“Invisible” noble metals in carbonaceous rocks and beneficiation products: feasibility of detection and coarsening

The decrease in the quality of raw materials coming for processing requires involvement of refractory ores in processing, the refractoriness of which is caused by the presence of organic carbonaceous matter sorption-active in relation to dissolved noble metals and impregnation of fine noble metals in mineral-carriers. In this connection, the actual research line is the development of new technological solutions with the use of energy methods of action in order to reduce the losses of valuable components in beneficiation tailings. Treatment with ultra-high frequency electromagnetic radiation has a number of advantages, including rapid and selective heating due to the differences in the ability of minerals to absorb this radiation. Carbon-containing materials represented by carbonaceous flotation concentrate and model samples of activated carbon with adsorbed silver were taken as the research subjects. Using the model samples as an example, the necessity of using magnetite to achieve coarsening fine silver particles during ultra-high frequency treatment was substantiated. The formation of active centers of local heating during the treatment in the points of magnetite addition was confirmed. The necessary content of magnetite of 10% for coarsening fine silver to spherical aggregates, the average size of which was 20–40 microns, was substantiated. Coarsening noble metal particles to sizes of 20–50 microns in treated carbonaceous concentrates containing silver and gold was achieved, when the substantiated amount of magnetite was added. Coarsened particles (aggregates) of noble metals can be recovered using traditional beneficiation methods.