1. 1School of Chemical Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, S.P.S. Penang, Malaysia
2. 2Department of Chemical Engineering, School of Engineering and Science, Curtin University Sarawak Campus, 250CDT, 98009 Miri, Sarawak, Malaysia
3. 3School of Chemical Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, S.P.S. Penang, Malaysia, Tel.: +(604) 599 6412, Fax: +(604) 594 1013, e-mail: siewchun@gmail.com