Effect of oxidized diesel oil on the flotation response of the low-rank coal by plasma oxidation method

The purpose of this investigation was to explore the influence of the oxidized diesel oil on the low-rank coal flotation response and flotation kinetics by plasma oxidation method. FTIR analysis showed that the polar groups of the diesel oil after oxidation, such as OH, C=O, COOH and C-O-C, showed an obvious increase; and the polar groups generated could bond with the polar functional groups on the low-rank coal surface. Moreover, compared to the diesel oil before oxidation, a stronger interaction between the low-rank coal and the diesel oil after oxidation was found according to the reaction heat analysis. And, the contact angle of the low-rank coal wetted by the diesel oil before and after oxidation is 34.5 degrees and 23.7 degrees, respectively. Therefore, the diesel oil after oxidation showed better positive effect on enhancing the contact angle of the low-rank coal and restraining the negativity of the wetting heat of the low-rank coal wetted by water compared to the raw diesel oil. The FTIR analysis illustrates that the polar oxygen functional groups of the low-rank coal surface are decreased with the oil addition, especially after the oxidized diesel oil addition, indicating that the oxidized diesel oil can better improve the surface hydrophobicity of coal sample compared with the raw diesel oil. Furthermore, five kinetics models were chosen to assess the effect of the diesel oil after oxidation on the kinetics performance of the low-rank coal flotation, and the five test kinetics flotation models could give the excellent fit for the low-rank coal flotation data obtained by the diesel oil before and after oxidation. And, the kinetics fitted results illustrated that the diesel oil after oxidation strongly influenced the flotation kinetics of the low-rank coal and could give a better kinetics effect for the low-rank coal flotation than diesel oil before oxidation.