Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/1999
Publication Date: N/A
Interpretive Summary: The agricultural by-products sugarcane bagasse, rice hulls, rice straw and pecan shells represent billions of pounds of waste on a yearly basis that offer an inexpensive and renewable source material for the production of value-added industrial products. One such industrial product would be granular activated carbon (GAC). We have converted these by-products to GACs and used them to remove the color components found in unrefined sugar. Carbons made with sugarcane bagasse and pecan shells, but not rice hulls and straw, removed color from sugar liquor as well as commercial reference GACs. Carbons made from rice hulls and straw were inferior products. Based on the cost of the starting material for carbon production, namely bagasse or shells versus more expensive coal for commercial carbons, our GACs could be lower in cost than commercial carbons while retaining the same ability to refine sugar. Use of by-product-based GACs in sugar refining would provide an excellent market for these adsorbents and help the bagasse producers and pecan shellers sell their raw material at increased cost.
Technical Abstract: Representative samples of soft, low density, group 1 (rice straw, rice hulls, sugarcane bagasse) and hard, high density, group 2 agricultural by-products (pecan shells) were converted into granular activated carbons (GACs). GACs were produced from group 1 and 2 materials by physical activation or from group 2 materials by chemical activation. Carbons were evaluated for their physical (hardness, bulk density), chemical (ash, conductivity, pH), surface (total surface area), and adsorption properties (molasses color removal, sugar decolorization) and compared with two commercial reference carbons. The results show that the type of by-product, binder, and activation method determine the properties of GACs. Regardless of binder, sugarcane bagasse showed a better potential than rice straw or rice hulls as precursor of GACs with the desirable properties of a sugar decolorizing carbon. Pecan shells produced GACs that were closest to the reference carbons in terms of all properties investigated.