Photoconversion of NO3−/NO2− at wastewater relevant concentrations as an advanced oxidation approach to degrade dimethyl pthalate (DMP), a relatively photoinert endocrine disruptor, were examined. Three different wavelengths (350 nm, 300 nm, 254 nm) were involved. The influence of NO3− or NO2− was found to be wavelength-dependent. The 254 nm UV light could decompose DMP efficiently, but photolysis of DMP was slow at λ =300 nm and noneffective at λ =350 nm, which could be catalyzed by the presence of NO3− or NO2−. Both [rad]OH and O2[rad]− were detected, while [rad]OH was identified as the primary contributor to DMP decomposition. NO2− plays a dual role as both a source and sink of [rad]OH, depending on the relative abundance between NO2− and DMP. NO3− was more efficient than NO2− for treating low-level DMP. However, higher organic content could effectively inhibit the quenching role of NO2−, making NO2− more efficient for catalyzing DMP decomposition. For irradiation at λ =350 nm, NO3− was completely ineffective, while self regeneration of NO2− enabled Δ[NO2−]:Δ[[rad]OH] <<1. For irradiation at λ =300 nm, cycling between NO2− and NO3− occurred, and the transformation from NO2− to NO3− proceeded much faster. Complete decomposition of DMP at concentrations higher than those of NO2− or NO3− was observed, and mineralization was also achieved. Based on the identification of the intermediates, [rad]OH addition to the aromatic ring and hydrogen atom abstraction by [rad]OH were the dominant pathways, while nitration products were detected at low levels.
- Dimethyl phthalate
ASJC Scopus subject areas
- Environmental Science(all)
- Process Chemistry and Technology