Selective Recovery of Palladium from PGM Containing Hydrochloric Acid Solution Using Thiocarbamoyl-substituted Adsorbents

Impregnation of an organic extractant into a polymeric support offers several advantages over solvent extraction system, for example easy phase separation, nontoxic, eco-friendly and economical [1]. The advantages of extractant impregnated resin (EIR) were wide choice of reagents of desired selectivity, easy preparation, and easy to operate etc. [1]. EIR technology synergistically combines the advantages of both extraction and adsorption [2]. The concept of EIRs is based on the incorporation of extractants with selective extractability for metal species into a porous polymer by physical impregnation [2,3]. Thiocarbamoylbased extractants are used as a versatile and selective extraction of transition metal ions [2]. In our previous study, solvent extraction of PGM from leach liquors of automotive catalyst using 2,2′ thiobis[4-t-butylphenol] and their thiocarbamoyl derivative 1,1-bis[(dimethylthiocarbamoyl)oxy]-2,2′ -thiobis-[4-t-butylbenzene] (2) was evaluated [4]. It was shown that thiocarbamoylbased extractants, 4-t-butyl -(dimethylthiocarbamoyloxy)benzene (1) and 2, dissolved in CHCl3 have an intrinsic selectivity for Pd(II) extraction [4]. However, the practical use of thiocarbamolylbased extractants and other supramolecular extractants in solvent extraction is still limited because of their insolubility in the hydrocarbon diluents for practical applications [5-7]. Amberlite XAD-7 (XAD) is a polyacrylic acid ester resin with good chemical stability, high porosity, uniform pore size, high surface area, and a non-ionic structure [2]. Hence, we have developed green hydrometallurgical processes based on thiocarbamoyl possessing extractants impregnated on amberlite XAD-7 and used as an adsorbent for selective separation and recovery of Pd(II) from PGM solutions.