Effect of Aqueous Media on the Recovery of Scandium by Selective Precipitation

Abstract

This research presents a novel precipitation method for scandium (Sc) concentrate refining from bauxite residue leachates and the effect of aqueous media on this triple-stage successive precipitation process. The precipitation pattern and the precipitation behavior of the constituent elements was investigated using different precipitation agents in three major mineral acid media, namely, H 2 SO 4 , HNO 3 , and HCl in a comparative manner. Experimental investigations showed behavioral similarities between HNO 3 and HCl media, while H 2 SO 4 media was different from them because of the nature of the formed complexes. NH 4 OH was found to be the best precipitation agent in every leaching media to remove Fe(III) with low Sc co-precipitation. To limit Sc loss from the system, Fe(III) removal was divided into two steps, leading to more than 90% of Fe(III) removal at the end of the process. Phosphate concentrates were produced in the final step of the precipitation process with dibasic phosphates which have a strong affinity towards Sc. Concentrates containing more than 50% of ScPO 4 were produced in each case from the solutions after Fe(III) removal, as described. A flow diagram of the selective precipitation process is proposed for these three mineral acid media with their characteristic parameters.

Quaternization of algal/PEI beads (a new sorbent): Characterization and application to scandium sorption from aqueous solutions

“…Leaching processes (sometimes associated to roasting, [7]) constitute the first step in the recovery of Sc(III) from solid wastes using acidic solutions [6,[8][9][10]. For valorization of leachates, processes such as selective precipitation [11,12] and solvent extraction [13][14][15][16] are frequently reported for the treatment of concentrated solutions. The loss of expensive and toxic reagents (extractant and solvent being partially dissolved in water) makes solvent extraction environmentally and economically debatable in the case of dilute solutions (i.e., below 100-150 mg Sc L −1 ).…”

Reductive Smelting of Neutralized Red Mud for Iron Recovery and Produced Pig Iron for Heat-Resistant Castings

“…The most perspective slag treatment is a leaching process by hydrochloric acid to obtain aluminum chloride solutions [20,21]. Then, aluminum chloride hexahydrate (AlCl3•H2O) and scandium (Sc) compounds may selectively be extracted from these solutions [22][23][24][25][26][27]. Silicon dioxides and titanium oxides will concentrate in a solid residue.…”

Efficiency of Sulfuric Acid on Selective Scandium Leachability from Bauxite Residue

“…Hydrometallurgical treatment is the most commonly used technique for REE (including Sc) recovery from BR [21,22]. Several conventional mineral [3,4,[17][18][19][21][22][23][24][25][26][27][28][29] and organic acids [3,28], as well as alkaline solvents (Na 2 CO 3 ) [30], have been studied. The use of organic acids shows very low recovery yields, while alkaline solvents hinder the following ion exchange and solvent extraction processes for Sc isolation and purification [14].…”