Wetting Process and Adsorption Mechanism of Surfactant Solutions on Coal Dust Surface

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To determine the wetting process and wetting mechanism of different surfactant solutions on coal dust surface, four types of surfactants (anionic surfactant 1227, anionic surfactant AOS, amphoteric surfactant CAB-35, and nonionic surfactant CDEA) are selected to measure their surface tension and contact angle. Based on the data, the adhesion work, spreading coefficient, and immersion work of the surfactant solutions on a coal dust surface are calculated and their adsorption mechanism is discussed. The results show that the surface tension and contact angle of AOS and CDEA are lower and smaller, respectively, their calculated spreading coefficients are higher, and their adhesion work and immersion work are less than those of 1227 and CAB-35. This shows that the wettability of the AOS and CDEA solutions for a coal dust surface is more than that of 1227 and CAB-35, whereas their adhesion is lower than that of the latter. The spreading coefficient can be used as an index to determine the wettability. The wetting ability of the AOS and CDEA aqueous solutions for coal dust is stronger than that of 1227 and CAB-35 because of the different adsorption forms of the surfactant molecules on the surface of the coal dust. The tail hydrophobic group of the AOS and CDEA surfactant molecules orient to the surface of the coal dust, whereas the head hydrophilic group directs to the solution, being easier to wet. The results show that anionic and nonionic surfactant solutions can significantly improve the wettability of a coal dust surface, providing a theoretical basis for selecting suitable surfactants as water-spray additives to improve the dust suppression efficiency.