Amitrole Degradation Research Articles

Concurrent Exfoliation and Controlled Coating of 2D-g-C3N4 Over 3DCe2(WO4)3 for Proficient Photocatalytic Degradation of Amitrole and Chlorpyrifos

Concurrent Exfoliation and Controlled Coating of 2D-g-C3N4 Over 3DCe2(WO4)3 for Proficient Photocatalytic Degradation of Amitrole and Chlorpyrifos

Degradation, Kinetics, and Mineralization in Solar Photocatalytic Treatment of Aqueous Amitrole Solution with Titanium Dioxide

Abstract Amitrole (3-amino-1H-1,2,4-triazole or aminotriazole) is a widely employed herbicide with strong estrogenic activity that can lead to abnormalities of the thyroid gland and cause mutations. Photocatalytic degradation conditions of amitrole in titanium dioxide (TiO2)-suspended solution were optimized under sunlight irradiation. The effect of various factors, such as photocatalyst loading, initial substrate concentration, temperature, pH, sunlight intensity, and irradiation time on the photocatalytic degradation of amitrole, was investigated. Photocatalytic degradation under sunlight irradiation was very effective for amitrole solution. The primary photocatalytic decomposition reaction followed a pseudo-first-order kinetic law, according to the Langmuir–Hinshelwood model. The activation energy (Ea) was estimated to be 6.73 kJ/mol. Nitrate (NO3−) and ammonium (NH4+) ions were detected as end inorganic products. Triazole was identified as the intermediate product. Solar photocatalytic degradation tre...

Influence of operational parameters on photocatalytic amitrole degradation using nickel organic xerogel under UV irradiation

The objectives of this study were to analyze the influence of different operational variables and to determine the time course of total organic carbon (TOC) and medium toxicity during amitrole (AMT) photodegradation in the presence of Ni xerogel (X-Ni) as photocatalyst. A further study objective was to analyze the influence of the type of water on the photodegradation process. Results show that the degradation rate is directly proportional to the initial X-Ni concentration up to a maximum of 250mg/L with a slight decrease thereafter, indicating progressive photon absorption saturation of the catalyst for a given incident radiation flow. At concentrations close to 250mg/L X-Ni, the AMT photodegradation rate is not affected by further increases in X-Ni concentration. In addition, AMT photolysis is highly pH-dependent and is generally favored at pH values at which AMT is in its ionic form. The increase observed in AMT degradation rate under alkaline conditions can be attributed to the higher generation of HO radicals. The presence of chloride reduces the AMT degradation rate, because Cl− anions behave as h+ and HO radical scavengers. The degradation rate is also decreased by addition to the medium of organic matter, which acts as a filter. The behavior of TOC removal kinetics during AMT degradation in the presence of X-Ni is similar to that observed for AMT degradation kinetics. Finally, we highlight that photocatalysis is more effective in ultrapure water than in wastewater or tap water. In all systems, the optimal catalyst concentration is 250mg/L. The medium toxicity increases with longer treatment time, indicating the formation of by-products that are smaller than AMT and can more readily penetrate the cell.

Effect of HO[rad], SO4[rad]− and CO3[rad]−/HCO3[rad] radicals on the photodegradation of the herbicide amitrole by UV radiation in aqueous solution

This study analyzed the photodegradation of the herbicide amitrole (AMT) in water by advanced oxidation processes (AOPs) based on ultraviolet (UV) radiation (UV, UV/H2O2, UV/Fe2+/H2O2, UV/K2S2O8, and UV/Na2CO3) and examined the influence of the initial concentration of radical generators, the solution pH, and the chemical composition of the water. The values of AMT reaction rate constants with HO, SO4− and CO3−/HCO3 radicals obtained at pH 7 were 5.85±0.25×108M−1s−1, 3.77±0.17×108M−1s−1, and 1.37±0.12×106M−1s−1, respectively. The AMT degradation rate constant in the absence of radical generators (0.013±0.001min−1) was considerably increased by their addition, yielding values of 0.037±0.005, 0.059±0.009, or 0.024±0.002min−1 with only 0.15×10−3molL−1 H2O2, K2S2O8, or Na2CO3, respectively. In all cases, these constants increased with greater amounts of reagent, reaching values of 0.309±0.032, 0.748±0.091, and 0.043±0.004min−1, respectively, with the addition of 3.47×10−3molL−1 of the corresponding radical generator. The percentage of total organic carbon removal showed the same trend as the AMT degradation rate, reaching 86.8% with the addition of 3.47×10−3molL−1 H2O2 and increasing to 99.0% when 0.04×10−3molL−1 Fe2+ was added to the system. We analyzed the effectiveness of three systems (UV/H2O2, UV/K2S2O8, and UV/Na2CO3) for AMT photodegradation in different types of water (ultrapure, tap, and treated urban wastewaters), verifying their high effectiveness, especially UV/K2S2O8. The high efficacy of these systems is related to the generation of both SO4− and HO radicals and the greater selectivity of SO4− radical in its reaction with AMT.

NF-TiO2 photocatalysis of amitrole and atrazine with addition of oxidants under simulated solar light: Emerging synergies, degradation intermediates, and reusable attributes

In order to investigate sustainable alternatives to current water treatment methods, the effect of NF-titania film thickness and subsequent photocatalysis in combination with oxidants was examined under simulated solar light. Such a combination presents a theoretical possibility for a synergistic interaction between the photocatalyst and the oxidant (activation of the oxidant by the catalyst under conditions under which it may not conventionally be activated). To investigate, peroxymonosulfate (PMS) and persulfate (PS) were used as oxidants, and two pesticides, amitrole and atrazine, were used as target contaminants. In the absence of a film, activation of PMS under simulated solar conditions is demonstrated by removal of atrazine, whereas PS provided minimal removal, suggesting inefficient activation. Combining photocatalytic films with PMS and PS manifested synergies for both oxidants. The effect was most pronounced for PS since PMS already underwent significant activation without the photocatalyst. Amitrole degradation results indicated a lack of removal of amitrole by activated PS alone, suggesting that this sulfate radical-based treatment technology may be ineffective for the removal of amitrole. The NF-TiO2 films demonstrated reusability under solar light both with and without oxidants. Finally, the degradation intermediates were analyzed, and a new intermediate appeared upon incorporating oxidants into the system.

Heterogeneous and homogeneous Fenton processes using activated carbon for the removal of the herbicide amitrole from water

The study objective was to investigate the removal of amitrole (AMT) by oxidation using the decomposition of hydrogen peroxide in heterogeneous and homogeneous Fenton reactions. For this purpose, an activated carbon cloth was used to prepare supported iron catalysts with different iron salts (sulfate, acetate and nitrate) and iron metal loadings. Homogeneous Fenton reactions were carried out by using iron sulfate or acetate in the absence or presence of the activated carbon cloth. In the heterogeneous Fenton reaction, the amounts of TOC (total organic carbon) and AMT removed depended on the iron metal loading and the Fe/H2O2 molar ratio; iron leaching was very low. The highest AMT degradation (∼90%) was achieved with the homogeneous Fenton reaction using FeSO4 in the presence of the activated carbon cloth, which may be due to a synergic effect between activated carbon and iron salt; with this procedure, ∼60% of the TOC was removed. The synergic effect was not observed when iron acetate was used as homogeneous catalyst. The presence of sulfate ions favored the oxidation of AMT to urazole. Nitrate and ammonium ions were observed but at negligible concentrations.

Integrated Process for Degradation of Amitrole in Wastewaters: Photocatalysis/Biodegradation

Preliminary studies highlight the positive effect of coupling photocatalysis and biological processes for the treatment of biorecalcitrant compounds. Before biological treatment, photocatalysis can be used as a pre-treatment process to increase pesticide biodegradability. Kinetics of amitrole biodegradation during cultures of Pseudomonas fluorescens was examined to ensure that the target compound was biorecalcitrant; its inhibitory effect justified a pre-oxidation. The biodegradation of cyanuric acid, one of the by-products resulting from photocatalyis of amitrole was confirmed. Pseudomonas fluorescens could metabolize this compound as a nitrogen source when a supplementary carbon source was added. The addition of supplementary carbon and nitrogen sources favoured growth and accordingly cyanuric acid degradation. Degradation yields (with TiO2 coated on cellulose fibers, 25 g.m-2) in the range 47% to 55% were obtained after 50h of irradiation for solutions of amitrole in the range concentrations between 70 to 6000 ppm. Between 10% and 34% of amitrole was mineralized to carbon dioxide. The production of ammonium and nitrate ions was negligible. An inhibition of TiO2 active sites was assumed to account for the weak mineralization. Identification of some of the intermediate by-products by LC-MS/MS shows negligible quantity of cyanuric acid. This work demonstrates that the hybrid process photocatalysis/bioremediation is a cost-effective promising solution for the treatment of wastewater containing biorecalcitrant compounds.

Degradation of amitrole by excitation of iron(III) aquacomplexes in aqueous solutions

The induced degradation of amitrole (3-amino-1,2,4-triazole or aminotriazole) by excitation of iron(III) aquacomplexes was investigated under irradiation at λ=365 nm. The process mainly involved the predominant monomeric species of iron(III), namely Fe(OH) 2+, which leads to the formation of hydroxyl radicals upon excitation in the UV-Vis region. Competitive reactions experiments using nanosecond laser flash photolysis were undertaken for the determination of the second-order rate constant for the reaction of amitrole with hydroxyl radical. A value of 1.5×10 9 mol −1 l s −1 was obtained. The quantum yield of amitrole disappearance upon irradiation of the mixture amitrole/iron(III) increased with increasing oxygen concentration and was found to be independent on iron(III) and amitrole concentration. The high performance liquid chromatography (HPLC) analyses showed the formation of two main photoproducts: 5-hydroxy amitrole and urazole (2-aminothiazole). The latter product accumulated in the solution while the former rapidly disappeared with the irradiation time. Efficient mineralisation of the solutions was obtained by artificial as well as by sunlight irradiations.

Amitrole degradation in vineyard soils in relation to pedo-climatic conditions

The fate of [14C]-amitrole herbicide was studied in eight soils having different capacities for amitrole mineralisation. Laboratory incubations were run combining different experimental conditions: temperature (4, 28 and 50°C), soil moisture (50, 100 and 150% of soil water holding capacity) and microbial activity (sterile and non-sterile conditions). During incubation, samples of the soils were periodically extracted with 0.5 M NH4OH and extracts were analysed by HPLC. The lengths of time needed for 50% dissipation of amitrole (DT50) in soils ranged from less than 1 day to more than 70 days. Amitrole mineralisation occurred only in non-sterile soils, showing that it is a biological process. Mineralisation was lower in soils with a coarse texture than in soils with a fine texture. Soil water content had little influence on the total amount of amitrole mineralised at the end of incubation. Temperature had a greater influence on mineralisation, although rates were still high at low and high temperatures. In non-sterile as in sterile soils, the major product detected in the extracts was amitrole. Additional non-identified radioactivity was occasionally extracted. However, it never represented more than 10% of initially applied amitrole. Non-extractable residues represented less than 15% of applied radioactivity in acidic soils and about 30% of applied radioactivity in alkaline and neutral soils. The amount of non-extractable radioactivity formed was enhanced in sterile as compared to non-sterile soils. Furthermore, in sterile soils, high temperature induced an increase of non-extractable residues, showing that amitrole is chemically quite reactive.

Isolation of amitrole-degrading bacteria

THE herbicide, amitrole (3-amino-1,2,4-triazole) is degraded in soil within a matter of weeks under favourable conditions1–4. This degradation may be microbiological since it is negligible in soils sterilised by steam1–3,5 or chemicals2,3. Kaufman et al.6, however, consider amitrole breakdown to be primarily due to chemical processes since amitrole-degrading organisms have never been isolated from soil. They found that degradation of amitrole continued in chemically sterilised, though not in autoclaved soil. We report here the isolation of amitrole-degrading microorganisms from soil, thus strengthening the case for microbial degradation.

Chemical Versus Microbial Decomposition of Amitrole in Soil

Degradation of 3-amino-l,2,4-triazole-5-C14 (amitrole-5-C14) in autoclaved, potassium azide, ethylene oxide, and dry-heat sterilized soil was compared with that observed in nonsterile soils by measuring evolved C14O2. Amitrole degradation occurred in azide and ethylene oxide-sterilized and nonsterile soils but not in autoclaved soils. Only slight degradation occurred in autoclaved soil re-inoculated with mixed cultures of soil microorganisms isolated from soil in which amitrole had been rapidly degraded. Addition of EDTA-Na to nonsterile and ethylene oxide sterilized soils reduced amitrole degradation. Addition of organic amendments to amitrole treated soil stimulated microbial activity but reduced amitrole degradation. Addition of specific metallic salts to certain soils increased the rate of amitrole degradation. Amitrole degradation occurred rapidly in several free radical generating chemical systems. These results and additional observations indicate that amitrole degradation, at least in three soils examined, was largely a chemical process, and that microbial involvement was only indirect.