Pyrazole functionalized organo-ceramic hybrids for noble metal separations

A series of pyrazole-functional adsorbents is synthesized by sol-gel processing technology and used to study the extraction characteristics for palladium, platinum, and gold chlorides from leaching solutions. An organosilicon compound, N-(trimethoxysilylpropyl)-pyrazole, is synthesized as the functional precursor for these adsorbents. Hydrothermal treatments for the gelled materials alter pore characteristics without chemical property changes. To study adsorptive extraction of Pd(II), Pt(IV), and Au(III) chlorides, the hydrothermally treated adsorbent is used. The experimental results show that this adsorbent has high Pd(II) uptake capacity (1.41 mmol/g), strong selectivity for Pd(II) chloride over Pt(IV) and Au(III) chlorides, and no reactivity for Cu(II) and Fe(II) in 2.0 M HCl solutions. The material also has sustainable stability over repeated metal loading and stripping in a short column. In addition to the experimental studies, the adsorption processes in batch and packed column systems are successfully modeled by using a pore diffusion model and presented.