Solvent extraction of neodymium(III) from acidic nitrate medium using Cyanex 921 in kerosene

The extraction of neodymium(III) from acidic nitrate medium was investigated using Cyanex 921 as extractant in kerosene. The metal concentration in the aqueous phase before and after extraction was determined spectrophotometrically by Arsenazo III method. The complete equilibration was achieved in 15 min. The effects of shaking time, nitric acid concentration, nitrate concentration, extractant concentration, and temperature on the extraction were studied. The extraction of Nd(III) was found to increase very slowly with increase in concentration of HNO3 in the range of 0.001–0.008 mol/L and then decreased when 0.01 mol/L HNO3 was used. The percentage of extraction was increased with increase in nitrate concentration from 0.01–0.45 mol/L and then decreased when nitrate concentration increased to 0.5 mol/L. Quantitative extraction of Nd(III) (98%) was obtained from the aqueous phase containing 0.001 mol/L HNO3 and 0.1 mol/L KNO3 using 0.5 mol/L Cyanex 921. On the basis of slope analysis, the extracted complex in the organic phase was proposed to be Nd(NO3)3.2Cyanex 921. The extraction of Nd(III) was found to increase with increase in concentration of metal ion in the range of 0.001–0.05 mol/L from 0.001 mol/L HNO3 and 0.1 mol/L KNO3 with 0.1 mol/L Cyanex 921. The percentage of extraction of neodymium was found to decrease with increase in temperature. From temperature variation studies, the negative value of ΔH indicated the extraction reaction to be exothermic and the negative value of ΔS indicated the formation of a stable complex. Almost 100% Nd(III) was recovered from the fully loaded organic phase using 0.002 mol/L H2SO4 and 0.01 mol/L HCl.