Flotation separation of molybdenite from chalcopyrite using mechanically degraded polyacrylamide as a novel depressant

In this work, cationic polyacrylamide (CPAM) which was degraded by mechanical shear was used as a chalcopyrite potential selective depressant to separate molybdenite from chalcopyrite by flotation while using kerosene as a collector. Micro-flotation experiments of single minerals show that CPAM was the most suitable to be used as the chalcopyrite depressant among the three different types of polyacrylamide. The molecular weight of CPAM was reduced from 12 million to 1.8 million and the depression performance of CPAM on chalcopyrite was increased after mechanical rotational shear degradation for 6 h. When the dosage of CPAM which was degraded by mechanical shear for 6 h (CPAM-6 h) was 6.0 mg/L, good separation results were achieved in the artificially mixed minerals experiment. In froth products, the recovery of molybdenite was 87.96 %, the grade of molybdenum was 54.60 %, and the grade of copper was only 2.58 %. The depression mechanism of CPAM-6 h on chalcopyrite and molybdenite was systematically investigated by contact angle measurement, zeta potential measurements, FT-IR spectra analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The analysis results show that CPAM-6 h has not only electrostatic adsorption but also chemical adsorption on the surface of chalcopyrite while only electrostatic adsorption on molybdenite, then the addition of kerosene can destroy the hydrogen bonding of CPAM-6 h on the surface of molybdenite and make it hydrophobic again, but kerosene cannot remove the copper-ammonium complex formed by CPAM-6 h on the surface of chalcopyrite, therefore, chalcopyrite remains hydrophilic.