Characterization of Chromium Immobilization in Hydrogen-Supplied Sediment Columns

摘要

This study characterized Cr(VI) removal from groundwater in aquifer sediment columns supplied with membrane-delivered H2. Three parallel columns were fed with groundwater spiked with Cr(VI) at 1.0 to 2.0 mg/L. The second column was also spiked with 10 mg/L of NO_3~-N as a competing electron acceptor. H2 was supplied to the first two columns as a reductant, while N2 was supplied in the third column as a negative control. Samples were collected along the length of each column and analyzed for H2, NO_3~- , Cr(VI), total Cr, SO_4~(2-) , and pH. Whereas total Cr removals were below 10% in the N2-supplied column, greater than 90% removals were sustained in both H2-supplied col- umns. However, significant total Cr removals were not observed in the NO_3~- -spiked - column until nearly complete NO3 removals were attained, indicating that NO_3~- inhibited Cr(VI) reduction. At the conclusion of the study, aquifer sediment samples were collected and analyzed for total Cr. Whereas sediment Cr concentrations in the N2-supplied control column were not statistically different from the original aquifer material, sediment con- centrations in the two H2-supplied soil columns averaged four times greater. However, increased total Cr concentrations were only observed in sediment samples collected from the NO_3~- -spiked column at locations downstream of where NO_3~- had been completely re- moved, again indicating that NO_3~- inhibited Cr(VI) reduction.