1. Chemical and Mining Engineering Department, College of Engineering and Technology, University of Dar es Salaam, P.O. Box 35131, Dar es Salaam, Tanzania
2. School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang, Malaysia
3. Chemistry Department, College of Natural and Applied Sciences, University of Dar es Salaam, P.O. Box 35065, Dar es Salaam, Tanzania