A systematic study on extraction and separation of scandium using phosphinic acid by both solvent extraction and hollow fibre membrane

ABSTRACT A method for separation of scandium and preparation of scandium oxide using hollow fibre supported liquid membrane (HFSLM) was described. Scandium was separated from a multi metal solution bearing copper, nickel, cobalt, zinc, iron, manganese and scandium using bis (2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) as the mobile carrier. The effect of parameters such as pH, extractant concentration, flow rate, metal ion concentration and strip solution concentration on extraction of scandium was investigated and maximum flux was obtained at pH 2.0, Cyanex 272 concentration of 0.3 M, flow rate of 240 mL/min and 1.0 M H2SO4 in strip solution. From the equilibrium studies the extracted species was determined to be ScR3.3RH. A comparative study between solvent extraction and HFSLM has also been carried out to predict the efficiencies of both the techniques for the present system which could be useful for the treatment of industrial wastes bearing very low amount of Sc. It was observed that Sc recovery using Cyanex 272 with HFSLM and solvent extraction was 99.9 and 91%, respectively. Scandium was separated from other metal ions with high separation factors which followed the trend Sc/Ni <  Sc/Mn <  Sc/Co <  Sc/Zn <  Sc/Fe <  Sc/Cu. High pure scandium oxide (Scandia) was prepared from the strip solution by precipitation with oxalic acid and thermal decomposition at 750°C for 1 h.