Protonation behavior study of the active sites on typical sulfide minerals surface using surface complexation model

Abstract

Sulfide minerals are the critical sources for extracting valuable nonferrous metals such as lead, copper, and zinc, which are indispensable across various industrial sectors. Flotation is the pivotal technology for separation and enrichment of these sulfide minerals. The core mechanism of flotation lies in the selective adsorption of flotation reagents on the minerals surface. However, there are few quantitative studies regarding the protonation reaction of active sites on the surface of sulfide minerals. In this research, the Surface Complexation Model (SCM) is innovatively applied to quantitatively analyze the protonation characteristics of active sites on sphalerite, galena, pyrite, and chalcopyrite surfaces, providing the basis for clarifying the adsorption behavior of flotation agents and developing efficient reagents. By analyzing the crystal lattice structures and cleavage plane characteristics of the minerals, the types of active sites were determined. Subsequently, the hydrogen ion interactions with mineral surfaces was investigated by potentiometric titration, and the equilibrium equations of protonation reaction was established. The corresponding protonation constants and site densities were calculated by iterative fitting using Newton-Raphson method. In the process of data validation, the theoretical and fitted site densities of the mineral primary cleavage planes were compared. Additionally, by substituting the protonation constants into the equilibrium equations, a high correlation between the fitted surface potential under different pH conditions and the measured zeta potential values was revealed. This result confirms the accuracy of the fitted protonation constants and site densities and further validates the reliability of the Surface Complexation Model. For the first time, this research systematically applies the surface complexation model (SCM) to accurately analyze the protonation characteristics of the surface active sites of typical sulfide ores, which provides an important prerequisite for deepening the understanding of the interaction between the typical sulfide ore surfaces and reagents and the surface charge distribution. It is helpful to improve the flotation process and design flotation reagents, thereby enhancing the efficiency and accuracy of the beneficiation process.