1. Key Lab of Bioelectrochemistry and Environmental Analysis of Gansu Province, Key Lab of Eco-Environment-Related Polymer Materials of MOE, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, Gansu, P. R. China
2. Department of Metallurgy and Chemical Engineering, Gansu Vocational & Technical College of Nonferrous Metallurgy, Jinchang 737100, Gansu, P. R. China
3. College of Chemistry and Chemical Engineering, Provincial Key Laboratory of Gansu Higher Education for City Environmental Pollution Control, Lanzhou City University, Lanzhou 730070, Gansu, P. R. China