Improvements in or relating to the purification of extraction solvents containing trialkyl phosphates

摘要

A solvent comprising a tri-alkyl phosphate in a hydrocarbon diluent and containing degradation products produced by the combined influence of nitric acid, and heat and/or nuclear radiation is purified by contacting it with a basic liquid organic amine which is substantially insoluble in the solvent and which does not substantially extract the tri-alkyl phosphate from the solvent. The amine may be diluted with an inert liquid which is substantially immiscible with the solvent. and does not substantially extract the tri-alkyl phosphate therefrom, suitable liquids being water and liquid alkylene glycols and condensed glycols, e.g. ethylene glycol and diethylene glycol. Suitable amines are alkanolamines and alkylene diamines such as mono-, di- and tri-ethanolamine, N-hydroxymethyl diethanolamine, 3-amino-propanol, monoisopropanolamine, monoisobutanolamine, ethylene diamine and mixtures thereof. It is preferred to use monoethanolamine or mixtures thereof with di- and tri-ethanolamines. The purification process may be preceded by a preliminary washing of the solvent with an aqueous alkali and may be followed by treatment with aqueous nitric acid solution. Examples are given in which the following solvents are purified: (1) a 20% tributyl phosphate-odourless kerosene solvent containing a small amount of dibutyl phosphate to simulate degradation and which has been equilibrated with an aqueous solution of uranyl nitrate, (2) a degraded tributyl phosphate-odourless kerosene solvent with retained Hf181 equivalent to an H number of 1360, and (3) a degraded tributyl phosphate-odourless kerosene solvent with a Z number of 23000.