Sorption of platinum and rhodium on carbon adsorbents from chloride solutions

Sorption recovery of platinum (II, IV) and rhodium (III) on different carbon adsorbents has been studied using fresh chloride model solutions with platinum and rhodium concentrations of 0.25-1.0 and 0.049 mmol/L, respectively. The concentration of hydrochloric acid in these solutions varied from 0.001 to 1.0 mol/L. The maximum recovery of platinum and rhodium was achieved with the carbon adsorbent based on charcoal (wood). This sorbent possesses the highest sorption ability to noble metals in medium acidic solutions (0.01-0.1 M HCl). However, the sorption from higher acid solutions (0.5-1.0 M HCl) proceeds on sufficiently high level as well (> 80%). The use of thiocarbamide (10%) solutions in sulfuric acid (0.3 mol/L) as a desorption agent results in almost complete elution of rhodium (more than 95%), whereas platinum is retained in carbon adsorbent. This brings out some prospects for separation of these noble metals during their recovery from solutions of spent platinum-rhodium catalysts.