Optimization of nimesulide oxidation via a UV-ABC/H2O2 treatment process: Degradation products, ecotoxicological effects, and their dependence on the water matrix

Exploring the phototransformation and assessing the in vitro and in silico toxicity of a mixture of pharmaceuticals susceptible to photolysis

The present study comprehensively investigates the phototransformation and ecotoxicity of a mixture of twelve pharmaceutically active compounds (PhACs) susceptible to photolysis. Namely, three antibiotics (ciprofloxacin, levofloxacin, moxifloxacin), three antidepressants (bupropion, duloxetine, olanzapine), three anti-inflammatory drugs (diclofenac, ketoprofen, nimesulide), two beta-blockers (propranolol, timolol) and the antihistamine ranitidine were treated under simulated solar irradiation in ultra-pure and river water. A total of 166 different transformation products (TPs) were identified by ultra-high performance liquid chromatography coupled with Orbitrap high resolution mass spectrometry (UHPLC-Orbitrap HRMS), revealing the formation of twelve novel TPs and forty-nine not previously described in photolytic studies. The kinetic profiles of the major TPs resulting from a series of chemical reactions involving hydroxylation, cleavage and oxidation, dehalogenation, decarboxylation, dealkylation and photo substitution have been investigated and the transformation pathways have been suggested. Additionally, an in vitro approach to the toxicity assessment of daphnids was contrasted with ecotoxicity data based on the Ecological Structure Activity Relationships (ECOSAR) software comprising the in silico tool to determine the adverse effects of the whole mixture of photolabile parent compounds and TPs. The results demonstrated that photolysis of the target mixture leads to a decrease of the observed toxicity.

Heterogeneous photocatalytic degradation of pharmaceuticals in synthetic and real matrices using a tube-in-tube membrane reactor with radial addition of H2O2

A tube-in-tube membrane reactor, with radial addition of hydrogen peroxide, was used for the oxidation of four pharmaceuticals, paracetamol (PCT), furosemide (FRS), nimesulide (NMD), and diazepam (DZP), in a continuous-mode operation, using photochemical and photocatalytic processes, driven by UVA or UVC photons. This reactor allows a controlled titration of small H₂O₂ doses (inside-out mode) to the catalyst particles immobilized in the membrane shell side and to the annular space between the membrane inner tubing and the concentric outer quartz tubing, where water to be treated flows. Tests were performed using synthetic (SWW) and real (urban wastewater after secondary treatment) (UWW) matrices, both spiked with the pharmaceutical mix solution (200 μg L^-1 of each). The photochemical and photocatalytic oxidation efficiency was evaluated as a function of H₂O₂ dose (5-20 mg L^-1), oxidant injection mode (radial permeation vs injection upstream from the reactor inlet), light source (UVA vs UVC lamps) and aqueous matrix (synthetic vs real matrix). At steady-state regime, the UVC/H₂O₂/TiO₂ system, with radial H₂O₂ addition (20 mg L^-1), showed the highest pharmaceuticals removal percentage, PCT (27.4%), FRS (35.0%), NMD (24.2%) and DZP (30.0%) in SWW. A substantial decrease in pharmaceuticals elimination was observed for UWW (PCT - 11.5%, FRS - 20.3%, NMD - 8.2% and DZP - 12.6%), in comparison with the SWW matrix. Finally, twelve transformation products (TPs) were identified; most of them showed in their structures hydroxylation in aromatic moiety; all TPs chemical structures were evaluated by BIOWIN software indicating that the TPs are non-biodegradables.

Organic Degradation Potential of Real Greywater Using TiO2-Based Advanced Oxidation Processes

In keeping with the circular economy approach, reclaiming greywater (GW) is considered a sustainable approach to local reuse of wastewater and a viable option to reduce household demand for freshwater. This study investigated the mineralization of total organic carbon (TOC) in GW using TiO2-based advanced oxidation processes (AOPs) in a custom-built stirred tank reactor. The combinations of H2O2, O3, and immobilized TiO2 under either dark or UVA irradiation conditions were systematically evaluated—namely TiO2/dark, O3/dark (ozonation), H2O2/dark (peroxidation), TiO2/UVA (photocatalysis), O3/UVA (Ozone photolysis), H2O2/UVA (photo-peroxidation), O3/TiO2/dark (catalytic ozonation), O3/TiO2/UVA (photocatalytic ozonation), H2O2/TiO2/dark, H2O2/TiO2/UVA, H2O2/O3/dark (peroxonation), H2O2/O3/UVA (photo-peroxonation), H2O2/O3/TiO2/dark (catalytic peroxonation), and H2O2/O3/TiO2/UVA (photocatalytic peroxonation). It was found that combining different treatment methods with UVA irradiation dramatically enhanced the organic mineralization efficiency. The optimum TiO2 loading in this study was observed to be 0.96 mg/cm2 with the highest TOC removal (54%) achieved using photocatalytic peroxonation under optimal conditions (0.96 mg TiO2/cm2, 25 mg O3/min, and 0.7 H2O2/O3 molar ratio). In peroxonation and photo-peroxonation, the optimal H2O2/O3 molar ratio was identified to be a critical efficiency parameter maximizing the production of reactive radical species. Increasing ozone flow rate or H2O2 dosage was observed to cause an efficiency inhibition effect. This lab-based study demonstrates the potential for combined TiO2-AOP treatments to significantly reduce the organic fraction of real GW, offering potential for the development of low-cost systems permitting safe GW reuse.

Photolysis and photocatalysis of the non-steroidal anti-inflammatory drug Nimesulide under simulated solar irradiation: Kinetic studies, transformation products and toxicity assessment

In this study, the degradation of Nimesulide (NIM), a non-steroidal anti-inflammatory drug, using photolysis, heterogeneous (TiO₂ in dispersion) and homogeneous (photo-Fenton reactant) photocatalysis, under simulated solar light (SSL) radiation, was investigated. Various parameters affecting the degradation rate of the target compound during the applied processes were optimized. The efficiency of all treatments used (direct photolysis; TiΟ₂/SSL; TiΟ₂/Η₂Ο₂/SSL; TiΟ₂/S₂Ο₈^2-/SSL; Fe³⁺/H₂O₂/SSL; Fe³⁺/S₂O₈^2-/SSL and [Fe(C₂O₄)₃]^3-/H₂O₂/SSL) was evaluated by means of initial reaction rate and mineralization. Moreover, the generated transformation products (TPs) by each basic process (photolysis; TiΟ₂/SSL and Fe³⁺/H₂O₂/SSL) were identified, using liquid chromatography coupled to high resolution mass spectrometry, and their formation kinetic profiles were given. The main transformation routes of NIM were hydroxylation and fragmentation, for all three treatments applied. Finally, toxicity measurements were conducted using Microtox bioassay in order to evaluate the potential risk of NIM and its TPs to aqueous organisms. Although, the acute toxicity increased during the first stages of treatment the final outcome lead to very low toxicity levels even within 60 min of TiO₂/SSL treatment. Concluding, the obtained results suggest that the photocatalytic degradation of NIM can lead to its complete elimination and simultaneously to the detoxification of the solution.

Elimination of trichloroanisoles by UV/H2O2: Kinetics, degradation mechanism, water matrix effects and toxicity assessment

The elimination of 2,3,6-trichloroanisole (2,3,6-TCA), which produces a musty-earthy off-odor in water, by an ultraviolet (UV)/H₂O₂ process was assessed. The removal of 88.1% of 2,3,6-TCA in ultrapure water (UPW) was achieved using an initial 2,3,6-TCA concentration of 1 μg L^-1 (4.73 nM), a H₂O₂ concentration of 20 mg L^-1 (0.588 mM), a UV intensity of 1.44 mW cm^-2 and a pH of 8.2. The reaction was found to be pseudo first order with a rate constant (k_obs) of 0.0340 min^-1. Both the removal efficiency and k_obs increased significantly upon increasing the H₂O₂ concentration from 10 to 50 mg L^-1. The second order rate constant (k_{HO·,2,3,6-TCA}) in competition kinetic trials was determined to be 8.17 × 10⁷ M^-1s^-1. Degradation products generated during both the UV photolysis and UV/H₂O₂ treatment of 2,3,6-TCA solutions were analyzed using ultrahigh resolution gas chromatography/mass spectrometry, and the degradation mechanism was proposed. The toxicities of water solutions during both processes were assessed via a luminescence method in conjunction with Vibrio fischeri. The pH and Cl^-, HCO₃^- and natural organic matter concentrations of the aqueous medium were all found to significantly affect the removal of 2,3,6-TCA. The degradation rates of trichloroanisoles (TCAs) in real-world water samples demonstrated that UV/H₂O₂ has significant potential with regard to controlling TCAs as pollutants in water.

H2O2-assisted photoelectrocatalytic degradation of Mitoxantrone using CuO nanostructured films: Identification of by-products and toxicity

CuO nanostructured thin films supported on silicon with 6.5 cm² area (geometric area greater than the studies reported in the literature) were synthesized by a chemical bath deposition technique. The electrodes were characterized by MEV, XRD, XPS, contact angle, cyclic voltammetry and electrochemical impedance spectroscopy analyses. To evaluate the photoelectrochemical properties of the CuO films, photocurrent-voltage measurements were performed using linear voltammetry. The catalytic activities of CuO nanostructures were evaluated by monitoring photodegradation of Mitoxantrone (MTX) under UV-A light irradiation. The method of photoelectrocatalysis (PEC), applying a voltage of 1.5 V and assisted by adding H₂O₂, was undertaken. To the best of our knowledge, no studies on the degradation of anticancer agents using PEC process have been found in the literature. For comparison purposes, experiments were performed under the same conditions by assisted photocatalysis (PC) with H₂O₂ and direct photolysis. CuO deposits consist of a needle-like morphology. The presence of CuO in the tenorite phase was evidenced by XRD and the XPS spectra showed the presence of copper(II) oxide. The increase in current under illumination shows that CuO exhibits photoactivity. The PEC system showed a 75% level of MTX degradation, while the level achieved using PC was 50%. Under UV-A light alone only 3% removal was obtained after 180 min. Up to 10 by-products were identified by chromatography-mass spectrometry (LC-MS) with m/z values ranging between 521 and 285 and a plausible degradation route has been proposed. It is worth mentioning that 9 by-products identified in this work, were not found in the literature in other studies of degradation or products generated as metabolites. The toxicity tests of MTX before and after PEC treatment with Artemia Salina and Allium cepa showed a decrease in the acute toxicity of the medium as the antineoplastic was degraded.