A study of the inhibition properties of gallic acid/lignin-modified hydrogel inhibitor prepared via graft copolymerization

In view of the shortcomings of pure hydrogels, such as a single inhibition effect and poor stability at high temperatures, this study aims to develop a new composite hydrogel inhibitor and to study its inhibition mechanism. To this end, gallic acid and lignin were added to modify the hydrogel, and a gallic acid/lignin-modified hydrogel (GA/LG-PAA) inhibitor was prepared. By scanning electron microscope, it was discovered that inhibited coal samples treated with gallic acid hydrogel (GA-PAA) and GA/LG-PAA had bigger particles. By using thermogravimetric analysis, it was found that after the inhibition treatment with GA/LG-PAA, the coal samples’ characteristic temperature points have increased to different degrees. Among these, the dry cracking temperature was increased by 53.87 °C, the ignition temperature was increased by 20.23 °C, and the burnout temperature was increased by 19.79 °C. Thermogravimetric experiments therefore showed that GA/LG-PAA had the best inhibition effect. Through infrared diffuse reflection experiments, it was found that the peak areas of methylene, carbonyl, carbon-carbon double bond, ether bond and other functional groups were all increased in coal samples after inhibition. The GA/LG-PAA inhibited spontaneous combustion by forming ether bonds. The results show that GA/LG-PAA can effectively inhibit coal spontaneous combustion.