Comparison of Photocatalytic and Photosensitized Oxidation of Paraben Aqueous Solutions Under Sunlight

Abstract

It is well-established that aquatic wildlife is exposed to natural and synthetic endocrine disrupting compounds which are able to interfere with the hormonal system. Although advanced oxidation processes (AOPs) have shown to be effective, their application is limited by a relatively high operational cost. In order to reduce the cost of energy consumed in the AOPs, widely available solar energy instead of UV light may be applied either as photocatalytic oxidation or as photosensitized oxidation. The main goal of the present study was to investigate the sunlight photodegradation of paraben mixture. Two processes, namely the photocatalytic oxidation with modified TiO2 nanoparticles and photosensitized oxidation with photosensitive chitosan beads, were applied. The oxidants were identified as singlet oxygen and hydroxyl radicals for photosensitized and photocatalytic oxidation, respectively. The toxicity, as well as ability to water disinfection of both processes under natural sunlight, has been investigated. Application of sunlight for the processes led to degradation of parabens. The efficiency of both processes was comparable. Despite the fact that singlet oxygen is weaker oxidant than hydroxyl radicals, the photosensitized oxidation seems to be more promising for wastewater purification, due to the possibility of chitosan bead reuse and more effective water disinfection. Graphical Abstractᅟ Electronic supplementary materialThe online version of this article (10.1007/s11270-018-3991-y) contains supplementary material, which is available to authorized users.

Comparison of radical-driven technologies applied for paraben mixture degradation: mechanism, biodegradability, toxicity and cost assessment

“…3b). Also, higher degradation was achieved in the case of TiO 2 -Pt rather than for TiO 2 -Ag, indicating that this photocatalyst has better visible light photocatalytic ability (Foszpańczyk et al 2018). However, the highest improvement has been observed for TiO 2 -Au, proving that the modification by Au increases the visible light ability, which is in agreement with absorption spectra.…”

“…Based on literature data, the most effective method of removing them is chemical oxidation using reactive oxygen species generated using ultraviolet (UV) or visible (Vis) radiation or ozone (Nakada et al 2007;Gottschalk et al 2010;Nawrocki and Kasprzyk-Hordern 2010;Tay et al 2010;Gmurek et al 2015Gmurek et al , 2017Wang and Wang 2016;Pipolo et al 2017;Gomes et al 2017a;Wang et al 2018;Foszpańczyk et al 2018). These methods often allow to obtain products more susceptible to biodegradation.…”

“…Nowadays, the best catalyst is sought; for example, the addition of a second semiconductor will shift the spectrum absorbed by the semiconductor towards the visible light. Moreover, photocatalyst surface modifications by metals are affected by changing the distribution of electrons on the properties of the semiconductor, which increases the photodegradation activity (Nawrocki and Kasprzyk-Hordern 2010;Grabowska et al 2016;Gmurek et al 2017;Gomes et al 2017b;Foszpańczyk et al 2018).…”

Solar Photocatalytic Degradation of Sulfamethoxazole by TiO2 Modified with Noble Metals

“…The catalysts used in this study were previously investigated with respect to parabens [25,26]. In this study, mineralization of parabens with 0.5% Pd/TiO2 was only 25% and less than 10% after exposure to UVA (3 h) and sunlight (2 h), respectively, when 70 mg/L of catalyst was applied.…”

“…Some studies with TiO 2 modified with noble metals have already been conducted. Photocatalytic oxidation with pure and TiO 2 modified with Ag, Au, Pd, and Pt for parabens mixture under UV-A [25], as well as natural sunlight [26], proved that the catalysis enhances the elimination of these compounds as compared with direct photolysis. Improved elimination efficiency was also reported with respect to trimethoprim in the process with Au, Ag, Cu, and Ni nanoparticles deposited on the TiO 2 surface [27].…”