Insight into Effects of Acid Treatment on Physicochemical Properties of Huadian Oil Shale

To explore the effects of acid treatment on the physicochemical properties of Huadian oil shale (OS), low-temperature nitrogen gas adsorption (LTN 2 GA), scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Electron Paramagnetic Resonance (EPR), and thermogravimetric (TG) analysis were used to analyze OS and the acid-treated OS (OSA). LTN 2 GA showed that acid treatment promoted the formation of mesopores and increased the pore connectivity of OS. SEM showed the acid treatment increased the surface roughness of OS. From XRD analysis, most quartz, corundum, and calcite were removed from OS caused by acid treatment. According to the FT-IR analysis, the content of carboxylic acid in OS increased after acid treatment. EPR showed that the concentration of free radicals in OS decreased after acid treatment because of the removal of transition metal free radicals. The TG results showed acid treatment increased the pyrolysis intensity of OS. Overall, acid treatment can effectively remove minerals, and its effects on organic matter were not obvious.