Novel insights into enhancing the flotation separation of low-grade magnesite ore: Effect behavior and mechanism of adding diethanolamine

The similar crystal structures and surface properties of carbonate minerals in low-grade magnesite ores pose significant challenges to selective flotation, while conventional grinding often generates excessive microfine particles that further hinder separation efficiency. In this study, diethanolamine (DEA) was introduced as an auxiliary additive in the magnesite grinding-flotation system to regulate particle size distribution and improve separation selectivity. A comprehensive investigation-integrating grinding-flotation experiments, particle size analysis, FTIR, adsorption measurements, XPS, DFT calculations, zeta potential, and contact angle analysis-was conducted to elucidate the underlying mechanism of DEA. Flotation tests on single minerals demonstrated that DEA addition during grinding significantly increased the recovery difference between magnesite and dolomite. In artificial mixed ore tests, a concentrate containing 46.31 % MgO with 74.52 % recovery was obtained, while in low-grade magnesite ore, the MgO grade reached 46.24 %. DEA improved particle size distribution by enhancing the dispersion difference between magnesite and dolomite, thus promoting more efficient separation. Spectroscopic and theoretical analyses revealed preferential DEA adsorption on dolomite surfaces, primarily through interactions with surface Ca atoms. This selective adsorption, combined with the synergistic depressing effect of DEA and sodium hexametaphosphate (SH), inhibited NaOL adsorption on dolomite, reduced its hydrophobicity, and weakened its floatability-while exerting minimal influence on magnesite. Overall, this strategy offers an efficient and practical approach for the high-value utilization of low-grade magnesite resources, demonstrating strong potential for large-scale industrial application.