Intensifying the separation efficiency of rhodochrosite from calcite in NaClO-oxidation flotation system with a dithiocarbamate-hydroxamate collector

The oxidation flotation mechanism in the HAHD-NaClO-rhodochrosite system. • The efficient beneficiation of rhodochrosite was proposed in an oxidized flotation system. • NaClO oxidation treatment enhanced the Mn(IV) content on the rhodochrosite surface. • High-efficiency separation of rhodochrosite from calcite was successfully achieved. • The dithiocarbamate group in HAHD was oxidized in the rhodochrosite flotation system. The dissolution characteristics of rhodochrosite and calcite results in their similar surface properties, which makes the separation of rhodochrosite from calcite more difficult. Therefore, surface modification was adopted to oxidize the Mn(II) species on rhodochrosite to higher valence states, reducing the solubility of Mn 2+ and differentiating the surface properties from calcite. Sodium hypochlorite (NaClO) was a suitable oxidant to enhance the floatability of rhodochrosite. Meanwhile, N -[(3-hydroxyamino)-propoxy]- N -hexyl dithiocarbamate (HAHD) was a versatile collector, which can be oxidized into a Gemini molecule of (HAHD) 2 and featured a selective performance in the NaClO-oxidized flotation system of rhodochrosite-calcite artificially mixed minerals. The selectivity index I Mn of HAHD in the oxidized flotation of mixed minerals reached 32.2, much higher than that of sodium oleate (9.9). Interestingly, UV spectra and XPS analyses indicated that HAHD was oxidized to a Gemini structure (HAHD) 2 in the oxidized flotation system. In HAHD-NaClO-rhodochrosite flotation system, REDOX reaction occurred, that was, the surface Mn(II) of rhodochrosite was first oxidized to Mn(IV) which oxidized HAHD to (HAHD) 2 , then some of Mn(IV) species were reduced to Mn(II). A potential mechanism was proposed finally to reveal the essence of the selective flotation of rhodochrosite from the mixture with calcite.