The surface energy of palygorskite

An average value for the surface energy (γ¯S) of palygorskite was determined from experimental data of spreading pressure, the surface tension of water and its contact angle using a formula based on the combination of the Young equation with a general equation of pair interaction. The value found is 226.6 mJ m− 2. Some factors that affect the determination of surface energy via solid–liquid interaction are exposed. The backgrounds of previous formulas for the calculation of the surface energy of palygorskite are also critically examined.