Rhodium Adsorption on Gallic Acid Resol Resin

A new adsorbent resin has been developed by immobilizing gallic acid with formaldehyde, and its adsorption properties to $Rh^{3+}$ were reviewed with respect to the collection in aqueous solution. Linear and nonlinear regression procedures have been applied to the Langmuir, Freundlich, Tempkin, Dubinin-Radushkevich, and Redlich-Peterson isotherms. The resin exhibited good adsorption capacity towards $Rh^{3+}$ from acidic aqueous solutions ($[H^{+}]$=1 M, $[Cl^{-}]$=1 M). The equilibrium adsorption capacity at 293 K was up to 69.43 mg $g^{-1}$. The adsorption isotherms could be well described by Langmiur equation. The experimental studies suggested that gallic acid formaldehyde resin was effective for the adsorption of $Rh^{3+}$ from chloride acid solutions, and the loaded $Rh^{3+}$ could be easily desorbed from the 1 M HNO₃ + 0.1 M NaClO₃ solution mixture with a hundred percent efficiency. Thermodynamic parameters such as the entropy change, enthalpy change and Gibbs free energy change were calculated. The adsorption of Rh^{3+} was found to be an endothermic adsorption process. This suggested that the resin can be used as an active biosorbent for the recovery of $Rh^{3+}$ from 1 M HCl concentrated acid solution.