Mechanism of removal of undesirable residual amylase, insoluble starch, and select colorants from refinery streams by powdered activated carbons

摘要

There is a need in the world-wide sugar industry to find a practical and economical solution to remove or inactivate residual alpha-amylases that are high temperature stable from factory or refinery streams. A survey of refineries that used amylase and had activated carbon systems for decolorization, revealed they did not have any customer complaints for residual amylase. Five commercial, high performance powdered activated carbons (PAC) were investigated for their ability to remove residual amylase as well as other impurities. Removal of the residual amylase protein by PAC was dependent on its surface area as well as mixing (retention) time. A select, high performance PAC (RFM-JH (TM)) with high surface area (1764 m(2)/g) performed the best and, because this PAC also had the largest particle size characteristics (mean particle size similar to 274 mu m), it was also the easiest to filter after use. Activated carbon also had the additional benefit of removing color, and RFM-JH (TM) preferentially removed cane derived flavonoid and phenolic colorants at pH 9 over process formed color at pH 4, which is opposite of color removal by the refinery phosphatation-clarification process and thus complementary. The dose of RFM-JH (TM) was more critical than retention time with respect to color removal. RFM-JH (TM) also consistently removed undesirable insoluble starch from raw sugar syrups and refinery liquors. A tentative mechanism for the removal of impurities is provided. Further studies are now warranted to investigate the use of high performance PAC as a tool to remove residual amylase, select colorants, and insoluble starch at the large-scale.