Physicochemistry in Service of Process Design: Case of Uranium Recovery by Liquid–Liquid Extraction

Abstract

Although solvent extraction seems to be easy to operate in hydrometallurgical processes, its implementation can be difficult and costly. In order to reduce capital and operation expenditures, process optimization is mandatory. It consists in the use of appropriate equipment, flowsheet, and parameters optimization in order to reduce energy and reactive consumption, effluent generation, etc. For this goal, two approaches can be implemented: (i) an empiric approach that relies on feedbacks and experiment design for optimizing operational parameters, and (ii) a more rigorous approach that relies on the comprehension of the physicochemistry taking place during process operation. The first approach is often used in industry, but it is never sure that the process could always operate under optimized conditions. The second approach is interesting as the comprehension of the physicochemistry can get the process more flexible towards external constraints, and it can lead to the development of breakthrough solutions. This paper will show how the comprehension of the physicochemistry involved in the solvent extraction process can contribute to improve process performances. Two examples are presented in this paper for the sake of illustration: (i) the comprehension of the physicochemical phenomena responsible for the chemical degradation of the extraction solvent during liquid–liquid extraction of uranium from acidic sulfate media in order to keep high uranium extraction efficiency, and (ii) the development of a new extractant for the recovery of uranium from wet phosphoric acid by means of a rational approach combining modelling of uranium (IV) extraction and investigation of uranium speciation in the extraction solvent.