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

• The effect of SiO 2 nanofluid with different concentrations on water adsorption capacity of coal is obtained. • The wettability-enhancing effect of SiO 2 nanofluid with different concentrations is investigated by contact angle tests. • The effect of nanofluid concentration on the wettability enhancement of coal is revealed. Water-based SiO 2 nanofluid, a wetting agent, has been proved to be feasible in improving the control effect of coal seam water injection against coal and gas outburst. However, the effect of nanofluid concentration on the control effect is not clear. Therefore, it is necessary to investigate the wettability-enhancing effect of nanofluid with different concentrations. In this paper, firstly, the effect of SiO 2 nanofluid with different concentrations on water adsorption capacity of coal was obtained. Then, the wettability-enhancing effect of SiO 2 nanofluid with different concentrations was investigated by contact angle tests. Finally, the effect of nanofluid concentration on the wettability enhancement of coal was revealed. The results showed that increasing the nanofluid concentration can enhance the water adsorption capacity and wettability of coal. In addition, the wettability-enhancing effect of nanofluid gradually got worse with time, while the stability of wettability-enhancing effect gradually got better. Furthermore, the 0.5 wt% nanofluid had the best sustainability and stability of the wettability-enhancing effect, while 1.0 wt% had the worst sustainability and stability. The research achievements could provide important basis for the selection of nanofluid concentrations in coal seam water injection. [ABSTRACT FROM AUTHOR]