Abstract
High content of gold in near-surface oxide zones above the gold ore deposit could be recovered using cyanidation. However, restricting the use of cyanide in mines has made it difficult to recover gold within the oxide zone. In this study, we investigated an application of the reductive microwave roasting and magnetic separation (RMR-MS) process for the effective gold recovery from ores in a near-surface oxide zone. Ore samples obtained from the near-surface oxide zone in Moisan Gold Mine (Haenam, South Korea) were used in RMR-MS tests for the recovery of iron and gold. The effect of the RMR process on the recovery of iron and gold was evaluated by given various conditions of the microwave irradiation as well as the dosages of reductant and additive. The microwave roasting resulted in a chemical reduction of non-magnetic iron oxide minerals (hematite) to magnetite minerals, such as magnetite and maghemite. This mineral phase change could induce the effective separation of iron minerals from the gangue minerals by magnetic separation process. The increased iron recovery was directly proportional to the gold recovery due to the coexistence of gold with iron minerals. The RMR-MS process could be a promising method for gold recovery from the ores in near-surface oxide zones.
Highlights
Gossans are highly oxidized and weathered rock, usually associated with the upper and exposed parts of an ore deposit or mineralized vein, and so it was an important guide to find the buried gold ore deposits in the 19th and 20th centuries
We investigated a method for gold concentration from the ores in near-surface oxide zone using the reductive microwave roasting and the magnetic separation processes
The major elementforcomposition mineralogical of the ore sample are in the ore sample accounted
Summary
Gossans (or iron cap) are highly oxidized and weathered rock, usually associated with the upper and exposed parts of an ore deposit or mineralized vein, and so it was an important guide to find the buried gold ore deposits in the 19th and 20th centuries. Fe-oxide, either internally or where concentric structures are produced [1]. Refractory gold is found together with hematite as coatings or internal cements in goethite, saprolite, laterite, Al-hydroxide, and ilmenite. The recovery of precious metals such as gold from refractory ores has received considerable attention [2,3,4,5,6]. To achieve a satisfactory recovery, a pretreatment stage is required to break down or at least to modify the matrix and release the precious metals before applying any conventional treatment [7]. A suitable pre-treatment process, such as roasting [8], pressure oxidation [9], Metals 2018, 8, 957; doi:10.3390/met8110957 www.mdpi.com/journal/metals
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