Visible-light photoelectrodegradation of diuron on WO3 nanostructures.

The degradation of pesticide diuron has been explored by photoelectrocatalysis (PEC) under visible light illumination using two different WO3 nanostructures, obtained by anodization of tungsten. The highest degradation efficiency (73%) was obtained for WO3 nanosheets synthesized in the presence of small amounts of hydrogen peroxide (0.05 M). For that nanostructure, the kinetic coefficient for diuron degradation was 133% higher than that for the other nanostructure (anodized in the presence of fluoride anions). These results have been explained by taking into account the different architecture and dimensions of the two WO3 nanostructures under study.

Synergistic signal-amplification effect of silver nanowires and bifunctional monomers on molecularly imprinted electrochemical sensor for diuron analysis.

Molecularly imprinted polymers (MIP) have been widely owing to their specificity, however, their singular structure imposes limitations on their performance. Current enhancement methods, such as doping with inorganic nanomaterials or introducing various functional monomers, are limited and single, indicating that MIP performances require further advancement. In this work, a dual-modification approach that integrates both conductive inorganic nanomaterials and diverse bifunctional monomers was proposed to develop a multifunctional MIP-based electrochemical (MMIP-EC) sensor for diuron (DU) detection. The MMIP was synthesized through a one-step electrochemical copolymerization of silver nanowires (AgNWs), o-phenylenediamine (O-PD), and 3,4-ethylenedioxythiophene (EDOT). DU molecules could conduct fluent electron transfer within the MMIP layer through the interaction between anchored AgNWs and bifunctional monomers, and the abundant recognition sites and complementary cavity shapes ensured that the imprinted cavities exhibit high specificity. The current intensity amplified by the two modification strategies of MMIP (3.7 times) was significantly higher than the sum of their individual values (3.2 times), exerting a synergistic effect. Furthermore, the adsorption performance of the MMIP was characterized by examining the kinetics and isotherms of the adsorption process. Under optimal conditions, the MMIP-EC sensor exhibits a wide linear range (0.2 ng/mL to 10 µg/mL) for DU detection, with a low detection limit of 89 pg/mL and excellent selectivity (an imprinted factor of 10.4). In summary, the present study affords innovative perspectives for the fabrication of MIP-EC sensor with superior analytical performance.

Rapid extraction and quantitative detection of the herbicide diuron in surface water by a hapten-functionalized carbon nanotubes based electrochemical analyzer.

A solid phase extraction micro-cartridge containing a non-polar polystyrene absorbent matrix was coupled with an electrochemical immunoassay analyzer (EIA) and used for the ultra-sensitive detection of the phenyl urea herbicide diuron in real samples. The EIA was fabricated by using carboxylated carbon nanotubes (CNTs) functionalized with a hapten molecule (an amine functionalized diuron derivative). Screen printed electrodes (SPE) were modified with these haptenized CNTs and specific in-house generated anti diuron antibodies were used for bio-interface development. The immunodetection was realized in a competitive electrochemical immunoassay format using alkaline phosphatase labeled secondary anti-IgG antibody. The addition of 1-naphthyl phosphate substrate resulted in the production of an electrochemically active product, 1-naphthol, which was monitored by using differential pulse voltammetry (DPV). The assay exhibited excellent sensitivity and specificity having a dynamic response range of 0.01 pg mL(-1) to 10 µg mL(-1) for diuron with a limit of detection of around 0.1 pg mL(-1) (n = 3) in standard water samples. The micro-cartridge coupled hapten-CNTs modified SPE provided an effective and efficient electrochemical immunoassay for the real-time monitoring of pesticides samples with a very high degree of sensitivity.

Development of a biosensor for environmental monitoring based on microalgae immobilized in silica hydrogels.

A new biosensor was designed for the assessment of aquatic environment quality. Three microalgae were used as toxicity bioindicators: Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii. These microalgae were immobilized in alginate and silica hydrogels in a two step procedure. After studying the growth rate of entrapped cells, chlorophyll fluorescence was measured after exposure to (3-(3,4-dichlorophenyl)-1,1-dimethylurea) (DCMU) and various concentrations of the common herbicide atrazine. Microalgae are very sensitive to herbicides and detection of fluorescence enhancement with very good efficiency was realized. The best detection limit was 0.1 µM, obtained with the strain C. reinhardtii after 40 minutes of exposure.

Magnetic permanently confined micelle arrays for treating hydrophobic organic compound contamination.

Magnetic permanently confined micelle arrays (Mag-PCMAs) have been successfully synthesized as sorbents for hydrophobic organic compound (HOC) removal from contaminated media. The synthesis of Mag-PCMAs involves coating a silica/surfactant mesostructured hybrid layer on the negatively charged Fe(3)O(4) microparticles to create a core/shell structure. The surfactant, 3-(trimethoxysily)propyl-octadecyldimethyl-ammonium chloride (TPODAC), has a reactive endgroup -Si(OCH(3))(3) on its hydrophilic groups, which allows the surfactant micelles to permanently anchor on the silica framework through covalent bonding. This unique structural property avoids surfactant loss during application and allows for sorbent regeneration. The isotherms and kinetics of four representative HOCs (atrazine, diuron, naphthalene, and biphenyl) onto Mag-PCMAs were determined, and the regeneration and reusability of Mag-PCMAs for diuron removal was also investigated. As a proof of principle for application of Mag-PCMAs for soil-washing, the use of Mag-PCMAs for removal of diuron from a contaminated soil was also demonstrated. All of the results showed that Mag-PCMAs are reusable sorbents for fast, convenient, and highly efficient removal of HOCs from contaminated media.

Diuron biodegradation in activated sludge batch reactors under aerobic and anoxic conditions.

Diuron biodegradation was studied in activated sludge reactors and the impacts of aerobic and anoxic conditions, presence of supplemental substrate and biomass acclimatization on its removal were investigated. Diuron and three known metabolites, namely DCPMU (1-(3,4-dichlorophenyl)-3-methylurea), DCPU (1-3,4-dichlorophenylurea) and DCA (3,4-dichloroaniline), were extracted by solid-phase extraction (dissolved phase) or sonication (particulate phase) and determined using High Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD). During the experiments only a minor part of these compounds was associated with the suspended solids. Under aerobic conditions, almost 60% of Diuron was biodegraded, while its major metabolite was DCA. The existence of anoxic conditions increased Diuron biodegradation to more than 95%, while the major metabolite was DCPU. Mass balance calculation showed that a significant fraction of Diuron is mineralized or biotransformed to other unknown metabolites. The presence of low concentrations of supplemental substrate did not affect Diuron biodegradation, whereas the acclimatization of biomass slightly accelerated its elimination under anoxic conditions. Calculation of half-lives showed that under aerobic conditions DCPMU, DCPU and DCA are biodegraded much faster than the parent compound. In the future, the sequential use of anoxic and aerobic conditions could provide sufficient removal of Diuron and its metabolites from runoff waters.

Sorption and desorption of atrazine and diuron onto water dispersible soil primary size fractions.

In this study, a low energy separation method was employed to separate water dispersible clay-, silt-, and sand-sized fractions. The batch equilibrium method was used to conduct atrazine and diuron sorption/desorption experiments with the bulk soils and their size fractions separately. A Freundlich sorption model provided the best fit for all sorption and desorption data. A mass balance calculation, taking into account the pesticide concentration differences in the size fraction and bulk soil, showed that pesticide sorption onto the different size fractions reproduces well the total amount of the pesticide sorbed onto the bulk soils. Due to their higher soil organic carbon content, the clay fractions were much more effective sorbents for the pesticides than the bulk soils, silt, and sand fractions. For all soils, the amount of the pesticide sorbed onto the clay fractions was more than 20% of the total amount of the pesticide sorbed by the bulk soils even though the clay fractions in these soils were only 5.3-14.0% (by weight). The clay fractions had the highest desorption hysteresis among all size fractions and the bulk soils, followed by silt fractions, implying the clay fractions had the strongest bound and least desorbable pesticide molecules. Our results suggest that attention should be paid to the pesticide sorbed to the smallest colloids, the water dispersible fraction, which can be potentially mobilized under field conditions, leading to wide spreading of contamination.

Partitioning of hydrophobic pesticides within a soil-water-anionic surfactant system.

Surfactants can be added to pesticide-contaminated soils to enhance the treatment efficiency of soil washing. Our results showed that pesticide (atrazine and diuron) partitioning and desorbability within a soil-water-anionic surfactant system is soil particle-size dependent and is significantly influenced by the presence of anionic surfactant. Anionic surfactant (linear alkylbenzene sulphonate, LAS) sorption was influenced by its complexation with both the soluble and exchangeable divalent cations in soils (e.g. Ca2+, Mg2+). In this study, we propose a new concept: soil system hardness which defines the total amount of soluble and exchangeable divalent cations associated with a soil. Our results showed that anionic surfactant works better with soils having lower soil system hardness. It was also found that the hydrophobic organic compounds (HOCs) sorbed onto the LAS-divalent cation precipitate, resulting in a significant decrease in the aqueous concentration of HOC. Our results showed that the effect of exchangeable cations and sorption of HOC onto the surfactant precipitates needs to be considered to accurately predict HOC behavior within soil-water-anionic surfactant systems.

Design and study of a cost-effective solar photoreactor for pesticide removal from water.

In order to remove pesticides from water, a basic photoreactor has been built. We evaluated the performance of this photoreactor using two commercial photocatalytic materials from Ahlstrom group and from Saint-Gobain, with solar and artificial UV-lamps. We compared the kinetics of photocatalytic degradation and mineralization of Diuron in the same reactor with of both photocatalyst supports. We showed that Diuron is easily degraded under solar or artificial irradiation, while the kinetics of mineralization in the same condition are very slow. The behaviour of these commercial materials has been studied after several uses in the same conditions. We showed the effectiveness of this basic and cheap photoreactor for the elimination of pesticide in water.

Combined Approach for Determining Diuron in Sugarcane and Soil: Ultrasound-Assisted Extraction, Carbon Nanotube-Mediated Purification, and Gas Chromatography-Electron Capture Detection.

Diuron is a urea herbicide that is frequently detected in surface water, groundwater, and marine waters. However, there are few methods or guidelines reported on ensuring the quality of sugarcane and soil. In this study, a method was developed for detecting diuron to ensure the quality and safety of food and sugar. Mass spectrometry was used to identify 3,4-dichloroaniline as a marker for the thermal decomposition of diuron, and thus, as a representative component for quantitative diuron analysis. This approach can be used to rapidly detect trace amounts of diuron. In addition, ultrasound-assisted extraction (UAE) and carbon nanotube column purification were used in conjunction with gas chromatography-electron capture detection to detect diuron. The method was then evaluated for its accuracy, detection limit, and viability. The effects of extraction solvent, ultrasound time, and ultrasound power on the extraction efficiency of the analyte from sugarcane and soil were also investigated. The efficiency and optimum conditions of UAE were examined through single-factor experiments and Box-Behnken design (BBD). The optimal extraction conditions were identified as follows: acetonitrile as the extraction solvent, extraction temperature of 27 °C, extraction time of 3.4 min, and ultrasound power of 70 W. Under these conditions, high linearity was achieved for diuron concentrations of 0.01 to 5.0 mg/L, and the purification correlation coefficient was consistently greater than 0.998. Hence, gas chromatography, combined with UAE and BBD, offers superior efficiency extraction, which is sufficiently accurate and precise for pesticide residue analysis. PRACTICAL APPLICATION: We developed an accurate and cost-effective method for detecting diuron (a commonly used herbicide) in soil and sugar samples. We performed experiments to determine the optimum detection conditions for our method. This method can be used for online monitoring of sugar manufacturing processes to ensure food safety and quality.

Coupled solar photo-Fenton and biological treatment for the degradation of diuron and linuron herbicides at pilot scale.

A coupled solar photo-Fenton (chemical) and biological treatment has been used to remove biorecalcitrant diuron (42 mg l(-1)) and linuron (75 mg l(-1)) herbicides from water at pilot plant scale. The chemical process has been carried out in a 82 l solar pilot plant made up by four compound parabolic collector units, and it was followed by a biological treatment performed in a 40 l sequencing batch reactor. Two Fe(II) doses (2 and 5 mg l(-1)) and sequential additions of H2O2 (20 mg l(-1)) have been used to chemically degrade the initially polluted effluent. Next, biodegradability at different oxidation states has been assessed by means of BOD/COD ratio. A reagent dose of Fe=5 mg l(-1) and H2O2=100 mg l(-1) has been required to obtain a biodegradable effluent after 100 min of irradiation time. Finally, the organic content of the photo-treated solution has been completely assimilated by a biomass consortium in the sequencing batch reactor using a total suspended solids concentration of 0.2 g l(-1) and a hydraulic retention time of 24h. Comparison between the data obtained at pilot plant scale (specially the one corresponding to the chemical step) and previously published data from a similar system performing at laboratory scale, has been carried out.

Steam activation of waste biomass: highly microporous carbon, optimization of bisphenol A, and diuron adsorption by response surface methodology.

Highly microporous carbons were prepared from argan nut shell (ANS) using steam activation method. The carbons prepared (ANS@H2O-30, ANS@H2O-90, and ANS@H2O-120) were characterized using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared, nitrogen adsorption, total X-ray fluorescence, and temperature-programmed desorption (TPD). The ANS@H2O-120 was found to have a high surface area of 2853 m2/g. The adsorption of bisphenol A and diuron on ANS@H2O-120 was investigated. The isotherm data were fitted using Langmuir and Freundlich models. Langmuir isotherm model presented the best fit to the experimental data suggesting micropore filling of ANS@H2O-120. The ANS@H2O-120 adsorbent demonstrated high monolayer adsorption capacity of 1408 and 1087 mg/g for bisphenol A and diuron, respectively. The efficiency of the adsorption was linked to the porous structure and to the availability of the surface adsorption sites on ANS@H2O-120. Response surface method was used to optimize the removal efficiency of bisphenol A and diuron on ANS@H2O-120 from aqueous solution. Graphical abstract ᅟ.

Life cycle assessment of the removal of Diuron and Linuron herbicides from water using three environmentally friendly technologies.

Nowadays, every chemical treatment must be developed taking into account its global impact on the environment. With this objective a life cycle assessment (LCA) has been used as a tool for the assessment of the environmental impact of three environmentally friendly processes for the removal of Diuron and Linuron herbicides from water: artificial light assisted photo-Fenton, photo-Fenton coupled to biological treatment and solar assisted photo-Fenton. The inventoried data has been classified considering the potential environmental impacts categories included in the CML 2 baseline 2000 method. Among the three scenarios considered, photo-Fenton coupled to biological treatment proved to have the lowest environmental impact in all the studied categories due to the lower hydrogen peroxide and electricity consumptions. The environmental impacts associated with hydrogen peroxide and electricity production imply more than 72% in all the impact categories of the three scenarios, except for aquatic eutrophication potential category, where the main impacts are related to nitrogen emissions.

Sorption potential of different biomass fly ashes for the removal of diuron and 3,4-dichloroaniline from water.

Hazardous contaminants in water and biomass fly ash spillage are causes for environmental and health concern. We selected five fly ashes generated from olive-mill (O,P, G and H) and greenhouse vegetable (I) waste used as biomass fuel in order to quantify their capacity to remove diuron and 3,4-dichloroaniline (DCA) from water. To understand the sorption processes involved, four kinetic models and two adsorption isotherms were assayed. The pseudo second-order kinetic showed the best fit (R2>0.99). The initial adsorption rate constant was found to be faster for DCA than for diuron. The Freundlich adsorption constants of ashes O, P, G and H for diuron were more than 2-fold higher than for DCA (Kf=109-16µg1-1/ng-1mL-1). The alkaline pH of these fly ashes plays an important role in the adsorption process. Sorption/desorption processes were significantly affected by iron oxide content. DCA sorption was also influenced by particle size and carbon content. Low hysteresis coefficient values (H=0.01-0.26) revealed an irreversible sorption process. The study presents novel information on the immobilization of hazardous chemicals in water by biomass fly ashes generated from olive-oil industry and greenhouse crop waste.

Pesticide removal from cotton farm tailwater by a pilot-scale ponded wetland.

A pilot-scale, ponded wetland consisting of an open pond and a vegetated pond in series was constructed on a cotton farm in northern New South Wales, Australia, and assessed for its potential to remove pesticides from irrigation tailwater. Ten incubation periods ranging from 7 to 13 days each were conducted over two cotton growing seasons to monitor removal of residues of four pesticides applied to the crop. Residue reductions ranging 22-53% and 32-90% were observed in the first and second seasons respectively. Average half-lives during this first season were calculated as 21.3 days for diuron, 25.4 days for fluometuron and 26.4 days for aldicarb over the entire wetland. During the second season of monitoring, pesticide half-lives were significantly reduced, with fluometuron exhibiting a half-life of 13.8 days, aldicarb 6.2 days and endosulfan 7.5 days in the open pond. Further significant reductions were observed in the vegetated pond and also following an algal bloom in the open pond, as a result of which aldicarb and endosulfan were no longer quantifiable. Partitioning onto sediment was found to be a considerable sink for the insecticide endosulfan. These results demonstrate that macrophytes and algae can reduce the persistence of pesticides in on-farm water and provide some data for modelling.

Investigation into the effects of temperature and stirring rate on the solid-phase extraction of diuron from water using a C18 extraction disk.

A novel experimental method for determining the equilibrium constant, Keq, and the uptake rate constant, kup, for the solid-phase extraction (SPE) of diuron from water using a C18 Empore extraction disk is reported. Log Keq and log kup are determined at 7.0, 11.0, 18.0 and 23.0 degrees C and for stirring rates of 100, 200 and 400 rpm. From a Van 't Hoff plot of log Keq versus T-1 the enthalpy of sorption, delta H0, is shown to be negative which indicates that the thermodynamic process of uptake is exothermic. The rate of stirring has no effect on log Keq over the temperature range 7.0-23.0 degrees C. The enthalpy of activation, delta H0, calculated from Arrhenius plots of log kup versus T-1 at 100, 200 and 400 rpm show that the kinetic process of uptake is endothermic. At 100 rpm the rate of uptake is limited by the aqueous diffusion of diuron. At 200 rpm or greater the aqueous diffusion layer around the disk is sufficiently small to prevent diffusion from being a limiting factor. The method described in this paper is limited to the analysis of analytes that contain a significant UV chromophore and are relatively soluble in water, but it can also be used to investigate pH and salinity effects on the SPE of diuron from water.

Application of the IAS theory combining to a three compartments description of natural organic matter to the adsorption of atrazine or diuron on activated carbon.

The study of natural organic matter (NOM) adsorption on an activated carbon showed that equilibrium cannot be described according to a simple model such as a Freundlich isotherm and confirms the need for a closer description of the organic matter to simulate the competitive adsorption with micropollutants. A representation of the organic matter in three fractions is chosen: non-adsorbable, weak and strong adsorbable. The Ideal Adsorbed Solution Theory (IAST) can, under restrictive conditions, be used to effectively predict the competition between the pesticides and the organic matter. Therefore, it was noted that the model simulated with good precision the competition between atrazine or diuron and natural organic matter in aqueous solution for two activated carbons (A and B). The same parameters for the modeling of organic matter adsorption (Freudlich constants for two absorbable fractions) are used with the two pesticides. However, IAST does not allow correct modeling of pesticide adsorption onto two other (C and D) activated carbons in solution in natural water to be described. IAS theory does not reveal competition between diuron and NOM and pore blockage mechanism by the NOM is proposed as the major effect for the adsorption capacity reduction. However, the difference observed between the two pesticides could be due to in addition to the pore blockage effect, a particular phenomenon with the diuron, especially with D activated carbon. We can suppose specific interactions between the diuron and the adsorbed organic matter and a competition between adsorption sites of NOM and activated carbon surface.

Activating persulfate by Fe° coupling with weak magnetic field: performance and mechanism.

Weak magnetic field (WMF) and Fe(0) were proposed to activate PS synergistically (WMF-Fe(0)/PS) to degrade dyes and aromatic contaminants. The removal rates of orange G (OG) by WMF-Fe(0)/PS generally decreased with increasing initial pH (3.0-10.0) and increased with increasing Fe(0) (0.5-3.0 mM) or PS dosages (0.5-3.0 mM). Compared to its counterpart without WMF, the WMF-Fe(0)/PS process could induce a 5.4-28.2 fold enhancement in the removal rate of OG under different conditions. Moreover, the application of WMF significantly enhanced the decolorization rate and the mineralization of OG. The degradation rates of caffeine, 4-nitrophenol, benzotriazole and diuron by Fe(0)/PS were improved by 2.1-11.1 fold due to the superimposed WMF. Compared to many other sulfate radical-based advanced oxidation technologies under similar reaction conditions, WMF-Fe(0)/PS technology could degrade selected organic contaminants with much greater rates. Sulfate radical was identified to be the primary radical species responsible for the OG degradation at pH 7.0 in WMF-Fe(0)/PS process. This study unraveled that the presence of WMF accelerated the corrosion rate of Fe(0) and thus promoted the release of Fe(2+), which induced the increased production of sulfate radicals from PS and promoted the degradation of organic contaminants. Employing WMF to enhance oxidation capacity of Fe(0)/PS is a novel, efficient, promising and environmental-friendly method since it does not need extra energy and costly reagents.

Microfunnel-supported liquid-phase microextraction: application to extraction and determination of Irgarol 1051 and diuron in the Persian Gulf seawater samples.

In the present work, microfunnel-supported liquid-phase microextraction method (MF-LPME) based on applying low density organic solvent was developed for the determination of antifoulings (Irgarol 1051, diuron and 3,4-dichloroaniline) from seawater samples. In this method, home-designed MF device was used for facile loading and retrieving of organic solvent during the extraction procedure. The extraction was carried out with introduction of 400 µL of toluene via syringe into the MF device placed on the surface of sample solution (300 mL) containing analytes. After the extraction, extractant layer was narrowed into the capillary part of MF by pushing the device inside the sample and withdrawn by using a syringe to evaporate by nitrogen purging. The residual redissolved into 50 µL methanol, diluted to 100 µL with deionized water and injected into the high performance liquid chromatography with UV detection (HPLC-UV). Several factors influencing the extraction such as the type and volume of extraction solvent, sample pH, extraction time and ionic strength were investigated and optimized. Under the optimized conditions, the limits of detection in seawater were 1.4, 4.8 and 1.0 ng L(-1) for 3,4-dichloroaniline (DCA), diuron and Irgarol 1051, respectively. Enrichment factors were obtained 333, 150 and 373 for DCA, diuron and Irgarol 1051, respectively. The precision of the technique was evaluated in terms of repeatability which was less than 12.0% (n=5). The applicability of the proposed method was evaluated by the extraction and determination of antifoulings from seawater samples collected from harbors of Bushehr located in northern Persian Gulf coast.

Coupling Fenton and biological oxidation for the removal of nitrochlorinated herbicides from water.

The combination of Fenton and biological oxidation for the removal of the nitrochlorinated herbicides alachlor, atrazine and diuron in aqueous solution has been studied. The H2O2 dose was varied from 20 to 100% of the stoichiometric amount related to the initial chemical oxygen demand (COD). The effluents from Fenton oxidation were analyzed for ecotoxicity, biodegradability, total organic carbon (TOC), COD and intermediate byproducts. The chemical step resulted in a significant improvement of the biodegradability in spite of its negligible or even slightly negative effect on the ecotoxicity. Working at 60% of the stoichiometric H2O2 dose allowed obtaining highly biodegradable effluents in the cases of alachlor and atrazine. That dose was even lower (40% of the stoichiometric) for diuron. The subsequent biological treatment was carried out in a sequencing batch reactor (SBR) and the combined Fenton-biological treatment allowed up to around 80% of COD reduction.