1. School of Metallurgy and Environment, Central South University, Changsha 410083, China
2. Chinese National Engineering Research Center for Control and Treatment of Heavy Metal Pollution, Central South University, Changsha 410083, China
3. School of Material Science and Engineering, Central South University, Changsha 410083, P. R. China
4. Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong 999077, P. R. China