Effect of SiO2 nanofluid with different concentrations on the wettability of coal

•The effect of SiO2 nanofluid with different concentrations on water adsorption capacity of coal is obtained.•The wettability-enhancing effect of SiO2 nanofluid with different concentrations is investigated by contact angle tests.•The effect of nanofluid concentration on the wettability enhancement of coal is revealed.