title: Quantum chemical investigation and experimental verification on the aquatic photochemistry of the sunscreen 2-phenylbenzimidazole-5-sulfonic acid.
abstract: For ecological risk assessment of the large and ever-increasing number of chemical pollutants, it is of importance to develop computational methods to screen or predict their environmental photodegradation behavior. This study developed a computational method based on the density functional theory (DFT) to predict and evaluate the photodegradation behavior and effects of water constituents, taking a sunscreen and personal care product 2-phenylbenzimidazole-5-sulfonic acid (PBSA) as a model compound. Energy and electron transfer reactions of excited state PBSA (PBSA*) with (3)O(2) and water constituents were evaluated. The computational results indicated that PBSA* could photogenerate (1)O(2) and O(2)(-)·, triplet excited state humic/fulvic acid analogs could not photosensitize the degradation, and the anions (Cl(-), Br(-), and HCO(3)(-)) could not quench PBSA* or its radical cation chemically. Experiments employing simulated sunlight confirmed that PBSA photodegraded via the direct and self-sensitization mechanism involving O(2)(-)·. The photodegradation was pH-dependent. The direct and self-sensitized photodegradation was inhibited by fulvic acid. The main photodegradation products were identified, and the pathways were clarified. These results indicate that the DFT-based computational method can be employed to assess the environmental photochemical fate of organic pollutants.
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, PR China.
authors.forename: Siyu
authors.initials: S
authors.lastname: Zhang
authors.forename: Jingwen
authors.initials: J
authors.lastname: Chen
authors.forename: Xianliang
authors.initials: X
authors.lastname: Qiao
authors.forename: Linke
authors.initials: L
authors.lastname: Ge
authors.forename: Xiyun
authors.initials: X
authors.lastname: Cai
authors.forename: Guangshui
authors.initials: G
authors.lastname: Na
mesh_terms: D001562:Benzimidazoles / Q000737:chemistry*; D010777:Photochemistry; D011789:Quantum Theory; D013451:Sulfonic Acids / Q000737:chemistry*; D013473:Sunscreening Agents / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D001562:Benzimidazoles; D013451:Sulfonic Acids; D013473:Sunscreening Agents; D014874:Water Pollutants, Chemical; C499767:ensulizole