Photocatalytic degradation of pharmaceutical and person care products (PPCPs) by commercial and synthesized catalysts under UV irradiation
Wang, Zhao (2023-07-06)
Väitöskirja
06.07.2023
Lappeenranta-Lahti University of Technology LUT
Acta Universitatis Lappeenrantaensis
School of Engineering Science
School of Engineering Science, Kemiantekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-335-950-5
https://urn.fi/URN:ISBN:978-952-335-950-5
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Tiivistelmä
Nowadays, with the rapid development of society, more and more chemical products have been developed and applied to people’s daily lives. Among them, pharmaceuticals and personal care products (PPCPs) are the ones that are the most closely related to human daily life. PPCPs have been detected in water environments both in developing and developed countries. This work aimed to enhance photocatalytic degradation of selected PPCPs (ibuprofen (IBP), benzophenone-3 (BP-3) and carbamazepine (CBZ)) in an aqueous matrix by utilizing UV light generated by LED lamps and by developing novel photocatalytic particles as well as by applying commercially available photocatalytic particles. The properties of catalytic particles are characterized and used to understand photocatalytic phenomena. The dominating oxidants in the photocatalysis and degradation mechanisms of selected PPCPs are identified.
The commercial catalysts, titanium oxide (TiO2) and zinc oxide (ZnO) significantly improved the degradation of ibuprofen (IBP) under UV light. UV light treatment alone enabled 30–40% degradation of IBP, but almost completely degradation was achieved with a catalyst. It was also shown that in acidic conditions higher degradation can be achieved. Both catalysts had the same efficiency on the degradation of IBP and the same by-product 1-(1-hydroxyethyl)-4-isobutylbenzene was identified from both UVLED/ TiO2 and UV-LED/ZnO catalyzed degradation processes. 1-(1-hydroxyethyl)-4- isobutylbenzene is biodegradable and less toxic than IBP.
Novel Sb2O3/TiO2 catalysts were synthesized aiming to reduce the bandgap energy of commercial catalysts. The synthesized catalysts were tested for the degradation of benzophenone-3 (BP-3) under UV irradiation. The best degradation efficiency of about 80% was achieved when the ratio of Sb2O3 and TiO2 was 2:1. This ratio led to the highest specific surface area (200 m2/g) and the smallest band gap energy (2.65 eV) of the studied catalysts which improved the photocatalytic properties of Sb2O3/TiO2. Furthermore, 1O2 was the main radical for BP-3 degradation. A non-toxic benzyl alcohol was identified as a by-product in the BP-3 degradation process.
To improve the efficiency of the Sb2O3/TiO2 catalyst, Nd-doping was carried out during the synthesis of the catalyst. The Nd-doping improved the photocatalytic degradation of carbamazepine (CBZ) by about 10% compared to undoped Sb2O3/TiO2 catalyst. At the best, 88% of the CBZ was eliminated after 120 minutes of UV treatment with 0.5 g 1% Nd-doped Sb2O3 /TiO2 catalyst. A hydroxyl radical and 1O2 were main radicals for CBZ degradation. Acridine-N-carbaldehyde was identified as a by-product from the CBZ degradation and it is a toxic compound found in water pollutants.
The results suggested that the radicals that participated in the oxidation reactions were different with synthetized Sb2O3/TiO2 and doped Sb2O3/TiO2 catalysts. 1O2 was the main radical for the BP-3 degradation and no hydroxyl radicals were observed with synthetized Sb2O3/TiO2 but when the same catalyst was Nd-doped both 1O2 and hydroxyl radicals were observed and role of hydroxyl radical was shown to be dominant.
The photocatalytic degradation of IBP and BP-3 generated less toxic and more biodegradable by-products, but the oxidation of CBZ led to toxic by-products. Therefore, not only the degradation of the original PPCPs but also their degradation by-products should be taken into account when usability of photocatalysis is evaluated.
The commercial catalysts, titanium oxide (TiO2) and zinc oxide (ZnO) significantly improved the degradation of ibuprofen (IBP) under UV light. UV light treatment alone enabled 30–40% degradation of IBP, but almost completely degradation was achieved with a catalyst. It was also shown that in acidic conditions higher degradation can be achieved. Both catalysts had the same efficiency on the degradation of IBP and the same by-product 1-(1-hydroxyethyl)-4-isobutylbenzene was identified from both UVLED/ TiO2 and UV-LED/ZnO catalyzed degradation processes. 1-(1-hydroxyethyl)-4- isobutylbenzene is biodegradable and less toxic than IBP.
Novel Sb2O3/TiO2 catalysts were synthesized aiming to reduce the bandgap energy of commercial catalysts. The synthesized catalysts were tested for the degradation of benzophenone-3 (BP-3) under UV irradiation. The best degradation efficiency of about 80% was achieved when the ratio of Sb2O3 and TiO2 was 2:1. This ratio led to the highest specific surface area (200 m2/g) and the smallest band gap energy (2.65 eV) of the studied catalysts which improved the photocatalytic properties of Sb2O3/TiO2. Furthermore, 1O2 was the main radical for BP-3 degradation. A non-toxic benzyl alcohol was identified as a by-product in the BP-3 degradation process.
To improve the efficiency of the Sb2O3/TiO2 catalyst, Nd-doping was carried out during the synthesis of the catalyst. The Nd-doping improved the photocatalytic degradation of carbamazepine (CBZ) by about 10% compared to undoped Sb2O3/TiO2 catalyst. At the best, 88% of the CBZ was eliminated after 120 minutes of UV treatment with 0.5 g 1% Nd-doped Sb2O3 /TiO2 catalyst. A hydroxyl radical and 1O2 were main radicals for CBZ degradation. Acridine-N-carbaldehyde was identified as a by-product from the CBZ degradation and it is a toxic compound found in water pollutants.
The results suggested that the radicals that participated in the oxidation reactions were different with synthetized Sb2O3/TiO2 and doped Sb2O3/TiO2 catalysts. 1O2 was the main radical for the BP-3 degradation and no hydroxyl radicals were observed with synthetized Sb2O3/TiO2 but when the same catalyst was Nd-doped both 1O2 and hydroxyl radicals were observed and role of hydroxyl radical was shown to be dominant.
The photocatalytic degradation of IBP and BP-3 generated less toxic and more biodegradable by-products, but the oxidation of CBZ led to toxic by-products. Therefore, not only the degradation of the original PPCPs but also their degradation by-products should be taken into account when usability of photocatalysis is evaluated.
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