Photochlorination of aniline in Fe3+-containing saline water under simulated solar light irradiation

Abstract

Environmental context. Aromatic amines are widely used chemicals, which show enhanced toxicity and longer environmental persistence when halogenated. We investigated the chlorination of aniline in seawater and in natural aqueous solutions containing Fe 3þ and Cl À , under simulated sunlight irradiation. The results increase our understanding of the transformation pathway of typical nitrogen-containing aromatic contaminants in the environment.Abstract. Photochlorination of aniline was observed in aqueous solutions containing dissolved Fe III and chloride ions under simulated solar light irradiation. Effects of O 2 , Cl À , Fe 3þ and pH on the formation of chloroanilines (CAs) were investigated. para-chloroaniline (4CA) was identified as the main chlorinated product. The formation of 4CA is enhanced with increased concentrations of Cl À or Fe 3þ , and decreased pH, whereas oxygen plays a negligible role in the process. The results indicate that, Cl is formed mainly by the photodissociation of FeCl 2þ -FeCl 2 þ complexes, and reacts with Cl À to produce Cl 2 À . Aniline is then oxidised by Cl 2 À into an anilino radical cation, which further reacts with Cl 2 À to generate CAs. The photochlorination of aniline in natural seawater was also observed. Other phototransformation products of aniline were detected and a transformation pathway was proposed. This work provides evidence for the photochemical chlorination path of aniline-based aromatic amines in aqueous solutions.

Self-sensitized photochlorination of benzo[a]pyrene in saline water under simulated solar light irradiation

“…In previous studies, the amount of chlorinated products formed correlated with the amount of chlorine radicals generated and with the rates of the reactions between the organic compounds and chlorine radicals at different pH values. In Fe-containing saline water, a low pH facilitated the formation of chlorine radicals under photoirradiation, resulting in the production of more chlorinated product (Liu et al, 2009;Wu and Hu, 2012). In an AgCl particle system, the formation of chlorine radicals was independent of the pH (Hu et al, 2015).…”

“…•− might be involved in the chlorination of aniline (Wu and Hu, 2012). However, no chlorinated aniline was detectable when aniline was added to the BaP photochlorination system.…”

“…Natural seawater is particularly rich in chloride ions, which greatly influence the transformation of various species in an aqueous environment under irradiation. To organic compounds that can not absorb solar light, chlorine radicals originating from other photosensitive substances are likely responsible for their chlorination (Vione et al, 2005;Wu and Hu, 2012;Hu et al, 2015). Our previous work investigated the photoreaction of aniline in aqueous solutions containing Ag + /Fe 3+ and Cl − under simulated sunlight irradiation (Wu and Hu, 2012;Hu et al, 2015), where chlorine radicals originating from the photolysis of Ag-Cl/Fe-Cl complex were responsible for aniline chlorination.…”

“…To organic compounds that can not absorb solar light, chlorine radicals originating from other photosensitive substances are likely responsible for their chlorination (Vione et al, 2005;Wu and Hu, 2012;Hu et al, 2015). Our previous work investigated the photoreaction of aniline in aqueous solutions containing Ag + /Fe 3+ and Cl − under simulated sunlight irradiation (Wu and Hu, 2012;Hu et al, 2015), where chlorine radicals originating from the photolysis of Ag-Cl/Fe-Cl complex were responsible for aniline chlorination. No chloroaniline was detectable in the absence of Ag + /Fe 3+ because aniline and Cl − are unable to absorb solar light effectively.…”

The treatment of aniline in aqueous solutions by gamma irradiation

“…Their tests revealed that sunlight is more effective than ultraviolet light in the photocatalytic oxidation of aniline. Other research projects have combined methods for degradating aniline with such processes as ozone/UV oxidation [9], electro-Fenton [10,11], photocatalytic processes [12,13] and γ/enzymatic hydrolysis [14].…”