Status and Future Directions

“…If the starting material is a lanthanide oxide or hydroxide, then CO 2 and a TBP/HNO 3 adduct are introduced to generate a nitrate and then extract with TBP (see eqs 2 and 3). Percent extraction can then be measured by directing the outlet fluid into a trap solution [44][45][46][47][48][49][50][51][52][53][54]56 or by measuring the remaining lanthanides in the solid/liquid phase left in the cell. 38,45,46,49 Many studies have distinguished between "dynamic extraction" and "static extraction".…”

“…Percent extraction can then be measured by directing the outlet fluid into a trap solution [44][45][46][47][48][49][50][51][52][53][54]56 or by measuring the remaining lanthanides in the solid/liquid phase left in the cell. 38,45,46,49 Many studies have distinguished between "dynamic extraction" and "static extraction". In static extractions, CO 2 and the TBP/adduct are introduced into the high-pressure vessel containing the starting material.…”

“…44,50 Dynamic extractions can be used for determining the kinetics of extraction from various lanthanide-containing materials. 46,49,50,53 First-order kinetic models have been fit to kinetic extraction data from dynamic systems, 46,50 but further study is required to elucidate the mechanism and rate-limiting steps.…”

Rare earth element extraction from pretreated bastnäsite in supercritical carbon dioxide

“…REEs can be extracted in supercritical CO 2 as a TBP/nitrate complex in several different ways. Supercritical CO 2 with TBP has been used to extract REEs (and actinides) from aqueous nitrate solutions [8][9][10] and from solid nitrate salts [11][12][13]. Another option is to premix TBP and HNO 3 to form a liquid adduct, dissolve this adduct in supercritical CO 2 , and use this modified CO 2 to extract REEs from acid-soluble mineral phases such as oxides [14][15][16][17][18][19].…”

Determination of Metals in Soils

“…Plutonium in soils has been quantified using plutonium-238 as a yield trace. 295 Hollenbach et al 216 used flow-injection preconcentration for the determination of 230 Th, 234 U, 239 Pu, and 240 Pu in soils. Detection limits were improved by a factor of about 20, and greater freedom from interferences was observed with the flow-injection system compared to direct aspiration.…”