Oxidative degradation of fensulfothion by hydroxyl radical in aqueous medium

Assembly of UiO-66 onto Co-doped Fe3O4 nanoparticles to activate peroxymonosulfate for efficient degradation of fenitrothion and simultaneous in-situ adsorption of released phosphate

Although sulfate radical-based advanced oxidation processes (SR-AOPs) have shown great potential for the efficient degradation of various organic contaminants, there is few research on the removal of organophosphorus pesticides (OPPs) through SR-AOPs. In this work, Co-doped Fe₃O₄ magnetic particles encapsulated by zirconium-based metal-organic frameworks (Co-Fe₃O₄@UiO-66) were prepared and employed to activate peroxymonosulfate (PMS) for the elimination of fenitrothion (FNT) and the simultaneous in-situ adsorption of produced phosphate. The catalyst exhibited efficient catalytic performance, achieving above 90.0% removal of FNT (10 mg/L) in the presence of PMS (1 mM) within 60 min. Moreover, the produced phosphate during the degradation process was also completely adsorbed onto the catalyst. Both sulfate and hydroxyl radicals were responsible for the degradation of FNT. The degradation products of FNT in the system were identified and the possible pathways were proposed. This study represents a promising and adoptable strategy to develop other versatile composite nanomaterials in a green manner hence broadening its environmental application range, as it can not only remove OPPs by catalytic oxidation but also immobilize degraded phosphorus by adsorption.

Oxidative Degradation of Pharmaceutical Waste, Theophylline, from Natural Environment

The elimination of organic contaminants from natural resources is extremely important to ensure their (re-)usability. In this report, the degradation of a model pharmaceutical compound, theophylline, is compared between natural and laboratory-controlled environments. While the concentration of H2O2 variably affected the degradation efficiency (approximately from 8 to 20 min for complete degradation) in the photo-irradiation experiments, the inorganic compounds (NaNO3, KH2PO4 and ZnSO4) present in the medium seemed to affect the degradation by scavenging hydroxyl radicals (•OH). The end-product studies using high-resolution mass spectrometry (HRMS) ruled out the involvement of secondary radicals in the degradation mechanism. The quantitative calculation with the help of authentic standards pointed out the predominant role of hydroxylation pathways, especially in the initial stages. Although a noticeable decline in the degradation efficiency was observed in river water samples (complete degradation after 25 min with an approximately 20% total organic carbon (TOC) removal), appreciable TOC removal (70%) was eventually achieved after prolonged irradiation (1 h) and in the presence of additional H2O2 (5 times), revealing the potential of our technique. The results furnished in this report could be considered as a preliminary step for the construction of •OH-based wastewater treatment methodologies for the remediation of toxic pollutants from the real environment.

Applications of electron spin resonance spectroscopy in photoinduced nanomaterial charge separation and reactive oxygen species generation

Nano-metals, nano-metal oxides, and carbon-based nanomaterials exhibit superior solar-to-chemical/photo-electron transfer properties and are potential candidates for environmental remediations and energy transfer. Recent research effort focuses on enhancing the efficiency of photoinduced electron-hole separation to improve energy transfer in catalytic reactions. Electron spin resonance (ESR) spectroscopy has been used to monitor the generation of electron/hole and reactive oxygen species (ROS) during nanomaterial-mediated photocatalysis. Using ESR coupled with spin trapping and spin labeling techniques, the underlying photocatalytic mechanism involved in the nanomaterial-mediated photocatalysis was investigated. In this review, we briefly introduced ESR principle and summarized recent advancements using ESR spectroscopy to characterize electron-hole separation and ROS production by different types of nanomaterials.

Fenton-like reaction driving the degradation and uptake of multi-walled carbon nanotubes mediated by bacterium

Carbon nanotubes (CNTs) have been widely studied because of their potential applications. The increasing applications of CNTs and less known of their environmental fates rise concerns about their safety. In this study, the biotransformation of multi-walled carbon nanotubes (MWCNTs) by Labrys sp. WJW was investigated. Within 16 days, qPCR analysis showed that cell numbers increased 4.92 ± 0.36 folds using 100 mg/L MWCNTs as the sole carbon source. The biotransformation of MWCNTs, which led to morphology and functional group change, was evidenced by transmission electron microscopy and X-ray photoelectron spectroscopy analyses. Raman spectra illustrated that more defects and disordered carbon appeared on MWCNTs during incubation. The underlying biotransformation mechanism of MWCNTs through an extracellular bacterial Fenton-like reaction was demonstrated. In this bacteria-mediated reaction, the OH production was induced by reduction of H₂O₂ involved a continuous cycle of Fe(II)/Fe(III). Bacterial biotransformation of MWCNTs will provide new insights into the understanding of CNTs bioremediation processes.

Biogenic fenton-like reaction involvement in aerobic degradation of C60 by Labrys sp. WJW

Buckminster fullerene (C₆₀), the most representative type among fullerenes, has attracted widely attentions because of its many potential applications. The increasing application of fullerene and limited knowledge of its environmental fate are required concerns. Herein, the biotransformation of C₆₀ by Labrys sp. WJW was investigated. Cell numbers reached 25.76 ± 1.85 folds within 8 days using 100 mg/L C₆₀ as sole carbon source. The biotransformation of C₆₀ by Labrys sp. WJW was analyzed by various characterization methods. Raman spectra indicated that strain WJW broke the soccer ball like structure of C₆₀. After 12 days, over 60% of C₆₀ was degraded evidenced by UV-vis spectrophotometry and liquid chromatography-mass spectrometry. The underlying biotransformation mechanism of C₆₀ through an extracellular Fenton-like reaction was illustrated. In this reaction, the ^•OH production was mediated by reduction of H₂O₂ involving a continuous cycle of Fe(II)/Fe(III). Bacterial transformation of C₆₀ will provide new insights into the understanding of C₆₀ bioremediation process.

Bacteria mediated Fenton-like reaction drives the biotransformation of carbon nanomaterials

Carbon nanomaterials (CNs), which gain heightened attention as novel materials, are increasingly incorporated into daily products and thus are released into the environment. Limited research on CNs environmental fates lags their industry growth, only few bacteria have been confirmed to biotransform CNs and the mechanism behind has not been revealed yet. In this study, four types of commercial CNs, i.e. graphene oxide (GO), reduced graphene oxide (RGO), single walled carbon nanotubes (SWCNTs), and oxidized (carboxylated) SWCNTs, were selected for investigation. The biotransformation of CNs by Labrys sp. WJW, which could grow with these CNs as the sole carbon source, was investigated. The bacterial transformation was proved by qPCR, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, liquid chromatography/time-of-flight/mass spectrometry, and gas chromatograph-mass spectrometry analyses. The biotransformation resulted in morphology change, defect increase and functional group change of these CNs. Furthermore, the underlying mechanism of CNs biodegradation mediated by extracellular Fenton-like reaction was demonstrated. In this reaction, the OH production was mediated by reduction of H₂O₂ involved a continuous cycle of Fe(II)/Fe(III). These findings reveal a novel degradation mechanism of microorganism towards high molecular weight substrate, which will provide a new insight into the environmental fate of CNs and the guidance for their safer use.

UV-Vis quantification of hydroxyl radical concentration and dose using principal component analysis

Hydroxyl radicals (∙OH) are powerful oxidizing species formed naturally in the environment or artificially produced to destroy contaminants in water treatment facilities. Their short lifetime and high reactivity, however, present a significant challenge to quantifying their concentration in solution. Herein, we developed a novel method to accurately measure the steady-state ∙OH concentration and total ∙OH dose produced during the UV photolysis of hydrogen peroxide (H₂O₂) by monitoring the loss of salicylic acid (SA). This information can be acquired using only benchtop UV-Vis spectroscopy, thus expanding measurement capabilities of resource-limited laboratories by eliminating the need for sophisticated instrumentation. To improve the precision with which the rate of SA loss was measured compared to previous methods, we applied principal component analysis (PCA) to fit the UV-Vis spectra collected during SA exposure to ∙OH. For our experimental conditions consisting of 12 mL solutions composed of ≤ 100 mM H₂O₂ and 0.07 mM SA, the steady-state ∙OH concentration throughout the complete photolysis of H₂O₂ was 1.33 × 10^-11 M ± 1.14 × 10^-12 M. This represents more than a ten-fold improvement in reducing the uncertainty of the measurement, with respect to narrowing the 95 % confidence interval, compared to a previous method that employed matrix analysis to process the spectra. Furthermore, the variance of the measured ∙OH concentrations was reduced by a factor of 100 compared to previous methods. Using PCA, the limit-of-detection and limit-of-quantitation for ∙OH are 5.33 × 10^-13 M and 1.23 × 10^-12 M, respectively. By developing quantitative relationships among ∙OH concentration, H₂O₂ concentration, and UV exposure time, we also show how to calculate the equivalent exposure to ∙OH generated in natural aquatic environments by indirect photolysis. Finally, we use this methodology to demonstrate that the presence of suspended carbonaceous nanoparticles at concentrations as high as 300 ppm does not affect ∙OH concentration.

Sonochemical degradation of benzenesulfonic acid in aqueous medium

Degradation of benzenesulfonic acid (BSA), the simplest aromatic sulfonic acid with extreme industrial importantance, by sonochemically generated hydroxyl radical (OH) have been thoroughly investigated. A reasonable reduction (∼50%) in the total organic carbon (TOC) was achieved only after prolonged irradiation (∼275 min, 350 kHz) of ultrasound, although a short irradiation of less than an hour is enough to degrade significant amount of BSA. The degradation efficiency of ultrasound has been reduced in lower and extremely higher frequencies, and upon increasing the pH. An irregular, but continuous, release of sulfate ions was also observed. Further, the release of protons upon the oxidation of BSA consistently reduces the experimental pH to nearly 2. High resolution mass spectrometric (HRMS) analyses reveals the formation of a number of aromatic intermediates, including three mono (I_a-c) and two di (II_a&b) hydroxylated BSA derivatives as the key products in the initial stages of the reaction. Pulse radiolysis studies revealed the generation of hydroxycyclohexadienyl-type radicals, characterized by absorption bands at 320 nm (k₂ = (7.16 ± 0.04) × 10⁹ M^-1 s^-1) and 380 nm, as the immediate intermediates of the reaction. The mechanism(s) leading to the degradation of BSA under sonolytic irradiation conditions along with the effect of various factors, such as the ultrasound frequency and reaction pH, have been explained in detail. The valuable mechanistic aspects obtained from our pulse radiolysis and HRMS studies are essential for the proper implementation of sonochemical techniques into real water purification process and, thus, receives extreme environmental relevance.

Enhanced degradation of acid red 1 dye using a coupled system of zero valent iron nanoparticles and sonolysis

The heterogeneous catalytic degradation of a model azo dye, acid red 1 (AR1), initiated by zero valent iron nanoparticles (ZVINP), and its synergic effect with ultrasound (US) have been investigated in the present study. The treatment of AR1 using ZVINP at pH 3 showed maximum efficiency in terms of colour removal (53.0%) and mineralization (48.5% TOC reduction) after 25 min of reaction. However, the coupling of this system with US showed an enhanced efficiency against the decolourization and mineralization of AR1. More than 95% colour removal was achieved within 5 min in the case of US/ZVINP system. Around 55% TOC reduction suggests the conversion of the parent molecules in to aromatic transformed products, and it is further supported by LC-Q-TOF analysis. The remarkably higher efficiency in the coupled system is attributed to the synergic effect of ZVINPs and ultrasound. The highest degradation rates observed at highly acidic (pH 3) and alkaline pH (pH 9) suggests that different mechanisms are operating at both pH. The products identified gave some insight into the mechanism. The ZVINPs prepared in the present study was easily recoverable (and reusable) and hence may be considered as an effective replacement for the conventional Fenton's reagent.

Characterization of metformin by-products under photolysis, photocatalysis, ozonation and chlorination by high-performance liquid chromatography coupled to high-resolution mass spectrometry

RATIONALE

Metformin (MTF) is the most widely prescribed drug for the treatment of patients with type 2 diabetes. Studies involving the removal of MTF from aqueous solutions and detailed information regarding the overall degradation process are scarce.

METHODS

The degradation of MTF in aqueous solution induced by direct photolysis, photocatalysis, ozonation and chlorination was evaluated. The process was continuously monitored focusing on the identification and monitoring of the by-products formed by applying high-performance liquid chromatography coupled to high-resolution mass spectrometry in positive ion mode. The cytotoxicity of metformin by-products was evaluated with an MTT assay.

RESULTS

The results from the chlorination and ozonation tests indicate metformin removal efficiencies of 60% after 30 min of exposure. On the other hand, direct photolysis (UV-C) and heterogeneous photocatalysis (TiO₂ /UV-C) led to a lower degree of metformin degradation, with removal efficiencies of 9.2% and 31%, respectively, after 30 min of exposure. The mineralization rates varied from 20% for ozonation to 0.72% for photolysis, thereby indicating there was accumulation of degradation by-products in all experiments. Mass spectrometric analysis indicated the presence of five metformin by-products. It was not possible to identify any by-product generated in the photolysis, and, in all oxidative assays, the treated samples were nontoxic to HepG2 cells.

CONCLUSIONS

It is also observed that all systems exhibited low mineralization rates, with the chlorination process being slightly more efficient in promoting the degradation, whereas the ozonation was more efficient in promoting the mineralization of metformin. Based on these results a route for the chlorination, photodegradation and ozonation of MTF, which comprised of its successive oxidation in the aqueous medium, could be proposed. It could also be concluded that the treated samples were not cytotoxic to HepG2 cells in a MTT assay. Copyright © 2016 John Wiley & Sons, Ltd.

Identification of position isomers by energy-resolved mass spectrometry

This study reports an energy-resolved mass spectrometric (ERMS) strategy for the characterization of position isomers derived from the reaction of hydroxyl radicals ((●)OH) with diphenhydramine (DPH) that are usually hard to differentiate by other methods. The isomer analogues formed by (●)OH attack on the side chain of DPH are identified with the help of a specific fragment ion peak (m/z 88) in the collision-induced dissociation (CID) spectrum of the protonated molecule. In the negative ion mode, the breakdown curves of the deprotonated molecules show an order of stability (supported by density functional theory (DFT) calculations) ortho > meta > para of the positional isomers formed by the hydroxylation of the aromatic ring. The gas phase stability of the deprotonated molecules [M - H](-) towards the benzylic cleavage depends mainly on the formation of intramolecular hydrogen bonds and of the mesomeric effect of the phenol hydroxyl. The [M - H](-) molecules of ortho and meta isomers result a peak at m/z 183 with notably different intensities because of the presence/absence of an intramolecular hydrogen bonding between the OH group and C9 protons. The ERMS approach discussed in this report might be an effective replacement for the conventional methods that requires very costly and time-consuming separation/purification methods along with the use of multi-spectroscopic methods.

Kinetic and mechanism investigation on the gamma irradiation induced degradation of endosulfan sulfate

The gamma irradiation was investigated for potential removal of endosulfan sulfate, an emerging water pollutant and central nervous system disruptor. A removal efficiency of 99.5% of initially 1.30 μM endosulfan sulfate was observed at an absorbed dose of 1020 Gy. Aqueous electron (eaq(-)) was found to play primary role in the removal of endosulfan sulfate which was possibly due to greater reactivity of eaq(-) with endosulfan sulfate, considering the second-order rate constant of 8.1×10(9) and 3.4×10(10) M(-1) s(-1) for hydroxyl radical (·OH) and eaq(-), respectively, with endosulfan sulfate. The removal efficiency of endosulfan sulfate was affected by the pH of aqueous solution, with observed removal efficiency of 99.5%, 98.3% and 31.3% at pH 6.2, pH 10.0, and pH 2.6, respectively. The efficiency was also influenced by inorganic anions and humic acid in the order of nitrate>nitrite>bicarbonate>carbonate ≃ humic acid. The initial degradation rate increased while degradation constant decreased with increasing initial concentrations of endosulfan sulfate. The degradation pathways showed that oxidative pathway was initiated at the SO2 bond while reductive pathways at the chlorine attached to the ring of endosulfan sulfate. The mass balance showed removal of 98% chloride and 72% sulfate ions from endosulfan sulfate at an absorbed dose of 1020 Gy. The removal of endosulfan sulfate followed by subsequent loss of by-products under extended treatment showed that gamma irradiation is potential technique for the remediation of organic pollutants from a water environment.

Sonochemical degradation of Coomassie Brilliant Blue: effect of frequency, power density, pH and various additives

Coomassie Brilliant Blue (CBB), discharged mainly from textile industries, is an identified water pollutant. Ultrasound initiated degradation of organic pollutants is one among the promising techniques and forms part of the Advanced Oxidation Processes (AOPs). Ultrasonic degradation of CBB under different experimental conditions has been investigated in the present work. The effect of frequency (200 kHz, 350 kHz, 620 kHz and 1 MHz) and power density (3.5 W mL(-1), 9.8 W mL(-1) and 19.6 W mL(-1)) on the degradation profile was evaluated. The optimum performance was obtained at 350 kHz and 19.6 W mL(-1). Similar to other sonolytic degradation of organic pollutants, maximum degradation of CBB was observed under acidic pH. The degradation profile indicated a pseudo-first order kinetics. The addition of ferrous ion (1×10(-4) M), hydrogen peroxide (1×10(-4) M), and peroxodisulphate (1×10(-4) M) had a positive effect on the degradation efficiency. The influence of certain important NOM like SDS and humic acid on the sonolytic degradation of CBB was also investigated. Both the compounds suppress the degradation efficiency. LC-Q-TOF-MS was used to identify the stable intermediate products. Nearly 13 transformed products were identified during 10min of sonication using the optimized operational parameters. This product profile demonstrated that most of the products are formed mainly by the OH radical attack. On the basis of these results, a degradation mechanism is proposed.

Role of aqueous electron and hydroxyl radical in the removal of endosulfan from aqueous solution using gamma irradiation

The removal of endosulfan, an emerging water pollutant, from water was investigated using gamma irradiation based advanced oxidation and reduction processes (AORPs). A significant removal, 97% of initially 1.0 μM endosulfan was achieved at an absorbed dose of 1020 Gy. The removal of endosulfan by gamma-rays irradiation was influenced by an absorbed dose and significantly increased in the presence of aqueous electron (eaq(-)). However, efficiency of the process was inhibited in the presence of eaq(-) scavengers, such as N2O, NO3(-), acid, and Fe(3+). The observed dose constant decreased while radiation yield (G-value) increased with increasing initial concentrations of the target contaminant and decreasing dose-rate. The removal efficiency of endosulfan II was lower than endosulfan I. The degradation mechanism of endosulfan by the AORPs was proposed showing that reductive pathways involving eaq(-) started at the chlorine attached to the ring while oxidative pathway was initiated due to attack of hydroxyl radical at the SO bond. The mass balance showed 95% loss of chloride from endosulfan at an absorbed dose of 1020 Gy. The formation of chloride and acetate suggest that gamma irradiation based AORPs are potential methods for the removal of endosulfan and its by-products from contaminated water.

Hydroxyl radical induced oxidation of theophylline in water: a kinetic and mechanistic study

Oxidative destruction and mineralization of emerging organic pollutants by hydroxyl radicals (˙OH) is a well established area of research. The possibility of generating hazardous by-products in the case of ˙OH reaction demands extensive investigations on the degradation mechanism. A combination of pulse radiolysis and steady state photolysis (H2O2/UV photolysis) followed by high resolution mass spectrometric (HRMS) analysis have been employed to explicate the kinetic and mechanistic features of the destruction of theophylline, a model pharmaceutical compound and an identified pollutant, by ˙OH in the present study. The oxidative destruction of this molecule, for intermediate product studies, was initially achieved by H2O2/UV photolysis. The transient absorption spectrum corresponding to the reaction of ˙OH with theophylline at pH 6, primarily caused by the generation of (T8-OH)˙, was characterised by an absorption band at 330 nm (k2 = (8.22 ± 0.03) × 10(9) dm(3) mol(-1) s(-1)). A significantly different spectrum (λmax: 340 nm) was observed at highly alkaline pH (10.2) due to the deprotonation of this radical (pKa∼ 10.0). Specific one electron oxidants such as sulphate radical anions (SO4˙(-)) and azide radicals (N3˙) produce the deprotonated form (T(-H)˙) of the radical cation (T˙(+)) of theophylline (pKa 3.1) with k2 values of (7.51 ± 0.04) × 10(9) dm(3) mol(-1) s(-1) and (7.61 ± 0.02) × 10(9) dm(3) mol(-1) s(-1) respectively. Conversely, oxide radicals (O˙(-)) react with theophylline via a hydrogen abstraction protocol with a rather slow k2 value of (1.95 ± 0.02) × 10(9) dm(3) mol(-1) s(-1). The transient spectral studies were complemented by the end product profile acquired by HRMS analysis. Various transformation products of theophylline induced by ˙OH were identified by this technique which include derivatives of uric acids (i, iv & v) and xanthines (ii, iii & vi). Further breakdown of the early formed product due to ˙OH attack leads to ring opened compounds (ix-xiv). The kinetic and mechanistic data furnished in the present study serve as a basic frame work for the construction of ˙OH induced water treatment systems as well as to understand the biological implications of compounds of this kind.

Exploring water catalysis in the reaction of thioformic acid with hydroxyl radical: a global reaction route mapping perspective

Hydrogen abstraction pathways, in the gas-phase reaction of tautomers of thioformic acid (TFA), TFA(thiol), and TFA(thione), with hydroxyl radical in the presence and absence of single water molecule acting as a catalyst, is investigated with high-level quantum mechanical calculations at CCSD(T)/6-311++G(2d,2p)//MP2/6-311++G(2d,2p), CCSD(T)/6-311++G(d,p)//DFT/BHandHLYP/6-311++G(d,p), and DFT/B3LYP/6-311++G(2df,2p) levels of the theory. A systematic and automated search of the potential energy surface (PES) for the reaction pathways is performed using the global reaction route mapping (GRRM) method that employs an uphill walking technique to search prereaction complexes and transition states. The computations reveal significant lowering of the PES and substantial reduction in the activation energy for the hydrogen abstraction pathway in the presence of water, thereby proving water as an efficient catalyst in the reaction of both the TFA tautomers with OH radical. The hydrogen-bonding interactions are observed to be responsible for the large catalytic effect of water. Notably, in the case of TFA(thiol), formyl hydrogen abstraction is observed to be kinetically more favorable, while acidic hydrogen abstraction is observed to be thermodynamically more feasible. Interestingly, in the case of TFA(thione), reaction pathways involving only formyl hydrogen abstraction were observed to be feasible. The water-catalyzed hydrogen abstraction reaction of TFA with hydroxyl radical, investigated in this work, can provide significant insights into the corresponding reaction in the biological systems.

Sonochemical degradation of a pharmaceutical waste, atenolol, in aqueous medium

Atenolol is a β-blocker drug and an identified emerging pollutant. Advanced oxidation processes (AOPs) utilise the reaction of a highly oxidising species (hydroxyl radicals, (•)OH) for the mineralisation of emerging pollutants since conventional treatment methodologies generally fail to degrade these compounds. In the present work, degradation of atenolol was carried out using ultrasound with frequencies ranging from 200 kHz to 1 MHz as a source of hydroxyl radical. The degradation was monitored by HPLC, total organic carbon (TOC) and chemical oxygen demand (COD) reduction and ion chromatography (IC). Nearly 90 % of degradation of atenolol was observed with ultrasound having 350 kHz. Both frequency and power of ultrasound affect the efficiency of degradation. Nearly 100 % degradation was obtained at a pH of 4. Presence of various additives such as sodium dodecyl sulphate, chloride, sulphate, nitrate, phosphate and bicarbonate was found to reduce the efficiency of degradation. Although nearly 100 % degradation of atenolol was observed under various experimental conditions, only about 62 % mineralisation (from TOC and COD measurements) was obtained. Nearly eight intermediate products were identified using high-resolution mass spectrometry (LC-Q-TOF). These products were understood as the results of hydroxyl radical addition to atenolol. The degradation studies were also carried out in river water which also showed a similar degradation profile. A mechanism of degradation and mineralisation is presented.

Efficient removal of endosulfan from aqueous solution by UV-C/peroxides: a comparative study

This study explored the efficiency of UV-C-based advanced oxidation processes (AOPs), i.e., UV/S2O8(2-), UV/HSO5(-), and UV/H2O2 for the degradation of endosulfan, an organochlorine insecticide and an emerging water pollutant. A significant removal, 91%, 86%, and 64%, of endosulfan, at an initial concentration of 2.45 μM and UV fluence of 480 mJ/cm(2), was achieved by UV/S2O8(2-), UV/HSO5(-), and UV/H2O2 processes, respectively, at a [peroxide]0/[endosulfan]0 molar ratio of 20. The efficiency of these processes was, however, inhibited in the presence of radical scavengers, such as alcohols (e.g., tertiary butyl alcohol and isopropyl alcohol) and natural organic matter (NOM). The inhibition was also influenced by common inorganic anions in the order of nitrite > bicarbonate > chloride > nitrate ≈ sulfate. The observed pseudo-first-order rate constant decreased while the degradation rate increased with increasing initial concentration of the target contaminant. The degradation mechanism of endosulfan by the AOPs was evaluated revealing the main by-product as endosulfan ether. Results of this study suggest that UV-C-based AOPs are potential methods for the removal of pesticides, such as endosulfan and its by-products, from contaminated water.