1. College of Chemistry and Chemical Engineering, Xi’an University of Science and Technology, Xi’an 710054, PR China
2. Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Natural Resources, Xi’an 710021, PR China
3. Coal Washing & Preparation Center, Ningxia Coal Industry Co., Ltd, CHN ENERGY, ShiZuishan, Ningxia 75300, PR China