Decomposition of atrazine by ionizing radiation: Kinetics, degradation pathways and influence of radical scavengers

Radiolysis performance of ibuprofen using ionizing processes: kinetics and energy consumption

ABSTRACTIonizing technologies are used for disinfection and treatment of different industrial wastewaters. For this purpose, the radiolytic degradation of ibuprofen (IBP), selected within the main detected pharmaceuticals in different water locations with different concentrations, was investigated. Irradiation was performed with a gamma irradiator (60Co) and with electron beam accelerator. The degree of ibuprofen degradation was monitored following the evolution of its absorbance, the residual concentration by HPLC, carbon oxygen demand and total organic carbon. The degradation of IBP was higher than the removal of TOC or COD and reached 95% according to residual concentration. This pollutant (at 0.1 mM) was totally degraded when irradiated at 3 kGy and needed higher doses (7-10 kGy) for the highest concentrations (0.8-1 mM). The addition of 1 mM of persulfate ion remarkably enhanced IBP degradation by around 2 and 2.8 times for 5 and 10 kGy, respectively. Pseudo-first-order reaction kinetics could be used to depict the degradation process of IBP in all conditions. Electrical energy per order (EEO) was estimated under various conditions. The smallest EEO was obtained when gamma radiation and persulfate ion were combined. The possible degradation pathways of IBP were proposed. The results achieved in this study can be used to optimize large-scale application of nuclear techniques in water treatment in particular in treating pharmaceutical effluents.

Differential interference of copper with endophytic bacterial inoculation: Atrazine decontamination in Acorus tatarinowii and culture solution

To clarify the interference effects of inorganic ions, Acorus tatarinowii and endophytic bacterium Herbaspirillum huttiense (Hh) were combined to decontaminate atrazine pollution under different copper levels. This study verified inoculation effects and revealed the complicated processes of atrazine transformation in solutions. 35.9% leaf biomass was promoted by Hh inoculation, and the value was lowered to 7.87% by high doses of copper. The changing trend of leaf N, K, and S contents, and tiller numbers were consistent with that of leaf biomass. Hh injection improved atrazine accumulation by 43.5% in roots, and under copper interference, this value lowered to 10.6%. Hh promoted atrazine deethylation in plants, which was copper-dose dependent in different plant organs. In solutions, atrazine was conjugated with small-molecule secretions at m/z 118, detoxicated into 2-hxydroatrazine and 2-hydroxy-4-acetamido-atrazine, then the triazine ring opened. Copper interference had a more significant impact on residual atrazine conversion products than Hh inoculation treatments. Hh treatment promoted the ring-opening degradation of atrazine in water. The addition of high doses of copper ions promoted the oxidative process of atrazine while inhibiting its ring-opening transformation process in water.

Effective degradation of lindane and its isomers by dielectric barrier discharge (DBD) plasma: Synergistic effects of various reactive species

Lindane is a broad-spectrum organochlorine insecticide which has been included in the persistent organic pollutants (POPs) list together with its two hexachlorocyclohexane (HCH) isomers. Due to its continuous use in the past decades, the environmental impacts of HCHs are still severe now. Therefore, in the present study, dielectric barrier discharge (DBD) plasma was used as an advanced oxidation process for the destruction of HCHs in water. The result indicated that in air-DBD system, over 95.4% of the initial 5 mg L-1 lindane was degraded within 60 min. Moreover, DBD plasma displayed high degradation efficiencies of other HCH isomers including α, β, and δ-HCH. Electron spin resonance spectra, scavenging experiments and theoretical calculations revealed that the synergistic effects of various reactive species were the main reason for the high efficiency of DBD plasma. For instance, both hydroxyl radicals (•OH) and electrons (e-) could initiate the degradation of HCHs, while other reactive species such as 1O2 and ONOOH played important roles in the decomposition of intermediates. Therefore, the present study not only provided an effective approach for the treatment of HCHs, but also revealed the underlying mechanism based on in-depth experimental investigation and theoretical calculation.

Determination of lindane in surface water samples and its degradation by hydrogen peroxide and persulfate assisted TiO2-based photocatalysis

Organochlorine pesticides (OCPs) have been used extensively as insecticides and herbicides. This study investigates the occurrence of lindane in surface water from the Peshawar valley (i.e., Peshawar, Charsadda, Nowshera, Mardan and Swabi districts of Khyber Pakhtunkhwa, Pakistan). Out of 75 samples tested (i.e., 15 samples from each district), 13 samples (including 2 from Peshawar, 3 from Charsadda, 4 from Nowshera, 1 from Mardan, and 3 from Swabi) are found to be contaminated with lindane. Overall, the detection frequency is 17.3%. The maximum concentration of lindane is detected in a water sample from Nowshera and found to be 2.60 μg L^-1. Furthermore, the degradation of lindane in the water sample from Nowshera, containing the maximum concentration, is investigated by simulated solar-light/TiO₂ (solar/TiO₂), solar/H₂O₂/TiO₂ and solar/persulfate/TiO₂ photocatalysis. The degradation of lindane by solar/TiO₂ photocatalysis is 25.77% after 10 h of irradiation. The efficiency of the solar/TiO₂ process is significantly increased in the presence of 500 μM H₂O₂ and 500 μM persulfate (PS) (separately), represented by 93.85 and 100.00% lindane removal, respectively. The degradation efficiency of lindane is lower in natural water samples as compared to Milli-Q water, attributed to water matrix effect. Moreover, the identification of degradation products (DPs) shows that lindane follows similar degradation pathways in natural water samples as the one in Milli-Q water. The results show that the occurrence of lindane in surface waters of Peshawar valley is a matter of great concern for human beings and the environment. Interestingly, H₂O₂ and PS assisted solar/TiO₂ photocatalysis is an effective method for the removal of lindane from natural water.

Real-Time Monitoring of the Atrazine Degradation by Liquid Chromatography and High-Resolution Mass Spectrometry: Effect of Fenton Process and Ultrasound Treatment

High resolution mass spectrometry (HRMS) was coupled with ultra-high-performance liquid chromatography (uHPLC) to monitor atrazine (ATZ) degradation process of Fenton/ultrasound (US) treatment in real time. Samples were automatically taken through a peristaltic pump, and then analysed by HPLC-HRMS. The injection in the mass spectrometer was performed every 4 min for 2 h. ATZ and its degradation metabolites were sampled and identified. Online Fenton experiments in different equivalents of Fenton reagents, online US experiments with/without Fe²⁺ and offline Fenton experiments were conducted. Higher equivalents of Fenton reagents promoted the degradation rate of ATZ and the generation of the late-products such as Ammeline (AM). Besides, adding Fe²⁺ accelerated ATZ degradation in US treatment. In offline Fenton, the degradation rate of ATZ was higher than that of online Fenton, suggesting the offline samples were still reacting in the vial. The online analysis precisely controls the effect of reagents over time through automatic sampling and rapid detection, which greatly improves the measurement accuracy. The experimental set up proposed here both prevents the degradation of potentially unstable metabolites and provides a good way to track each metabolite.

Degradation of Residual Herbicide Atrazine in Agri-Food and Washing Water

Atrazine, an herbicide used to control grassy and broadleaf weed, has become an essential part of agricultural crop protection tools. It is widely sprayed on corn, sorghum and sugar cane, with the attendant problems of its residues in agri-food and washing water. If ingested into humans, this residual atrazine can cause reproductive harm, developmental toxicity and carcinogenicity. It is therefore important to find clean and economical degradation processes for atrazine. In recent years, many physical, chemical and biological methods have been proposed to remove atrazine from the aquatic environment. This review introduces the research works of atrazine degradation in aqueous solutions by method classification. These methods are then compared by their advantages, disadvantages, and different degradation pathways of atrazine. Moreover, the existing toxicological experimental data for atrazine and its metabolites are summarized. Finally, the review concludes with directions for future research and major challenges to be addressed.

Impact of gamma-irradiation on the degradation and mineralization of hydroxychloroquine aqueous solutions

In this work, the effect of gamma irradiation emitted by Cobalt 60 source has been investigated for the degradation of hydroxychloroquine (HCQ). The monitoring of the gamma irradiation treatment of HCQ aqueous solutions was followed by UV-visible, chemical oxygen demand, total organic carbon (TOC) and LC/MS analyses. Effects of several important parameters such as concentration, dose rate and pH on the degradation efficiency were studied then evaluated. Achieved results showed that % TOC removal efficiency of 98.5 was obtained after 8 kGy absorbed dose which warrants HCQ mineralization. The process was found to be more efficient when the initial pollutant concentration was low, with higher dose rate and at neutral pH. Furthermore, HCQ degradation kinetic study revealed a pseudo-first-order kinetic. Additionally, based on by-products identified by LC/MS, a degradation mechanistic schema mediated through hydroxyl radicals generated by water radiolysis has been proposed. Finally, in order to check the potential industrial application viability the energy consuming was evaluated.

Decontamination of fenitrothion from aqueous solutions using rGO/MoS2/Fe3O4 magnetic nanosorbent: synthesis, characterization and removal application

In the present work, rGO/MoS2/Fe3O4 nanocomposite was synthesized and after confirmation of the structure by FTIR, XRD, and FESEM techniques, its performance as nanosorbent was investigated for the removal of fenitrothion pesticide from the aqueous media. The parameters affecting the removal process including agitation time, pH of the reaction medium, adsorbent content, initial analyte concentration as well as desorption parameters were investigated and optimized. Under optimum conditions (pH = 7, adsorbent amount: 30 mg, adsorption and desorption time: 5 min, eluent type and volume: 0.01 M ethanol-acetic acid and 4 mL), the synthesized adsorbent was able to remove fenitrothion pesticide up to 98% with an adsorption capacity of 33.4 mg/g. By investigation of the line equation and the correlation coefficient value, it was found that the adsorption process, in this study, follows the Langmuir model.

Degradation of benzimidazoles by photoperoxidation: metabolites detection and ecotoxicity assessment using Raphidocelis subcapitata microalgae and Vibrio fischeri

Benzimidazoles (BZ) are among the most used drugs to treat parasitic diseases in both human and veterinary medicine. In this study, solutions fortified with albendazole (ABZ), fenbendazole (FBZ), and thiabendazole (TBZ) were subjected to photoperoxidation (UV/H₂O₂). The hydroxyl radicals generated by the process removed up to 99% of ABZ, and FBZ, in the highest dosage of H₂O₂ (i.e., 1.125 mmol L^-1; 4.8 kJ L^-1). In contrast, 20% of initial TBZ concentration remained in the residual solution. In the first 5 min of reaction (i.e., up to 0.750 mmol L^-1 of H₂O₂), formation of the primary metabolites of ABZ-ricobendazole (RBZ), albendazole sulfone (ABZ-SO₂), and oxfendazole (OFZ)-was observed. However, these reaction products were converted after the reaction time was doubled. The residual ecotoxicity was investigated using the Raphidocelis subcapitata microalgae and the marine bacteria Vibrio fischeri. The results for both microorganisms evidence that the residual solutions are less harmful to these microorganisms. However, after 30 min of reaction, the treated solution still presents a toxic effect for V. fischeri, meaning that longer reaction times are required to achieve an innocuous effluent.

Dramatically enhanced degradation of recalcitrant organic contaminants in MgO2/Fe(III) Fenton-like system by organic chelating agents

Herein, the application of organic acids as chelating agent, including citric acid (CA), tartaric acid (TA), oxalic acid (OA) and ethylenediaminetetraacetic acid (EDTA), to enhance the degradation performance of MgO₂/Fe(III) system was investigated in the terms of chelating agent dosage, Fe(III) dosage, reaction temperature, initial solution pH and inorganic anion. When the molar ratio of MgO₂/Fe(III)/chelating agent was 1 : 0.7 : 0.3, the degradation efficiencies of Rhodamine B (RhB) increased from 6.7% (without chelating agent) to 42.3%, 98.5%, 48.9% and 25.8% within 30 min for CA, TA, OA, and EDTA, respectively. The promotion effect was mainly attributed to the chelation between chelating agents and Fe(III), rather than the acidification of chelating agents. The pseudo-first-order kinetic model well fitted RhB degradation in MgO₂/Fe(III)/TA system, and the kinetic rate constant reached up to 0.295 min^-1. Hydroxyl radical was confirmed to be the dominant active species to degrade organics in the MgO₂/Fe(III)/TA system. Notably, the degradation system could work in a broad pH (3-11) and temperature (5-35 °C) range. Moreover, the MgO₂/Fe(III)/TA system can also effectively degrade methylene blue, tetracycline and bisphenol A. This work provided a new, efficient and environmentally-friendly Fenton-like system for stubborn contaminant treatment.

Application of electron beam water radiolysis for sewage sludge treatment-a review

A review of the applicability of electron beam water radiolysis for sewage sludge treatment is presented. Electron beam treatment has been proven to be a successful approach to the disinfection of both wastewater and sewage sludge. Nevertheless, before 2000, there were concerns about the perceived high capital costs of the accelerator and with public acceptance of the usage of radiation for water treatment purposes. Nowadays, with increased knowledge and technological development, it may be not only possible but also desirable to use electron beam technology for risk-free sewage sludge treatment, disposal and bio-friendly fertiliser production. Despite the developing interest in this method, there has been no attempt to perform a review of the pertinent literature relating to this technology. It appears that understanding of the mechanism and primary parameters of disinfection is key to optimising the process. This paper aims to reliably characterise the sewage sludge electron beam treatment process to elucidate its major issues and make recommendations for further development and research. Graphical abstract.

A critical review of ionizing radiation technologies for the remediation of waters containing Microcystin-LR and M. aeruginosa

Harmful algal and cyanobacterial blooms pose threats to human and ecological health due to their release of hazardous toxins. Microcystin-LR (MC-LR), a potent hepatotoxin, is the most prevalent cyanotoxin found in freshwater blooms. Although produced by many species of cyanobacteria, Microcystis aeruginosa is most commonly associated with MC-LR production. These blooms are increasing in occurrence in lakes, ponds, and other surface waters and, therefore, require efficient treatment methods to be removed from water supplies. Ionizing radiation technologies offer promising approaches for the removal of organic pollutants in water, including cyanotoxins and cyanobacteria. Gamma irradiation for the degradation of cyano-bacteria and toxins is effective for overall MC-LR degradation as well as reducing cell concentrations. However, gamma irradiation technology involves use of radioactive isotopes and, therefore, may not feasible commercially from a security perspective. Electron beam (eBeam) irradiation technology, which relies on regular electricity to generate highly energetic electrons, is able to achieve the same results without the confounding challenges of radioactive isotopes and related security issues. In this critical review, the current state of the science concerning the remediation of MC-LR and M. aeruginosa with ionizing radiation technologies is presented and future necessary research is discussed.

The effect of ozonation on the degradation of carbaryl in aqueous solution

The aim of this study is to investigate the synergetic effect of ozonation on ultraviolet irradiation on the degradation of carbaryl (CBL) (1-naphthyl-N-methylcarbamate) in aqueous solutions (40 mg L^-1). The degradation of CBL and the intermediates formed during ozonation were determined by gas chromatography-mass spectrometer. The change in formaldehyde, dissolved oxygen, pH, and total acidity were determined as a function of ozonation time. It was found that the dissolved oxygen and total acidity were increased with the increasing ozonation time but the pH was decreased with the increasing ozonation time. The aliphatic acids formed during ozonation were followed by ion chromatography as a function of ozonation time. It was found that the effect of ozonation is highly effective on the degradation of CBL. The complete degradation of CBL has occurred at 75-second ozonation time. As a consequence of the obtained results the possible degradation pathway was proposed. The results confirmed that ozonation is an effective method for the degradation of CBL.

Photochemical transformation of C3N4 under UV irradiation: Implications for environmental fate and photocatalytic activity

In this study, the photo-transformations of bulk C₃N₄ (CN) and oxidized C₃N₄ (OCN) under UV-irradiation were examined. Through NO₃^- release measurements, we found that the photo-transformation rate of OCN is higher than that of CN. Various characterization results revealed the structural and chemical properties changes of CN and OCN after photo-transformation. We proposed that under reactive oxygen species attack, CN and OCN were gradually broken into smaller fragments and finally mineralized into NO₃-, CO₂, and H₂O through the circular reactions of deamination-hydroxylation-decarboxylation. Through the zeta potential measurements and sedimentation experiments, the influence of photo-transformation on the water stabilities of CN and OCN were assessed. The stability of CN in water increased while the water stability of OCN decreased after photo-transformation, implying that the changes to C₃N₄-based materials caused by photo-transformation may significantly impact their environmental behaviors. Moreover, the photocatalytic activities of the photo-transformed OCN and CN substantially decreased, indicating that the structural changes might be the main reason for their photocatalytic activity loss. These findings highlight the non-negligible influence of photo-transformation on the fate of C₃N₄ in aquatic environments, as well as on the photochemical stability during its use.

Alleviation of atrazine toxicity to maize seedlings grown in soils with amendment of biochar derived from wheat under different temperatures

The effects of different biotransformation temperatures (250, 550, and 850 °C) and different dose (0-1%) of biochar on the physiological characteristics of maize seedlings under the stress of atrazine were studied. The results show that atrazine significantly inhibits the growth of maize seedlings, while biochar can alleviate the toxicity of atrazine to seedlings. Compared with the low temperature of biochar, the addition of BC850, the germination rate of maize was significantly increased. The biochars prepared at higher temperatures and adding 1% dose could significantly increase the plant height, while the effect of biochar on root growth of maize seedlings was not significant. According to the data, with the increase of biochar application, the accumulation of atrazine in maize leaves and roots gradually decreased. At the maximum application rate of 1%, the content of atrazine in maize leaves decreased by 58.94%, 60.70%, and 62.75%. The content of atrazine in maize roots decreased by 52.93%, 54.57%, and 55.42%, respectively. Meanwhile, the addition of biochar could slightly increase the chlorophyll content, but the change was not significant statistically, while the content of chlorophyll b increases with the application amount. The content of malondialdehyde (MDA) in roots and leaves decreased first and the increased with the dose of biochar from 0 to 1%. Compared with the atrazine treatment, the content of MDA in leaves and roots decreased significantly, and the lipid peroxidation of maize significantly decreased. With the addition of three kinds of biochar, the soluble content of plant tissues increased gradually, BC550 biochar has the most noticeable remediation effect. Given the toxicity of atrazine in soil, the quality and yield of agricultural products, and the potential health risks to human beings, biochar can be the soil remediation product.

Degradation of some organophosphorus pesticides in aqueous solution by gamma irradiation

This study reviews the effect of different gamma radiation doses (1, 3, 5, 10 and 20 kGy) on the degradation of chlorfenvinphos, diazinon, dimethoate, and profenofos at different concentrations (0.5, 1.0, and 5 μg/mL) in aqueous solutions (deionized, tap, and groundwater). The role of initial concentration, measured total dissolved solids and pH on degradation was investigated. The degradation of the four tested organophosphates due to gamma irradiation was determined using LC-MS/MS. The radiolytic degradation products were studied using the scan mode of GC-MS/MS. The radiation chemical yield, dose constant, D_0.5, and D_0.9 were calculated to evaluate degradation efficiency for each compound. All pesticides are completely eliminated, despite water type, at low concentration levels of 0.5 and 1 μg/mL. At concentration level 5 μg/mL, gamma irradiation could completely remove pesticides concentration in de-ionized water, but the binding effect of total dissolved solids decreased degradation efficiency of some organophosphates such as diazinon. The D_0.9 of 5 μg/mL concentration of chlorfenvinphos, diazinon, dimethoate, and profenofos in de-ionized water were 6.6, 8.7, 11.0, and 17.6 respectively. Also, Gamma irradiating of an agriculture wastewater sample resulted in the removal of carbaryl, carbosulfan, and diazinon at 6 kGy dose.

Photocatalytic oxidation of diuron using nickel organic xerogel under simulated solar irradiation

In this study, a nickel organic xerogel (X-Ni) was used as semiconductor photocatalyst for the degradation of the herbicide diuron (DRN) in aqueous solution. The main objective of this work was to analyze and compare the effectiveness of solar irradiation to remove DRN from water both by direct photolysis and photocatalytic degradation. We examined the influence of the initial concentration of the herbicide, the solution pH, the presence of different ions in the medium, the chemical composition of the water, and the presence of a photocatalyst, after 240 min of irradiation. Direct photolysis achieved a low percentage of DRN degradation but was favored: i) by a reduction in the initial concentration of the herbicide (from 35.6% to 79.0% for 0.150 × 10^-3 mol/L and 0.021 × 10^-3 mol/L of DRN, respectively) and ii) at solution pHs at which diuron is positively charged (78.6% for pH 2 and 50.4% for pH 7), as suggested by DFT calculations carried out for DRN and its protonated form (DRN-H⁺). The corresponding mono-demethylated DRN derivative, 1-(3,4-dichlorophenyl)-3-methylurea (DCPU), was identified as a DRN degradation byproduct. In addition, the presence of certain anions in the medium significantly affected the overall degradation process by direct photolysis, due to the additional generation of HO radicals. We highlight that the presence of X-Ni considerably improved the photodegradation process under solar irradiation. The photocatalytic degradation rate constant was directly proportional to the xerogel concentration, because an increase in catalyst dose produced an increase in surface active sites for the photodegradation of DRN, enhancing the overall efficiency of the process. Thus, when 4167 mg/g of X-Ni was added, the DRN removal rate was 3-fold higher and both percentage of degradation and mineralization increased 88.5% with respect to the results obtained by direct photolysis.

Engineering nanomaterials for water and wastewater treatment: review of classifications, properties and applications

Based on their characteristics and applicability, a new category of NMs is proposed for water and wastewater treatment.

Photocatalytic removal of fluoroquinolones and their antimicrobial activity from water matrices at trace levels: a comparison of commercial TiO2 catalysts

In this study, a solution containing the fluoroquinolones (FQs) ciprofloxacin, lomefloxacin, and ofloxacin (antimicrobial agents) was subjected to photocatalytic oxidation under UVA irradiation, employing the commercial titanium dioxide as catalyst. On-line solid phase extraction coupled to ultra-high-performance liquid chromatography-mass spectroscopy was used to pre-concentrate and quantify the analytes. The process provided an almost 95% degradation efficiency for all the FQs. The TiO₂ PC500 (100% anatase) was more efficient than TiO₂ P25 (80% anatase) for FQs degradation. The matrix effect on the efficiency of the process was evaluated by ultrapure water - UW, simulated water - SW, bottled water -BW, and public drinking tap water - TW. Simulated water showed lower interference, compared to drinking water and bottled mineral water, due to the lower concentrations of hydroxyl radical scavengers. The assessment of the residual antimicrobial activity in the solution, when using 50 mg L^-1 PC500 or 100 mg L^-1 P25, showed reductions of biological activity (after 120 min of reaction) of 92.4% and 95.4% for Escherichia coli, and 78.1% and 84.2% for Bacillus subtilis, respectively. It shows that the photocatalytic oxidation process was able to not only degrade the FQs but also deactivate its biological activity in the resultant solution.

Decomposition of antibiotic ornidazole by gamma irradiation in aqueous solution: kinetics and its removal mechanism

An efficient gamma radiolytic decomposition of one of the extensively used pharmaceutical ornidazole (ORZ) was explored under different experimental conditions by varying initial concentrations, solution pHs, and doses and concentrations of inorganic ([Formula: see text]) and organic (t-BuOH) additives. The results showed that low ORZ concentrations could be efficiently decomposed using gamma irradiation. The decomposition was followed by pseudo first-order reaction kinetics with rate constant values of 2.34, 1.48, 1.11, and 0.80 kGy^-1 for the following initial concentrations: 25, 50, 75, and 100 mg L^-1 with their corresponding (G(-ORZ)) values of 1.004, 1.683, 2.237, and 2.273, respectively. Decomposition rate of ORZ was remarkably improved under acidic condition when compared to neutral or alkaline medium. It was also observed that the decomposition was primarily caused by the reaction of ORZ with radiolytically generated reactive HO^• radicals. The addition of H₂O₂ had a synergistic effect on the decomposition and mineralization extent of ORZ. However, the removal of total organic carbon (TOC) was not as effective as the decomposition of ORZ. Finally, the quantum chemical calculations were employed to optimize the geometry structure of ORZ and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) was used to identify the decomposition intermediates. On the basis of Gaussian calculations and analysis of LC-QTOF-MS, it can be inferred that ORZ radiolytic decomposition was mainly attributed to oxidative HO^• radicals and the direct cleavage of ORZ molecules. Possible pathways for ORZ decomposition using gamma irradiation in aqueous medium were proposed.

Microparticles based on ionic and organosolv lignins for the controlled release of atrazine

Lignins are natural polymers of the lignocellulosic biomass. Nowadays, there is a growing interest in developing value-added products based on lignins due to their renewability, low cost and abundance. In this work, lignin microspheres from organosolv and ionic isolation processes were prepared for the controlled release of atrazine. Microspheres were prepared by the solvent extraction/evaporation technique. The controlled release of atrazine from organosolv and ionic lignins microparticles was studied in water. Mobility experiments were performed in an agricultural soil from Argentina. The results showed that microparticles prepared using dichloromethane as the dispersed phase were spherical, while lignins dispersed in ethyl acetate produce irregular microparticles. Organosolv lignin microparticles presented higher encapsulation efficiency for all herbicide loads. About 98% and 95% of atrazine was released in 24 and 48 h approximately from organosolv and ionic lignin microparticles, respectively. The release profiles of atrazine from both lignin microparticles were not affected by the herbicide load. Atrazine mobility experiments in soil showed that about 80% of free atrazine was leached in 37 days, while 65.0% and 59.7% of the herbicide was leached from ionic and organosolv lignin microparticles, respectively. Thus, atrazine-loaded microparticles could reduce leaching compared to a commercial formulation of free atrazine.

Characterization of spectral responses of dissolved organic matter (DOM) for atrazine binding during the sorption process onto black soil

This study was aim to investigate the interaction between soil-derived dissolved organic matter (DOM) and atrazine as a kind of pesticides during the sorption process onto black soil. According to the experimental data, the adsorption capacity of Soil + DOM, Soil and DOM were 41.80, 31.45 and 9.35 mg kg^-1, separately, which indicated that DOM significantly enhanced the adsorption efficiency of atrazine by soil. Data implied that the pseudo-second-order kinetic equation could well explain the adsorption process. The adsorption isotherms (R² > 0.99) had a satisfactory fit in both Langmuir and Freundlich models. Three-dimensional excitation-emission matrix (3D-EEM), synchronous fluorescence, two-dimensional correlation spectroscopy (2D-COS) and Fourier transform infrared spectroscopy (FT-IR) were selected to analyze the interaction between DOM and atrazine. 3D-EEM showed that humic acid-like substances were the main component of DOM. The fluorescence of DOM samples were gradually quenched with the increased of atrazine concentrations. Synchronous fluorescence spectra showed that static fluorescence quenching was the main quenching process. 2D-COS indicated that the order of the spectral changes were as following: 336 nm > 282 nm. Furthermore, the fluorescence quenching of humic-like fraction occurred earlier than that of protein-like fraction under atrazine surroundings. FT-IR spectra indicated that main compositions of soil DOM include proteins, polysaccharides and humic substances. The findings of this study are significant to reveal DOM played an important role in the environmental fate of pesticides during sorption process onto black soil and also provide more useful information for understanding the interaction between DOM and pesticides by using spectral responses.

Antimicrobial activity against Gram-positive and Gram-negative bacteria during gatifloxacin degradation by hydroxyl radicals

Gatifloxacin, an antimicrobial drug belonging to the fluoroquinolone family, is active against Gram-positive and Gram-negative bacteria and is extensively used for the control of infections in humans. The presence of the drug in environmental matrices has already been reported. This study investigated the degradation of gatifloxacin in water by hydroxyl radicals generated by the UV_254 nm/H₂O₂ process ([Formula: see text] 0.4-2.4 mmol L^-1) and evaluated the capacity of the radicals to reduce the antimicrobial activity against Gram-positive and Gram-negative bacteria. Acute toxicity assays were performed with Vibrio fischeri, and the degradation products were proposed. The hydroxyl radicals formed in the processes were able to degrade the fluoroquinolone and remove the antimicrobial activity from the aqueous solution. Approximately 97 % gatifloxacin degradation was observed after applying 2.4 mmol L^-1 of initial H₂O₂ concentration and 20 min of UVC_254nm irradiation (130 J s^-1). The acute toxicity assays showed that the toxicity of the treated solution for V. fischeri increased as the gatifloxacin concentration in the solution decreased.

Degradation of quinolone antibiotic, norfloxacin, in aqueous solution using gamma-ray irradiation

This study reports the efficiency of gamma-ray irradiation to degrade quinolone antibiotic, norfloxacin, in aqueous solution. Laboratory batch experiments were conducted to determine the "pseudo-first" order degradation kinetics of norfloxacin in the concentration ranges of 3.4-16.1 mg L(-1) by gamma-ray irradiation. The dose constant was found to be dependent on the initial concentration of norfloxacin and gamma-ray irradiation dose rate (D r). The saturation of norfloxacin sample solutions with N2, air or N2O, and the presence of tert-butanol and 2-propanol showed that (•)OH played more crucial role in the degradation of norfloxacin. The second order rate constants of (•)OH, eaq (-), and (•)H with norfloxacin were calculated to be 8.81 × 10(9), 9.54 × 10(8), and 1.10 × 10(9) M(-1) s(-1), respectively. The effects of various additives including CO3 (2-), HCO3 (-), NO3 (-), NO2 (-), and thiourea and the pH of the medium on the degradation of norfloxacin were also investigated. Norfloxacin degradation was lower in surface water and wastewater than in ultrapure water. Several degradation byproducts of norfloxacin were identified from which the possible degradation pathway was proposed.

Gamma radiolytic decomposition of endosulfan in aerated solution: the role of carbonate radical

The present study elaborates the removal of endosulfan, an emerging water pollutant and potential carcinogenic, in aerated solution. The influence of Cl(-), NO3 (-), NO2 (-), CO3 (2-), HCO3 (-), SO3 (2-), and humic acid was assessed on the radiolytic degradation of endosulfan. A strong inhibition on the radiolytic degradation of endosulfan was observed in the presence of NO3 (-), NO2 (-), and SO3 (2-). Instead, a slight increase in the removal efficiency of endosulfan was observed at high concentrations of CO3 (2-) and HCO3 (-). The formation of CO3 (•-) in radiolytic degradation of endosulfan in the presence of CO3 (2-) and HCO3 (-) was demonstrated by adding SO3 (2-) that rapidly react with CO3 (•-). The results indicate that CO3 (•-) formed from the reactions of CO3 (2-) and HCO3 (-) and commonly found in natural water can play an important role in the degradation of endosulfan and other sulfur containing electron-rich compounds. The study showed faster degradation of endosulfan at lower concentration compared to high concentration and removal was found to follow pseudo-first-order kinetic. Endosulfan ether was found as the main degradation product and degradation pathway was found to be initiated at the S=O bond of endosulfan. The efficiency of gamma irradiation in the removal of endosulfan was examined in terms of formation of short chain organic acids and chloride ion accumulation.