Selective separation mechanism of hematite from quartz by anionic reverse flotation: Implications from surface hydroxylation

Reverse flotation desilication with anionic collector sodium oleate (OL) and activator Ca2+ is a common bene-ficiation method to purify hematite. Herein, the separation mechanism of hematite and quartz were systemati-cally investigated by experiments and DFT calculations with the effect of surface hydroxylation fully considered. Flotation results showed that the success of anionic reverse flotation of hematite was inseparable from the activation of quartz by Ca2+. In addition, the use of sodium humate (HM), which selectively inhibited hematite, was also very critical. The Zeta potential revealed that the activator Ca2+ ions were highly selective for quartz and depression HM was highly selective for hematite. SEM clearly showed that Ca species were adsorbed on the quartz surface, which was confirmed as chemisorption by XPS. DFT calculations further confirmed that the adsorption of HM on the surface of hematite was more favorable than that of quartz, while Ca2+ on the surface of quartz was more favorable than that of hematite, and the chemisorbed Ca2+ ions on the quartz surface provided targeted reaction sites for the subsequent adsorption of OL, which enabled the activated quartz to overflow into the froth products, while the inhibited hematite to sink and concentrate in the flotation cell.

Automated summary

Reverse flotation desilication using anionic collector sodium oleate and activator Ca2+ is an effective method for purifying hematite. This study systematically investigated the separation mechanism of hematite and quartz, considering the effect of surface hydroxylation. Experimental results showed that the success of anionic reverse flotation of hematite relied on the activation of quartz by Ca2+ and the selective inhibition of hematite by sodium humate. The use of DFT calculations and SEM analysis confirmed the adsorption and chemisorption processes on the surfaces of quartz and hematite, respectively.