Enhanced adsorption of octyl hydroxamic acid on bastnaesite surface by ultrasonic activation: insights from experiments and molecular dynamics simulations

In this study, ultrasonic treatment was introduced to improve the activation of octyl hydroxamic acid (OHA) as a collector, enhancing the flotation of bastnaesite. The mechanism of OHA activation by ultrasonic treatment and its role in strengthening adsorption of octyl hydroxamic acid on bastnaesite surface were investigated via flotation experiments combined with solution chemistry calculations, conductivity tests, bubble-particle wrap angle (BPWA), atomic force microscopy (AFM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and molecular dynamics simulations (MDS). Solution chemistry calculations and conductivity measurements indicated that ultrasonic treatment enhanced the dissociation of OHA molecules significantly, generating more active OHA − anions and thereby improving OHA activation. The increased BPWA confirm enhanced the adhesion of bastnaesite to bubbles following OHA adsorption. AFM and SEM-EDS analysis showed that the adsorption amount of OHA on the surface of bastnaesite increased after ultrasonic treatment. XPS analysis demonstrated that the chemical adsorption of ultrasonic-treated OHA on the bastnaesite surface is enhanced, which improves the hydrophobicity and flotation performance of bastnaesite. This also confirmed that ultrasonic-treated OHA produced more active OHA − anions. MD simulations indicated that as the proportion of OHA − increased, the adsorption and spreading ability of OHA collector clusters on the bastnaesite surface were enhanced, repelling water molecules from the bastnaesite surface. Consequently, the hydrophobicity of the bastnaesite surface increased, further strengthening its flotation performance.