Abstract

FORNER, E.L. et al. Uranium recovery from high-chloride sulphate leach solutions: A cost tradeoff study of using treated water vs. saline water as make-up water. J. S. Afr. Inst. Min. Metall. [online]. 2018, vol.118, n.2, pp.95-102. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/2018/v118n2a1.

A well-established technology for uranium recovery comprises sulphuric acid leaching, followed by solvent extraction (SX) with tertiary amines such as Alamine 336. The inherent challenge with uranium processing in arid mining regions, such as Namibia and Australia, is that good quality water sources are in short supply. Supplying water through a desalination facility is a costly solution, and the use of high-salinity water, for example, seawater or saline bore water, could provide an alternative option. However, the presence of chlorides above 3 g/L in the pregnant leach solution hinders uranium loading on the conventional tertiary amine solvent extraction organic. In this paper, the opportunity to utilize high-salinity water (20 g/L Cl^-) as make-up water in the plant is evaluated using two uranium solvent-extraction (SX) recovery options: Option 1 employs a large seawater reverse-osmosis treatment plant for the supply of fresh water throughout the process, together with Alamine 336 organic for SX; option 2 uses saline water for the front-end water requirements, with the chloride-tolerant Cyanex 272 organic for purification and a smaller reverse osmosis plant for fresh water supply downstream of SX. The main focus is the selection of materials of construction as well as the capital and operating expenditure differentials for water treatment and front-end unit operations. A high-level techno-financial trade-off study using cost differentials revealed that a flow sheet incorporating a high-salinity water source is an economical option when mild steel rubber-lined platework and super-duplex SAF2507 steel mechanicals are used.

Keywords : uranium recovery; solvent extraction; chloride tolerance; high-salinity.

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