Activation of manganese dioxide with bisulfite for enhanced abiotic degradation of typical organophosphorus pesticides: Kinetics and transformation pathway

Exploring the potent hydrolytic activity of chitosan-cerium complex microspheres resin for organophosphorus pesticide degradation

Chitosan is a biocompatible, non-toxic and renewable natural basic polysaccharide that can be cross-linked and reacted with Ce(IV) to form a physiologically active chitosan-Ce(IV) complex. To investigate this novel complex and its potential to hydrolyze phosphate ester bonds, chitosan-cerium complex microspheres resin (CS-CCMR) was prepared from chitosan and ceric ammonium nitrate by reversed-phase suspension cross-linking polymerization. CS-CCMR was characterized, its ability to hydrolyze disodium p-nitrobenzene phosphate (PNPP2Na) and organophosphorus pesticides was investigated, and the hydrolytic mechanism was explored. CS-CCMR was composed of dark yellow microspheres with smooth surfaces and dense pores. It was found that CS-CCMR contained 4.507 mg/g Ce(IV), indicating that coordination polymerization between Ce(IV) and chitosan was successful. The presence of Ce(IV) in CS-CCMR was confirmed by multiple analytical methods and it was found that coordination of Ce(IV) by chitosan was mediated by the nitrogen atom of the amino group and the oxygen atom of the hydroxyl group of chitosan. It was shown that CS-CCMR efficiently hydrolyzed the phosphate ester bonds of PNPP2Na and five organophosphorus pesticides. Hydrolysis of PNPP2Na is potentially accomplished by charge neutralization and nucleophilic substitution. The mechanism of parathion degradation by CS-CCMR involves modification of the nitro group to give aminoparathion, followed by cleavage of the P-O bond to generate diazinphos. Consequently, the novel chitosan-Ce(IV) complex exhibits great efficiency for hydrolysis of phosphate ester bonds and CS-CCMR is expected to be developed as an agent to reduce the possibility of contamination of fruit and vegetable drinks by organophosphorus pesticides.

Degradation kinetics and transformation pathway of methyl parathion by δ-MnO2/oxalic acid reaction system

Methyl parathion (MP) is a typical organophosphorus pesticide that is widely used worldwide, and hydrolysis, oxidation and reduction are the main abiotic degradation processes. Manganese dioxide (MnO₂) and organic acid can participate in various geochemical processes of pollutants, a reaction system was constructed to degrade MP using δ-MnO₂ and oxalic acid. The δ-MnO₂/oxalic acid reaction system could efficiently degrade MP, and the removal rate of MP (20 μM) reached 67.83% within 30 h under the optimized conditions (pH 5, [δ-MnO₂] = 2 mM, [oxalic acid] = 100 mM). MP was hydrolyzed by substitution reactions of S_N@P and S_N@C, and reduced by conversion of the nitro groups (-NO₂) in MP and its hydrolysates to amino groups (-NH₂). The primary active substance produced in the reaction system was the complexes dominated by Mn(III)-oxalic acid. This study provides a scientific basis for the degradation of organophosphorus pesticides using MnO₂ and an organic acid. The results have important theoretical significance and application value for pollution control and remediation of organophosphorus pesticides.

Photocatalysis of carbamazepine via activating bisulfite by ultraviolet: Performance, transformation mechanism, and residual toxicity assessment of intermediates products

Carbamazepine (CBZ) as an extensively distributed emerging pollutant has menaced ecological security. The degradation performance of CBZ by UV driven bisulfite process was investigated in this work. The kinetics results indicated that CBZ was high-efficiently degraded by UV/bisulfite following a pseudo first-order kinetic model (K_obs = 0.0925 min^-1). SO₄^•- and •OH were verified as the reactive oxidants by EPR test and the radicals scavenging experiment using MeOH and TBA. SO₄^•- played a dominant role for CBZ degradation. The Density functional theory (DFT) and LC-qTOF-MS/MS clarified that hydroxylation, ketonation, ring opening reaction, and ring contraction were main transformation patterns of CBZ. As to influence factors, CBZ degradation was significantly hindered in presence of CO₃^2-, HPO₄^2- and NOM. Toxicological analysis derived from metabonomics suggested that the remarkable alteration of metabolic profile was triggered by exposure to intermediates mixture. CBZ intermediates interfered in several key metabolic pathways, including pentose phosphate, amino acids, lysine degradation, glycerophospholipid, glutathione, nucleotides and carbohydrate, which was alleviated after UV/bisulfite treatment. This work provided a meaningful support to potential risk of CBZ intermediates products, which shed light on the future application in eliminating drugs using UV /bisulfite.

Enhanced degradation of atrazine through UV/bisulfite: Mechanism, reaction pathways and toxicological analysis

Atrazine residue in the environment continues to threaten aquatic ecosystem and human health owing to its adverse effect. However, limited researches focused on degradation mechanism of atrazine by UV/bisulfite, especially risk of intermediates at cellular and molecular level has not been seriously elaborated. In current work, transformation patterns and residual toxicity of intermediates of atrazine by UV/bisulfite were systematically investigated. The atrazine degradation was described by a pseudo first-order kinetic model (K_obs = 0.1053 min^-1). The presence of H₂PO₄^-, HCO₃^- and HA had a powerful inhibition. Scavenging test of radicals illustrated that SO₄^•-, •OH and O₂^•- existed in UV/bisulfite system, SO₄^•- and •OH were mainly responsible for atrazine degradation. Eight degradation intermediates were identified, which were involved in dealkylation, alkyl oxidation, dechlorination-hydroxylation, and alkylic-hydroxylation. E. coli as a model microorganism was selected to assess the risk of degradation intermediates. The levels of reactive oxygen species, MDA and Na⁺/K⁺-ATPase were declined, suggesting that oxidative damage induced by these intermediates was weakened. According to differential metabolites expression analysis, several key metabolites including aspartate, L-tryptophan, L-asparagine, cytidine, cytosin, stearic acid, behenic acid, were up-regulated, and glutathione, cadaverin, L-2-hydroxyglutaric acid and phytosphingosine were downregulated, clarifying that effective detoxification of atrazine can be performed by UV/bisulfite.

Deep Learning-Based Multicapturer SERS Platform on Plasmonic Nanocube Metasurfaces for Multiplex Detection of Organophosphorus Pesticides in Environmental Water

In situ rapid detection of contaminants in environmental water is crucial for protecting the ecological environment and human health; however, it is always hindered by the complexity of sample matrices, trace content, and unknown species. Herein, we demonstrate a deep learning-based multicapturer surface-enhanced Raman scattering (SERS) platform on plasmonic nanocube metasurfaces for multiplex determination of organophosphorus pesticides (OPPs) residues. Poly(vinylpyrrolidone), 4-mercaptobenzoic acid, and l-cysteine are assembled on Ag nanocubes (AgNCs) and act as capturers to chemically define OPPs. Meanwhile, the OPPs-captured AgNCs efficiently close the interparticle distance and generate plasmonic metasurfaces, guaranteeing ultrasensitive and reproducible SERS analysis. Furthermore, by strategically combining all capturer-OPP SERS spectra, comprehensive "combined-SERS spectra" are reconstructed to enhance spectral variations of each OPP. Based on the combined-SERS spectra, a deep learning model is trained to predict OPPs, which significantly improve the qualitative and quantitative analysis accuracy. We successfully identified multiple OPPs in farmland, river, and fishpond water using this strategy. The whole detection procedure requires only 30 min, including sampling, SERS measurements, and deep learning analyses. This combination of a multicapturer SERS platform with the deep learning algorithm creates a rapid and reliable analytical strategy for multiplex detection of target molecules, providing a potential paradigm shift for environment-related research.

Activation of Bisulfite with Pyrophosphate-Complexed Mn(III) for Fast Oxidation of Organic Pollutants

Aqueous complexes of Mn(III) ion with ligands exist in various aquatic systems and many stages of water treatment works, while HSO₃⁻ is a common reductant in water treatment. This study discloses that their encounter results in a process that oxidizes organic contaminants rapidly. Pyrophosphate (PP, a nonredox active ligand) was used to prepare the Mn(III) solution. An approximate 71% removal of carbamazepine (CBZ) was achieved by the Mn(III)/HSO₃⁻ process at pH 7.0 within 20 s, while negligible CBZ was degraded by Mn(III) or HSO₃⁻ alone. The reactive species responsible for pollutant abatement in the Mn(III)/HSO₃⁻ process were SO₄^•− and HO^•. The treatment efficiency of the Mn(III)/HSO₃⁻ process is highly related to the dosage of HSO₃⁻ because HSO₃⁻ acted as both the radical scavenger and precursor. The reaction of Mn(III) with HSO₃⁻ follows second-order reaction kinetics and the second-order rate constants ranged from 7.5 × 10³ to 17 M⁻¹ s⁻¹ under the reaction conditions of this study, suggesting that the Mn(III)/HSO₃⁻ process is an effective process for producing SO₄^•−. The pH and PP:Mn(III) ratio affect the reactivity of Mn(III) towards HSO₃⁻. The water background constituents, such as Cl⁻ and dissolved organic matter, induce considerable loss of the treatment efficiency in different ways.

Exploring a novel silicone surfactant-based deep eutectic solvent functionalized magnetic iron particles for the extraction of organophosphorus pesticides in vegetable samples

The current study discussed the use of silicone surfactant-based deep eutectic solvent as a surface modifier for magnetic iron particles (Fe₃O₄) to produce a novel adsorbent and its application for the extraction of organophosphorus pesticides (OPPs) in vegetable samples. A deep eutectic solvent (DES) was prepared using low toxic and inexpensive substances such as silicone surfactant (SS) and dodecanoic acid (DoAc). This new eco-friendly SS:DoAc based DES was explored as a substitution to traditional organic reagents for surface modification of Fe₃O₄ to increase the adsorption capacity and to reduce the matrix interferences, hazardous waste generation and environmental pollution. The newly synthesized SS:DoAc@Fe₃O₄ adsorbent was successfully characterized and applied in magnetic solid phase extraction (MSPE). Under optimized conditions, the proposed approach exhibited excellent linearity ranging from 0.1 to 200 µg/kg (R² ≥ 0.9970), low detection limit (0.03-0.1 µg/kg) and acceptable relative recovery (80-119 %) for the studied OPPs.

Hydrolysis and photolysis of flupyradifurone in aqueous solution and natural water: Degradation kinetics and pathway

Flupyradifurone (FPO) easily spreads to the water environment after application because of its high solubility in water (3200 mg/L, 20 °C), but as a novel neonicotinoid pesticide, its environmental fate study is still lacking. Here, laboratory experiments were conducted to investigate the degradation kinetics and pathways of FPO in aqueous solutions and natural waters. The results showed that FPO was fairly stable in water under natural conditions (the hydrolysis half-lives at 15 °C, 25 °C, and 35 °C were >150 d, and the photolysis half-lives under sunlight were >168 h). However, FPO was photodegraded rapidly under ultraviolet (UV) light (half-lives of 2.37-3.81 min). Then, indirect photolysis under UV light was examined with the addition of photosensitizers, revealing that direct photolysis is the main FPO degradation pathway in water, and the contribution of indirect photolysis was limited. Moreover, two photoproducts were separated, purified and collected via preparative HPLC, and identified via high resolution mass spectrometry. Then, the plausible photolysis pathway was proposed. The results of this study will contribute to a better understanding of the fate of FPO in the water environment.

Tributyl phosphate degradation and phosphorus immobilization by MnO2: Reaction condition optimization and mechanism exploration

The treatment of tributyl phosphate (TBP) extractant waste from specific industry, eg., nuclear industry, is a great challenge due to its stability and high environmental risk of phosphorus-containing species releasing. Inspired by chemical looping combustion (CLC) technology, a MnO₂-assisted thermal oxidation strategy is proposed for TBP degradation and simultaneously P immobilization. Under recommended reaction conditions of 220 °C, 10 g MnO₂ mL^-1 TBP and 3 h reaction duration, a high P immobilization efficiency of 93.99% is achieved. Material characterization results indicate that P is mainly immobilized in the form of Mn₂P₂O₇, which greatly reduces the environmental risk of P-containing species. TBP degradation intermediates are further identified by thermogravimetric-gas chromatography-mass spectrometry (TG-GC-MS), liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS), which facilitates understanding of reaction mechanisms as well as proposing possible pathways of TBP degradation. It is suggested that MnO₂ provides essential oxygen as oxygen carrier for flameless combustion. Meantime, MnO₂ reduction leads to the generation of Mn(III) species. The existence of oxygen vacancy in MnO₂ also facilitates •O₂^- radical generation. Under flameless combustion and attacks of Mn(III) and •O₂^-, TBP is firstly degraded into intermediates and finally mineralized into CO₂ and H₂O, while P is mainly immobilized as pyrophosphate.

Bisulfite activated permanganate for oxidative water decontamination

Recently, bisulfite-activated permanganate (MnO₄^-; Mn(VII)) process has attracted considerable attention as a novel class of advanced oxidation technology for destruction of organic contaminants in water. However, disputes over the underlying activation mechanism as well as reactive species generated in the Mn(VII)/bisulfite system remain for a long period due to the fairly complex chemistry involved in this system. This article aims to present a critical review on scientific development of the Mn(VII)/bisulfite system, with particular focus on the generation and contribution of various reactive intermediates. Both reactive manganese species (RMnS) (i.e., soluble Mn(III), Mn(V), and Mn(VI)) and radical species (primarily SO₄^•-) are identified as the oxidizing components responsible for enhanced degradation of organic contaminants by the Mn(VII)/bisulfite system. Bisulfite plays a dual role of being an activating agent for reactive intermediates generation and acting as a complexing agent to stabilize RMnS. Solution chemistry (e.g., the [Mn(VII)]/[bisulfite] molar ratio, solution pH, the type of contaminants, ligands, and water matrix components) greatly impacts the generation and consumption of RMnS and radicals, thus influencing the degradation kinetics and pathways of organics. Particularly, dissolved oxygen (DO) is a vital factor for driving the oxidation of organics since the absence of DO can block the generation of SO₄^•- and meantime causes the consumption of RMnS by excess SO₃^•- as a strong reductant. Interestingly, ferrate (FeO₄^2-, Fe(VI)) and hexavalent chromium (CrO₄^2-/HCrO₄^-, Cr(VI)) that are high-valent metal oxyanions analogous to Mn(VII) can be activated by bisulfite via a similar pathway (i.e. both high-valent metal-oxo intermediates and reactive radicals are involved). Furthermore, key knowledge gaps are identified and future research needs are proposed to address the potential challenges encountered in practical application of the Mn(VII)/bisulfite oxidation technology.

Spatiotemporal distribution and risk assessment of organophosphorus pesticides in surface water and groundwater on the North China Plain, China

90 groundwater samples and 14 surface water samples were collected in wet season (summer) and dry season (winter) in the North China Plain (NCP), and analyzed for 11 organophosphorus pesticides (OPPs). The results showed that the main types of OPPs in surface water and groundwater were dimethoate, dichlorvos, methyl-parathion, malathion in both summer and winter. The OPP concentrations in groundwater and surface water were higher in summer than in winter. In the vertical direction, the distribution characteristics of different four types of groundwater sampling points are different. In the horizontal direction: farmland adjacent to a river (FAR) > central farmland (CF) > nonfarm area adjacent to a river (NFAR) > central nonfarm area (CNF). The OPPs concentrations in surface water adjacent to farmland were higher than that in surface water adjacent to nonfarm area. The main factors influencing the distribution of OPPs in the groundwater and surface water were the interaction process between them, the groundwater flow field and the OPPs used in agricultural activities. The ecological risk of OPPs to surface water was greater in summer than in winter. Water Flea was at medium risk, and malathion had the greatest influence on Water Flea in both summer and winter. The non-carcinogenic and carcinogenic risks of the four main OPPs in surface water were higher than in groundwater, and were higher in summer than in winter, but they would not lead to adverse health effects on local residents.

Roles of Sulfites in Reverse Osmosis (RO) Plants and Adverse Effects in RO Operation

More than 60 years have passed since UCLA first announced the development of an innovative asymmetric cellulose acetate reverse osmosis (RO) membrane in 1960. This innovation opened a gate to use RO for commercial use. RO is now ubiquitous in water treatment and has been used for various applications, including seawater desalination, municipal water treatment, wastewater reuse, ultra-pure water (UPW) production, and industrial process waters, etc. RO is a highly integrated system consisting of a series of unit processes: (1) intake system, (2) pretreatment, (3) RO system, (4) post-treatment, and (5) effluent treatment and discharge system. In each step, a variety of chemicals are used. Among those, sulfites (sodium bisulfite and sodium metabisulfite) have played significant roles in RO, such as dechlorination, preservatives, shock treatment, and sanitization, etc. Sulfites especially became necessary as dechlorinating agents because polyamide hollow-fiber and aromatic thin-film composite RO membranes developed in the late 1960s and 1970s were less tolerable with residual chlorine. In this review, key applications of sulfites are explained in detail. Furthermore, as it is reported that sulfites have some adverse effects on RO membranes and processes, such phenomena will be clarified. In particular, the following two are significant concerns using sulfites: RO membrane oxidation catalyzed by heavy metals and a trigger of biofouling. This review sheds light on the mechanism of membrane oxidation and triggering biofouling by sulfites. Some countermeasures are also introduced to alleviate such problems.

Insight into the adsorption properties of a β-cyclodextrin/phillipsite organophilic composite for effective removal of toxic organophosphorus pesticides: kinetic and advanced equilibrium studies

β-Cyclodextrin/phillipsite was used in the uptake of three pesticides from water achieving Qsat values of 360 mg g−1 (MPn), 321.6 mg g−1 (OM), and 434.5 mg g−1 (AC). The uptake energies suggested endothermic physisorption reactions.

Enhanced removal of oxytetracycline antibiotics from water using manganese dioxide impregnated hydrogel composite: Adsorption behavior and oxidative degradation pathways

The present work provides the first attempt of using manganese dioxide loaded poly(sodium acrylate) hydrogel (MnO₂@PSA) to address potential threats posed by oxytetracycline (OTC) antibiotics in aqueous environment. The MnO₂@PSA was prepared via a facile approach and demonstrated enhanced removal performance even under extremely high concentrations of OTC. The outstanding performance exhibited by MnO₂@PSA was attributed to synergetic effects of adsorption oxidative degradation. The synthesized composite was characterized evaluated under varying conditions. The adsorption pH was optimized at pH 5, at which the removal efficiency OTC was reached 91.46%. According to the kinetics study, the pseudo-second-order kinetic model was the best to explain the adsorption data, implying the interaction mechanisms were dominated by chemisorption. The Langmuir isotherm model was the best to explain the isotherm data, and the corresponding maximum adsorbed amount of OTC was 1150.4 mg g^-1. The MnO₂@PSA was highly selective for OTC adsorption and degradation under the presence of natural organic matter and common environmental metal ions. The oxidative degradation study indicated that OTC molecules were structurally degraded into 15 intermediate products via six reaction pathways. Both the theoretical models and spectroscopic methods demonstrated the removal mechanism of OTC onto MnO₂@PSA was governed by ion exchange, cation-π bonding, hydrogen-bonding, and π-π electron donor-acceptor. Overall, MnO₂@PSA is an excellent and environmentally sustainable material to remove OTC from water and wastewater via the combined effects of adsorption and oxidative degradation.

ZrO2 Nanoparticles and Poly(diallyldimethylammonium chloride)-Doped Graphene Oxide Aerogel-Coated Stainless-Steel Mesh for the Effective Adsorption of Organophosphorus Pesticides

A novel sorbent based on the ZrO₂ nanoparticles and poly(diallyldimethylammonium chloride)-modified graphene oxide aerogel-grafted stainless steel mesh (ZrO₂/PDDA-GOA-SSM) was used for the extraction and detection of organophosphorus pesticides (OPPs). Firstly, the PDDA and GO composite was grafted onto the surface of SSM and then freeze-dried to obtain the aerogel, which efficiently reduced the accumulation of graphene nanosheets. It integrated the advanced properties of GOA with a thin coating and the three-dimensional structural geometry of SSM. The modification of ZrO₂ nanoparticles brought a selective adsorption for OPPs due to the combination of the phosphate group as a Lewis base and ZrO₂ nanoparticles with the Lewis acid site. The ZrO₂/PDDA-GOA-SSM was packed into the solid-phase extraction (SPE) cartridge to extract OPPs. According to the investigation of different factors, the extraction recovery was mainly affected by the hydrophilic-hydrophobic properties of analytes. Effective extraction and elution parameters such as sample volume, sample pH, rate of sample loading, eluent, and eluent volume, were also investigated and discussed. Under the optimal conditions, the linearity of phoxim and fenitrothion was in the range of 1.0-200 μg L^-1, and the linearity of temephos was in the range of 2.5-200 μg L^-1. The limits of detection were ranged from 0.2 to 1.0 μg L^-1. This established method was successfully applied to detect OPPs in two vegetables. There was no OPP detected in real samples, and results showed that the matrix effects were in the range of 46.5%-90.1%. This indicates that the ZrO₂/PDDA-GOA-SSM-SPE-HPLC method could effectively extract and detect OPPs in vegetables.

Degradation of ciprofloxacin by the Mn cycle system (MnCS): Construction, characterization and bacterial analysis

The release of Mn(II) occurs in the degradation of organic matters by manganese ore (MnO₂), resulting in a reduced efficiency. During the degradation of ciprofloxacin (CIP), in a biofilter, this paper put forward a novel method that similar to the geo-cycle of Mn (MnCS) on the Earth to regenerate MnO₂. The freshly prepared MnO₂ was suitable for the use in the MnCS. It indicated that the mutual conversion between Mn(II), Mn(III), and Mn(IV) in the MnCS, which was driven by CIP and manganese oxidizing bacteria (MnOB), could maintain the activity of MnO₂. The MnCS showed feasibility in the coexistence of ammonia or humic acid, and provided a kinetic degradation. The physicochemical features of MnO₂ before and after bio-regeneration were characterized by TEM, XRD, BET, and XPS. It was found that the morphological structure of MnO₂ became loose and the maximum peak of pore size distribution became smaller, but the increase of surface area, the change of Mn(III/IV) content, and the decrease of crystallinity favored the bio-regeneration process. Moreover, as a mediator in the MnCS, the group of MnOB was dramatically inhibited by CIP, and the bacterial community had changed significantly. The typical MnOB shared low abundance in the biofilter, while the rarely reported genera (e.g. Sphingomonas) that related to the formation of Mn deposits appeared to be involved in the MnCS.

Influence of surface-water irrigation on the distribution of organophosphorus pesticides in soil-water systems, Jianghan Plain, central China

Surface-water irrigation is one of the most important irrigation methods in areas with abundant surface water. Although this method of irrigation is both economical and convenient, many contaminants are also introduced into the soil-water systems such as organophosphorus pesticides (OPPs). To study the influence of surface-water irrigation on the distribution of OPPs in soil-water systems, 42 water samples (38 groundwater and four surface water) and 85 soil samples (78 profile soil samples and seven topsoil samples) were taken from Shahu in the Jianghan Plain, China. Shahu is a typical Chinese surface-water irrigation district. During sampling, three types of areas were considered: surface-water irrigated areas, groundwater-irrigated areas away from rivers, and non-irrigated areas adjacent to rivers. The results showed that the concentrations of OPPs in the groundwater and soil in the surface-water irrigated farmland were higher than those in groundwater-irrigated farmland. The groundwater flow field and surface-water irrigation were responsible for the OPPs. Thus, it is clear that the surface-water irrigation had a strong influence on the distribution of OPPs in soil-water systems. Principal component analysis for OPPs content in groundwater showed that the key influencing factors on the distribution of OPPs in groundwater were the groundwater flow field and current pesticide use.

A treatise on Organophosphate pesticide pollution: Current strategies and advancements in their environmental degradation and elimination

Pesticides have been used in the field of agriculture ever since their role in protection of crops from pests which include four different categories namely insects, mites, rodents and animals has been identified. Organophosphate pesticides are one of the most extensively applied insecticides in the field of agriculture such that around 40% of all the pesticides that are produced and used commercially belong to this category. The main toxicological effect of these pesticides when exposed to a living being encompasses the irremediable inhibition of the acetylcholinesterase (AChE) enzyme which is involved in the neurotransmission of signals and hence its inhibition causes impairment of the respiratory tract and neuromuscular transmission. Apart from being used as a pesticide, organophosphates have also been applied as herbicides to some extent. The residues of these highly toxic chemicals have found route into the underground water system by seeping into the ground, in rivers where the agricultural run off water is disposed, and in the air when sprayed on the crops hence posing a threat to all the living strata exposed to these chemicals in various ways which are discussed further. Many significant studies have been carried out in order to evaluate the health risks associated with these pesticides which commonly include acute neurological disorders. This review emphasizes on the toxicological effects of organophosphate pesticides and the recent methods of detection that are used to identify trace amounts of organophosphate pesticides along with strategies which are used for their degradation.

Degradation of parathion methyl in bovine milk by high-intensity ultrasound: Degradation kinetics, products and their corresponding toxicity

The removal of pesticide residues in food by ultrasound has attracted more attention in recent years, and the formation of intermediate products may have some profound effects on the toxicity of treated food. Therefore, degradation of parathion methyl (PM) in bovine milk by ultrasonic treatment was studied in this paper. Results showed that the ultrasonic intensity and the initial concentration of PM had a significant effect on the degradation rate of PM (P < 0.05). The maximum degradation rate of PM was 97.10%. Three transformation products were identified through UPLC-QTOF/MS analysis, and the oxidation pathway was proposed as the consequence of ultrasonication. Furthermore, according to Quantitative Structure Activity Relationship (QSAR) model prediction, the ecotoxicity of the transformation products may be higher than that of PM. These findings showed that although ultrasonic treatment can effectively degrade pesticide residues in food, it may also generate transformation products with the higher ecotoxicity.

Instantaneous oxidation of levofloxacin as toxic pharmaceutical residuals in water using clay nanotubes decorated by ZnO (ZnO/KNTs) as a novel photocatalyst under visible light source

Kaolinite nanotubes were synthesized by a simple scrolling process and decorated by ZnO nanoparticles as a novel nanocomposite (ZnO/KNTs). The synthetic ZnO/KNTs composite was characterized as an effective photocatalyst in the oxidation of levofloxacin pharmaceutical residuals in the water resources. The composite displays a surface area of 95.4 m²/g, average pore diameter of 5.8 nm, and bandgap energy of 2.12 eV. It is of high catalytic activity in the oxidation of levofloxacin in the presence of visible light source. The complete oxidation for 10 mg/L of levofloxacin was recognized after 55 min, 45 min, and 30 min with applying 30 mg, 40 mg, and 50 mg of ZnO/KNTs as catalyst dosage, respectively. Additionally, it achieved complete oxidation for 20 mg/L and 30 mg/L of levofloxacin after 45 min and 75 min, respectively using 50 mg as catalyst dosage. The degradation efficiency was confirmed by detecting the residual TOC after the treatment tests and the formed intermediate compounds were identified to suggest the degradation pathways. In addition to the oxidation pathway, the mechanism was evaluated based on the active trapping tests that proved the dominance of hydroxyl radicals as the essential active species. Finally, the ZnO/KNTs composite is of promising recyclability properties and achieved better results than several studied photocatalysts in literature.

Activation of persulfate and removal of ethyl-parathion from soil: Effect of microwave irradiation

Advanced persulfate oxidation technology is widely used in organic pollution control of super fund sites. In recent years, microwave radiation has been proven a promising method for persulfate activation. However, most of the prior works were focused on the treatment of polluted water, but there are few reports aiming at contaminated sites, especially the knowledge of using microwave activated persulfate technology to repair pesticide-contaminated sites. In this study, an effective activation/oxidation method for the remediation of pesticide-contaminated soil, i.e., microwave/persulfate, was developed to treat soil containing ethyl-parathion. The concentration of persulfate, reaction temperature, and time were optimised. The results showed that up to 77.32% of ethyl-parathion was removed with the addition of 0.1 mmol·persulfate·g^-1 soil under the microwave temperature of 60 °C. In comparison, 19.43% of ethyl-parathion was removed at the same reaction temperature under the condition of water bath activated persulfate. Electron paramagnetic resonance (EPR) spectroscopy combined with spin-trapping technology was used to detect reactive oxidation species, and OH and SO₄^- were observed in the microwave/persulfate system. Quenching experiments suggested that ethyl-parathion was degraded by the generated OH and SO₄^-. Paraoxon, phenylphosphoric acid, 4-nitrophenol, dimethyl ester phosphate, and some alkanes were the dominant oxidative products identified by gas chromatography-mass spectrometry (GC-MS) analysis. A possible pathway for ethyl-parathion degradation was proposed in this study. The results obtained serve as the guidance to the development of remediation technologies involving persulfate and microwave for soil contaminated by organic contaminants such as pesticides.

Enhanced photocatalytic degradation of acephate pesticide over MCM-41/Co3O4 nanocomposite synthesized from rice husk silica gel and Peach leaves

Novel green nanocomposite from mesoporous MCM-41 and Co₃O₄ was synthesized from rice husk based silica gel and using the green extract of Peach leaves as reducing reagent. The composite was labeled as RH-MCM-41/Co₃O₄ and characterized by different techniques as green photocatalyst in the degradation of Acephate pesticide under visible light illumination. The composite showed well developed spherical MCM-41 particles decorated by nano Co₃O₄ nanoparticles with stunning surface area and low bandgap energy (1.51 eV). The composite displayed superior photocatalytic activities in the oxidation of Acephate which reflected in a complete degradation of different concentrations of it after 40 min (50 mg/L), 60 min (100 mg/L), 100 min (150 mg/L) and 140 min (200 mg/L) using 0.25 g of the composite. The complete removal of the present TOC for treatment of 100 mg/L acephate was achieved using 0.25 g after 70 min reflecting the formation of intermediate compounds during the oxidation steps. The reported intermediate compounds are CH₃C(O)NH₂, CH₃O(CH₃S)P(O)NH₂, (CH₃O)₂P(O)SCH₃, CH₃OP(O)(OH)₂, CH₃SS(O)₂CH₃, and (COOH)₂. All the formed intermediate compounds were degraded under the visible light photocatalytic activity of RH-MCM-41/Co₃O₄ into NO₃^-, SO₄^2-, PO₄^3-, and CO₂ as final products.

Effective oxidation of methyl parathion pesticide in water over recycled glass based-MCM-41 decorated by green Co3O4 nanoparticles

Pieces of glass as solid wastes were recycled in the synthesis of highly order MCM-41 that decorated by green fabricated Co₃O₄ nanoparticles using the green extract of green tea leaves forming novel green nano-composite. The synthetic Co₃O₄/MCM-41 exhibit high surface area, low bandgap energy (1.63 eV), and typical spherical morphology decorated by Co₃O₄ nanoparticles. The composite was evaluated as green photocatalyst in effective oxidation of methyl parathion pesticide in the presence of a visible light source. The degradation results revealed complete removal of 50 mg/L and 100 mg/L after 60 min and 90 min, respectively using 0.25 of the catalyst at pH 8. The detection of the TOC in the treated methyl parathion solution gives strong indications about the formation of organic intermediate compounds during the oxidation steps. The main detected intermediate compound are C₆H₅OH(NO₂), C₆H₅OH, (CH₃O)₃P(S), C₆H₄(OH)₂, C₆H₃(OH)₃, C₆H₄(NH₂)OP(O)(OCH₃)₂, (CH₃O)₂P(O)OH, (CH₂)₂C(OH)OH(CHO)OC(O), and HO₂C(CH₂)₂C(O)CHO. The detected intermediate compounds converted into SO₄^2-, PO₄^3-, NO₃^-, and CO₂ under the extensive photocatalytic of them over Co₃O₄/MCM-41. The oxidizing species trapping test verified the controlling of the methyl parathion degradation pathway by the hydroxyl radicals. Finally, the composite showed significant reusability properties and applied five times in the oxidation of methyl parathion with considerable degradation percentages.

Investigation of catalytic activity and mechanism for RhB degradation by LaMnO3perovskites preparedviathe citric acid method

LaMnO₃exhibits an excellent degradation ability of RhB under highly acidic conditions without adding additional oxidants or light irradiation.