1. Centre of Material and Process Synthesis, School of Chemical and Metallurgical Engineering; University of the Witwatersrand; Johannesburg South Africa
2. Dept. of Civil and Chemical Engineering; University of South Africa; Pretoria South Africa
3. Dept. of Chemical Engineering; Texas A&M University; College Station TX 77843
4. Dept. of Chemical and Materials Engineering; King Abdulaziz University; Jeddah Saudi Arabia