Enhanced reduction of chromate and PCE by palletized surfactant-modified zeolite/zerovalent iron

The current research focuses on enhanced removal of chromate and perchloroe thylene from contaminated water by a combination of a reduction material (r epresented by zerovalent iron, ZVI) and a sorption material (represented by surfactant-modified zeolite, SMZ). Natural zeolite and ZVI were homogenize d and pelletized to maintain favorable hydraulic properties while minimizin g material segregation due to bulk density differences. The zeolite/ZVI pel lets were modified with the cationic surfactant hexadecyltrimethylammonium bromide to increase contaminant sorption and, thus, the contaminant concent ration on the solid surface. Results of chromate sorption/reduction indicat e that the chromate sorption capacity of pelletized SMZ/ZVI is at least 1 o rder of magnitude higher than that of zeolite/ NI pellets. Compared to SMZ pellets, the chromate removal capacity of SMZ/ZVI pellets in a 24-h period is about 80% higher, due to the combined effects of sorption by SMZ and red uction by ZVI. The chromate and PCE degradation rates with and without surf actant modification were determined separately. The pseudo-first-order redu ction constant increased by a factor of 3 for PCE and by a factor of 9 for chromate following surfactant modification. The enhanced contaminant reduct ion capacity of SMZ/ZVI pellets may lead to a decrease in the amount of mat erial required to achieve a given level of contaminant removal.