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Photocatalytic degradation of ibuprofen using titanium oxide: insights into the mechanism and preferential attack of radicals. | LitMetric

Photocatalytic degradation of ibuprofen using titanium oxide: insights into the mechanism and preferential attack of radicals.

RSC Adv

Laboratório de Peneiras Moleculares (LABPMOL), Programa de Pós-graduação em Química, Universidade Federal do Rio Grande do Norte (UFRN) Av. Sen. Salgado FIlho, Campus Universitário, Lagoa Nova 59.078-970 Natal RN Brazil +55 84 933422323.

Published: August 2021

AI Article Synopsis

  • - The study examined how titanium dioxide works as a photocatalyst to degrade ibuprofen, detailing the preferred attack sites of hydroxyl radicals (OH˙) on the ibuprofen molecule and identifying the formation of different by-products, including 4-isobutylacetophenone.
  • - Successful photodegradation occurred at pH 5.0 using 0.03 g of titanium dioxide, achieving complete decontamination of ibuprofen in just 5 minutes, with the zeta potential curve revealing how pH affects the interaction between TiO and ibuprofen, influencing by-product formation.
  • - The proposed degradation mechanism involves a series of reactions with multiple radicals (OH˙, O˙, OOH˙)

Article Abstract

The present work studied ibuprofen degradation using titanium dioxide as a photocatalyst. Mechanistic aspects were presented and the preferred attack sites by the OH˙ radical on the ibuprofen molecule were detailed, based on experimental and simple theoretical-computational results. Although some previous studies show mechanistic proposals, some aspects still need to be investigated, such as the participation of 4-isobutylacetophenone in the ibuprofen degradation and the preferred regions of attack by OH˙ radicals. The photodegradation was satisfactory using 0.03 g of TiO and pH = 5.0, reaching 100% decontamination in 5 min. The zeta potential curve showed the regions of attraction and repulsion between TiO and ibuprofen, depending on the pH range and charge of the species, influencing the amount of by-products formed. Different by-products have been identified by GC-MS, such as 4-isobutylacetophenone. Ibuprofen conversion to 4-isobutylacetophenone takes place through decarboxylation reaction followed by oxidation. The proposed mechanism indicates that the degradation of ibuprofen undergoes a series of elementary reactions in solution and on the surface. Three different radicals (OH˙, O ˙ and OOH˙) are produced in the reaction sequence and contribute strongly to the oxidation and mineralization of ibuprofen and by-products, but the hydroxyl radical has a greater oxidation capacity. The simple study using the DFT approach demonstrated that the OH˙ radical attacks preferentially in the region of the ibuprofen molecule with high electronic density, which is located close to the aromatic ring (C[double bond, length as m-dash]C bond). The presence of the OH˙ radical was confirmed through a model reaction using salicylic acid as a probe molecule.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9037810PMC
http://dx.doi.org/10.1039/d1ra04340dDOI Listing

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