Activation of Dolomite Flotation by Ferrous Hydroxide and Carbonate

The major problem with Carlin-type gold deposit flotation is that the high dolomite content in the concentrate decreases the quality of gold. Further, the activation mechanisms involved in dolomite flotation are still not fully understood. Herein, the correlation of Fe²⁺ conversion with xanthate adsorption and dolomite flotation was investigated to reveal the effect of dolomite embedded with pyrite. Flotation tests suggested that Fe²⁺ rather than Fe³⁺ improved the floatability of dolomite from 20% to 45%. Contact angles and thermodynamic tests indicated that the hydrophobicity of Fe²⁺-modified dolomite corresponds to the adsorption of xanthate. Importantly, time-of-flight secondary ion mass spectroscopy (Tof-SIMS) and x-ray photoelectron spectroscopy (XPS) attributed the activation of dolomite flotation to the formation of Fe(OH)₂ and FeCO₃. The coordination model of flotation successfully elucidated the selective adsorption of xanthate between Fe(OH)₂, FeCO₃ and FeOOH surfaces. The density function theory (DFT) simulation calculation was performed to identify the reaction rate at the atomic level, and the density of states (DOS) was also conducted to verify the conclusions at the electronic level. This study presents important surface chemistry evidence for understanding and regulating the poor selectivity in the flotation of Carlin-type gold deposits.