Study on the Inhibition Characteristics and Mechanisms of Polydopamine on Coal Spontaneous Combustion

Based on coal spontaneous-combustion mechanisms, clarifying polydopamine’s(PDA) inhibitory characteristics and molecular pathways is essential for mussel-inspired fire prevention in mining; therefore, comprehensive experiments and molecular simulations were performed to probe PDA’s suppression of coal self-heating. First, PDA solutions of different concentrations were prepared using covalent oxidative polymerization, and their inhibitory effects on coal were studied. The impact of PDA on the functional groups of coal was investigated using Fourier Transform Infrared Spectroscopy (FTIR). The results indicated that a 3 g/L PDA solution exhibited the most significant inhibitory effect, and the functional groups required for PDA solution to inhibit coal samples of different particle sizes varied. The influence of PDA on the microcrystalline structure of coal was investigated using X-ray diffraction (XRD). The results indicated that PDA disrupts the branched-chain structure of coal. The inhibitory effect of PDA on coal was investigated using an Electron Spin Resonance (ESR) spectrometer and a synchronous thermal analyzer. The results showed that the inhibition rate of PDA on coal samples of different particle sizes could reach around 30%, effectively suppressing the oxidation reaction of coal. Finally, the mechanism of PDA inhibiting coal oxidation reaction was investigated using quantum chemical methods. Through charge distribution analysis, molecular orbital analysis, and bond dissociation energy calculations, the reactive sites of PDA were identified as H27 and H28. Furthermore, the reaction processes of PDA scavenging RO·、ROO·, and RH2· radicals were determined by transition state search. This study provides a theoretical basis for designing self-adhesive fire-suppression gels in coal mines.