Surface hydration of zircon and its influence on the adsorption of typical flotation collectors: First-principle calculations

Zirconium and hafnium are critical metals mainly extracted from the zircon mineral. However, due to the unclear surface properties of zircon, most designed flotation collectors (Surfactants to selectively enhance the hydrophobicity of targeted materials) cannot recover zircon effectively. Herein, zircon surface hydration microstructures and their effects on the adsorption of typical flotation collectors (i.e., phosphates, hydroxamic acids, carboxylic acids) have been revealed by systematic first-principles calculations. The speciation diagram and the surface hydration microstructures of zircon have shown that surface Zr sites with small coordination numbers have stronger water affinity. Water molecules have affected the final stable adsorption configurations of the collector. The further obtained adsorption energy of collectors shows that water molecules have weakened the activity of zircon surfaces and reduced the interaction intensity between collectors and surfaces. These results indicate that collectors with stronger negative charges and a lower highest occupied molecular orbital (HOMO) energy can tightly bind with the zircon surface. The electron localization function, density of states, and crystal orbital overlap population have consistently shown that collectors have formed ionic bonds with surface Zr sites. These conclusions should be meaningful for further design of flotation collectors to realize selective zircon flotation.