Formation of Chlorinated Intermediate from Bisphenol A in Surface Saline Water under Simulated Solar Light Irradiation

Chlorinated organic compounds are generally of great concern, but many uncertainties exist regarding how they are generated. To illustrate the possibility of photochemical formation of organochlorine compounds in natural water, the phototransformation of bisphenol A (BPA) in aqueous saline solution containing Fe(III) and fulvic acid (FA), and in coastal seawater under simulated solar light irradiation was investigated. 2-(3-Chloro-4-hydroxyphenyl)-2-(4-hydroxyphenyl) propane (3-CIBPA) and 2,2-bis(3-chloro-4-hydroxyphenyl) propane (3,3-diCIBPA) were the main chlorinated derivatives during the processes, Laser flash photolysis (LFP) and electron spin resonance (ESR) results indicated that the chlorination of BPA was most likely due to the formation of Cl-2(center dot) radical as a consequence of Fe(III) irradiation, yielding Cl-center dot and OH center dot radical species and finally forming Cl-2(center dot) radical upon further reaction with chloride, The formation of Fe(III)-FA complex, which is a normal coexistence configuration of Fe(III) and FA in natural water, promoted the BPA chlorination through producing more Cl-2(center dot) radical. Moreover, FA had two opposite effects: forming Fe (III)-FA complex to enhance Cl-2(center dot) formation and competing radicals with BPA, which resulted in different overall effects at different concentrations: BPA chlorination was enhanced with the increasing of FA concentration ([FA]) when [FA] < 3.2 mg L-1; when the concentration of FA was as high as 10 mg L-1, it slowed down obviously. The described BPA photo-chlorination process took place from pH 6.3 to 8.5 and increased with the increasing of chloride concentration, indicating it could occur universally in natural saline surface water. These results propose a natural photochemical source for organochlorine compounds.