Hydrogen Peroxide Quenching with Mineral Catalysts after UV/H2O2 Advanced Oxidation

Abstract

This study explored mineral catalysts for H2O2 quenching after UV/H2O2 advanced oxidation as an alternative to granular activated carbon or chlorine (two of the most common methods). The following mineral catalysts were evaluated in batch reactors: activated alumina, aluminum oxide, iron (III) oxide, titanium dioxide, titanium, silver, zinc, and magnesium oxide. Of these, aluminum oxide and iron (III) oxide were the most promising catalysts and were further tested in column studies and compared with granular activated carbon (GAC). Aluminum oxide performance in column studies was inferior to the results obtained from GAC and iron (III) oxide, possibly due to the hygroscopic nature of the material. Additional rapid small-scale column tests (RSSCTs) were conducted with iron (III) oxide to mimic a three-year full-scale column operation and achieved 90%–99% removal of H2O2. The decomposition of H2O2 on the catalytic surface appears to generate hydroxyl radicals, although not at a sufficient level to provide considerable additional contaminant destruction after advanced oxidation. The process did not elevate iron concentration in the treated water to a level above the secondary USEPA standard of 0.3 mg/L (0.12 mg/L maximum, 0.03 mg/L average). Longer-term pilot-scale study is necessary to determine operational requirements, such as backwashing, and to determine whether the observed loss of activity over time can be regenerated. Overall, the process appears to be a viable option for H2O2 quenching, making application of UV/H2O2 advanced oxidation more practical for drinking water treatment where residual H2O2 can interfere with chlorination.