Flotation behavior and mechanism of microfine apatite and illite in different electrolyte solution systems

The deep sea is rich in mineral resources, and due to the scarcity of freshwater resources, the use of seawater is becoming more widespread. However, the presence of a large number of electrolyte ions in seawater can pose a challenge to mineral flotation and the effects of different electrolytes vary. This study investigated the effects of common chloride (Cl-) electrolyte solutions of Na+, Mg2+ and Ca2+ on the flotation behavior of microfine apatite and illite using sodium oleate (NaOL) as the collector and acidified sodium silicate (ASS) as the depressant. The results showed that ASS can selectively adsorb to the surface of illite as Si(OH)4, hindering the action of NaOL but having little effect on apatite. The electrolyte solution improved the foaming performance of the slurry. It also reduced the critical micelle concentration (CMC) of NaOL and promoted the formation of NaOL micelle, which promoted the adsorption of NaOL on the surface of apatite. However, the reaction of free Mg2+ and Ca2+ in the slurry with oleic anion consumed the effective components of the collector, which was not conducive to mineral flotation. After NaOL interacted with apatite, it had hydrophobic agglomeration effect, which strengthened the flotation recovery of microfine apatite and the separation efficiency from illite.