Application and interaction mechanisms of sodium methyl-phosphonate sulfonate as novel selective depressant in the flotation separation of dolomite from malachite

Dolomite often is found as a gangue mineral and shares similar chemical properties with the malachite, posing a significant challenge to the effective separation of copper oxide ore. There are many studies on the depressants of dolomite, however, those applicable to the flotation system of copper oxide ore have not been reported. In this study, the sodium methyl-phosphonate sulfonate (SMPS) was first introduced as a selected depressant of dolomite for effective separation from malachite. The micro-flotation results indicated that SMPS had selective depressant of dolomite flotation, while it was pretty poor for malachite. The batch flotation experiments further demonstrated that SMPS was an effective dolomite depressant. Zeta potential measurement and FTIR analysis suggested that the addition of SMPS powerfully stopped the NaOL adsorption onto dolomite surface, with little influence on malachite, leading to remarkable differences in their floatability. XPS analysis demonstrated that the SMPS adsorption onto dolomite can be contributed to the interaction of the electron-rich -SOO- group of SMPS with the Ca and Mg exposed in dolomite-water interface. DFT calculations indicated that the sulfonic acid groups in SMPS reacted strongly with the dolomite Mg sites, which was significantly stronger than that of sodium oleate (NaOL), further demonstrating the greater chemical bonding ability of SMPS onto dolomite. These findings provide promising insights into the potential of SMPS as critical depressant for optimizing the flotation of copper oxide ores.