Degradation of the nonsteroidal anti-inflammatory drug piroxicam from environmental matrices with UV-activated persulfate

Neem plant extract-assisted synthesis of CeO2 nanoparticles for photocatalytic degradation of piroxicam and naproxen

Piroxicam and naproxen are well-known non-steroidal anti-inflammatory drugs that are frequently detected in aquatic environments due to their widespread usage and improper disposal practices. This research investigates the photocatalytic degradation of these drugs by using CeO2 nanoparticles. The nanoparticles were synthesized by using Azadirachta indica plant extract and were characterized through various characterization techniques such as UV-visible spectroscopy, FTIR spectroscopy, SEM, EDX, and XRD. The photocatalytic degradation of piroxicam and naproxen using CeO2 nanoparticles led to the efficient removal of these pharmaceutical drugs in a short time duration with photodegradation efficiencies of 89% and 97% for naproxen and piroxicam, respectively. The photodegradation reaction was found to follow pseudo-order first-order kinetics. The recyclability of the catalyst was also studied for up to six cycles where the degradation efficiency was maintained at 100% till the 2nd cycle and was decreased by 11 and 13% for piroxicam and naproxen respectively after the 6th cycle. The current work focused on the achievement of sustainable development goals (SDGs) for water purification via environmentally benign nanoparticles to remedy water pollution as it is the most prevalent issue in developed and underdeveloped countries throughout the world.

Degradation of Antibiotics via UV-Activated Peroxodisulfate or Peroxymonosulfate: A Review

The ultraviolet (UV)/H2O2, UV/O3, UV/peroxodisulfate (PDS) and UV/peroxymonosulfate (PMS) methods are called UV-based advanced oxidation processes. In the UV/H2O2 and UV/O3 processes, the free radicals generated are hydroxyl radicals (•OH), while in the UV/PDS and UV/PMS processes, sulfate radicals (SO4•−) predominate, accompanied by •OH. SO4•− are considered to be more advantageous than •OH in degrading organic substances, so the researches on activation of PDS and PMS have become a hot spot in recent years. Especially the utilization of UV-activated PDS and PMS in removing antibiotics in water has received much attention. Some influencing factors and mechanisms are constantly investigated and discussed in the UV/PDS and UV/PMS systems toward antibiotics degradation. However, a systematic review about UV/PDS and UV/PMS in eliminating antibiotics is lacking up to now. Therefore, this review is intended to present the properties of UV sources, antibiotics, and PDS (PMS), to discuss the application of UV/PDS (PMS) in degrading antibiotics from the aspects of effect, influencing factors and mechanism, and to analyze and propose future research directions.

A comprehensive review on persulfate activation treatment of wastewater

With increasingly serious environmental pollution and the production of various wastewater, water pollutants have posed a serious threat to human health and the ecological environment. The advanced oxidation process (AOP), represented by the persulfate (PS) oxidation process, has attracted increasing attention because of its economic, practical, safety and stability characteristics, opening up new ideas in the fields of wastewater treatment and environmental protection. However, PS does not easily react with organic pollutants and usually needs to be activated to produce oxidizing active substances such as sulfate radicals (SO₄^-) and hydroxyl radicals (OH) to degrade them. This paper summarizes the research progress of PS activation methods in the field of wastewater treatment, such as physical activation (e.g., thermal, ultrasonic, hydrodynamic cavitation, electromagnetic radiation activation and discharge plasma), chemical activation (e.g., alkaline, electrochemistry and catalyst) and the combination of the different methods, putting forward the advantages, disadvantages and influencing factors of various activation methods, discussing the possible activation mechanisms, and pointing out future development directions.

Degradation of 3,5-dichlorophenol by UV-C photolysis and UV-C-activated persulfate oxidation process in pure water and simulated tertiary treated urban wastewater

UV-C and UV-C/peroxydisulfate (PS) treatments of 3,5-dichlorophenol (3,5-DCP), a model industrial pollutant, were comparatively investigated in two different water matrices namely distilled water (DW) and simulated treated urban wastewater (SWW). The treatment performance of the selected treatment processes was comprehensively examined by following changes in 3,5-DCP, dissolved organic carbon (DOC), PS consumption, Cl^- release, aromatic/aliphatic degradation products and acute toxicities towards the marine photobacterium Vibrio fischeri and freshwater microalga Pseudokirchneriella subcapitata. The treatability of 2 mg/L (12.3 µM) 3,5-DCP in DW was investigated under different operating conditions such as initial PS concentrations (0.00-1.00 mM) and pH values (3-11) at a fixed light intensity (0.5 W/L). Increasing the pH and PS concentration exhibited positive effects on 3,5-DCP degradation. Even 10 mg/L 3,5-DCP was completely degraded with UV-C/PS treatment in 40 min in the presence of 0.03 mM PS at pH 6.3 accompanied with 95% DOC removal that was achieved after 120 min treatment. The second-order rate constant of 3,5-DCP (10 mg/L) with SO4⋅- was determined as 1.77×10⁹ M^-1s^-1 using competition kinetics. Cl^- release and formation of hydroquinone were evidences of 3,5-DCP degradation involving SO4⋅-. 3,5-DCP (2 mg/L) was also subjected to UV-C and UV-C/PS treatments in SWW. 3,5-DCP (100% after 60 min) and in particular DOC (26% after 120 min treatment) removal efficiencies observed in DW decreased dramatically in SWW. The original and UV-C/PS-treated samples were non-toxic towards Vibrio fischeri; however, Pseudokirchneriella subcapitata toxicity increased from 20% to 47% through 80 min UV-C/PS treatment of 3,5-DCP.

Peracids - New oxidants in advanced oxidation processes: The use of peracetic acid, peroxymonosulfate, and persulfate salts in the removal of organic micropollutants of emerging concern - A review

In recent years, there has been increasing interest in using of advanced oxidation processes in water and wastewater decontamination. As a new oxidants peracids, mainly peracetic acid (PAA) and peracid salts, i.e. peroxymonosulfate (PMS) and persulfate (PS) are used. The degradation process of organic compounds takes place with the participation of radicals, including hydroxyl (^•OH) and sulfate (SO₄^•-) radicals derived from the peracids activation processes. Peracids can be activated in homogeneous systems (UV radiation, d-electron metal ions, e.g. Fe²⁺, Co²⁺, Mn²⁺, base, ozonolysis, thermolysis, radiolysis), or using heterogeneous activation (metals with zero oxidation state, metal oxides, quinones, activated carbon, semiconductors). As a result of oxidation, products of a lower mass than the parent compounds, less toxic, and more susceptible to biodegradation are formed. An important task is to investigate the effect of the peracid activation method and matrix composition on the efficiency of contamination removal. The article presents the latest information about the application of peracids in the removal of organic micropollutants of emerging concern (mainly focuses on endocrine disrupted compounds). The most important information on peracetic acid, peroxymonosulfate and persulfate salts, and methods of their activation are presented. Current uses of these oxidants in organic micropollutants removal are also described. Information was collected on the factors influencing the oxidation process and the effectiveness of pollutant removal. This paper compares PAA, PMS and PS-based processes for the first time in terms of kinetics and efficiency.

Tube-in-tube membrane photoreactor as a new technology to boost sulfate radical advanced oxidation processes

This work proposes a tube-in-tube membrane photoreactor, operated in a continuous-mode, to boost the efficiency of peroxydisulfate (PDS), through the photolytic (UV-C radiation) and photocatalytic (TiO₂-P25) processes. This new technology can efficiently facilitate the transportation of PDS to the catalyst surface and water to be treated. The ultrafiltration tubular ceramic membrane was used as support for the TiO₂-P25 and oxidant-catalyst/water contactor. Tests were performed using a synthetic solution and a municipal secondary effluent, both spiked with a pharmaceutical mix solution (paracetamol (PCT), furosemide (FRS), nimesulide (NMD), and diazepam (DZP); 200 μg L^-1 of each). At steady-state regime, the UVC/S₂O₈^2-/TiO₂ system, with radial PDS addition, showed the highest removal of pharmaceuticals in both matrices. Furthermore, twenty-two transformation products (TPs) were identified by applying LC-QTOF MS technique. Hence, the transformation pathways including hydroxylation in aromatic moiety by an electrophilic attack, electron transfer reactions, cleavage of C-O, C-N bond, H-abstraction and ring opening were proposed. TPs chemical structures were evaluated by in silico (Q)SAR approach using TOXTREE and EPI Suite™ software.

Degradation kinetics and mechanism of bis(2-chloroethyl) ether by electromagnetic induction electrodeless lamp activated persulfate

Bis(2-chloroethyl) ether (BCEE) has become one of the most frequently detected chlorinated ether contaminants in the US and Europe, and is classified as a B2 carcinogen. In this study, the degradation rate of BCEE by mercury lamps, xenon lamp and electromagnetic induction electrodeless lamp (EIEL) activated persulfate were compared, and EIEL activated persulfate was confirmed to have higher degradation capability and lower energy consumption. In this sense, the degradation kinetics and mechanism in EIEL system were further investigated. The degradation reaction followed pseudo first-order, and the removal rate of BCEE exceeded 95% in 60 min when the initial pH, the concentration of BCEE and Na₂S₂O₈ were 3, 4 mg L^-1 and 15 mM, respectively. Presence of inorganic anions and humic acids would reduce the degradation rate constant. In accordance with the results of electron paramagnetic resonance and quenching experiments, SO₄^-· was dominant in the acidic regime and OH· was dominant in the alkaline regime. Meanwhile, OH· had higher degradation rate with BCEE when initial pH was 7. Seven degradation products were identified and the reaction pathways included OH· substitution and free radical coupling. Although the total organic carbon was eliminated slowly during the degradation of BCEE, the predicted toxicity of most degradation products to Fathead minnow, Daphnia magna and oral rat were lower than BCEE.

UV-C-activated persulfate oxidation of a commercially important fungicide: case study with iprodione in pure water and simulated tertiary treated urban wastewater

Recently, the European Food Safety Authority (EFSA) has banned the use of iprodione (IPR), a common hydantoin fungicide and nematicide that was frequently used for the protective treatment of crops and vegetables. In the present study, the treatment of 2 mg/L (6.06 μM) aqueous IPR solution through ultraviolet-C (UV-C)-activated persulfate (PS) advanced oxidation process (UV-C/PS) was investigated. Baseline experiments conducted in distilled water (DW) indicated that complete IPR removal was achieved in 20 min with UV-C/PS treatment at an initial PS concentration of 0.03 mM at pH = 6.2. IPR degradation was accompanied with rapid dechlorination (followed as Cl^- release) and PS consumption. UV-C/PS treatment was also effective in IPR mineralization; 78% dissolved organic carbon (DOC) was removed after 120-min UV-C/PS treatment (PS = 0.30 mM) compared with UV-C at 0.5 W/L photolysis where no DOC removal occurred. LC analysis confirmed the formation of dichloroaniline, hydroquinone, and acetic and formic acids as the major aromatic and aliphatic degradation products of IPR during UV-C/PS treatment whereas only dichloroaniline was observed for UV-C photolysis under the same reaction conditions. IPR was also subjected to UV-C/PS treatment in simulated tertiary treated urban wastewater (SWW) to examine its oxidation performance and ecotoxicological behavior in a more complex aquatic environment. In SWW, IPR and DOC removal rates were inhibited and PS consumption rates decreased. The originally low acute toxicity (9% relative inhibition towards the photobacterium Vibrio fischeri) decreased to practically non-detectable levels (4%) during UV-C/PS treatment of IPR in SWW.

Insights into nonylphenol degradation by UV-activated persulfate and persulfate/hydrogen peroxide systems in aqueous matrices: a comparative study

Nonylphenol ethoxylates are widely used industrial surfactants. Once released into environment compartments, these chemicals undergo degradation and generate more toxic short chain artificial compound nonylphenol (NP). The latter is a known endocrine disrupting compound and persistent micropollutant. In the present study, the performance of NP degradation in UV-induced PS, PS/Fe²⁺, PS/H₂O₂, and PS/H₂O₂/Fe²⁺ systems was examined. The effect of concentration of oxidant and activators on the efficiency of target compound decomposition was studied. The trials were conducted in ultrapure water and groundwater to assess the influence of matrix composition. The obtained results indicated that NP degradation by all the systems studied followed a pseudo-first-order kinetics. The application of UV-activated PS at lower concentrations of the oxidant improved NP oxidation in both water matrices. The addition of iron activator at a cost-effective concentration showed slight improvement in the studied PS-based systems. The application of UV-induced dual oxidant PS/H₂O₂ system demonstrated promising results in NP oxidation. In turn, the addition of Fe²⁺ to the UV/PS/H₂O₂ system accelerated the target compound oxidation at an optimized dose of iron activator. The radicals scavenging studies indicated that HO^• was the predominant radical in all UV-induced PS-based systems. The results of this research could provide significant information for the removal of NP from different water matrices by means of UV-induced persulfate-based oxidation processes.

Coupling Persulfate-Based AOPs: A Novel Approach for Piroxicam Degradation in Aqueous Matrices

The activated persulfate degradation of piroxicam, a non-steroidal anti-inflammatory drug (NSAID) belonging to oxicams, was investigated. Persulfate was activated with thermal energy or (UV-A and simulated solar) irradiation. Using 250 mg/L sodium persulfate at 40 °C degraded almost completely 0.5 mg/L of piroxicam in 30 min. Increasing piroxicam concentration from 0.5 to 4.5 mg/L decreased its removal. The observed kinetic constant was increased almost ten times from 0.077 to 0.755 min−1, when the temperature was increased from 40 to 60 °C, respectively. Process efficiency was enhanced at pH 5–7. At ambient conditions and 30 min of irradiation, 94.1% and 89.8% of 0.5 mg/L piroxicam was removed using UV-A LED or simulated solar radiation, respectively. Interestingly, the use of simulated sunlight was advantageous over UV-A light for both secondary effluent, and 20 mg/L of humic acid solution. Unlike other advanced oxidation processes, the presence of bicarbonate or chloride in the range 50–250 mg/L enhanced the degradation rate, while the presence of humic acid delayed the removal of piroxicam. The use of 0.5 and 10 g/L of methanol or tert-butanol as radical scavengers inhibited the reaction. The coupling of thermal and light activation methods in different aqueous matrices showed a high level of synergy. The synergy factor was calculated as 68.4% and 58.4% for thermal activation (40 °C) coupled with either solar light in 20 mg/L of humic acid or UV-A LED light in secondary effluent, respectively.

Photocatalytic Evaluation of Ag2CO3 for Ethylparaben Degradation in Different Water Matrices

The present study examines the photocatalytic properties of silver carbonate (Ag2CO3) for ethyl paraben (EP) degradation under simulated solar irradiation. Ag2CO3 was prepared according to a solution method and its physicochemical characteristics were studied by means of X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method, diffuse reflectance spectroscopy (DRS), and transmission electron microscopy (TEM). Complete EP (0.5 mg/L) removal was achieved after 120 min of irradiation with the use of 750 mg/L Ag2CO3 in ultrapure water (UPW), with EP degradation following pseudo-first-order kinetics. The effect of several experimental parameters was investigated; increasing catalyst concentration from 250 mg/L to 1000 mg/L led to an increase in EP removal, while increasing EP concentration from 0.25 mg/L to 1.00 mg/L slightly lowered kapp from 0.115 min−1 to 0.085 min−1. Experiments carried out with the use of UV or visible cut-off filters showed sufficient EP degradation under visible irradiation. A series of experiments were performed in real water matrices such as bottled water (BW) and wastewater (WW), manifesting Ag2CO3’s equally high photocatalytic activity for EP degradation. To interpret these results different concentrations of inorganic anions (bicarbonate 100–500 mg/L, chloride 100–500 mg/L) present in aqueous media, as well as 10 mg/L organic matter in the form of humic acid (HA), were added sequentially in UPW. Results showed accelerating effects on EP degradation for the lowest concentrations tested in all cases.

Oxidation of flumequine in aqueous solution by UV-activated peroxymonosulfate: Kinetics, water matrix effects, degradation products and reaction pathways

The degradation of flumequine (FLU) in aqueous solution by ultraviolet (UV)-activated peroxymonosulfate (PMS) was investigated in this work. Under the conditions of [PMS]₀:[FLU]₀ = 1:1, T = 25 ± 2 °C, pH = 7.0 ± 0.1, nearly complete removal of FLU was achieved after 60 min. The effects of various operating parameters, including oxidant doses, pH, the presence of typical ions (NH₄⁺、Mg²⁺、Fe³⁺、Cl^-、NO₃^-、HCO₃^-) and humic acid were evaluated. It was found that the pseudo-first-order rate constants of FLU degradation increased with increasing PMS dosage and decreasing solution pH. The presence of Mg²⁺ could accelerate FLU removal, while Fe³⁺, HCO₃^-, NO₃^- and HA inhibited the reaction. Moreover, the degradation of FLU in different water matrices were also explored, and the removal followed the order of Tap water > Ultrapure water > River water > Secondary clarifier effluent. According to the control and radical quenching experiment results, direct photolysis and reactive radicals (SO₄^- and HO) contributed mainly to FLU degradation in the UV/PMS system. Initial FLU molecule underwent reactions such as hydroxylation, hydroxyl substitution, demethylation, decarboxylation/decarbonylation and ring opening, leading to the formation of nineteen oxidation products. The effective degradation by UV/PMS suggests a feasible technology for treating FLU in waters and wastewaters.

Degradation of propranolol by UV-activated persulfate oxidation: Reaction kinetics, mechanisms, reactive sites, transformation pathways and Gaussian calculation

Contamination with β-blockers such as propranolol (PRO) poses a potential threat to human health and ecological system. The present study investigated the kinetics and mechanisms of PRO degradation by UV-activated persulfate (UV/PS) oxidation. Here, the experimental results showed that the degradation of PRO followed pseudo-first-order reaction kinetics, the degradation rate constant (k_obs) was increased dramatically with increasing PS dosage or decreasing initial PRO concentration. And increasing the initial solution pH could also enhance the degradation efficiency of PRO. Radical scavenging experiments demonstrated that the main radical species was sulfate radicals (SO₄^•-), with hydroxyl radicals (HO·) playing a less important role. Meanwhile, the second-order rate constants of PRO degradation with SO₄^•- and HO· were determined to be 1.94 × 10¹⁰ M^-1 s^-1 and 6.77 × 10⁹ M^-1 s^-1, respectively. In addition, the presence of natural organic matter (NOM) and nitrate anion (NO₃^-) showed inhibitory effect on PRO degradation, whereas bicarbonate anion (HCO₃^-) and chlorine anion (Cl^-) greatly enhanced the degradation of PRO. Moreover, the transformation products of PRO were identified by applying ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) technique. Molecular orbital calculations were used to estimate the reaction site of PRO with radicals, simultaneously. Hence, the transformation pathways including hydroxylation, dehydration, naphthalene ring opening, and the cleavage of aldehyde groups were proposed. This work enriches the mechanism of PRO degradation under UV/PS system on the basis of results obtained by experimental characterization and Gaussian theoretical calculation.