Selective separation of chalcopyrite from pyrite using an acetylacetone-based lime-free process

Abstract

• Acetylacetone (AA) can selectively collect chalcopyrite from pyrite without lime at pH 9.0. • Fe atoms on chalcopyrite surface interact with AA to form a six-membered ring complex. • The reactivity of Fe atoms on chalcopyrite surface is higher than that on pyrite surface. • The adsorption energy of AA on chalcopyrite is greater than that on pyrite. In the flotation separation of chalcopyrite and pyrite, the commonly used high-lime process often causes problems such as losses of precious metals, blockage in pipelines and environmental pollution. In this study, acetylacetone (AA) was used as a novel collector to separate chalcopyrite from pyrite without adding limes. The flotation results indicate that AA can selectively separate chalcopyrite from pyrite without depressants at pH 9.0. Flotation kinetics and entrainment calculations show that compared with potassium ethyl xanthate (KEX), AA reduces pyrite entrainment and produces the concentrate with a higher Cu grade and a higher separation efficiency. Solution chemistry calculations show that enolate (AAE - ) and ketone (AAK) are the dominant species of AA at pH 9.0. Contact angle measurements, zeta potential measurements and Fourier transform infrared (FTIR) analysis indicate that the dominant species of AA chemically adsorb onto chalcopyrite surfaces at pH 9.0 while the adsorption on pyrite is minimal. Density functional theory (DFT) analysis reveals that the Fe atoms on chalcopyrite are the active sites interacting with AA to form six-membered ring complexes. The selective adsorption of AA relies on the spatial distribution and reactivity of Fe atoms on the commonly exposed cleavage surfaces of chalcopyrite and pyrite. After surface relaxation, a layer of Fe atoms appears on the outermost layer of chalcopyrite (1 1 2) surface, which is beneficial for the adsorption of AA species while a layer of S atoms for pyrite (1 0 0) surface. The Fe (III) on chalcopyrite (1 1 2) surface has a higher reactivity than the Fe (II) on pyrite (1 0 0) surface, leading to a higher adsorption energy of AA species on the chalcopyrite. Therefore, this acetylacetone-based lime-free process has a great potential for industrial application in the separation of chalcopyrite from pyrite.