Photodegradation performance and mechanism of sulfadiazine in Fe(III)-EDDS-activated persulfate system

ABSTRACT

In order to overcome the shortcomings in the traditional Fenton process, Fe(III)-EDDS-activated persulfate advanced oxidation process under irradiation is carried out as a promising technology. The photodegradation of sulfadiazine (SD) in Fe(III)-EDDS-activated persulfate system was investigated in this paper. The results showed that SD could be effectively degraded in Fe(III)-EDDS/${\mathrm{S}}_2{\mathrm{O}}_8^{2-}$/hv system. The effects of Fe(III):EDDS molar ratio, the concentration of Fe(III)-EDDS, and the concentration of ${\mathrm{S}}_2{\mathrm{O}}_8^{2-}$ on SD degradation were explored. At neutral pH, when Fe(III):EDDS = 1:1, Fe(III)-EDDS = 0.1 mM, ${\mathrm{S}}_2{\mathrm{O}}_8^{2-}$ = 1.5 mM, the best SD degradation was achieved. The experiment of external influence factors showed that the degradation of SD could be obviously inhibited by the presence of ${\mathrm{C}\mathrm{O}}_3^{2-}$, ${\mathrm{S}\mathrm{O}}_4^{2-}$, whereas the degradation of SD was almost unaffected by the addition ofCl⁻. The degradation of SD could be slightly inhibited by the presence of humic acid and NO₃⁻. The effect of pH on SD degradation was investigated, and SD could be degraded effectively in the pH range of 3–9. ESR proved that ¹O₂, ·OH, $\mathrm{S}{\mathrm{O}}_4^{-}$, and O₂⁻ were produced in the process. $\mathrm{S}{\mathrm{O}}_4^{-}$ and ·OH were identified as the main radicals while O₂^·− also played non-ignorable role. Eleven intermediate products of SD were analysed. The C = N, S–N, and S–C bonds of SD were attacked by radicals firstly, leading to a series of reactions that eventually resulted in the destruction of SD molecules and the formation of small organic molecules.

GRAPHICAL ABSTRACT

KEYWORDS:

• Fe(III)-EDDS/${\mathrm{S}}_2{\mathrm{O}}_8^{2-}$/hv system
• radicals
• sulfadiazine
• internal and external influence factors
• mechanism analysis

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Corresponding author would provide data on a reasonable request.

Additional information

Funding

This work was supported by National Natural Science Foundation of China (NSFC No: 21968005).