Nanoscale zero-valent iron immobilized inside the mesopores of ordered mesoporous carbon by the “two solvents” reduction technique for Cr(VI) and As(V) removal from aqueous solution

Nanoscale zero-valent iron particles (NZVIs) were well dispersed into the mesopores of ordered mesoporous carbon (OMC). Structure characterization of the obtained NZVIs/OMC composites found that OMC mesopores could remarkably keep NZVIs from aggregation and effectively alleviate iron oxidation. Batch experiments for Cr(VI) and As(V) removal were employed to evaluate activity of NZVIs/OMC. Results showed that either Cr(VI) or As(V) in aqueous, got nearly 100% uptake by NZVIs/OMC, which was higher than that by NZVIs. Both Cr(VI) and As(V) removal showed little dependence on solution pH, and their kinetic models were fitted the pseudo first-order model with the Kobs 0.419 min−1 of Cr(VI) and 0.820 min−1 of As(V), which was 34–28 times of Kobs on NZVIs. Mechanism of Cr(VI) and As(V) removal by NZVIs/OMC included adsorption process and reduction process between the immobilized NZVIs and the adsorbed contaminant inside the mesopores of OMC. The intra-particle diffusion was the control process during the adsorption step. Chemical reduction presented an important role in the removal process. The adsorbed Cr(VI) was remarkably reduced to Cr(III) in forms of FeCr2O4 and Cr(OH)3. As(V) was rapidly adsorbed by the composite and gradually reduced to As(III).