1. School of Chemical Engineering & Technology, China University of Mining & Technology, Xuzhou 221116, China
2. Shenhua Xinjiang Energy Co., Ltd., Heishan open-pit
coal mine, Toksun 838100, China
3. Department of Chemistry, School of Arts & Sciences, National University of Mongolia, Ulaanbaatar 210646, P.O. Box 624, Post Office 46A, Mongolia
4. School of Chemistry and Environmental Engineering, North China Institute of Science & Technology, Sanhe 065201, China