Novel method for reducing NDMA formation from daminozide during ozonation: Performances and mechanisms

The widespread amines have been found to generate carcinogenic nitro-dimethylamine (NDMA) during ozonation, it's urgent to search effective methods to control its formation. This work investigated the performance and mechanisms of bimetallic organic framework (MIL-100(Fe-Mn)) on reducing NDMA production during ozonation of daminozide (DMNZD). The results demonstrated that NDMA concentration raised from 27.6 to 248.4 μg/L when ozone dosages enhanced from 0.5 to 4 mg/L; while just slightly increased from 0.9 to 3.7 μg/L when MIL-100 (Fe-Mn) was added, with a reduction rate up to 98.5 %. When catalyst dosages increased from 0 to 200 mg/L, NDMA reduction rates enhanced from 54.5 to 97.4%. Moreover, neutral conditions facilitated the exploitation of MIL-100(Fe-Mn) during ozonation. Water bodies containing high concentrations of CO₃²⁻, HA, and Br⁻ should be avoided to prevent high NDMA risk. MIL-100(Fe-Mn) enhanced the transformation of ozone molecular (O₃) to hydroxyl radical (·OH) other than superoxide radicals (·O₂⁻) and singlet oxygen (¹O₂). EPR and scavengers quenching experiments verified that ·OH played important roles in NDMA reduction. Except ·OH, hydrogen radicals (·H) were detected in catalyzed ozonation system for the first time. The results would provide new insights for NDMA risks control during ozonation.