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

Abstract

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 S2O32− 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.