Wettability of coal by room temperature ionic liquids

Abstract

ABSTRACT The wettability of room temperature ionic liquids (ILs) on coal structure was studied by measuring contact angle, water-retaining property, and FTIR spectra. The eight ILs utilized were [EMIm][BF4], [EMIm][NTf2], [PMIm][BF4], [BMIm][BF4], [HOEtMIm][BF4], [HOEtMIm][NTf2], [P4,4,4,1][MeSO4] and [P4,4,4,2][DEP]. The contact angle results showed that compared with distilled water, the contact angles of ILs decreased, indicating good wetting effect. However, different ILs showed different wetting effects. Among of them, the [HOEtMIm][NTf2] had the best wetting effect, the [P4,4,4,2][DEP] and [P4,4,4,1][MeSO4] were in the second place, and the worst one was [HOEtMIm][BF4]. The water-retaining experiments showed that the evaporation rate of coal containing ILs was slower and the water-retaining time was longer, indicating that the coal containing ILs had stronger resistance to moisture evaporation. The water-retaining property of [EMIm][BF4] was the best. The FTIR experiments showed that the main structure of coal was not changed but some structures changed by ILs treatment. The significant changes were the aliphatic hydrogen groups (1435 and 1371 cm−1), the C-O bond (1300–1000 cm−1) and the mineral structures (1032 and 472 cm−1). This study will provide a new development platform for the ILs used for coal dust prevention.