Conversion Reactions of Uranyl Ions to Uranium Oxides in Supercritical Ethanol

Abstract

Conversion reactions of UO 22+ ions to uranium oxides in supercritical ethanol have been studied to develop the method for recovering uranium from liquid wastes containing uranyl ions(UO 2 2+ ). The UO 2 precipitates were formed efficiently in supercritical ethanol medium under 300 • C and 40 MPa. The conversion reaction of UO 2 2+ to UO 2 is proposed to proceed through two steps, i.e., the first step is the hydrolysis of UO 2 2+ , followed by the reduction of resulting hydrolysis product to U 3 O 8 , and the second one is the conversion of U 3 O 8 to UO 2 . From the detection of acetal and ethyl acetate in the liquid residue, acetaldehyde is proposed to be the most probable candidate as reducing agent.

NMR Studies on Effects of Temperature, Pressure, and Fluorination on Structures and Dynamics of Alcohols in Liquid and Supercritical States

“…Supercritical alcohols have recently become of interest, since they are more reactive and less corrosive media compared with scw. Several important chemical operations have been reported, e.g., polymer recycling by depolymerization in sc methanol (scMeOH), [8][9][10] isomerization reactions in sc ethanol (scEtOH), 11 synthesis of functional carbon nanotubes in sc-EtOH, 12 recovery of uranium oxides from radioactive wastes by using scEtOH, 13 and hydrogenation reactions without catalysis in sc 2-propanol (scPrOH). 14 Since the unique properties of sc alcohols should be considerably affected by their microscopic behavior, technologies using sc alcohols can be expected to be further developed by understanding the molecular interactions of alcohols under sc conditions.…”

“…Supercritical alcohols have recently become of interest, since they are more reactive and less corrosive media compared with scw. Several important chemical operations have been reported, e.g., polymer recycling by depolymerization in sc methanol (scMeOH), − isomerization reactions in sc ethanol (scEtOH), synthesis of functional carbon nanotubes in scEtOH, recovery of uranium oxides from radioactive wastes by using scEtOH, and hydrogenation reactions without catalysis in sc 2-propanol (scPrOH) …”

Influence of additives on low-temperature hydrothermal synthesis of UO2+x and ThO2

“…[25][26][27] Triuranium octoxide (U 3 O 8 ) and uranium dioxide (UO 2 ) were prepared by the heat treatment of a uranylIJVI) nitrate solution in supercritical ethanol. 28,29 The hydrothermal conversion of actinide oxalates to dioxides resulted in the production of actinide oxide nanocrystals at relatively low temperatures of around 100 °C (ref. 30 and 31).…”