Calcium ions and dextrin assembly adsorbed onto pyrite surfaces to enhance hydrophilicity: Synergistic coordination mechanism

Abstract

The separation of pyrite from other sulfide minerals during non-ferrous metal extraction holds significant environmental and economic value. Successful separation is closely related to the adsorption of depressants on pyrite surfaces. In this study, species-distribution and density functional theory calculations were used to systematically investigate the adsorption mechanism of the synergistic coordination between Ca^2 + and dextrin on pyrite surfaces. Species-distribution calculations show that changes in the pH of Ca-bearing solutions primarily affected the content of CaOH⁺, suggesting that CaOH⁺ is the key substance influencing the hydrophilicity of pyrite under high-alkalinity conditions. Bond length and sorption energy data suggest weak sorption of dextrin alone on pyrite surfaces, which is enhanced in the presence of CaOH⁺. Electronic difference density, density of states, and frontier orbital analyses showed that dextrin could coordinate adsorption with CaOH⁺, which had been preabsorbed onto the pyrite surface. Hybridization occurred between the O 2p orbital of CaOH⁺ and the Fe 3d orbital on pyrite surfaces, as well as between the Ca 3d orbital of CaOH⁺ and the O 2p orbital of dextrin, resulting in stable chemical bonds. Surface wettability analysis, collector adsorption capacity analysis, and flotation tests confirmed that CaOH⁺ enhanced pyrite depression by dextrin. This study may contribute to the development of environmentally friendly, polysaccharide-based depressants for pyrite.