CTMAB-Modified Bentonite-Based PRB in Remediating Cr(VI) Contaminated Groundwater

Cetyl trimethylammonium bromide (CTMAB)-modified bentonite was synthesized as adsorbent for the removal of Cr(VI) from aqueous solutions. Batch adsorption studies show that the adsorption capacity of CTMAB-modified bentonite (1.962 mg g(-1)) was about 19 times higher than that of natural bentonite (0.101 mg g(-1)). The weakly acidic or neutral environment can improve the adsorption ability of both natural and modified bentonites. Cr(VI) adsorption onto CTMAB-modified bentonite follows the Langmuir model and obeys the pseudo-second-order model. In a fixed-bed column test, the adsorption capacities of 5% modified bentonite with 95% sand, and 10% modified bentonite with 90% sand were 0.31 mg g(-1) and 0.35 mg g(-1), respectively. These values were much lower than their theoretical maximum adsorption capacity using the Langmuir model.