Abstract
The solvent extraction of scandium by the mixture of di-(2-ethylhexyl) phosphate (D2EHPA) and tri-n-butyl phosphate (TBP) has been investigated in the acidic leaching solution of vanadium slag. Thermodynamic analysis of the species distribution diagrams on the Sc-S-H2O system showed that scandium mainly exists as Sc3+ and Sc(SO4)+, and sulfur mainly exists as HSO4− in the actual leaching solution of vanadium slag (pH = −0.75). The extraction process was studied to optimize various parameters such as the extractant concentration, dosage of TBP, phase ratio, and stirring speed. The results indicated that 83.64% of scandium and less than 2% of co-extracted elements were extracted under optimal conditions. Then, over 95% of the co-extracted elements and less than 1.1% of scandium were scrubbed from the loaded organic phase by 4.0 mol/L of HCl. Finally, 87.20% of scandium was stripped with 2 mol/L of NaOH and 1 mol/L of NaCl at a stripping O/A of 1:1.
Highlights
Scandium, as a valuable by-product, has been mainly recovered from waste liquors, residues and tailings in the production process of other metals such as titanium, rare earths, aluminium, uranium, and tungsten [1]
Based on the above thermodynamic analysis, in the actual leaching solution of vanadium slag by titanium white waste acid, the main existing forms of Sc were the cations of Sc3+ and
Based on the above thermodynamic analysis, in the actual leaching solution of vanadium slag titanium white waste acid, the main existing forms of Sc were the cations of Sc3+
Summary
As a valuable by-product, has been mainly recovered from waste liquors, residues and tailings in the production process of other metals such as titanium, rare earths, aluminium, uranium, and tungsten [1]. Neutralization and concentration methods have been widely used to treat waste acid in China and other countries These processes generally possess the following problems: (1) the cost of processing is high, and (2) it is difficult to effectively utilize the acid resources and recover the valuable components (especially scandium) in waste acid [5,6]. The research in this paper is a new exploration for the extraction of scandium from the new feed solution system, but is of great significance for the treatment and utilization of vanadium slag and titanium white waste acid [22,23,24,25,26,27,28,29,30,31,32,33]. The behaviours of valuable metals in the solvent extraction were studied systematically
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