A novel process for the separation and recovery of value-added metals from manganese silver ores by EDTA/EDTA-2Na and thiosulfate

A novel process for the recovery of manganese by EDTA/EDTA-2Na leaching and the recovery of silver by thiosulfate leaching with resultant EDTA-Mn as the catalyst from manganese-silver ores was developed in this study. Initially, insoluble manganese(IV) was reductively leached by EDTA/EDTA-2Na in an aqueous medium, and then silver was extracted by thiosulfate with EDTA-Mn(II/III) as the catalyst that was produced in situ in the manganese leaching stage, instead of a copper(II) and ammonia catalytic system. The EDTA-S2O32- leaching system gave higher manganese and silver leaching efficiencies with lower solution pH of 5-6. And the EDTA-2Na-S2O32- leaching system, a relatively moderate solution with pH of 7-8, presented less consumption of thiosulfate in the leaching of silver. In total, 97.5% of manganese and 92.6% of silver were leached in the EDTA-S2O32- leaching system, and 93.7% of manganese and 91.2% of silver were leached in the EDTA-2Na-S2O32- leaching system under the most suitable conditions. Moreover, most of EDTA/EDTA-2Na can be recovered by acidification, and the consumption of SS2O32- can be reduced in the presence of EDTA complex. This new process can be used to recover manganese and silver from manganese-silver ores effectively and interoperably.