Method for the adsorption of surfactants by lignite in a dry condition using mechanical mixing

Abstract

Previous studies verified that the moisture adsorption on the lignite can be reduced by adsorption of surfactant on the surface. However, these surfactant adsorption processes were realized in aqueous solutions, result in a great deal of water bring into the system. It seems that the surfactant is affinity to the surface of lignite and the adsorption can be realized in dry condition with a well-designed method. In this study, we propose a method to reduce the adsorption of moisture by lignite in dry condition, by mechanically mixing it with a surfactant in a ball mill. The surfactant is adsorbed by the lignite surface toward due to the electrostatic interactions during the mixing process, which makes the lignite surface hydrophobic. Untreated and treated samples of lignite were exposed in an environment of 100% relative humidity, maintained at 20 °C, for 36 h. Compared to the untreated sample, the moisture content in the treated sample decreased from 25.9% to 11.6%. This reduction in the adsorbed moisture content is due to the modification of the hydrophobicity of the original sample. The particle size of the lignite decreases significantly after ball milling. As the particle size required for the commercial utilisation of lignite is usually low, the proposed method can be applied after the dry beneficiation process.