1. Key Laboratory of Attapulgite Science and Applied Technology of Jiangsu Provincial, Huaiyin Institute of Technology, Huaian, Jiangsu 223003, P.R. China
2. University of the Chinese Academy of Sciences, Beijing 100049, P.R. China
3. Center for Eco-material and Green Chemistry, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000 P. R. China