Wet dedusting is the main
coal dust suppression technique in coal mines, and coal wettability
is the main factor affecting dust suppression efficiency. To investigate
the main factors affecting the coal wettability and improve it, the
coal–water contact angle was used as an index to characterize
the coal wettability, and the wettability of six coal samples with
different metamorphic degree was studied by analyzing the relationship
between the physicochemical properties and the contact angle. To improve
the coal wettability, the nonionic surfactant alkyl polyglycoside
(APG), anionic surfactant sodium dodecyl benzene sulfonate (SDBS),
and polymer surfactant polyacrylamide (PAM) were applied to the coal
samples. The results show that SDBS is the most effective surfactant
to improve the coal wettability, followed by APG, while the application
of PAM would lead to more hydrophobic coal. It is also found that
the coal wettability shows a high–low–high trend with
the increase in the metamorphic degree. The wettability of long flame
coal is the strongest and that of gas coal is the weakest. Moisture
is the main hydrophilic factor of coal, while 1,4-dimethylbenzene
is the main hydrophobic factor. The main factors affecting the treatment
effect of APG, SDBS, and PAM on wettability are the aromatic methylbenzene,
hydroxyl, and hydroxyl content of coal, respectively. Therefore, according
to the content of hydroxyl in different coals, an SDBS solution can
be prepared to improve the coal wettability. For coal with a low hydroxyl
content, a higher concentration SDBS solution could be needed.