Purification of scandium from concentrate generated from titanium pigments production waste

Nowadays 80% of scandium in China is obtained from titanium pigments production waste through a complex purification process. The study mainly focused on the purification of Sc from its concentrate generated from titanium pigments production waste by solvent extraction. Several extractants have been tried and 10% D 2 EHPA - 5% TBP - 85% sulfonated kerosene exhibited the best extraction performance towards Sc in 7 mol/L H 2 SO 4 solution, so it was selected as the oil phase. 0.5% of H 2 O 2 was added into the concentrated solution which can effectively inhibit the extraction of Ti. Both the extraction and back extraction parameters are optimized. The preferred extraction conditions were obtained, i.e., acidity: 7 mol/L H 2 SO 4 , the phase ratio A/O: 10, room temperature, mixed contact time: 30 min, Sc concentrate: 10 g/L, that the extraction rate of Sc in the above conditions was nearly 100%. NaOH was used for back extraction with the stripping rate 99% on the following conditions: 5 mol/L NaOH stripping for 30 min at a phase ratio A/O: 1 at 90 °C. Finally, H 2 C 2 O 4 was used to further purify the back extraction product and Sc 2 (C 2 O 4 ) 3 precipitant formed. The final product Sc 2 O 3 with a purity over 99.5% was obtained by calcining Sc 2 (C 2 O 4 ) 3 at 1000 °C for 2 h. A conceptual process for Sc purification was put forward and proved. The total recovery yield of Sc in the whole process is 95%. 10% D 2 EHPA - 5% TBP - 85% sulfonated kerosene was selected with the extraction efficiency of Sc over 99.9%. The usage of H 2 O 2 can promote the extraction of scandium and inhibit the extraction of titanium. NaOH was used for back extraction with the stripping rate of 99%. H 2 C 2 O 4 was used to further purify the back extraction product and Sc 2 (C 2 O 4 ) 3 precipitant formed, which is roast obtained Sc 2 O 3 . Finally, a conceptual process of purification Sc from its concentrate was put forward and proved in the laboratory with 99.5% Sc 2 O 3 product obtained with a yield of 95%. • Several extractants were tried to purify Sc from its concentrate. • 10% D 2 EHPA - 5% TBP - 85% sulfonated kerosene was selected with the extraction efficiency of Sc over 99%. • 0.5% of H 2 O 2 was added into the feed solution to inhibit the extraction of Ti. • 5 mol/L NaOH at 90 °C can effectively strip Sc with the stripping rate of about 99%. • A simple flowsheet for Sc purification was proposed and 99.5% Sc 2 O 3 was obtained with the yield over 95%.