Some Parametric Studies on Separation of Palladium from Perchloric Acid Medium by Radiolytic Reduction

Abstract

The radiolytic reduction of palladium ions to palladium metal in perchloric acid solutions has been studied with the aim of separating palladium from aqueous acidic waste. Fraction of Pd separated out as precipitate has been studied as a function of initial Pd concentration and strength of HClO4. Addition of t‐butanol to the system has been found to cause substantial enhancement in the amount of Pd precipitated as compared to that in its absence. At a given absorbed dose, the extent of Pd separated is found to increase with the concentration of HClO4 in presence of t‐butanol. However, the converse is true for the radiolysis in absence of t‐butanol. The decrease in the extent of reduction of Pd(II) to Pd(0) has been found to be due to increasing formation of chloride ions that tend to form reduction resistant cholorocomplexes of Pd. This is supported by the red‐shifting in the absorption bands of Pd(ClO4)2 observed for the spectra of gamma radiolysed solutions of Pd(II) at higher HClO4 concentrations. External addition of chloride ions to aqueous Pd(II)/HClO4 system even in presence of t‐butanol has been found to cause substantial inhibition to the radiolytic reduction of Pd(II) owing to formation of reduction‐resistant complexes. Correspondingly, the addition of nitrate ions to Pd(II)/HClO4/t‐butanol system showed inhibition effect at much greater stoichiometric amount of nitrate.