EXTRACTION AND CONCENTRATION OF RHENIUM FROM NITRATE-CONTAINING RHENIUM DESORBATE

Abstract

Extraction technology plays a key role in the industrial production of rhenium, accounting for more than 70% of the world's production of this element. In aqueous and alkaline solutions, rhenium is present in the form of the anion ReO4 - , which necessitates the use of anion exchange extractants based on tertiary amines. Despite the widespread application and many years of research on rhenium extraction with amines, the obtained data remain contradictory. The extraction of rhenium from aqueous solutions by an amine extractant occurs through an anion exchange mechanism with the formation of the complex TAAHReO4. To increase the solubility of amine salts in the organic phase, high-molecular-weight aliphatic alcohols, such as decyl alcohol, are added, which act as modifiers of the organic phase without extracting rhenium themselves. The aim of this work is to investigate the extraction of rhenium with trialkylamine from a model solution that simulates the composition of nitrate desorbate obtained from the processing of uranium ores. Specifically, various factors affecting the extraction and reextraction of rhenium are studied to determine the optimal parameters of these processes. The study uses trialkylamine as the extractant and decyl alcohol as the modifying additive. The results of the study show that the optimal parameters for rhenium extraction are: an extractant concentration of TAA:DA:kerosene=40:5:55 (% by volume), an organic to aqueous phase ratio of V_org/aq = 1:5, an extraction time of 5 minutes, and a rhenium extraction rate of up to 75%. Similar results were obtained with an extractant concentration of TAA:DA:kerosene = 30:10:60 and an extraction time of 5 minutes, where the rhenium extraction rate was about 74%. The re-extraction of rhenium is most efficiently carried out using an ammonia solution with a concentration of 114 g/L NH3⋅H2O and a phase contact time of 10 minutes, with a re-extraction rate of 85.5%. Similar results were obtained with the addition of 174 g/L (NH4)2SO4, where the rhenium re-extraction rate was 82%.