As shown in the DTG results, MD reaches the point of maximum thermal
decomposition rate at 362.3°C, which indicates the dehydration of
surface hydroxyl groups, which is consistent with the OSMD[40]. OSMD
shows another jump discontinuity at 561.8°C, which may be due to the
loss of grafted octadecyl and
sulfonyl groups[41]. Throughout the process, the overall mass loss
of MD was 7.6%, while the overall mass loss of OSMD was 8.6%, this
indicated that diatomite was successfully modified, while the support
itself has excellent thermal stability.
The contact angle serves as a quantitative indicator of surface
wettability, which quantifies the angle formed between the interface of
the liquid or vapor and the solid surface. According to the
Young-According to the Young-Laplace equation, the morphology of a
droplet is influenced by the relative hydrophobic or hydrophilic
properties of the material’s surface with respect to the liquid. A
larger contact angle corresponds to a greater repulsive force exerted by
the droplet on the surface, signifying a relatively higher degree of
hydrophobicity of the material’s surface[24]. As depicted inFigure 3D (a) , diatomaceous earth exhibits pronounced
hydrophilicity owing to the abundance of surface Si-OH groups[41].
Conversely, the contact angle of OSMD increased to 133.5° following
additional octadecyl modification, indicative of its heightened
hydrophobicity, which can also support that the successful modification
of octadecyl.
Figure 4 . TG of MD and OSMD (A), DTG of MD (B) and OSMD (C),
the contact angle of MD and OSMD (D)