1. Energy
Systems, School of Chemical and Minerals Engineering, North-West University, Potchefstroom 2520, Republic of South Africa
2. School
of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney NSW 2052, Australia
3. ALS-ACIRL Pty. Ltd., P. O. Box 242, Booval Qld 4304 Australia
4. School
of Physical and Chemical Sciences, North-West University, Potchefstroom 2520, Republic of South Africa