Sorption of aqueous amino acid species on sulphidic mineral surfaces—DFT study and insights on biosourced‐reagent mineral flotation

Abstract

AbstractThe interaction between the 20 natural amino acids and the surfaces of sphalerite, pyrite, and chalcopyrite was examined in the light of density functional theory (DFT) simulations. The electronic properties of the active functional groups and the equilibrium geometries of the sorbed amino acid species were characterized as a function the 65 species resulting from their (de)protonations. Covalent bonds are predicted between the surface metallic atoms and the carboxyl groups and, though to a lesser extent, with the side and main amino groups. Chemisorption as a determining factor in the uptake of amino acid species was assessed in terms of sorption affinities for the mineral surfaces. The largest affinities result from the carboxyl groups of the deprotonated species at intermediate pH, whereas the fully protonated amino acids in acidic media predict the lowest affinities. Affinity of amino acids towards the mineral surfaces followed the trend: pyrite >> chalcopyrite > sphalerite with speciation‐dependent decreasing sequence: ∼2.5 < pH < ∼9.5; pH > ∼9.5; pH < ∼2.5. By targeting the most suitable amino acid building blocks in bio‐sourced collectors, either high collecting powers or superior selectivities can be aimed at depending on pH for improved separation of sulphidic minerals in flotation processes.