The relationship between anion distribution in process water and flotation properties of iron oxides

Abstract

It is inevitable for the presence of dissolved ions, especially inorganic cations or anions, in the process water of an industrial flotation system. They could alter the chemistry of a flotation system and interfere with the interaction between minerals and reagents. The purpose of this study was to identify the relationship between anion distribution in the process water and the flotation performance of a typical industrial iron ore concentrator when the process conditions were stable. An effort was also made to understand how the anions affect the flotation properties of the iron ore through a series of water chemical analyses by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), ore sample analysis by X-ray Diffraction (XRD), bench flotation tests by using the industrial iron ore, micro-flotation tests by using pure quartz, and zeta potential measurement. The data from water chemical analyses indicated that sulfate ion concentrations in the process water, especially from the roughing stage, are more relevant to the SiO2 content and Fe recovery in concentrate than chloride ion. This can be explained by the results from flotation tests, suggesting that the anions at higher valence tend to have more significant influences on lowering the SiO2 content. But it substantially depends on anion concentration, pulp pH, and type of metal ions. At 8.5–9.2, SO42− ions have promotive effects on the recovery of the quartz pre-modified by FeCl2, or FeCl3 in the water. This is probably due to a shift towards acidic direction on the zeta potential of quartz surfaces in the presence of sulfate ions. These anions, however, have negative effects on the quartz recovery with the occurrence of Ca2+ ions. The precipitation of CaSO4 on the mineral surfaces could be attributed to it.