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

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• 作者：Shintaro Morisada ; Yoen-Ho Kim ; Shinpei Yakuwa ; Takeshi Ogata ; Yoshio Nakano
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2011
• 出版时间：November 16, 2011
• 年：2011
• 卷：50
• 期：22
• 页码：12366-12371
• 全文大小：805K
• 年卷期：v.50,no.22(November 16, 2011)
• ISSN：1520-5045

文摘

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^{鈥?/sup>) 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鈥?/sup>-retaining tannin gel (SCN-TG), we have investigated the introduction mechanism of SCN鈥?/sup> into the TG at 298 K and HCl concentrations less than or equal to 1 M, where the decomposition of SCN鈥?/sup> can be negligible. The adsorption amount of SCN鈥?/sup> onto the TG increased with increasing HCl concentration, indicating that SCN鈥?/sup> is adsorbed onto the TG through the electrostatic attraction between anionic SCN鈥?/sup> 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.}