Monday, April 30, 2007

Production of microcrystalline cellulose from tropical agricultural residues

Foster Agblevor1, Maha Ibrahim2, and Waleed K. El-Zawawy2. (1) Biological Systems Engineering, Virginia Polytechnic Institute and State University, 200 Seitz Hall, Blacksburg, VA 24061, (2) Cellulose and Paper, National Research Center, El Tahirir, Cairo, Egypt

Economical and environmentally-friendly methods of disposing agricultural residues in many countries are becoming major concerns especially for small scale producers. The cotton ginning industry in the USA has major challenges disposing of cotton gin waste at small cotton gins and the Nile delta in Egypt has major pollution problems from burning of agricultural residues in the fields. We investigated steam treatment technology for adding value to the agricultural residues such as cotton gin waste, cotton stalks, banana stem and rice straw as a method of waste disposal as well as generating new product streams. The agricultural residues were steam exploded at severities parameters of 3.0 to 4.8. After steam treatment, the hemicellulose fraction was extracted with hot water at 80°C and the lignin fraction was extracted with 20 wt% NaOH at 80°C. The extracted solid residues were washed with water and bleached with hydrogen peroxide. All four materials were very difficult to bleach with hydrogen peroxide at one stage.  However, after three stages of bleaching the materials were bright. The products were characterized with FTIR, TGA, X-ray diffraction, scanning electron microscope, and the degrees of polymerization (DP) for each were determined by intrinsic viscosity method. The products had similar characteristics as commercial Avicel PH101 microcrystalline cellulose. In general, the DP of the microcrystalline cellulose decreased with increased severity of steam treatment. The crystallinity index determined from FTIR analysis showed a higher degree of crystallinity for the cotton gin waste sample compared to the other samples.