Photocatalytic Transformations of 1H-Benzotriazole and Benzotriazole Derivates

Comparison of benzotriazole ultraviolet stabilizers (BUVs) removal from wastewater after subsequent stages of sequencing batch reactor (SBR) treatment process

The research focused on benzotriazole ultraviolet stabilizers (BUVs) which are commonly used compounds despite being found dangerous, e.g. promoting breast cancer cell proliferation, damaging vital organs such as hearts, brains livers and kidneys. The aim of the study was to analyse the efficiency and removal rate of BUVs from wastewater depending on the quantity of tested compounds and SBR anaerobic-aerobic conditions. The study was conducted in sequencing batch reactors (SBRs - 17 L) with real flocculent activated sludge (8 L) and model wastewater (5 L) containing UV-326, UV-327, UV-328, UV-329 and UV-P from 50 to 600 μg∙L-1. The SBR were operated in 390 cycles of 7 h and 10 min over 130 days. The similarity of the technological parameters of the treatment process to those used in a real wastewater treatment plant was maintained. Efficiency removal of individual BUVs was strictly dependent on the dose of compounds introduced into wastewater and ranged from 68.2 to 97 %. Removal of UV-329 occurred with lowest efficiency (from 68.2 to 85.2 %) while UV-326 was most efficiently removed from the wastewater (from 94.1 to 97 %). UV-329 was removed from wastewater with the lowest (0.0968-0.9524 μg∙L-1∙min-1) average removal rate while UV-327 with the highest (0.16-1.3357 μg∙L-1∙min-1), irrespective of BUVs dose in the influent. Secondary release of BUVs into the wastewater occurred in SBR during the settling phase and was dependent on the type and concentration of the BUVs in the raw wastewater. This occurrence was noted for UV-326 ≥ 100; UV-327 = 600; UV-328 ≥ 200; UV-329 ≥ 50 and UV-P ≥ 100 μg∙L-1. The settling phase needs to be shortened to the required minimum. This is an important conclusion for WWTPs in regards to SBR cycle duration and technological parameters of the treatment process.

Solar photocatalysis application in UWWTP outlets - simulations based on predictive models in flat-plate reactors and pollutant degradation studies with in silico toxicity assessment

The application of the solar photocatalysis for the degradation of residual pollutants found in surface water was demonstrated. Semi-pilot scale flat-plate cascade reactor (FPCR) was used to study the degradation of model organic pollutants: enrofloxacin (ENRO), 17β-estradiol (E2) and 1H-benzotriazole (1H-BT) over TiO2 thin-film supported on glass fibers. A modular panel with full-spectra solar lamps with appropriate UVB and UVA irradiation levels was used as a simulation of sunlight. Pollutant degradation in FPCR was estimated using predictive models; intrinsic reaction rate constants (ki) for ENRO, E2 and 1H-BT independent of the reactor size, flow rate and irradiation conditions were determined: 9.60, 3.35 and 0.37 109 s-1 W-0.5 m1.5, respectively. Main degradation products (DPs), formed upon hydroxylation, ring opening and oxidation, were identified using LC-QTOF-MS. The ecotoxicological impact was assessed via T.E.S.T. and ECOSAR open-source tools showing the formation of less harmful DPs after sufficient reaction time. Pollutant degradation was simulated at four locations of interest, i.e. exhausts from urban wastewater treatment plants (UWWTPs) in Zagreb, Croatia (45°N), Krakow, Poland (50°N), Sevilla, Spain (37°N) and Ioannina, Greece (39.6°N). Results have proved that a simple flat-plate system with supported photocatalysts can be easily scaled up and incorporated at the outlet of UWWTP for the reduction of pollutant load and related toxicity. The exhaust canal in Zagreb with the estimated length of a photocatalytic layer of 122 m for the > 90% degradation of all target pollutants was discussed as the best installation site among studied locations. ENVIRONMENTAL IMPLICATION: A multi-disciplinary approach to the tentative application of TiO2 solar photocatalysis outdoors to reduce pollutant loads and toxicity in surface waters was demonstrated. Possible application at four selected locations in Europe, as an additional step in water treatment after urban wastewater treatment plants (UWWTPs) was discussed. Target pollutants were studied under environmentally relevant conditions (sunlight levels, water matrix, simulation of process on a real scale at selected geographical location), at both higher and low concentrations.

Study of Photocatalytic Oxidation of Micropollutants in Water and Intensification Case Study

During the last decades, heterogenous photocatalysis has shown as the most promising advanced oxidation process for the removal of micropollutants due to degradation rate, sustainability, non-toxicity, and low-cost. Synergistic interaction of light irradiation, photocatalysts, and highly reactive species are used to break down pollutants toward inert products. Even though titanium dioxide (TiO2) is the most researched photocatalyst, to overcome shortcomings, various modifications have been made to intensify photocatalytic activity in visible spectra range among which is modification with multiwalled carbon nanotubes (MWCNTs). Therefore, photocatalytic oxidation and its intensification by photocatalyst’s modification was studied on the example of four micropollutants (diclofenac, DF; imidacloprid, IMI; 1-H benzotriazole, BT; methylene blue, MB) degradation. Compound parabolic collector (CPC) reactor was used as, nowadays, it has been considered the state-of-the-art system due to its usage of both direct and diffuse solar radiation and quantum efficiency. A commercially available TiO2 P25 and nanocomposite of TiO2 and MWCNT were immobilized on a glass fiber mesh by sol-gel method. Full-spectra solar lamps with appropriate UVB and UVA irradiation levels were used in all experiments. Photocatalytic degradation of DF, IMI, BT, and MB by immobilized TiO2 and TiO2/CNT photocatalysts was achieved. Mathematical modelling which included mass transfer and photon absorption was applied and intrinsic reaction rate constants were estimated: kDF=3.56 × 10−10s−1W−0.5m1.5, kIMI=8.90 × 10−11s−1W−0.5m1.5, kBT=1.20 × 10−9s−1W−0.5m1.5, kMB=1.62 × 10−10s−1W−0.5m1.5. Intensification of photocatalysis by TiO2/CNT was observed for DF, IMI, and MB, while that was not the case for BT. The developed model can be effectively applied for different irradiation conditions which makes it extremely versatile and adaptable when predicting the degradation extents throughout the year using sunlight as the energy source at any location.

New Organic Materials Based on Multitask 2H-benzo[d]1,2,3-triazole Moiety

Multifunctionality is a desirable aspect in materials science. Indeed, the development of multifunctional compounds is crucial for sustainable chemistry by saving resources and time. In this sense, 2H-benzo[d]1,2,3-triazole (BTz) is an excellent candidate with promising characteristics, including its ability to self-assemble; its acceptor character, which enables the synthesis of donor-acceptor structures; and its facile modulation using standard chemical methods. Thus, due to its interesting properties, it is possible to produce different derivatives with applications in different fields, as summarized in this article, with the correct substitution at the BTz cores. Optoelectronic or biomedical applications, amongst others, are highlighted.

Hydrothermal Synthesis of FeOOH and Fe2O3 Modified Self-Organizing Immobilized TiO2 Nanotubes for Photocatalytic Degradation of 1H-Benzotriazole

In this study, titanium dioxide nanotubes were prepared by electrochemical anodization technique and modified with an aqueous solution of FeCl3 using hydrothermal synthesis method to control the amount and distribution of iron compounds on the anatase TiO2 nanotubes. The objective was to synthesize immobilized FeOOH@TiO2 or Fe2O3@TiO2 photocatalysts designed for the flow-through reactor systems; to investigate thermal treatment effect on the photocatalytic efficiency; to determine appropriate Fe-compounds concentration for the maximum photocatalytic activity improvement, and to explain the mechanism responsible for the enhancement. The photocatalysts were tested for the degradation of 1H-benzotriazole in water under UV/solar light irradiation. Up to two times increase in the photocatalytic activity was obtained when TiO2 nanotubes were modified with 0.8 mM Fe. At higher Fe concentrations (8 mM and 80 mM), the photocatalytic activity of the given photocatalysts decreased. To confirm the formation of FeOOH or Fe2O3 species, and to clarify the mechanism of photoactivity, X-ray diffraction (XRD), Raman spectroscopy (RS), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDS) and UV-Vis spectroscopy were used.