An improved sessile drop method for assessing the wettability of heterogeneous coal surface

ABSTRACT

To assess the wettability of heterogeneous coal surface, a new modified sessile drop technique named volume–length method is proposed to calculate the contact angle according to the spreading ability of droplet on the coal surface. The tested contact angles were compared with the predicted contact angles using Cassie–Baxter model. Low ash coal and kaoline powders are mixed with different mass ratios and mixing degrees. The mixtures were pressed to plates for sessile drop contact angle tests. The surface chemical component and nonuniform degree determine the droplet spreading on the coal surface, thereby affecting the contact angle.

KEYWORDS:

• Coal surface
• contact angle
• heterogeneity
• sessile drop
• wettability

Funding

This work was supported by the National Natural Science Foundation of China (51604272), the National Natural Science Foundation of Jiangsu Province (BK20160260), China Postdoctoral Science Special Foundation (2017T100422), and China Postdoctoral Science Foundation (2015M580497).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (51604272), the National Natural Science Foundation of Jiangsu Province (BK20160260), China Postdoctoral Science Special Foundation (2017T100422), and China Postdoctoral Science Foundation (2015M580497).