Rapid Small-Scale Column Tests on the Adsorption of Arsenate by Cationic Surfactant-Modified GAC

Cationic surfactants were employed to modify granular activated carbon (GAC) for the purpose of improving GAC's adsorption of arsenate from water. Rapid small-scale column tests (RSSCTs) were set up to test the adsorption capacities. Results indicated that surfactant cetyltrimethylammonium chloride (CTAC) modification manifested the highest improvement in GAC's adsorption for arsenate. GAC modified by 2 mmol/L of CTAC was able to operate approximately 64,000 bed volumes before 10 mu g/L of arsenate breakthrough as compared with 2,100 bed volumes for virgin GAC. GAC also performed much better than zeolite and bentonite both in surfactant retention and arsenic removal. Arsenate adsorption was affected by influent concentration, pH, and presence of other anions. The effect of competitive anions on arsenate adsorption was in the order of PO43- > SO42- > NO3-. Breakthrough tests on tap water spiked with arsenate indicated that the modified GAC had high selectivity for arsenate and considerable amount of arsenate was removed though the influent contained interfering anions and total organic carbon (TOC) in concentrations of magnitude higher than that of arsenate. DOI: 10.1061/(ASCE)EE.1943-7870.0000546. (C) 2012 American Society of Civil Engineers.