Abstract
An efficient process for the recovery of palladium from waste printed circuits boards (PCBs) is detailed.Palladium is employed as an electrode material in multi-layer ceramic capacitors (MLCCs). These componentscan be easily removed from PCBs by de-soldering. As palladium is alloyed with silver, its dissolution is readilyachieved using dilute nitric acid. As a result, a solution containing palladium along with base metals, mostlycopper and iron, is obtained. This solution is then processed through solvent extraction (SX) with a solvent basedon N,N′-dimethyl,N,N′-dibutyltetradecylmalonamide (BDMA), a robust extracting molecule previously developed in the frame of the reprocessing of waste nuclear fuel. The volume of effluents generated during the SXsequence is limited: iron scrubbing is operated with a very low aqueous to organic phase volume ratio, nospecific metal chelator is required for palladium stripping, and no shift from acidic to basic media is required.Finally, a ca 1 g/L Pd(II) aqueous solution with 99,4% purity is obtained, from which palladium is directlyisolated as dichlorodiammine palladium(II) salt (Pd(NH3)2Cl2) after precipitation with ammonia. Overall, palladium is quantitatively recovered from the leaching solution, and no palladium was detected in the remainingsolid residue. Purity is high, as no contaminating metal could be detected in the final palladium salt. The proposed approach is simple and complementary to existing hydrometallurgical processes dedicated to gold andcopper recovery.