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

Abstract

Thermal tailoring of a bituminous granular activated carbon (GAC) by ammonia gas at 500–800 °C 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 °C. 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].