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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/207487
Abatement of bisphenol analogues through ozone, hydroxyl radical and UV radiation in water: Kinetics, transformation products and toxicity
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[eng] Bisphenol A (BPA) has been one of the most produced chemicals during the last decades. However, as a result of its endocrine-disrupting behaviour, the use of this compound was restricted by legislation in different countries. To face restrictions, BPA has been replaced by other bisphenol analogues, such as bisphenol AF (BPAF), bisphenol AP (BPAP), bisphenol B (BPB), bisphenol C (BPC), bisphenol C-Cl (BPC-Cl), bisphenol E (BPE), bisphenol F (BPF), bisphenol S (BPS) and bisphenol Z (BPZ).
These substitutes are expected to exhibit similar endocrine-disrupting effects compared to BPA, as the chemical structure of all bisphenol analogues is similar. In fact, some of them exhibit even higher estrogenic activity than that of BPA. Additionally, the extended use of its substitutes is resulting in the increase of their occurrence in aquatic environments. Considering these facts, the replacement of BPA by other bisphenol analogues is environmentally concerning, evidencing the requirement to study several removal strategies. Thus, this thesis evaluated the abatement of these BPA substitutes through some of the most efficient and technologically mature treatments, such as ozonation, UV/H2O2 and UV processes. This included the evaluation of the reactivity, the identification of the main transformation products (TPs) and the assessment of the resulting toxicity.
The reactivity of ozone with bisphenol A substitutes resulted high under basic pH conditions (k = 8.83 x 108 - 1.43 x 109 M-1 s-1), while it decreased significantly at strong acidic pH (k = 5.01 - 1.22 x 105 M-1 s-1). This arises from the lower electron density placed in the phenol rings of the di-protonated species, resulting in lower reactivity with ozone. Then, the reactivity of hydroxyl radical with bisphenols under neutral pH conditions was determined to be high and similar for all bisphenols ((5.89 - 14.1) x 109 M-1 s-1). On the other hand, the efficiency of the UV-photolysis treatment ( λ = 254 nm) for the removal of these bisphenols at pH 7 was generally low, as well as the determined values of the quantum yield ((4.8 - 28.7) x 10-3 mol E-1). One exception was the favoured photolysis of BPC-Cl, whose determined value of the quantum yield was 4.7 x 10-1 mol E-1, which is approximately 45 times higher than that of BPA.
Regarding the elucidation of the main transformation products, hydroxylation was distinguished as the main degradation pathway of bisphenol analogues by ozone and
hydroxyl radical. Generally, this resulted in the formation of catechol and ortho-quinone derivatives as primary and most relevant TPs. Excluding the case of BPC-Cl, the detected TPs from the photolysis of bisphenols were equivalent to those from the UV/H2O2 treatment. This suggests the involvement of hydroxyl radical during their photolytic removal. On the other hand, BPC-Cl presented a unique photolysis mechanism, which is based on the favoured cleavage of the C-Cl bonds under UV radiation. Among the detected TPs, phenanthrene-3,6-diol was suggested as the most relevant initial product.
Considering the toxicity assessment, the acute toxicity and endocrine-disrupting activity were experimentally evaluated during the oxidation of BPA, BPAF and BPC-Cl by ozone, and throughout the UV-photolysis of BPC-Cl. This was conducted by the exposure of zebrafish eleutheroembryos to several treatment samples, with the subsequent determination of the survival and swim bladder inflation rates and the execution of transcriptomic analysis. Results demonstrated that ozone is able to reduce the acute toxicity and the endocrine-disrupting activity of these bisphenols. The acute toxicity of BPC-Cl and most of the altered biological pathways in zebrafish eleutheroembryos were also mitigated during its photolysis treatment. However, the estrogenic activity increased significantly, indicating that certain of its photolysis products may exhibit higher estrogenic activity than the parent compound.
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PORCAR SANTOS, Oriol. Abatement of bisphenol analogues through ozone, hydroxyl radical and UV radiation in water: Kinetics, transformation products and toxicity. [consulta: 5 de desembre de 2025]. [Disponible a: https://hdl.handle.net/2445/207487]