The emergence of peracetic acid (PAA) as an alternative water treatment disinfectant to chlorination has shown promising potential in recent years. PAA-based advanced oxidation processes (AOPs) may incorporate metal ion catalysts such as Co, Fe, Ru, Cu, and Mn. This prompted the exploration of chromium (Cr) – PAA reactions since Cr may be present in water treatment systems. Interestingly, it was found that Cr(III) can be oxidized to the highly toxic Cr(VI) by PAA in alkaline conditions. In 1.0 h at pH 8.0, 263 μM Cr(III) in solution with 1315 μM PAA was found to degrade 39% of 5.0 μM trimethoprim (TMP) and continued to react even after 5.0 h of the reaction, yielding 79% degradation of TMP. Significantly, PAA alone (1315 μM at pH 8.0) degraded only 3.2% and 13%TMP in 1.0 and 5.0 h, respectively. The reactive intermediates CrIV and CrV are likely responsible for pollutant degradation in this system. Results from other contaminants in this system under the same conditions mentioned suggested that the degradation depended on pollutant molecular structure. For example, 95% enrofloxacin (ENR) was degraded in 1.0 h. However, only 23% of sulfamethoxazole (SMX) was degraded in 1.0 h. The presentation will demonstrate the involvement of intermediates CrIV and CrV in the studied Cr(III)-PAA-pollutant system. The potentially overlooked presence of CrIV and CrV may be beneficial in treatment processes and need attention.

Oxidation of chromium(III) by peracetic acid: Potential role of chromium(IV/V) in degradation of pollutants in water

ACS Spring 2022

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