Highly efficient recovery and purification of scandium from the waste sulfuric acid solution from titanium dioxide production by solvent extraction

The waste sulfuric acid solution generated from titanium dioxide production is called titanium dioxide waste acid (TWWA), which is an important resource for scandium production. A way including enrichment and purification stages for recovery and purification of Sc from TWWA with 10% P204 - 5% TBP synergistic extraction system was studied. In the enrichment stage, the preferred experimental conditions were obtained, i.e., the A/O ratio: 30, 25 °C, contact time: 30 min. In the following purification stage, the above-obtained enrichment products by stripping with 5 M NaOH were dissolved with 3 M HCl with 1% H2O2 added. The added H2O2 can lead to Ti form peroxy complex ([TiO(H2O2)]2+) that can effectively inhibit its co-extraction into the oil phase. The optimized purification conditions were the A/O ratio of 5, 30 min and 11 mmol/L Sc concentration. The stripping products obtained from the purification stage were dissolved with 2 M HCl, and then 0.5 M H2C2O4 was added to precipitate scandium. After washing and calcining, a product of 99.28% Sc2O3 was obtained. The recovery rate of scandium in the whole process was 90.34%. [Display omitted] •A process for recovery of Sc from waste acid was proposed using 10% P204 - 5% TBP - 85% sulfonated kerosene.•An excellent extraction selectivity towards Sc over Fe was achieved in 3 M HCl feed solution.•The co-extraction of Ti was inhibited by adding 1% H2O2 to the enrichment solution in the purification stage.•The scrubbing stage was eliminated so that large volume of scrubbing agent can be avoided.•A 99.28% Sc2O3 product was obtained with a yield of 99.34%.