1. College of Chemistry and Chemical Engineering; Central South University; Changsha Hunan 410083 P.R. China
2. Dept. of Bioengineering and Environmental Science; Changsha University; Changsha Hunan 410003 P.R. China
3. Key Laboratory of Resources Chemistry of Nonferrous Metals (Ministry of Education); Changsha Hunan 410083 P.R. China