Synthesis of thiosemicarbazone derivative of 2-OH naphthaldehyde and its application in synergistic extraction of gold (III)

Abstract

A widely useful class of chelating ligand, i.e., thiosemicarbazone derivative of 2-OH naphthaldehyde, has been synthesised by the reaction of 2-OH naphthaldehyde and thiosemicarbazide and characterised. Application of this ligand in synergistic extraction of Au(III), from hydrochloric acid medium in presence of amine donors like TOA, Adogen 464, Amberlite LA-2 and some phosphorus oxide donors like TOPO, bis(2-ethyl hexyl) phosphonate, TBPO, TPPO and TBP, using methyl isobutyl ketone as the solvent has been studied and log <i>k</i>_ex values for binary organic phase [Au(A)(Cl)₂] found to be 11.89, which is by far the largest among the corresponding values known for other thiosemicarbazones. The overall equilibrium (log <i>K</i>) constants have been calculated for all the ternary adducts, [Au(A)(Cl)₂S], where S represents donor and A the ligand. The synergistic studies have been performed at <i>pH </i>= 6.5 and the effect of various diluents on the extent of synergism of Au³⁺ by this ligand have also been studied.