1. Chemical
Resource Beneficiation, North-West University, Potchefstroom Campus, Private Bag
X6001, Potchefstroom 2520, South Africa
2. School
of Chemical and Minerals Engineering, Unit for Engineering Research, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa
3. Department
of Energy and Mineral Engineering, and The EMS Energy Institute, The Pennsylvania State University, 126 Hosler Building, University
Park, Pennsylvania 16802, United States