Determination of Contact Angle Measurement of Sub-bituminous and bituminous Coal Particles through Capillary Rise Method Using Washburn Equation for Surface Free Energy and Interfacial Energy
Ikebudu Kingsley Okechukwu
This study presents Determination of Contact Angle Measurement of Sub-bituminous and Bituminous Coal Particles through Capillary Rise Method Using Washburn Equation for Surface Free Energy and Interfacial Energy. This study aided in determination of Contact Angles of Sub-bituminous and bituminous Coal. The Lucas-Washburn equation was used to determine the contact angles θ = 64.8˚ for sub-bituminous coal and θ = 68.66˚ for bituminous coal. The coals were ground dry with a milling machine into powder form and sieved with seven standard sieves of size ranges 75mm - 850mm. The sieved coal powders and 50% ethanol/water concentrate were used for capillary rise experiment. Washburn equation was adopted for measurement of contact angle; the slope (m) of the graph between the height (Hd2) of liquid rise and the time (t) taken for the liquid to rise, the viscosity of the liquid (η), the capillary radius ( ), and the surface tension of the liquid ( ) were used for the determination of contact angles. The values of the contact angle shows that the two materials are nonpolar materials and hydrophobic solids that are characterised by covalent and weak molecular bonds.