A novel eco-friendly depressant using Chlorella pyrenoidosa for flotation separation of hematite from quartz

• Chlorella pyrenoidosa (CP) is used in the flotation separation of hematite and quartz. • CP selectively adsorbed on the quartz surface. • The chemical interaction between pre-adsorbed Fe(III) ions on quartz surface and CP. The flotation separation of hematite and quartz presents significant challenges due to the easy activation of quartz by metal cations, which reduces the selectivity of fatty acid collectors. In this work, Chlorella pyrenoidosa (CP) was employed as a quartz depressant in iron ore flotation. Micro-flotation results indicated that CP showed excellent separation efficiency for hematite from quartz using sodium oleate (NaOL) as a collector, and the artificial mixed mineral tests indicated that the TFe grade of the concentrate and recovery rate reached 60.40 % and 83.74 %, respectively. The adsorption measurements and contact angle analysis results show that the adsorption of CP on the hematite surface is lower than on the quartz surface, and the binding of CP to Fe(III) hinders the adsorption of NaOL on the quartz surface. The functional groups and adsorption mechanism of CP were further investigated by FTIR and XPS analysis. The results demonstrate that combining Fe(III) with –COOH and –OH groups on the surface of the CP cell wall facilitate selective adsorption on the mineral surface. The weak adsorption of Fe(III)-CP on the hematite surface does not hinder the strong chemical adsorption of NaOL on the hematite surface, whereas the chemical adsorption of Fe(III)-CP on the quartz surface prevents the adsorption of NaOL on the quartz surface and depresses the flotation of quartz. Therefore, the flotation separation of hematite from quartz was successfully accomplished. The model of flotation separation of hematite from quartz system with CP and NaOL was drawn.