The removal of perchlorate from groundwater by activated carbon tailored with cationic surfactants.

In rapid small-scale column tests, cationic surfactant-tailored activated carbons (ACs) effectively removed perchlorate to below detection levels for up to 30 times longer than virgin AC. By pre-loading bituminous AC with dicocodimethylammonium chloride, tallowtrimethylammonium chloride, cetyltrimethylammonium chloride, or cetylpyridinium chloride, 75 ppb perchlorate was removed for 27,000-35,000 bed volumes before the effluent perchlorate rose above 1 ppb. These tests employed a natural groundwater that also contained 30 mg/L sulfate, 26 mg/L nitrate (as NO3-), and other ions. By the time of 25 ppb perchlorate breakthrough, 7.3-10.1% of quaternary ammonium sites had perchlorate associated with them. Although some of the surfactants leached out of the tailored carbon beds (0.6-21.2% of the amount loaded), the leached surfactant could be removed to below detectable limits with a virgin AC polishing bed that chased the tailored bed.