1. School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg 2050, South Africa
2. Department of Chemical Engineering, Faculty of Engineering, Built Environment and Information Technology, University of Pretoria, Hatfield, Pretoria 0028, South Africa
3. Department of Chemical Engineering, Federal University of Petroleum Resources, Effurun (FUPRE), Warri 330102, Nigeria