Improving lignite flotation performance by enhancing the froth properties using polyoxyethylene sorbitan monostearate

In this study, polyoxyethylene sorbitan monostearate (Tween 80) was applied to improve the flotation performance of fine lignite separation. The results show that combustible matter recovery of lignite increased when the lignite was pre-conditioned with Tween 80 before the addition of the collector. Tween 80 primarily improved the combustible matter recovery of low density (< 1.4 kg/dm3) particles. However, the flotation recoveries of medium (1.4-1.8 kg/dm3) and high (> 1.8 kg/dm3) density particles also increased at higher dosages of Tween 80. A Fourier transform infrared (FTIR) technique was used to investigate the surface properties of lignite. According to the FTIR test, there were numerous oxygen-bearing functional groups on the surface of the lignite. The maximum height and half-life time of the three-phase froth were measured by the gas pulsation method. The surface tension and viscosity of the flotation pulp were also examined by an automatic surface tension meter and a rotational viscometer, respectively. The results show that the maximum froth height and half-life time of the three-phase froth increased because the Tween 80 was capable of decreasing the surface tension and increasing the viscosity of the flotation pulp. The enhancement of the froth properties by Tween 80 was the main reason for the increase in the combustible matter recovery of lignite in flotation.