Selective extraction and recovery of scandium from sulfate medium by Cextrant 230

Scandium is an important member of rare earths and always associated with other metals. A novel aminophosphonate compound di-(2-ethylhexyl)[N-(2-ethylhexyl) amino methyl] phosphonate (Cextrant 230, L) was applied for the selective extraction and recovery of scandium from sulfate medium. The extraction mechanism was determined by the slope analysis method and the extracted chelate was deduced to be Sc(HSO4)SO4·2L. Thermodynamic parameters (ΔH, ΔG, ΔS) were calculated, implying that the extraction reaction of scandium is an exothermic process. Cextrant 230 was found to be an efficient extractant for the selective extraction of scandium. By just one stage extraction, the concentration of scandium in the sulfuric acid leaching of red mud decreased obviously from 3.57 mg/L to about 0.3 mg/L while the main element aluminium was nearly not extracted. A flow sheet for the recovery of scandium from red mud was proposed.