Recovery of Ag and Au from synthetic and industrial wastewater by 2-step ferritization and Lt-delafossite process via precipitation

Due to the global rising demand there is an enormous interest to recover noble metals most efficiently from aqueous solutions, in particular industrial wastewater. Herein we demonstrate a new concept to recover Ag and Au from sulfate, chlorine and nitrate containing waters e.g. from catalysis production. Therefore two different treatment procedures, called 2-step ferritization and Lt-delafossite process, are presented which are based on a modified ferrite process. The phase assemblage can be controlled by the adjustment of the reaction parameters. During the 2-step ferritization process, Ag-0 and Au-0 are precipitated within one separate step. The precipitated phases obtained by the Lt-delafossite process are pure delafossite AgFeO2 and composite particles of Ag-0, AgFeO2 and Fe3O4. By using these low energy, fast (< 20 min) and easy to handle precipitation processes, Ag and Au can be recovered to >= 99.99% from wastewater. In consequence, these procedures help to avoid additional waste streams.