1. School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, P. R. China
2. State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming 650093, P. R. China
3. Key Laboratory of Solid Waste Treatment and Resource Recycle Ministry of Education, Southwest University of Science and Technology, Mianyang, Sichuan 621010, P. R. China
4. Chinese National Engineering Research Center of Coal Preparation and Purification, China University of Mining and Technology, Xuzhou, Jiangsu 221116, P. R. China