New Low-Temperature Collector for Flotation Separation of Quartz and Hematite after Reduction Roasting and Its Mechanism

It is an effective method to separate hematite by converting it to magnetite by reduction roasting and then separating it by magnetite separation. However, quartz will partially remain in the concentrates. Therefore, it is significant to separate quartz from the concentrates to produce high-quality iron concentrates. In this work, N-{3-[(2-propylheptyl)oxy]propyl}propane-1,3-diamine (PPPDA) was synthesized and served as a collector for low-temperature flotation to separate quartz from magnetite that was generated by reduction roasting of hematite. The flotation experiment and principle of the PPPDA collector on quartz and the new generated magnetite surface were studied by flotation experiments, ζ potential measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. Flotation data showed that, in the pH range of 5–9, when PPPDA dosage was 15 mg/L and temperature was 10–30 °C, PPPDA has good collecting ability on quartz minerals, which could make the recovery difference between quartz and the new generated magnetite reach more than 95%. Artificial mixed ore experiments at a low temperature of 10 °C yielded a concentrate with an iron grade of 64.41% and an iron recovery of 78.98%. The data of ζ potential, FTIR spectrum, and XPS and DFT calculations confirmed that PPPDA could not be adsorbed on the new generated magnetite, and the adsorption principle between PPPDA and quartz was mainly electrostatic adsorption and hydrogen bond adsorption.