Thio β -diketonates of lanthanides-I: Solvent extraction behavior of neodymium (III) with 1,1,1-trifluoro-4-(2-thienyl)-4-mercapto but-3-en-2-one (HSTTA) as the extractant

Abstract

The solvent extraction behavior of Nd³⁺ using thiothenoyltrifluoroacetone (HSTTA) as extractant has been described. The distribution constant (P_HA) and the dissociation constant (K_a) of the reagent in the aqueous-organic phases have been determined. The order of P_HA values with respect to the organic solvents are chloroform > cyclohexane > benzene. Among the three solvents the trend in extraction is benzene > cyclohexane > chloroform. The extraction process is predominantly governed by the following reaction equilibrium Nd_aq³⁺ + 3 HSTTA(a) ⇋ Nd(STTA)3(a) + 3H⁺_(aq) The mixed equilibrium constant for extraction (K*_3.0), biphase stability constant (PMA . β₃) and pH for 50% extraction have been computed for each solvent systems. The cause of superiority of HTTA over HSTTA as an extractant has been discussed.