1. Department of Civil and Chemical Engineering, College of Science, Engineering and Technology; University of South Africa; Christian de Wet and Pioneer Avenue, Private Bag X6 Florida 1710 Johannesburg South Africa
2. School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment; University of the Witwatersrand; Private Bag 3 Wits 2050 Johannesburg South Africa
3. School of Computational and Applied Mathematics, Faculty of Science; University of the Witwatersrand; Private Bag 3 Wits 2050 Johannesburg South Africa