An in-situ AFM investigation of the dynamic collector adsorption on KCl surfaces in saturated brine

Unveiling the dynamic adsorption behavior of collectors at the solid-liquid interfaces of soluble salts is crucial for understanding flotation mechanisms. Here, utilizing in-situ fluid atomic force microscopy (AFM) imaging, we directly visualized the dynamic adsorption behavior of octadecylamine hydrochloride (ODH) on KCl surfaces in saturated brine, incorporating dispersion agitation, rapid collector-mineral collision and static adsorption. We observed dynamic ODH particles and flat layers with a reduced modulus on the KCl surface in brine. The scratching experiment confirmed that these structures originated from adsorption rather than precipitation. Force spectroscopy provided a quantitative measurement of their thickness, which was found to be dependent on the ODH concentration. After removing the brine, the KCl surface exhibited small particles, crater-shaped aggregates, and island-shaped monolayers (hemimicelles). The prevalence of these hemimicelles suggests the formation of ordered ODH multilayers in the static liquid environment, while the crater-shaped structure likely stemmed from ruptured ODH-covered nanobubbles. Based on these observations, we propose a novel adsorption mechanism tailored to the rapid collision and static adsorption: initiated by aggregate adsorption, followed by molecular rearrangement and multilayer adsorption. The first direct in-situ visualization of collector adsorption behavior on water-soluble salts confirms the dominant role of colloidal particles and nanobubbles in the adsorption process, establishing a critical link connecting adsorption theory to industrial flotation practice.