Hydrometallurgical recovery of platinum-group metals from spent auto-catalysts – Focus on leaching and solvent extraction

• Recovery of platinum and palladium from spent auto-catalysts by hydrometallurgy. Best conditions for leaching: 11.6 mol L ?1 HCl, 1%vol H 2 O , 60 °C, L/S = kg 3 h. solvent extraction systems Pd Pt: Cyanex® 471X Cyphos® IL 101. Efficient stripping agents Pt 101 need further research. To ensure the supply raw materials products extreme importance in strategic sectors, recovery critical metals secondary sources becomes increasingly urgent. Platinum group (PGMs), being rare very valuable, fall into this demand, catalytic converters that contain them are recognized as one main sources. Hydrometallurgical processes have been proposed an alternative to pyrometallurgical ones, with leaching separation core operations type processing. This article investigates these two operations, seeking optimize propose new arrangements improve them. Two different catalyst samples were considered experimental work. Leaching was carried out involving concentrated HCl solutions (with oxidant) low liquid/solid ratios, maximize PGMs recovery, guaranteeing their high concentration leachates minimizing aluminum co-dissolution. Cerium also followed since is a rare-earth metal potential interest. Temperature, concentration, ratio (L/S), time particle size factors evaluated, optimized found h, leading PGM yields 90–98% Pt, 99% 70–96% Rh, leachate compositions 0.41–0.78 g 1.6 Pd, 0.062–0.066 depending on sample. For (SX), several commercial extractants dissolved/diluted toluene checked, firstly model solution, then applied real auto-catalyst (SAC) produced in-situ . The overall results showed most promising SX among those tested allowed quantitative Pd(II) Fe(III), but latter conveniently scrubbed water prior acidic thiourea solution. Pt(IV) values encouraging, only Fe(III) Zn(II) appreciably co-extracted, however, scrubbing contaminating metals, stripping, did not Hence, investigation find proper scrubbing/stripping system, recover recycled SACs, needed.