Application of organo-ceramic adsorbents functionalized with imidazole for noble metal separations

Imidazole-functionalized organo-ceramic adsorbents are synthesized by sol-gel processing to selectively extract noble metals. For the synthesis of these materials, N-(3-triethoxysilylpropyl)- 4,5-dihydroimidazole is used as the functional precursor and tetraethoxysilane is used as the cross-linking agent. The adsorbent synthesized at optimal conditions (SOL-IPS-F-22) has 3.0 mmol/g of ligand density and maximum uptake capacities of 1.54, 1.41, and 2.43 mmol/g for Pd(II), Pt(IV), and Au(III), respectively, at 0.1 M HCl concentration. This adsorbent has high stability, fast palladium uptake kinetics, and no adsorption of copper and iron ions. A multi-metal breakthrough experiment shows SOL-IPS-F-22 has high potential to extract these noble metals from other transition metal ions and the possibility to separate individual noble metals by a multiple column operation.