1. School of Mining and Mechanical Engineering, Liupanshui Normal University, Liupanshui 553004, Guizhou, China
2. Chinese National Engineering Research Center of Coal Preparation and Purification, China University of Mining and Technology, Xuzhou 221116, Jiangsu, China
3. School of Chemistry and Chemical Engineering, Qiannan Normal University for Nationalities, Duyun 558000, Guizhou, China
4. School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China