1. Institute for the Development of Energy for African Sustainability (IDEAS), Florida Campus, University of South Africa, Johannesburg, Gauteng 1710, South Africa
2. Department of Chemical Engineering, National University of Science and Technology, P.O. Box AC
939, Ascot, Bulawayo 029, Zimbabwe
3. Department of Mechanical Engineering Science, University of Johannesburg, Johannesburg, Gauteng 2092, South Africa