Flotation Behavior of Arsenopyrite and Pyrite, and Their Selective Separation

Abstract

This study investigated the effect of pH and pulp potential (E H ) on the floatability of arsenopyrite and pyrite, which are single minerals, in Hallimond tube, by using xanthate as a collector. On this basis, the study further investigated the selectivity index of arsenopyrite and pyrite, using a mixed sample of arsenopyrite and pyrite. To examine the flotation behavior of each mineral by pH change, flotation was carried out at pH 4 and pH 10. The test results showed arsenopyrite had higher floatability at pH 4, regardless of the potassium ethyl xanthate (PEX) concentration. This is because xanthate ion was oxidized to be stable dixanthogen, which was well adsorbed onto arsenopyrite surface, due to the high E H of pulp. Meanwhile, arsenopyrite had relatively lower floatability at pH 10 than at pH 4, which was because the dixanthogen remained unstable, and was not adsorbed onto the arsenopyrite surface, due to the relatively low E H of pulp. Pyrite had low floatability at both pH 4 and pH 10. Just as for arsenopyrite, the result for pH 10 was caused by the low E H of pulp. Yet, interestingly enough, different from the case of arsenopyrite, pyrite at pH 4 had low floatability, despite its high E H . FTIR analysis was performed, to examine the reason for such contradictory behavior. The analysis result showed that this was caused by poor adsorption with xanthate, due to sulfate ion (SO 4 2¹ ) that was generated by the oxidation of pyrite surface in reaction with oxygen in pulp at pH 4. To further investigate the selectivity index (i.e., the pyrite recovery/ arsenopyrite recovery ratio) of arsenopyrite and pyrite, additional flotation tests were carried out on mixed sample of the two minerals. Different from the flotation behavior of single minerals, the results showed that the recovery of arsenopyrite was lower than that of pyrite, and the selectivity index of arsenopyrite and pyrite was the highest when the PEX concentration was the lowest. Such a different trend in flotation behavior of the mixed sample from the flotation behavior of the single minerals was because the surface oxidation reaction of arsenopyrite, which was more affected by E H among the mixed arsenopyrite and pyrite, generated ferric arsenate, a hydrophilic compound, on the surface of arsenopyrite, resulting in poor adsorption with xanthate; in turn, this depressed the floatability of arsenopyrite.

Application of Depletion Attraction in Mineral Flotation: II. Effects of Depletant Concentration

“…By adding polymer molecules, also termed as a depletion agent or a depletant, we can increase the attractive interaction between a mineral particle and a bubble. ((Zn,Fe)S)) [10,20,[23][24][25]. These studies showed that sulfide minerals could provide better floatability in certain oxidation and reduction potential ranges by adjusting the solution pH, at which elemental sulfur forms a hydrophobic surface of sulfide minerals.…”

“…During this process, a collector is used to impart hydrophobicity to desired mineral particles; these hydrophobic particles are then better attached onto the surface of a bubble, leaving undesired particles in the bulk solution. Among these collectors is xanthate, which is a typical collector used for sulfide minerals and for oxide minerals after the sulfidization process [7][8][9][10]. Although this collector has been exploited extensively over the last several decades, a reduction in its use is desired because it is environmentally harmful [11][12][13].…”

“…In fact, attempts have been made to separate particles without a collector [10,[20][21][22][23]. For example, several groups have investigated the flotation behavior of sulfide minerals without collectors (e.g., galena (PbS), pyrite (FeS 2 ), arsenopyrite 2 of 11 (FeAsS), chalcopyrite (CuFeS 2 ), chalcocite (Cu 2 S) and sphalerite ((Zn,Fe)S)) [10,20,[23][24][25]. These studies showed that sulfide minerals could provide better floatability in certain oxidation and reduction potential ranges by adjusting the solution pH, at which elemental sulfur forms a hydrophobic surface of sulfide minerals.…”

Application of Depletion Attraction in Mineral Flotation: I. Theory

“…Flotation is a physico-chemical separation technique for particles and it has been used extensively for a wide range of mineral processes [1][2][3][4][5]. Although it is useful and powerful, flotation involves extremely complicated dynamic processes with various phase components (gas, liquid and solid) under flow; examples include the attachment of solid minerals to gas bubbles, the mixing of solid minerals under vigorous liquid flows, the formation of gas bubbles and the motion of bubbles due to buoyant force; none of which are completely understood.…”

Oxidative Depression of Arsenopyrite by Using Calcium Hypochlorite and Sodium Humate

“…Figure 7 shows that SBX rendered the zeta potential of arsenopyrite more negatively. When xanthate ions were oxidized to dixanthogen on the arsenopyrite surface, negative zeta potential increased [36]. With SH, the zeta potential of arsenopyrite decreased sharply over the entire pH range.…”