1. State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources; Institute of Resources and Environmental Engineering; Shanxi University; Taiyuan 030006 P. R. China
2. Engineering Research Center of Ministry of Education for Fine Chemicals; Shanxi University; Taiyuan 030006 P. R. China
3. State Key Laboratory of Coal Conversion; Institute of Coal Chemistry; Chinese Academy of Sciences; Taiyuan 030001 P. R. China