Effects Of Grain Size And Mineral Composition On Adsorption Characteristic Of Surfactants And Lignite Wettability

Although the lignite is an important fossil energy, the developed void space structure and the high content of oxygen containing functional groups give rise to highly hydrophilic and limits its application in industry, so what is important is to change the wettability of lignite, in this way can improve its industrial value significantly. Surfactant is a chemical with the molecular structure containing hydrophilic group and hydrophobic group, so it could be absorbed in the surfactant of solid to modify the wettability of lignite. The paper made a comparison of adsorption properties to coal particle size and mineral components in coal(kaolin, calcium carbonate, quartz sand, etc.) and organic matter. The main results were as follows:Different coal particle size of the adsorption characteristics of surfactants on the surface of coal and wettability effect is obvious. The adsorbing capacity of CTAB on the surface of MangLai lignite increases with the decrease of coal particle size; adsorbing CTAB in the lignite surface reduces the MangLai Lignite of hydrophilic; the wetting action of different particle size of lignite with polarity wetting liquid such as distilled water and absolute ethyl alcohol is stronger than the wetting action of lignite with nonpolar wetting liquid as alkanes, and the heat of wetting decrease when carbon chain of n-alkanes increase; At the same initial concentration under adsorption conditions(300 mg/L), modified effect which has different particle size of brown coal with surfactant CTAB are different, and does not render the modification effects of particle size decreases more obvious;With the decrease of the particle size, the reduction value of the hydrophilic lignite and the added value of oily all showed increase first and then decrease; the modification effect is most obvious when the coal particle size is 80-120 mesh.A comparison among sodium dodecyl sulfate(SDS), Gemini and CTAB is made to indicate that, all these surfactant occurred adsorption reaction with mineral components and on the organic matter surface, and adsorption quantity increases with the increase of initial concentration. The adsorption reaction of surfactant in the mineral components and organic matter is different: Minerals adsorption reaction of brown coal is mainly Van der Waals’ force, and demineralized coal adsorption interaction of lignite is mainly electrostatic interactions. The adsorption on the surface of mineral components, organic matter in coal are significantly different, The adsorption of CTAB in raw coal and organic matter are the most, Adsorption quantity of Gemini surfactant on quartz sand and kaolin are relatively more, the adsorption of SDS on calcium carbonate is maximum. Three kinds of surfactant adsorption all change mineral components in the lignite and the wettability of the organic matter, however the change of wettability are very different. The wettability change effect of adsorption with SDS on calcium carbonate is obvious, and Kaolin adsorbed CTAB also obviously change its wettability. For raw coal and demineralized coal, we could choose the Gemini in CMC concentration, at that time, the wettability change is most obvious, so we can indicate that relative to the CTAB, the wettability change effect of Gemini surfactant adsorption on coal surface is more prominent.