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Aquatic photodegradation of clofibric acid under simulated sunlight irradiation: kinetics and mechanism analysis.

ABSTRACT: Clofibric acid is one of the most frequently detected pharmaceuticals in various aquatic environments. Photodegradation of clofibric acid in water under simulated sunlight was investigated. The effects of different initial concentrations, pH conditions and dissolved oxygen were examined. Photodegradation of clofibric acid followed a pseudo-first-order kinetics model, and the rate decreased gradually with the increasing initial concentration of clofibric acid. Dissolved oxygen inhibited the photodegradation of clofibric acid. As a result of varying reaction species of clofibric acid, the initial pH conditions greatly influenced its photodegradation. Quenching experiments showed that the self-sensitization process via ·OH and ¹O₂ occured during photodegradation of clofibric acid, and the bimolecular reaction rate constants of clofibric acid with ·OH and ¹O₂ were determined via the competition kinetics method to be 3.93(±0.20) × 10⁸ and 2.38(±0.12) × 10⁶ L mol^-1 s^-1, respectively. In addition, the transformation products of clofibric acid were identified by the UPLC-Q-TOF-MS microsystem, and eight products were detected. It is proposed that the photodegradation of clofibric acid occurred mainly via decarboxylation, dechlorination, ·OH addition and ¹O₂ attack reaction.

SUBMITTER: Zhang X

PROVIDER: S-EPMC9083450 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Aquatic photodegradation of clofibric acid under simulated sunlight irradiation: kinetics and mechanism analysis.

Zhang Xiangdan X Liu Zongchao Z Kong Qingqing Q Liu Guoguang G Lv Wenying W Li Fuhua F Lin Xiaoxuan X

RSC advances 20180803 49

Clofibric acid is one of the most frequently detected pharmaceuticals in various aquatic environments. Photodegradation of clofibric acid in water under simulated sunlight was investigated. The effects of different initial concentrations, pH conditions and dissolved oxygen were examined. Photodegradation of clofibric acid followed a pseudo-first-order kinetics model, and the rate decreased gradually with the increasing initial concentration of clofibric acid. Dissolved oxygen inhibited the photo ...[more]

PMID: 35542726

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Project description:Quantum dots (QDs) are widely used in optoelectronics, lighting, and photovoltaics leading to their potential release into the environment. The most promising alternative to the highly toxic cadmium selenide (CdSe) QDs are indium phosphide (InP) QDs, which show reduced toxicity and comparable optical and electronic properties. QD degradation leads to the release of toxic metal ions into the environment. Coating the QD core with robust shell(s) composed of another semi-conductor material enhances their properties and protects the QD from degradation. We recently developed double-shelled InP QDs, which proved to be less toxic than single-shell QDs. In the present study, we confirm their reduced cytotoxicity, with an LC50 at 77 nM for pristine gradient shell QDs and >100 nM for pristine thin and thick shell QDs. We also confirm that these three QDs, when exposed to simulated sunlight, show greater cytotoxicity compared to pristine ones, with LC50 ranging from 15 to 23 nM. Using a combination of spectroscopic and microscopic techniques, we characterize the degradation kinetics and transformation products of single- and double-shell QDs, when exposed to solar light at high temperature, simulating environmental conditions. Non-toxic pristine QDs degrade to form toxic In−phosphate, In−carboxylate, Zn−phosphate, and oxidized Se, all of which precipitate as heterogeneous deposits. Comparison of their degradation kinetics highlights that the QDs bearing the thickest ZnS outer shell are, as expected, the most resistant to photodegradation among the three tested QDs, as gradient shell, thin shell, and thick shell QDs lose their optical properties in less than 15 min, 60 min, and more than 90 min, respectively. They exhibit the highest photoluminescence efficiency, i.e., the best functionality, with a photoluminescence quantum yield in aqueous solution of 24%, as compared to 18% for the gradient shell and thin shell QDs. Therefore, they can be considered as safer-by-design QDs.

Dataset Information

Aquatic photodegradation of clofibric acid under simulated sunlight irradiation: kinetics and mechanism analysis.

Publications

Aquatic photodegradation of clofibric acid under simulated sunlight irradiation: kinetics and mechanism analysis.

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