1. a Department of Chemistry, Faculty of Sciences, University of Ngaoundere, Ngaoundere, Cameroon
2. b Department of Mineral Engineering, School of Chemical Engineering and Mineral Industries, University of Ngaoundere, Ngaoundere, Cameroon
3. c Department of Chemical Engineering, School of Chemical Engineering and Mineral Industries, University of Ngaoundere, Ngaoundere, Cameroon
4. d Department of Applied Chemistry, ENSAI, University of Ngaoundere, Ngaoundere, Cameroon