Unraveling anisotropic hydration behaviors and mechanisms of fine molybdenite in alkaline conditions: A combined experimental and computational study

It is well known that poor recovery has been suffered always for molybdenum ore flotation in alkaline conditions. To elucidate this phenomenon, we systematically investigated the anisotropic hydration behavior and mechanisms of molybdenite surface through integrated computational and experimental approaches. Density functional theory (DFT) calculations revealed that NaOH exhibits preferential edge adsorption on molybdenite, with adsorption energies on (001) surfaces (−228.67 to −92.42 kcal/mol) being significantly less than those on (110) surfaces. Simulations demonstrated that NaOH chemisorption enhances water molecule stabilization, whereas Na⁺ shows negligible influence on H₂O adsorption. Notably, OH⁻ forms stable [OH(H₂O)₅]⁻ hydration clusters and induces a triple-layered hydration film (peak positions at 9.37 Å, 12.30 Å, and 14.98 Å) upon edge adsorption. Comparative analysis indicated 6.54 % and 8.07 % enhancement in hydration layer strength for basal and edge surfaces of molybdenite, respectively, in alkaline conditions versus neutral pH. The fundamental mechanism was identified as OH⁻-mediated formation of hydrated anions that reinforce interfacial hydrogen-bond networks. These findings, validated by XPS, zeta potential, and Visual MINTEQ analyses, provide critical insights into the hydration stabilization process and establish a theoretical framework for optimizing alkaline molybdenite flotation.