Improvement of wettability of coal seams in water injection via co-deposition of polydopamine and polyacrylamide

Water injection into coal seams is important for dust prevention in mines. However, owing to the hydrophobicity of coal itself, the wetting effect of water injection on coal seams has yet to be enhanced. Herein, based on the hydrophobicity of coal, hydrophilic modification of the coal surface has been proposed via co-deposition of polydopamine (PDA) and polyacrylamide (PAM). Using water contact angle (WCA) test, atomic force microscope (AFM) test, X-ray photoelectron spectroscopy (XPS) characterization, and 1H nuclear magnetic resonance spectroscopy (1H NMR) measurements, the feasibility of hydrophilicity modification of coal by PDA/PAM has been investigated. The results indicate that when DA concentration is 2 mg/mL, deposition time is 45 min, and DA/PAM feeding molar ratio is 1:1, the wettability of modified coal sample clearly improves. In the water content test and dust-production test using gravity drop hammer, the modified coal exhibits good wettability and low dust production. Also, UV-Vis absorption spectroscopy and WCA results suggest that PDA/PAM coating exhibits good stability. Therefore, the modification method can effectively enhance the wetting effect of injected water on coal seam, providing a novel approach for dust prevention.