Solvent extraction of scandium from leaching solution of red mud roasted with ammonium sulfate using D2EHPA/TBP

Red mud is an important secondary resource for scandium production. The red mud leaching solution containing scandium in this study was derived from environmentally friendly ammonium sulfate roasting and water leaching process. A synergistic extraction with a mixture of di(2-ethylhexyl) phosphate acid (D2EHPA) and tributyl phosphate (TBP) for recovery of scandium from red mud leaching solution is proposed. The effects of D2EHPA concentration, H2SO4 concentration, rare earth elements, dosage of TBP, phase ratio (A/O), contact time and H2O2 concentration on scandium extraction were investigated. The results show that more than 99% scandium is extracted under the optimal conditions while Fe, Al, Ti, Ca and rare earth elements (Ce, Y, La, Nd, Er, etc.) are hardly extracted. The stripping efficiency of Sc reaches above 92.37% under the optimal stripping conditions of 5 mol/L NaOH with an A/O of 1 at 90 °C for 30 min. The proposed technology could provide an effective method for extraction of scandium from red mud leaching solution.