Study of the degradation of an organophosphorus pesticide using electrogenerated hydroxyl radicals or heat-activated persulfate

Mechanism and toxicity assessment of carbofuran degradation by persulfate-based advanced oxidation process

The advanced oxidation process based on persulfate has been proven to be a promising method for degrading the highly toxic carbamate pesticide carbofuran (CBF). However, the mechanism of CBF degradation by sulfate radicals (SO4·-) and hydroxyl radicals (·OH) is still unclear and requires further research and discussion. This study investigated the mechanism and toxicity assessment of CBF degradation using density functional theory (DFT) theory calculation methods. The results indicated that SO4·- and ·OH can undergo addition and abstraction reactions with CBF. Thermodynamic and kinetic analysis showed that the abstraction reaction between SO4·- and the secondary H atom is the optimal reaction pathway, exhibiting the highest branching ratio (Γ = 41.84%). The rate constants for the reactions of CBF with SO4·- and ·OH at room temperature were found to be 3.66 × 109 and 8.96 × 108 M-1 s-1, respectively, which are consistent with experimental data reported in previous studies. The acute and chronic toxicity of CBF and its degradation products to aquatic organisms was predicted through an ecological toxicity assessment model. The toxicity of the degradation products was lower than that of the parent CBF, confirming the viability of using persulfate-based advanced oxidation processes for water treatment.

Innovative strategy for the effective utilization of coal waste slag in the Fenton-like process for the degradation of trichloroethylene

In response to environmental concerns at the global level, there is considerable momentum in the exploration of materials derived from waste that are both sustainable and eco-friendly. In this study, CS-Fe (carbon, silica, and iron) composite was synthesized from coal gasification slag (CGS) and innovatively applied as a catalyst to activate PS (persulfate) for the degradation of trichloroethylene (TCE) in water. Scanning electron microscope (SEM), fourier transmission infrared spectroscopy (FTIR), energy dispersive x-ray spectroscopy (EDS), brunauer, emmet, and teller (BET) technique, and x-ray diffractometer (XRD) spectra were employed to investigate the surface morphology and physicochemical composition of the CS-Fe composite. CS-Fe catalyst showed a dual nature by adsorption and degradation of TCE simultaneously, displaying 86.1% TCE removal in 3 h. The synthesized CS-Fe had better adsorption (62.1%) than base material CGS (36.4%) due to a larger BET surface area (770.8 m2 g-1), while 24.0% TCE degradation was recorded upon the activation of PS by CS-Fe. FTIR spectra confirmed the adsorption and degradation of TCE by investigating the used and fresh samples of CS-Fe catalyst. Scavengers and Electron paramagnetic resonance (EPR) analysis confirmed the availability of surface radicals and free radicals facilitated the degradation process. The acidic nature of the solution favored the degradation while the presence of bicarbonate ion (HCO3-) hindered this process. In conclusion, these results for real groundwater, surfactant-added solution, and degradation of other TCE-like pollutants propose that the CS-Fe composite offers an economically viable and favorable catalyst in the remediation of organic contaminants within aqueous solutions. Further investigation into the catalytic potential of coal gasification slag-based carbon materials and their application in Fenton reactions is warranted to effectively address a range of environmental challenges.

A review on recent advancements in the treatment of polyaromatic hydrocarbons (PAHs) using sulfate radicals based advanced oxidation process

Polyaromatic hydrocarbons (PAHs) are the most persistent compounds that get contaminated in the soil and water. Nearly 16 PAHs was considered to be a very toxic according US protection Agency. Though its concentration level is low in the environments but the effects due to it, is enormous. Advanced Oxidation Process (AOP) is an emergent methodology towards treating such pollutants with low and high molecular weight of complex substances. In this study, sulfate radical (SO4‾•) based AOP is emphasized for purging PAH from different sources. This review essentially concentrated on the mechanism of SO4‾• for the remediation of pollutants from different sources and the effects caused due to these pollutants in the environment was reduced by this mechanism is revealed in this review. It also talks about the SO4‾• precursors like Peroxymonosulfate (PMS) and Persulfate (PS) and their active participation in treating the different sources of toxic pollutants. Though PS and PMS is used for removing different contaminants, the degradation of PAH due to SO4‾• was presented particularly. The hydroxyl radical (•OH) mechanism-based methods are also emphasized in this review along with their limitations. In addition to that, different activation methods of PS and PMS were discussed which highlighted the performance of transition metals in activation. Also this review opened up about the degradation efficiency of contaminants, which was mostly higher than 90% where transition metals were used for activation. Especially, on usage of nanoparticles even 100% of degradation could be able to achieve was clearly showed in this literature study. This study mainly proposed the treatment of PAH present in the soil and water using SO4‾• with different activation methodologies. Particularly, it emphasized about the importance of treating the PAH to overcome the risk associated with the environment and humans due to its contamination.

Sustainable approach for the expulsion of metaldehyde: risk, interactions, and mitigation: a review

All pests can be eliminated with the help of pesticides, which can be either natural or synthetic. Because of the excessive use of pesticides, it is harmful to both ecology and people's health. Pesticides are categorised according to several criteria: their chemical composition, method of action, effects, timing of use, source of manufacture, and formulations. Many aquatic animals, birds, and critters live in danger owing to hazardous pesticides. Metaldehyde is available in various forms and causes significant impact even when small amounts are ingested. Metaldehyde can harm wildlife, including dogs, cats, and birds. This review discusses pesticides, their types and potential environmental issues, and metaldehyde's long-term effects. In addition, it examines ways to eliminate metaldehyde from the aquatic ecosystem before concluding by anticipating how pesticides may affect society. The metal-organic framework and other biosorbents have been appropriately synthesized and subsequently represent the amazing removal of pesticides from effluent as an enhanced adsorbent, such as magnetic nano adsorbents. A revision of the risk assessment for metaldehyde residuals in aqueous sources is also attempted.

Synthesis of FeOOH-Loaded Aminated Polyacrylonitrile Fiber for Simultaneous Removal of Phenylphosphonic Acid and Phosphate from Aqueous Solution

Phosphorus is one of the important metabolic elements for living organisms, but excess phosphorus in water can lead to eutrophication. At present, the removal of phosphorus in water bodies mainly focuses on inorganic phosphorus, while there is still a lack of research on the removal of organic phosphorus (OP). Therefore, the degradation of OP and synchronous recovery of the produced inorganic phosphorus has important significance for the reuse of OP resources and the prevention of water eutrophication. Herein, a novel FeOOH-loaded aminated polyacrylonitrile fiber (PAN_AF-FeOOH) was constructed to enhance the removal of OP and phosphate. Taking phenylphosphonic acid (PPOA) as an example, the results indicated that modification of the aminated fiber was beneficial to FeOOH fixation, and the PAN_AF-FeOOH prepared with 0.3 mol L^-1 Fe(OH)₃ colloid had the best performance for OP degradation. The PAN_AF-FeOOH efficiently activated peroxydisulfate (PDS) for the degradation of PPOA with a removal efficiency of 99%. Moreover, the PAN_AF-FeOOH maintained high removal capacity for OP over five cycles as well as strong anti-interference in a coexisting ion system. In addition, the removal mechanism of PPOA by the PAN_AF-FeOOH was mainly attributed to the enrichment effect of PPOA adsorption on the fiber surface's special microenvironment, which was more conducive to contact with SO₄•^- and •OH generated by PDS activation. Furthermore, the PAN_AF-FeOOH prepared with 0.2 mol L^-1 Fe(OH)₃ colloid possessed excellent phosphate removal capacity with a maximal adsorption quantity of 9.92 mg P g^-1. The adsorption kinetics and isotherms of the PAN_AF-FeOOH for phosphate were best depicted by pseudo-quadratic kinetics and a Langmuir isotherm model, showing a monolayer chemisorption procedure. Additionally, the phosphate removal mechanism was mainly due to the strong binding force of iron and the electrostatic force of protonated amine on the PAN_AF-FeOOH. In conclusion, this study provides evidence for PAN_AF-FeOOH as a potential material for the degradation of OP and simultaneous recovery of phosphate.

A systematic review on the implementation of advanced and evolutionary biotechnological tools for efficient bioremediation of organophosphorus pesticides

Ever since the concept of bioremediation was introduced, microorganisms, microbial enzymes and plants have been used as principal elements for Organophosphate pesticide (OPP) bioremediation. The enzyme systems and genetic profile of these microbes have been studied deeply in past years. Plant growth promoting rhizobacteria (PGPR) are considered as one of the potential candidates for OPP bioremediation and has been widely used to stimulate the phytoremediation potential of plants. Constructed wetlands (CWs) in OPP biodegradation have brought new prospects to microcosm and mesocosm based remediation strategies. Application of synthetic biology has provided a new dimension to the field of OPP bioremediation by introducing concepts like, gene manipulation andediting, expression and regulation of catabolic enzymes, implementation of whole-cell based and enzyme based biosensor systems for the detection and monitoring of OPP pollution in both terrestrial and aquatic environment. System biology and bioinformatics tools have rendered significant knowledge regarding the genetic, enzymatic and biochemical aspects of microbes and plants thereby, helping researchers to analyze the mechanism of OPP biodegradation. Structural biology has provided significant conceptual information regarding OPP biodegradation pathways, structural and functional characterization of metabolites and enzymes, enzyme-pollutant interactions, etc. Therefore, this review discussed the prospects and challenges of most advanced and high throughput strategies implemented for OPP biodegradation. The review also established a comparative analysis of various bioremediation techniques and highlighted the interdependency among them. The review highly suggested the simultaneous implementation of more than one remediation strategy or a combinational approach creating an advantageous hybrid technique for OPP bioremediation.

Advances on removal of organophosphorus pesticides with electrochemical technology

Widespread use of organophosphorus pesticides (OPs), especially superfluous and unreasonable use, had brought huge harm to the environment and food chain. It is because only a small part of the pesticides sprayed reached the target, and the rest slid across the soil, causing pollution of groundwater and surface water resources. These pesticides accumulate in the environment, causing environmental pollution. Therefore, in recent years, the control and degradation of OPs have become a public spotlight and research hotspot. Due to its unique advantages such as versatility, environmental compatibility, controllability, and cost-effectiveness compatibility, electrochemical technology has become one of the most promising methods for degradation of OPs. The fundamental knowledge about electrochemical degradation on OPs was introduced in this review. Then, a comprehensive overview of four main types of practical electrochemical technologies to degrade pesticides were presented and evaluated. The knowledge contained herein should conduce to better understand the degradation of pesticides by electrochemical technology, and better exploit the degradation of pesticides in the environment and food. Overall, the objective of this review is to provide comprehensive guidance for rational design and application of electrochemical technology in the degradation of OPs for the safety of the environment and food chain in the future.

Role of cytochrome P450 genes of Trichoderma atroviride T23 on the resistance and degradation of dichlorvos

The Trichoderma has been extensively used to degrade the xenobiotics. In the present study, thirty-nine open reading frames of cytochrome P450 genes from T. atroviride T23 genome was cloned and it was found to be distributed in 29 families under 21 clades. Among them, 21 cytochrome P450 genes were involved in the degradation of xenobiotics. The quantitative expression of P450 genes in the presence of dichlorvos at 24 h showed 7 different expression patterns in the presence of 100 μg/mL, 300 μg/mL, 500 μg/mL and 1000 μg/mL of dichlorvos. The relative expression of P450 genes belongs to the family of TaCyp548, TaCyp620, TaCyp52, TaCyp528, TaCyp504 were upregulated at least 1-fold compared to the control. Significantly, the deletion of TaCyp548-2 reduced the concentration of 2,2-dichloroethanol. Further, it was observed that TaCyp548-2 belongs to the ω-hydroxylase family was responsible for fatty acid oxidation and the production of acetic acid, propionic acid, isobutyric acid and dibutyric acid to convert the 2,2-dichloroethanol to 2,2-dichloroethanolacetate. This study evidenced the involvement of Trichoderma P450 genes on dichlorvos degradation as an environmentally significant Biological control agent for the sustainable agriculture.

Improving methane production from algal sludge anaerobic fermentation by peroxydisulfate (PDS) pretreatment

This study investigated the potential of improving methane production from algal sludge anaerobic digestion by peroxydisulfate (PDS) pretreatment. The results show that with PDS dosage at 0.02 g PDS/g algal sludge TSS, PDS added system has highest accumulative methane production after 60 days fermentation. The accumulative methane production was 1.08, 1.15, 1.14, 1.13, 1.08, 0.76, and 0.15 times as compared with control, at 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1 g PDS/g algal sludge TSS added, respectively. The SCOD in the system was keep increasing with the increment of PDS dosage after 120 min pretreatment. The algal sludge dewatering rate was increased with adding of PDS as pretreatment. The addition of PDS has inhibited the activities of microbes involved in digestion, while the short chain fatty acids production was improved after 3 days digestion. One-substrate model can be used to simulate the methane yield. The hydrolysis rate was decreased after dosing with PDS, while highest actual and predicted accumulative methane yield was occurred at 0.02 g PDS/g algal sludge TSS. Proteobacteria has higher percentage when the PDS was not higher than 0.1 g PDS/g algal sludge TSS, Acetothermia has higher percentage at 0.01 g PDS/g algal sludge TSS. The microcystin-LR (MC-LR) in algal sludge was largely removed after digestion, including the intracellular MC-LR. The higher PDS dosage could cause heavy metal release from algae cell to the digestate during fermentation. The addition of PDS to algal sludge can improve the accumulative methane production and mitigate microcystin concentration.

Different activation methods in sulfate radical-based oxidation for organic pollutants degradation: Catalytic mechanism and toxicity assessment of degradation intermediates

With the continuous development of industrialization, a growing number of refractory organic pollutants are released into the environment. These contaminants could cause serious risks to the human health and wildlife, therefore their degradation and mineralization is very critical and urgent. Recently sulfate radical-based advanced oxidation technology has been widely applied to organic pollutants treatment due to its high efficiency and eco-friendly nature. This review comprehensively summarizes different methods for persulfate (PS) and peroxymonosulfate (PMS) activation including ultraviolet light, ultrasonic, electrochemical, heat, radiation and alkali. The reactive oxygen species identification and mechanisms of PS/PMS activation by different approaches are discussed. In addition, this paper summarized the toxicity of degradation intermediates through bioassays and Ecological Structure Activity Relationships (ECOSAR) program prediction and the formation of toxic bromated disinfection byproducts (Br-DBPs) and carcinogenic bromate (BrO₃^-) in the presence of Br^-. The detoxification and mineralization of target pollutants induced by different reactive oxygen species are also analyzed. Finally, perspectives of potential future research and applications on sulfate radical-based advanced oxidation technology in the treatment of organic pollutants are proposed.

Engineering Z-scheme TiO2-OV-BiOCl via oxygen vacancy for enhanced photocatalytic degradation of imidacloprid

The development and application of photocatalysts with strong redox ability to degrade refractory pesticides is the key to eliminating pesticide contamination. In this work, we develop a facile, time-saving, and surfactant-assisted method to fabricate a new Z-scheme heterojunction based on TiO2/BiOCl. This photocatalyst is rich in oxygen vacancy defects (TiO2-OV-BiOCl), and displays an excellent photocatalytic degradation performance for imidacloprid (IMD), and a possible degradation pathway of IMD is provided. The surfactant F127 plays an essential role in regulating the oxygen vacancy defects (OVDs) of TiO2-OV-BiOCl, where the OVD mainly exists in 5 layer BiOCl ultrathin nanosheets. Free radical trapping experiments demonstrate that the introduction of an OVD in BiOCl as a 'charge mediator' changes the charge-transfer mode from a type-II mechanism to a Z-scheme mechanism. The formation of a Z-scheme heterojunction leads to an excellent light utilization and higher separation efficiency of photogenerated charge carriers with a prolonged lifetime compared to those of BiOCl and TiO2/BiOCl. This work highlights the critical role of an OVD in the construction of a Z-scheme heterojunction of TiO2/BiOCl, and it can be applied to construct efficient photocatalytic systems for pesticide degradation.

Tin dioxide decorated on Ni-encapsulated nitrogen-doped carbon nanotubes for anodic electrolysis and persulfate activation to degrade cephalexin: Mineralization and degradation pathway

In this study, bamboo-shaped carbon nanotubes exhibiting high nitrogen content and Ni encapsulation (Ni@NCNT) were effectively synthesized by a simple pyrolysis method. The catalytic peroxydisulfate activation for cephalexin (CPX) degradation was investigated using the prepared material. SnO₂ was further decorated and fabricated on the anode material (SnO₂/Ni@NCNT) for electrochemical degradation of CPX in an aqueous solution. Transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy indicated that the SnO₂ nanoparticles were uniformly distributed on the surface of Ni@NCNT. Electrochemical characterization employing cyclic voltammetry and linear sweep voltammetry demonstrated that SnO₂/Ni@NCNT displayed higher oxygen evolution potential and electrocatalytic activity than Ni@NCNT. Mineralization of CPX in wastewater was performed using electrolysis coupled with persulfate oxidation. The analysis revealed a synergistic strengthening effect. The electropersulfate oxidation resulted in higher total organic carbon (TOC) removal (70.3%) than the sum of electrooxidation (48.1%) and persulfate oxidation (9.2%) toward CPX. This phenomenon might result from the regeneration of sulfate radicals (SO₄^•-) on the anode and complementary oxidation by SO₄^•- and OH. Persulfate oxidation alone was shown to result in low TOC removal, although CPX was mostly degraded. Additionally, the CPX degradation pathway involving electropersulfate oxidation was proposed and it is indicated that CPX molecules were completed decomposed by the examination of short chain acids, mineralized ions, and ecotoxicity evolution indicated that the antibiotic was completely degraded. This study provides a new approach for the design and preparation of novel electrode materials and electrochemical degradation facilities for the removal of pollutants via persulfate activation.

Sulfate radical-based oxidation of the aminopyralid and picloram herbicides: The role of amino group on pyridine ring

The widespread utilization of pesticides has attracted increasing attention to their environmental impacts and effective removal strategies. In the present study, the degradation of herbicides picloram (PCLO) and aminopyralid (AMP) with similar structures were investigated systematically by thermo activated persulfate. Overweight SO₄^•- was determined to be the predominant oxidizing species by quenching experiment. Obtained by laser-flash photolysis (LFP), reaction rate constants of SO₄^•- towards AMP and PCLO were determined at 1.56 × 10⁹ M^-1s^-1 and 1.21 × 10⁹ M^-1s^-1, respectively. Product analysis revealed that both substances underwent similar oxidation paths, namely, successive oxidation on pyridine ring and formation of coupling-products as well as further hydroxylation and decarboxylation. Amino group on the pyridine ring was identified as the main reactive site, which was further confirmed by DFT calculation. It was susceptible attacked by SO₄^•- to form deamination, nitration, and self-coupling products. These couples could be further oxidatively dehydrated to form azo and a series of azo derivatives. EOCSAR program predicted significant hazards on aquatic species during the formation of these couplings and azo derivatives. Our work emphasized the potential ability and toxicity of contaminates to produce azo substances in the presence of amino groups on the pyridine ring.

Occurrence, statutory guideline values and removal of contaminants of emerging concern by Electrochemical Advanced Oxidation Processes: A review

A wide variety of chemical compounds are used in human activities; however, part of these compounds reach surface water, groundwater and even water considered for potable uses. Due to the limited efficiency of water treatment by the Water and Wastewater Treatment Plants, the presence of these compounds in natural and human consumption waters can be very harmful due to their high persistence and adverse effects; these characteristics define the contaminants of emerging concern (CECs). Water treatment by Electrochemical Advanced Oxidation Processes (EAOPs) has been evaluated as a promising process for the removal of persistent and recalcitrant organic contaminants. With this background, the present review aims to gather studies and information published between 2015 and 2020 regarding the occurrence of CECs in surface, potable and groundwater, its treatment by EAOPs, the main operating conditions and by-product generation of EAOPs, contaminant toxicity assessments and international statutory guideline values concerning CEC standards and allowable concentrations in the environment and treated drinking water. Therefore, in this review it was found that the compounds bisphenol A (BPA), diethyltoluamide (DEET), 17α-ethinyl estradiol (EE2), perfluorobutanoic acid (PFBA), carbamazepine, caffeine and atrazine were the most frequently detected in water sources, with concentrations ranging from 35.54-4800, 1.21-98, 0.005-38.5, 5-742.904, 0.0071-586, 0.89-1040, and 100-323 (ng L-1), respectively. Among the operational conditions of EAOPs, current density, pH and oxidant concentration are the main operational parameters that have an influence on these treatment technologies, besides the by-products generated, which might be removed by the integration of EAOPs with biological digestion treatments. Regarding the values of water quality standards, many CECs do not have established standard allowable concentration values, which represents a concern toward the possible toxic effects of these compounds on non-target organisms.

Impact of hydrochar and biochar amendments on sorption and biodegradation of organophosphorus pesticides during transport through Danube alluvial sediment

This work investigates the transport behaviour of selected organophosphorus pesticides, OPPs (chlorpyrifos, CP; chlorpyrifos-methyl, CPM; chlorfenvinphos, CF) through Danube alluvial sediment in the presence of hydrochars and biochars. The investigated hydrochar, obtained at three different temperatures (180 °C, 200 °Cand 220 °C), originated from sugar beet shreds (SBS) and Miscanthus×giganteus (MIS). Results are described by conventional advective-dispersive equation (ADE). Retardation coefficients (R_d) for all OPPs were in the range 6.2-16. Biodegradation was 4.15 and 1.80 for CPM and CP, respectively, while for CF biodegradation did not occur. The addition of carbon rich materials increases retardation of all OPPs in the range from 4 to 18 times depending on the material. Column experiment results indicated that biodegradation of OPPs occurred (up to λ = 13). In order to confirm that biodegradation occurred in the column experiments, we isolated OPPs degrading microorganisms for the first time from the alluvial sediment. A strain capable of degrading CP and CPM was isolated and identified as Bacillus megaterium BD5 based on biochemical properties, MALDI TOF and 16S rRNA analysis (99.54% identity). The results demonstrate that hydrochars, biochars and isolated degrading bacteria may be effective agents for reducing the mobility of or removing OPPs in contaminated soils or sediments.

Rapid degradation of dimethoate and simultaneous removal of total phosphorus by acid-activated Fe(VI) under simulated sunlight

Ferrate (Fe(VI)) is usually effective for oxidizing a variety of organic pollutants within a few seconds, but some recalcitrant asorganophosphorus pesticides such as dimethoate require higher dose of Fe(VI) and inorganic phosphorus produced by mineralization is difficult to remove. In this study, acid-activated ferrate (Fe(VI)) was firstly used to degrade organophosphorus pesticides dimethoate and simultaneously remove total phosphorus (TP) from solution under simulated sunlight. At a Fe(VI):dimethoate molar radio of 15:1, dimethoate was almost completely removed within 20 min and 47% of TP in the solution was removed by the reduction product of Fe(VI) within 240 min. Electron paramagnetic resonance (EPR) and terephthalic acid (TA) fluorescence experiments showed that •OH radicals were continuously generated in the system, and •OH formation pathway was proposed. Importantly, the involvement of •OH in acid-activated Fe(VI) process was confirmed for the first time by EPR. In the acid-activated Fe(VI)/simulated sunlight system, the removal of dimethoate and TP gradually increased with the decrement of activation pH, whereas the increase of molar ratio of Fe(VI):dimethoate enhanced the removal of dimethoate and TP. The addition of inorganic anions (HCO₃^- and NO₂^-) had obvious inhibitory effects on dimethoate and TP removal. Eight degradation products including O,O,S-trimethylphosphorothiate, omethoate and 2-S-methyl-(N-methyl) acetamide were determined by gas chromatography mass spectrometry (GC-MS) analysis, and two possible degradation pathways were proposed. The insights gained from this study open a new avenue to simultaneously degrade and remove organic contaminants.

Improved dark ambient degradation of organic pollutants by cerium strontium cobalt perovskite

This work investigates the effect of cerium substation into strontium cobalt perovskites (CeSrCoO) for the oxidative degradation of Orange II (OII) in dark ambient conditions without the aid of any external stimulants such as light, heating or chemical additives. The OII degradation rate by CeSrCoO reached 65% in the first hour, whilst for the blank sample without cerium (SrCoO) took over 2 hr to reach the same level of OII degradation. Hence, the cerium substitution improved the catalytic activity of the perovskite material, mainly associated with the Ce_0.1Sr_0.9CoO₃ perovskite phase. Upon contacting CeSrCoO, the -NN- azo bonds of the OII molecules broke down resulting in electron donation and the formation of by-products. The electrons are injected into the CeSrCoO and resulted in a redox pair of Co³⁺/Co²⁺, establishing a bridge for the electron transfer between OII and the catalysts. Concomitantly, the electrons also formed reactive species (·OH) responsible for OII degradation as evidenced by radical trapping experiment. Reactive species were formed via the reaction between O₂ and donated electrons from OII with the aid of cobalt redox pair. As the prepared materials dispensed with the need for light irradiation and additional oxidants, it opens a window of environmental applications for treating contaminated wastewaters.

Solid-phase microextraction of organophosphorous pesticides from food samples with a nitrogen-doped porous carbon derived from g-C3N4 templated MOF as the fiber coating

A nitrogen-doped metal organic framework (MOF) based porous carbon (C-(C₃N₄@MOF)) was produced by the carbonization of a graphitic carbon nitride (g-C₃N₄) templated MOF (NH₂-MIL-125). The C-(C₃N₄@MOF) was then coated on a stainless steel wire by sol-gel technique to serve as a solid-phase microextraction (SPME) fiber coating. The coated fiber was studied for the extraction of fourteen organophosphorous pesticides (OPPs) from different fruit and vegetable samples followed by gas chromatography-mass spectrometer (GC-MS) detection. The C-(C₃N₄@MOF) coated fiber exhibited a high extraction capability for the OPPs. Both single factor optimization and response surface analysis (Box-Behnken Design) methods were implemented to optimize the experiment conditions for the extraction. The results indicated that the linear response for the fourteen OPPs was in the range from 0.69 to 3000 ng g^-1 and the coefficients of determination (r²) ranged from 0.9981 to 0.9998. The limits of detection (LODs, S/N = 3) ranged from 0.23 to 7.5 ng g^-1. The method recoveries (R) of the fourteen OPPs for spiked fruit and vegetable samples were between 82.6% and 118%, with the relative standard deviations (RSDs) varying from 2.8% to 11.7%. The fiber can be reused over 100 times without a significant loss of extraction efficiency.

Study of the atenolol degradation using a Nb/BDD electrode in a filter-press reactor

The present paper deals with the atenolol (ATL) degradation by advanced anodic oxidation using a boron-doped diamond anode supported on niobium (Nb/BDD). Cyclic voltammetry performed on this electrode revealed that it presents a high quality (diamond-sp³/sp²-carbon ratio), high potential for OER and that ATL can be oxidized directly and/or indirectly by the electrogenerated oxidants, such as hydroxyl radicals, persulfate ions and sulfate radicals. Electrolysis experiments demonstrated that ATL degradation and mineralization follow a mixed (first and zero) order kinetics depending on the applied current density. At high applied current densities, the amount of OH radicals is very high and the overall reaction is limited by the transport of ATL (pseudo first-order kinetics) whereas for low applied current densities, the rate of OH radicals generation at the anode is slower than the rate of arrival of ATL molecules (pseudo-zero order kinetics). Estimated values of k_zero and k_first based on the assumption of pseudo-zero or pseudo-first order kinetics were carried oud as a function of the supporting electrolyte concentration, indicating that both parameters increased with its concentration due the higher production of sulfate reactive species that play an important role in degradation. Finally, MCE increased with the decrease of current density, due to the lower amount of OH present in solution, since this species could be rapidly wasted in parasitic reactions; and the increase of sulfate concentration due to the more efficient production of persulfate.

A facile heterogeneous system for persulfate activation by CuFe2O4 under LED light irradiation

In this study, the removal performance for rhodamine B (RB) by persulfate (PS) activated by the CuFe2O4 catalyst in a heterogeneous catalytic system under LED light irradiation was investigated. The effect of vital experimental factors, including initial solution pH, CuFe2O4 dosage, PS concentration, co-existing anion and initial RB concentration on the removal of RB was systematically studied. The removal of RB was in accordance with the pseudo first-order reaction kinetics. Over 96% of 20 mg L-1 RB was removed in 60 min using 0.5 g L-1 CuFe2O4 catalyst and 0.2 mM PS at neutral pH. In addition, free radical quenching experiments and electron spin resonance (EPR) experiments were performed, which demonstrated the dominant role of sulfate radical, photogenerated holes and superoxide radical in the CuFe2O4/PS/LED system. The morphology and physicochemical properties of the catalyst were characterized by XRD, SEM-EDS, TEM, N2 adsorption-desorption isotherm, UV-vis DRS, and XPS measurements. Moreover, 18.23% and 38.79% total organic carbon (TOC) removal efficiency was reached in 30 min and 60 min, respectively. The catalyst revealed good performance during the reusability experiments with limited iron and copper leaching. Eventually, the major intermediates in the reaction were detected by GC/MS, and the possible photocatalytic pathway for the degradation of RB in the CuFe2O4/PS/LED system was proposed. The results suggest that the CuFe2O4/PS/LED system has good application for further wastewater treatment.

Non-thermal plasma needle as an effective tool in dimethoate removal from water

Intensive use of pesticides requires innovative approaches for their removal from the environment. Here we report the method for degradation of dimethoate in water using non-thermal plasma needle and analyze kinetics of dimethoate removal and possible degradation pathways. The effects of dimethoate initial concentration, plasma treatment time, Argon flow rate and the presence of radical promoters on the effectiveness of proposed method are evaluated. With argon flow rate of 0.5 slm (standard litres per minute) 1 × 10^-4 M dimethoate can be removed within 30 min of treatment. Using UPLC analysis it was confirmed that one of the decomposition products is dimethoate oxo-analogue omethoate, which is in fact more toxic than dimethoate. However, the overall toxicity of contaminated water was reduced upon the treatment. The addition of H₂O₂ as a free radical promoter enhances dimethoate removal, while K₂S₂O₈ results with selective conversion to omethoate. Using mass spectrometry in combination with the theoretical calculations, possible degradation pathways were proposed. The feasibility of the proposed method for dimethoate degradation in real water samples is confirmed. The proposed method is demonstrated as a highly effective approach for dimethoate removal without significant accumulation of undesirable toxic products and secondary waste.

Improved degradation of anthraquinone dye by electrochemical activation of PDS

Electrochemical oxidation (EO) coupled with peroxydisulfate (PDS) activation as a synergistic wastewater treatment process (PDS/EO) was performed to degrade anthraquinone dye-Reactive Brilliant Blue (RBB) in aqueous solution. Introducing PDS into the EO improved the RBB removal than the sole PDS and conventional EO systems. The RBB could activate PDS to a certain degree by itself. By the comparison of various inorganic ions addition, it showed that adding NO₃^- as the background electrolyte was more effective than the systems using the Cl^- and SO₄^2-, respectively. In this PDS/EO-NO₃^- system, increasing PDS concentration (1-5 mmol L^-1) and current density (5-10 mA cm^-2) considerably promoted the degradation of RBB. The adjustment of the solution pH displayed that the acidic and neutral condition was beneficial to the RBB removal, and the synergistic effect was inverse ratio to the RBB initial concentration. Furthermore, the scavenger experiments verified that both SO₄^·- and HO· were the major active substances in the RBB decomposition, and other reactive oxygen species also had considerable contributions. Thereinto NO₃^- only act a catalytic agent to improve the generation of active matters in the PDS/EO-NO₃^-. Overall, the proposed synergistic process could serve as an efficient method for the degradation of anthraquinone dye.

Removal and extraction efficiency of Quaternary ammonium herbicides paraquat (PQ) from aqueous solution by ketoenol-pyrazole receptor functionalized silica hybrid adsorbent (SiNPz)

Pesticides and herbicides have been used extensively in agricultural practices to control pests and increase crop yields. Paraquat (PQT²⁺, 1,1-dimethyl-4,4-dipyridinium chloride) is one of the herbicide that belois classified as bipyridines and is used over the world. The objective of this study is to use ketoenol–pyrazole receptor functionalized silica hybrid as adsorbent for removal PQT²⁺ from aqueous solution. The adsorbent was synthesized, and characterized using scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), Thermal analysis and other techniques. Different experimental parameters such as the effect of the amount of adsorbent, solution pH and temperatures and contact times were studied. Pseudo-order kinetics models were studied, and our data followed a pseudo second order. Experimental data were analyzed for both Langmuir and Freundlich models and the data fitted well with the Langmuir isotherm model. To understand the mechanism of adsorption, thermodynamic parameters like standard enthalpy, standard Gibbs free energy, and standard entropy were studied. The study indicated that the process is spontaneous, exothermic in nature and follow physisorption mechanisms. The novelty of this study showed surface of pyrazol-enol-imine-substituted silica (SiNPz) has the ability to highlight the surface designed for efficient removal of PQT²⁺, from aqueous solutions more than other studies. The study also showed that ketoenol–pyrazole receptor can be regenerated in five cycles using HNO₃ without affecting its adsorption capacity.

Construction of coated Z-scheme Pd-BaZrO3@WO3 composite with enhanced sonocatalytic activity for diazinon degradation in aqueous solution

The coated Z-scheme Pd-BaZrO₃@WO₃ composite as a new-type sonocatalyst with highly sonocatalytic performance is first constructed through sol-gel and hydro-thermal synthesis methods. The chemical configuration, structure and component are characterized by a series of characterization methods. The sonocatalytic degradation of diazinon as a model pollutant is studied to estimate the sonocatalytic performance of coated Z-scheme Pd-BaZrO₃@WO₃ composite. Some affecting factors such as Pd-BaZrO₃ and WO₃ mass proportions, ultrasonic (US) irradiation time, reusability and catalyst dosage are researched in detail through UV-vis spectra and gas chromatography (GC). The produced intermediates are detected in the degradation process of diazinon by using gas chromatography-mass spectrometer (GC-MS). The possible reaction mechanism of coated Z-scheme Pd-BaZrO₃@WO₃ sonocatalyst in sonocatalytic degradation process is also explored. Subsequently, the hydroxyl radicals (OH) and holes (h⁺) are discriminated to further elaborate the possible sonocatalytic mechanism. The experimental results manifest that the coated Z-scheme Pd-BaZrO₃@WO₃ sonocatalyst displays a preeminent sonocatalytic performance under ultrasonic irradiation because it can efficaciously suppress recombination of electrons (e^-) and holes (h⁺), extend light response scope and provide almost 100% oxidization surface. In addition, the introduced palladium (Pd) nanorods connecting BaZrO₃ and WO₃ can expedite e^- transfer. Under optimal conditions, the most of diazinon molecules can be disintegrated in the existence of the coated Z-scheme Pd-BaZrO₃@WO₃ under ultrasonic irradiation for 150 min. This study provides a feasible method for the treatment of environmental pollutions.

Assessment of Sulfate Radical-Based Advanced Oxidation Processes for Water and Wastewater Treatment: A Review

High oxidation potential as well as other advantages over other tertiary wastewater treatments have led in recent years to a focus on the development of advanced oxidation processes based on sulfate radicals (SR-AOPs). These radicals can be generated from peroxymonosulfate (PMS) and persulfate (PS) through various activation methods such as catalytic, radiation or thermal activation. This review manuscript aims to provide a state-of-the-art overview of the different methods for PS and PMS activaton, as well as the different applications of this technology in the field of water and wastewater treatment. Although its most widespread application is the elimination of micropollutants, its use for the disinfection of wastewater is gaining increasing interest. In addition, the possibility of combining this technology with ultrafiltration membranes to improve the water quality and lifespan of the membranes has also been discussed. Finally, a brief economic analysis of this technology has been undertaken and the different attempts made to implement it at full-scale have been summarized. As a result, this review tries to be useful for all those people working in that area.