Abstract
This paper reports the leaching of seafloor massive sulphides (SMS) from the Loki’s Castle area at the Arctic Mid-Ocean Ridge in sulphuric acid with manganese dioxide and sodium chloride. The results presented are of various leaching experiments conducted under different conditions in order to optimise the dissolution of copper and silver. It was shown that the main copper bearing minerals in the SMS were chalcopyrite and isocubanite, while silver could occur as an admixture in the crystallographic lattice of sulphides or as disseminated micro inclusions. Based on the results, the leaching mechanism was discussed and elucidated. It was shown that the dissolution of the SMS was mainly due to galvanic interactions between the primary marine minerals of SMS and manganese dioxide. Addition of sodium chloride promoted the extraction mechanism.
Highlights
The major copper-bearing mineral in the seafloor massive sulphides (SMS) from the Loki’sCastle area at the Arctic Mid-Ocean Ridge is isocubanite (CuFe2 S3 ), rather than chalcopyrite (CuFeS2 ), which causes difficulties in flotation
Manganese dioxide can act as the oxidizing agent for silver, the results showed that leaching in the sulphate media was very slow and inefficient
The results show that the leaching performance of silver and copper was strongly affected by the dosage of MnO2, while the addition of sodium chloride only influenced the dissolution rate of silver (Figures 2 and 3)
Summary
The major copper-bearing mineral in the seafloor massive sulphides (SMS) from the Loki’s. Several authors have investigated copper dissolution from sulphides in sulphuric acid (H2 SO4 ), with manganese dioxide (MnO2 ) [2–4] and sodium chloride (NaCl) [5–8]. Direct hydrometallurgical processing of manganese nodules involves leaching with ammonia, hydrochloric, or sulphuric acid in the presence of other reductants, such as glucose, charcoal, and even sulphide minerals, including chalcopyrite, sphalerite, pyrrhotite, and pyrite [10–12]. Both the seafloor massive sulphides and the deep-sea polymetallic nodules can serve as potential sources of critical raw materials. I.e., potentially from the sea (seawater evaporation), may even promote the extraction mechanism For such a leaching system, no artificial introduction of air is needed. The leaching mechanism was discussed and elucidated
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