Studies on the selective flotation of pyrite from fine serpentine by using citric acid as depressant

Abstract Fine serpentine can form slimes coating on sulfide surface, which worsens sulfide flotation. To solve this problem, in this study, the effect of citric acid (CA) on the flotation separation of pyrite from serpentine and its mechanisms were systematically investigated. Micro-flotation results showed that the serpentine with −10 µm fraction had a significant depression effect on pyrite flotation. However, the utilization of CA could efficiently limit the adverse effect of serpentine on pyrite flotation with an increase of pyrite recovery from 16% to 95%. The results of adsorption, Fourier transform infrared spectrometry (FTIR), and X-ray photoelectron spectroscopy (XPS) indicated that CA could adsorb on serpentine surface, which might be caused by the chelation between the carboxyl groups in CA and the magnesium species on serpentine surface. Besides, the results of inductively coupled plasma-optical emission spectroscopy (ICP-OES) showed that the introduce of CA also accelerated the dissolution of magnesium cations on serpentine surface. In this way, the surface charge of serpentine was converted from positive to negative after interacting with CA, and the hetero-coagulation between serpentine and pyrite was broken, which was further verified by turbidity results. Therefore, the floatability of pyrite was restored. Based on these findings, CA is likely to act as an effective depressant in the flotation separation of sulfide ore from serpentine.