Recovery of palladium (II) from aqueous solution through photocatalytic deposition in presence of ZnO under UV/Visible-light radiation

A shortage of market supplies is nowadays recorded for precious metals such as palladium, due to a wide range of applications in which they are used. The development of efficient and inexpensive recovery methodologies of precious metals from waste materials is thus necessary and urgent. In the present study a zinc oxide based photocatalytic system under UV/Visible-light radiation was chosen for palladium (II) deposition from solutions containing it. The effect of ethanol as sacrificial agent was investigated at varying catalyst load, irradiation conditions (UV+visible/visible/dark), metal starting concentration as well as the presence of cupric and chloride ions in solution. Moreover, ZnO dissolution at pH under 6.0 was proposed for the recovery of pure metallic palladium. A network of reactions and a kinetic model were proposed.