Adsorption of Denatonium benzoate using activated carbon

The Antifreeze Bittering Act of 2009 (H.R. 615) was introduced to the U.S. House of Representatives on January 21, 2009, and it mandates the addition of 30-50 mg/L denatonium benzoate (DB), a bittering agent, to antifreeze and engine coolant. At 1-10 mg/L, denatonium benzoate\u27s bitter taste can be detected; and water with 30-100 mg/L denatonium benzoate is unpalatable. This project addressed concerns related to the potential release of DB to water supplies by determining if activated carbon treatment, a common method employed to remove taste and odor contaminants from water, is suitable for DB removal. After conducting several contact time tests, powdered activated carbons NORIT GAC 1240 and HYDRODARCO 4000 had the most success at removing denatonium benzoate at the 24-hour time period. Both activated carbons are good treatment methods for removing 5 mg/L concentrations of denatonium benzoate from water. Batch tests conducted using higher concentrations of DB; (70 mg/L) concluded that activated carbon would not be sufficient for the removal of DB from water supplies. The NORIT GAC 1240, a bituminous based activated carbon, performed slightly better than HYDRODARCO® 4000, a lignite based carbon under all conditions. Batch tests were also conducted with the use of the organic acid potassium hydrogen phthalate (KHP) to determine the effects of organic material on adsorption. KHP increased the adsorption capacity of the NORIT GAC 1240 activated carbon. A 3 mg/L concentration of KHP mixed with 5 mg/L concentration of DB and a 5 mg/L concentration of NORIT® GAC 1240 had an 86% removal rate in 24 hours. Ionic strength experiments indicated that no ion exchange was taking place in the presence of KHP. It was surmised that complexation or bonding mechanisms may have contributed to the satisfactory removal of denatonium benzoate in the presence of KHP. Rapid small-scale column tests (RSSCTs) examined the performance of granular activated carbon (GAC) for removing denatonium benzoate from water. For GAC treatment, using the empty bed contact time (EBCT) of three minutes was found to be sufficient with longer EBCTs yielding inconclusive results. In conclusion, it was determined that activated carbon was sufficient for the removal of low DB concentrations. For higher concentrations of DB, other treatment methods should be considered