1. School of Environmental and Chemical Engineering, Xi’an Polytechnic University, Xi’an 710048, P. R. China
2. College of Chemistry and Chemical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P. R. China
3. Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi’an 710062, P. R. China