Ammonia-tailoring of GAC to enhance perchlorate removal. II: Perchlorate adsorption

Thermal tailoring of a bituminous granular activated carbon (GAC) by ammonia gas at 500-800 degreesC for 60 min achieved as much as 4-fold improvement in perchlorate adsorption as determined by rapid small-scale column tests (RSSCTs). When treating natural groundwater that contained 70-78 ppb perchlorate, the bed volumes to 4 ppb perchlorate breakthrough increased from 1100 bed volumes for commercial bituminous carbon up to 4400 bed volumes for carbon that was tailored in ammonia at 700 degreesC. Increased perchlorate adsorption corresponded to increased positive surface charges with R-2 0.956. The increase in positive surface charge was closely related to the increase in nitrogen content after ammonia tailoring. The ammonia-tailored activated carbons also exhibited a moderate increase in TOC removal and higher selectivity for erchlorate. The work herein interfaces with a companion paper by the same authors in which the ammonia-tailored carbon surfaces are characterized relative to physical-chemical features [1]. (C) 2004 Elsevier Ltd. All rights reserved.