Interaction mechanism of tannic acid with pyrite surfaces and its response to flotation separation of chalcopyrite from pyrite in a low-alkaline medium

In the process of chalcopyrite-pyrite flotation, depression of pyrite is of great significance. In this study, tannic acid (TA) was used to replace traditional inorganic reagents for depression of pyrite under the low-alkalinity condition, and the interaction mechanism of TA with the pyrite surface was studied. Adsorption experiments showed that adsorption of xanthate on the pyrite surfaces was greatly inhibited after treatment with TA, while that of chalcopyrite was only slightly affected. Zeta potential measurements suggested that TA decreased the surface potential of pyrite among pH 3-10. A new characteristic peak appeared in the pyrite-TA infrared spectrum. Time-of-flight secondary-ion mass spectrometry and X-ray photoelectron spectroscopy measurements revealed that Fe atoms were the active sites on the pyrite surface, and they strongly interacted with TA. Microflotation tests confirmed that TA had an obvious depression effect on pyrite, but it had no distinct depression effect on chalcopyrite. These results verified that TA can selectively weaken the floatability of pyrite in Cu-Fe flotation, thereby enabling separation of chalcopyrite from pyrite at low alkalinity. (C) 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).