Mixed halides and thiocyanate complexes of compounds of palladium (II) in aqueous solutions

Biryukov, A. A.; Shlenskaya, V. I.; Alimarin, I.P.

doi:10.1007/bf00845824

Cited by 1 publication

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“…To clarify the effect of SCN – loading on the adsorbability of the tannin gels, the adsorption behavior of Pd(II) onto the SCN-TG at [HCl] = 1 M and 298 K was compared to that onto the original TG, as shown in Figure . The TG can hardly adsorb Pd(II) at [HCl] = 1 M because at such a high HCl concentration, most Pd(II) exists as PdCl 4 2– , which is highly unfavorable for the formation of the ligand-substituted Pd(II)–tannin complex as reported in the previous studies. ,, As for the SCN-TG, on the other hand, Pd(II) was adsorbed immediately, and its adsorption amount reached more than 0.06 mmol-Pd/g-dry gel at 6 h. This enhancement of the Pd(II) adsorbability is attributable to the extremely strong complexation of Pd(II) with SCN – retained in the gel, compared to that with Cl – . The adsorption mechanism of Pd(II) onto the SCN-TG is presumed as shown in Figure .…”

Section: Resultsmentioning

confidence: 59%

Preparation of Thiocyanate-Retaining Tannin Gel for Adsorption Recovery of Palladium from Strong Hydrochloric Acid Solutions

Morisada

Kim

Yakuwa

et al. 2011

Ind. Eng. Chem. Res.

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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 introduced thiocyanate ions (SCN À ) into the TG by adsorption process in acidic thiocyanate solutions to improve its adsorbability for palladium ion, Pd(II). To determine the optimum conditions for preparing the SCN À -retaining tannin gel (SCN-TG), we have investigated the introduction mechanism of SCN À into the TG at 298 K and HCl concentrations less than or equal to 1 M, where the decomposition of SCN À can be negligible. The adsorption amount of SCN À onto the TG increased with increasing HCl concentration, indicating that SCN À is adsorbed onto the TG through the electrostatic attraction between anionic SCN À and the protonated hydroxy groups in the TG at higher HCl concentrations. Using the resultant SCN-TG and the TG, we have conducted the Pd(II) adsorption experiment at molar-level concentrations of HCl and found that the SCN-TG can adsorb Pd(II) efficiently, whereas the TG adsorbs almost no Pd(II). Besides, the adsorbability of the SCN-TG for Pd(II) decreased only slightly with increasing HCl concentration up to at least 5 M.

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Section: Resultsmentioning

confidence: 59%