Impact and mechanism of bisphosphonate depressant 1-hydroxypropane-1,1-diphosphonic acid on flotation decalcification of dolomite-rich magnesite ore

Given the depletion of high-quality magnesite deposits and the rising demand for high-end magnesium materials, the separation and utilization of high-calcium magnesite ores have become essential. However, the similar surface properties and solubility of semi-soluble salt-type minerals, pose significant challenges for the utilization of dolomite-rich magnesite resources. In this study, 1-hydroxypropane-1,1-diphosphonic acid (HPDP) was identified for the first time as a high-performance depressant for dolomite. Various tests, including contact angle measurements, ζ potential analysis, X-ray photoelectron spectroscopy, and atomic force microscopy, were conducted to elucidate the interfacial interaction mechanisms of HPDP on the surfaces of the two minerals at different scales. Additionally, molecular modeling calculations were used to detail the spatial matching relationship between HPDP and the crystal faces of the two minerals. It was emphasized that HPDP specifically adsorbed onto the dolomite surface by forming calcium phosphonate, ensuring that the dolomite surface remained hydrophilic and sank. Moreover, it was found that the adsorption strength of HPDP on the mineral surfaces depended on the activity of the metal sites and their spatial distribution. These findings provide a theoretical foundation for the molecular design of flotation reagents for high-calcium magnesite ores.