Calorimetric study of the wettability properties of low-rank coal in the presence of CTAB

Abstract

The wettability changes of lignite after adsorption of cetyltrimethylammonium bromide (CTAB) were studied with the aim of disclosing the contributions of particle size and mineral matter. The adsorptions of CTAB from aqueous solution onto lignite samples with different particle sizes and pure mineral matter (kaolinite, calcite, and quartz) were investigated. Changes in hydrophilicity of samples were evaluated by wetting heat with different reagents using a microcalorimeter. It was observed that the wetting heat of lignite wetted by water was much higher than that wetted by alkanes. The hydrophilicity of lignite decreased significantly after adsorption of CTAB, and the hydrophobicity subsequently enhanced. Though adsorption density of CTAB on lignite surface increased with the diminishment of particle size, the efficiency of hydrophobicity enhancement decreased. In addition, the results of wetting heat suggested that organic content of lignite played a dominant role for the hydrophilicity properties of lignite. Adsorption of CTAB not only decreased the hydrophilicity of organic content but also that of mineral matter. The effect of mineral matter on the hydrophilicity modification of lignite by CTAB depended on its species. Kaolinite and calcite had more intensity for hydrophilicity modification by adsorption of CTAB than that of quartz.