1. Res. Asst./Sci., School of Chemical Engrg., Univ of Natal, Durban, 4041, South Africa.
2. Res. Asst./Sci., Dept. of Chemical Engrg. and Chemical Technol., Imperial Coll. of Sci. Technol. and Medicine, Prince Consort Rd., London SW7 2BY, UK.
3. Prof., School of Chemical Engrg., Univ. of Natal, Durban, 4041, South Africa.
4. Reader, Dept. of Chemical Engrg. and Chemical Technol., Imperial Coll. of Sci. Technol. and Medicine, Prince Consort Rd., London SW7 2BY, U.K. (Corresponding author). E-mail: d.stuckey@ic.ac.uk