Utilization and Mechanisms of Tannic Acid as a Depressant for Chalcopyrite and Pyrite Separation

Current flotation practices using lime or cyanide asdepressantsin chalcopyrite and pyrite separation have significant disadvantages,such as substantial reagent consumption, high slurry pH, and environmentalhazards. This work aimed to explore the utilization and mechanismsof tannic acid (TA) as an eco-friendly alternative to lime or cyanidein chalcopyrite-pyrite separation. Flotation results showedthat TA selectively depressed pyrite yet allowed chalcopyrite to floatat neutral or alkaline pH. Adsorption density and zeta potential resultsindicated that TA adsorbed intensely on pyrite but minorly on chalcopyrite.Besides, potassium ethyl xanthate was still largely adsorbed on chalcopyritebut not on pyrite after TA adsorption. Surface analysis by Fouriertransform infrared spectroscopy and X-ray photoelectron spectroscopyfurther showed that the oxidation species of FeOOH and Fe-2 (SO4)(3), particularly FeOOH were the main activesites for TA chemical adsorption. Owing to the greater and fasteroxidation of pyrite, more FeOOH and Fe-2 (SO4)(3) were generated on the pyrite surface, and the chemicaladsorption of TA was more pronounced on the pyrite surface than onthe chalcopyrite surface.