Study on the mechanism of an enteromorpha-based compound inhibitor for inhibiting the spontaneous combustion of coal using in situ infrared spectroscopy and thermal analysis kinetics

To alleviate the environmental pressure caused by enteromorpha (EP) and improve the efficiency of inhibiting spontaneous combustion of coal, attapulgite (ATP) was combined with EP to prepare an enteromorpha-based composite inhibitor (EPH-ATP). The effect of adding different substances on the surface morphology of the synthesized inhibitor was investigated using scanning electron microscopy (SEM). The effects of three inhibitors (enteromorpha hydrogel (EPH), ATP, and EPH-ATP) were analyzed using thermal analysis kinetics and in situ fourier transform infrared spectroscopy (FTIR). The results showed that the addition of ATP had little effect on the apparent morphology and was uniformly distributed in EPH. At heating rates of 5.0, 10.0, 15.0, and 20.0 K/ min, it was found that the degree of the completion of spontaneous combustion of coal was directly related to the heating rate, and coal was more likely to react at low heating rates. In addition, during the combustion and decomposition stage, the average activation energy of coal samples treated with EPH-ATP increased by 306%, which greatly improved the reaction difficulty of the spontaneous combustion of coal. According to the changes in the functional groups with temperature, the in situ infrared process was divided into three stages of slow reaction, violent reaction and stable reaction for the first time. Moreover, the mechanism of EPH-ATP reducing the intensity of reaction by scavenging free radicals was clarified. The results show that the enteromorpha-based composite inhibitor has a good inhibitory effect, realizes the sustainable use of EP, and provides a new scientific basis for the prevention and control of the spontaneous combustion of coal.