Work

Carbon, hydrogen, nitrogen and chlorine isotope fractionation during 3-chloroaniline transformation in aqueous environments by direct photolysis, TiO2 photocatalysis and hydrolysis

Year: 2024

Type: article

Abstract: • Multi-element isotopic fractionation (ε) ( 2 H, 13 C, 15 N, 37 Cl) of 3-CA were assessed. • Fractionation factors (ε) of 3-chloroanilin has been employed to probe reactions. • Degradation pathways of 3-CA were characterized using fractionation pattern. • The ε of direct photolysis, hydrolysis and TiO 2 photocatalysis were compared. • ME-CSIA for identification of degradation pathways in aquatic environments. This study investigates carbon, hydrogen, nitrogen and chlorine isotope fractionation during the transformation of 3-chloroaniline (3-CA) via direct photolysis, TiO 2 photocatalytic degradation at neutral condition and hydrolysis at pH 3, pH 7 and pH 11. Direct photolysis and ∙OH reaction (UV/H 2 O 2 ) showed similar inverse isotope fractionation (ε) for carbon (1.9 ± 0.4 ‰ and 1.9 ± 0.6 ‰), for hydrogen (6.9 ± 1.6 ‰ and 5.0 ± 2.6 ‰), and inverse chlorine (13.9 ± 3.8 ‰ and 11.9 ± 2.9 ‰) and no nitrogen isotope fractionation, respectively. In contrast, significantly different normal carbon (-0.5 ± 0.1 ‰), inverse hydrogen (6.6 ± 1.5 ‰), and normal nitrogen (-0.8 ± 0.2 ‰) and inverse chlorine (5.2 ± 3.7 ‰) isotope fractionations were observed for the photocatalysis of 3-CA by TiO 2 indicating a different degradation pathway as expected from ∙OH. For hydrolysis, inverse carbon (0.7 ± 0.3 ‰) and hydrogen (12.5 ± 3.3 ‰) isotope fractionation have been found at pH 3 while a normal carbon isotope fractionation was observed at pH 7 (-0.9 ± 0.3 ‰) and pH 11 (-1.3 ± 0.4 ‰), respectively. The correlation of 2 H and 13 C, 15 N and 13 C, and 37 Cl and 13 C isotope fractionation (Λ) allowed to distinguish direct photodegradation (Λ H C = -4.6 ± 1.7 (Λ H C-YORK =-5.2 ± 1.0) and Λ Cl- C = 8.7 ± 0.9 (Λ Cl-C-YORK =8.0 ± 0.3)), UV/H 2 O 2 oxidation (Λ H C = -4.7 ± 1.0 (Λ H C-YORK =-4.5 ± 0.6) and Λ Cl- C = 6.7 ± 0.8 (Λ Cl-C-YORK =7.0 ± 1.0)), UV/TiO 2 photocatalysis (Λ H C = -9.2 ± 3.1 (Λ H C-YORK =-9.3 ± 1.4), Λ Cl-C = -10.2 ± 1.5 (Λ Cl-C-YORK =-12.4 ± 1.7) and Λ N C -2.2 ± 0.3 (Λ N C-YORK =-2.3 ± 0.4)) and the modes of hydrolysis (Λ H C = 15.2 ± 5.3 (Λ H C-YORK =17.9 ± 2.9) and Λ Cl- C = 0.9 ± 0.2 (Λ Cl-C-YORK =1.1 ± 0.1) at pH 3) of 3-CA. The results were mechanistically interpreted highlighting the potential of CSIA to elucidate chemical oxidation and hydrolysis mechanisms of 3-CA.

Source: Water Research

DOI: 10.1016/j.watres.2024.122956