Study on the Differential Adsorption Mechanism of Dodecylamine on the Surface of Hydroxide Minerals

This study investigated the differential adsorption mechanism of dodecylamine (DDA) in the flotation processes of brucite, diaspore, and limonite. The mechanism of DDA on different hydroxide minerals was systematically analyzed at the microscopic level through characterization techniques such as zeta potential testing, contact angle measurement, adsorption capacity, X‐ray photoelectron spectroscopy (XPS) analysis, and density functional theory (DFT) calculation. Microflotation experiments have shown that under the same conditions, DDA has a stronger collection ability for diaspore and limonite than for brucite. When the flotation time is 2 min and the DDA concentration is 75 mg/L, the highest flotation recovery of 21.34%, 90.41%, and 69.01% was achieved for brucite, diaspore, and limonite, respectively. Contact angle and zeta potential analysis indicate that DDA significantly enhances the hydrophobicity of diaspore and limonite but has the least effect on brucite. At higher DDA concentrations, only significant potential changes were observed in the first two minerals. The adsorption capacity and XPS confirmed that DDA has a stronger adsorption effect on the surfaces of diaspore and limonite because the N of DDA enhances the activity of Al 3+ and Fe 3+ sites. DFT calculations further revealed a significant amount of charge transfer between the N atoms and surface metal sites in DDA.