Trialkyl Phosphine Oxide as an Extracting Agent for Solvent Extraction of Nd(III) from HNO3/NaNO3 Solution

Abstract

Neodymium, one of the critical rare earth metals is in demand nowadays due to enormous technological applications and its limited supply has enforced the metallurgists to search resources for its efficient recovery. Solvent extraction is widely used as a separation technique for rare earth extraction and separation. The present investigation represents detailed investigation on solvent extraction of Nd(III) from acidic nitrate solution utilising trialkyl phosphine oxide (TAPO) in kerosene. The effects of operating variables like shaking time, TAPO molarity, HNO3 and nitrate ion concentration, nature of diluents and influence of temperature on the extraction of Nd(III) were analysed. With rise in HNO3 molarity from 0.01 M to 0.1 M, increased extraction percentage has been exhibited but extraction trend tends to decrease when the concentration of acid increased to 1 M. Using 0.2 M TAPO in kerosene, 96% Nd(III) has been extracted. Thermodynamic studies showed negative value of enthalpy change indicating exothermic extraction and negative value of change in entropy confirming the constitution of Nd(III)-TAPO complex. Maximum extraction of Nd(III) has been achieved on using kerosene as diluent due to its lower dielectric constant value compared to other diluents under consideration.