POTENTIAL OF AGRICULTURAL BY-PRODUCT-BASED ACTIVATED CARBONS FOR USE IN RAW SUGAR DECOLORIZATION

The physical (bulk density and hardness) and chemical (pH and mineral content) characteristics of granular activated carbons (GACs) made fro m rice straw, pecan shells and hulls of soybean and rice were determin ed. The adsorption properties (iodine test, molasses test and raw suga r decolourisation efficiency) of these by-product-based carbons were a lso evaluated. A commercial decolourising carbon (Calgon CPG LF) was u sed as a comparison. Pecan-based carbons had bulk densities and hardne ss numbers higher than Calgon CPG LF. They also showed a mineral conte nt and pH similar to or lower than the commercial carbon. The adsorpti on properties of the pecan-based carbons were, however, about 40% belo w that of the reference carbon. In contrast, rice (hull and straw)-bas ed carbons exhibited good adsorption properties similar to the referen ce carbon in both iodine test and molasses test, but their ash content and their inherent pHs were higher than Calgon CPG LF. Both types of rice-based carbons were also more friable and had lower bulk densities than the commercial carbon. However, rice-hull-based carbon was stati stically as effective as Calgon CPG-LF in decolourising raw sugar solu tions at the 5% confidence level. Of the by-product-based carbons eval uated, pecan-shell-based GACs would be most suitable as raw sugar deco lourisers if their adsorption efficiencies could be improved.