Characteristics of nanoscale zero-valent iron (NZVI) particles formed under controlled air contact

The effect of controlled air contact on the shell formation and on the TCE degradation efficiency on the shell-stabilized nanoscale zero-valent iron (NZVI) particles was investigated. TEM images indicate that NZVI particles prepared under different aerial exposure conditions have shells with the same thickness of about 5 nm, while NZVI particles exposed to atmospheric oxygen under controlled condition displayed pyrophoric characteristics, no shell layers were observed, and have main peaks of amorphous phase Fe. A pseudo-first-order rate law was adequate to describe TCE degradation kinetics of the slurries containing various NZVI particle types. The degradation rates for the particles prepared under different aerial exposure conditions (4, 8, 12 mL/min) were almost identical, as were the shell characteristics. TCE degradation started without delay in the slurries containing the rapidly oxidized particles, suggesting that the rapidly oxidized NZVI particle that was coated by an amorphous iron shell could recover its reductive capacity after the shell was depassivated in the solution.