Mechanical activation improves green depressant starch for the flotation separation of pyrite from chalcopyrite via molecular structure optimization

Abstract

For the first time, the present study uses the mechanically activating method to enhance the depression selectivity of natural polymers, which applies the mechanically activated starch (MAS) for the flotation depression of pyrite from chalcopyrite. After the addition of MAS prepared in an appropriate condition, the flotation recovery of pyrite decreased by 72 % while the chalcopyrite recovery remained nearly unaffected. Adsorption tests, Zeta potential measurements and X-ray photoelectron spectroscopy (XPS) analysis show that MAS primarily chemisorbed onto the pyrite surface by forming covalent bonds with surface iron atoms, thereby reducing its hydrophobicity. Proton nuclear magnetic resonance (¹HNMR) test results indicate that mechanical activation can alter the internal structure of MAS, thereby increasing its activity. Frontier orbital analysis and molecular dynamics simulations further confirm the chemisorption of MAS on the pyrite surface and the MAS prepared under different intensities of mechanical activations have different adsorption abilities on the pyrite surface. The MAS prepared under moderate mechanical activation has the best adsorption and depression abilities, which is attributed to the exposure of more interacting sites and remains of relatively large molecular weight. This research highlights the potential of MAS as an environmentally friendly alternative to traditional macromolecular depressants, offering a sustainable approach that can reduce environmental impact. It also provides valuable insights into the novel application of mechanically activated polymers in the field of mineral flotation.