Improved adsorption and separation of palladium(II) and platinum(IV) in strong hydrochloric acid solutions using thiocyanate‐retaining tannin gel

Abstract A tannin gel (TG) synthesized from condensed tannin molecules has a remarkable ability to adsorb various metal ions in aqueous solutions. In the present study, we have investigated the adsorption behaviors of palladium and platinum ions, Pd(II) and Pt(IV), in strong HCl solutions using the thiocyanate‐retaining tannin gel (SCN‐TG) prepared by adsorption of thiocyanate ion (SCN − ) onto the TG in acidic thiocyanate solutions as reported previously (Ind Eng Chem Res 2011, 50, 12366). Although the adsorption rate of Pt(IV) is slow compared to that of Pd(II), the SCN‐TG was able to adsorb both Pd(II) and Pt(IV) in a 1 M HCl solution, where the TG can never adsorb them. Besides, we have succeeded in the selective adsorption of Pd(II) from the mixture solution of Pd(II) and Pt(IV) at a temperature somewhat lower than room temperature using the SCN‐TG. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012