Spectroscopic monitoring of photocatalytic degradation of the insecticide acetamiprid and its degradation product 6-chloronicotinic acid on TiO₂ catalyst

Integrated Electrochemical Oxidation and Biodegradation for Remediation of a Neonicotinoid Insecticide Pollutant

A novel integrated electrochemical oxidation (EO) and bacterial degradation (BD) technique was employed for the remediation of the chloropyridinyl and chlorothiazolyl classes of neonicotinoid (NEO) insecticides in the environment. Imidacloprid (IM), clothianidin (CL), acetamiprid (AC), and thiamethoxam (TH) were chosen as the target NEOs. Pseudomonas oleovorans SA2, identified through 16S rRNA gene analysis, exhibited the potential for BD. In EO, for the selected NEOs, the total percentage of chemical oxygen demand (COD) was noted in a range of 58-69%, respectively. Subsequently, in the biodegradation of EO-treated NEOs (BEO) phase, a higher percentage (80%) of total organic carbon removal was achieved. The optimum concentration of NEOs was found to be 200 ppm (62%) for EO, while for BEO, the COD efficiency was increased up to 79%. Fourier-transform infrared spectroscopy confirms that the heterocyclic group and aromatic ring were degraded in the EO and further utilized by SA2. Gas chromatography-mass spectroscopy indicated up to 96% degradation of IM and other NEOs in BD (BEO) compared to that of EO (73%). New intermediate molecules such as silanediamine, 1,1-dimethyl-n,n'-diphenyl produced during the EO process served as carbon sources for bacterial growth and further mineralized. As a result, BEO enhanced the removal of NEOs with a higher efficiency of COD and a lower consumption of energy. The removal efficiency of the NEOs by the integrated approach was achieved in the order of AC > CL > IM > TH. This synergistic EO and BD approach holds promise for the efficient detoxification of NEOs from polluted environments.

Superior photo-Fenton degradation of acetamiprid by α- Fe2O3-pillared bentonite/L-cysteine complex: Synergy of L-cysteine and visible light

Acetamiprid is a potential threat to human health, aquatic life, soil microorganisms and beneficial insects as a recalcitrant pollutant in wastewater treatment plant effluents. In this work, the synthesized α-Fe2O3-pillared bentonite (FPB) was used to degrade acetamiprid in the photo-Fenton process with the assistance of L-cysteine (L-cys) existing in natural aquatic environment. The kinetic constant k of acetamiprid degradation by FPB/L-cys in the photo-Fenton process was far more than that in the Fenton process of FPB/L-cys lacking light and the photo-Fenton process of FPB without L-cys. The positive linear correlation between k and ≡Fe(II) content indicated the synergy of L-cys and visible light accelerated the cycle of Fe(III) to Fe(II) in FPB/L-cys during the degradation of acetamiprid by elevating the visible light response of FPB, and promoting the interfacial electron transfer from the active sites of FPB to hydrogen peroxide and photo-generated electron transfer from conduction band of α-Fe2O3 to the active sites of FPB. The boosting •OH and 1O2 were predominantly responsible for acetamiprid degradation. Acetamiprid could be efficiently degraded into less toxic small molecules in the photo-Fenton process via C-N bond breaking, hydroxylation, demethylation, ketonization, dechlorination, and ring cleavage.

Photolysis and photo-enhanced toxicity of three novel designed neonicotinoids: Impact of novel modifying groups

Three novel neonicotinoids (cycloxaprid, flupyradifurone and sulfoxaflor) were designed to reduce the biotoxicity for non-target organisms. These neonicotinoids were photolyzed under light radiation, but it was unclear for the photo-enhanced toxicity and influences of the novel modifying group of the three neonicotinoids. The photolysis and photo-enhanced toxicity experiments were performed for the three neonicotinoids, coupled with quantum chemistry calculation, the mechanisms of photolysis, photo-enhanced toxicity and the influences of novel modifying groups were analyzed. The results showed the photolysis pathways were enriched as compared with previous neonicotinoids due to the composition of modifying groups, singlet oxygen and hydroxyl participated the photolysis of cycloxaprid and flupyradifurone. All tested neonicotinoids exhibited photo-enhanced toxicity to Vibrio fischeri. Due to the difference of photolysis mechanism and toxicity to V. fischeri, the photo-enhanced toxicity curves showed diverse variation when histidine, tert-butanol or dissolved organic matters was in presence of the test solutions. The impact of novel modifying groups over photolysis and photo-enhanced toxicity were analyzed based on the comparison with previous neonicotinoids, theoretically predicted UV-Vis spectra and photo-physical/chemical property descriptors. The data showed the composition of novel modifying group increased the light absorption and photo-chemical activities for the three neonicotinoids.

Hansen parameter evaluation for the characterization of titania photocatalysts using particle size distributions and combinatorics

Titania photocatalysts have great potential as remediators of air pollution. Although various aspects of photocatalyst synthesis, adsorption and photoactivity have been investigated, a thorough understanding of the particle surface behavior has not yet been fully realized. In order to learn more about the principles behind the surface behavior, we investigate the Hansen solubility/similarity parameters (HSPs) for analyzing and evaluating three photocatalysts synthesized by the gas phase method, solvothermal reaction and sol-gel method, respectively. A particle size distribution-based categorization scheme is introduced for characterizing each material's Hansen parameters based on its interaction with a list of selected probe liquids. The latter was deduced from particle size distributions assessed by analytical centrifugation. Subsequent comparison of the Hansen parameters of the investigated materials shows how HSPs can potentially be used as a model for predicting the pollutant adsorption behavior on the photocatalyst surface. This serves as a first step in heading towards an improved understanding of the particle behavior and translating it into a knowledge-based design, i.e., synthesis and hybridization of novel photocatalysts.

Simultaneous determination of acetamiprid and 6-chloronicotinic acid in environmental samples by using ion chromatography hyphenated to online photoinduced fluorescence detector

This study aims to introduce a simple, sensitive, and cost-effective method for the simultaneous determination of acetamiprid and its main metabolite 6-chloronicotinic acid in environmental samples by using a nonsuppressed ion chromatography hyphenated with an online postcolumn photoinduced fluorescence detection system. The fluorescence detector wavelengths λ_ex /λ_em  = 257/382 nm was set for up to 6.0 min for acetamiprid, while λ_ex /λ_em  = 231/370 nm programmed for 6-chloronicotinic acid for the rest of the analysis time. Both samples were treated by applying miniaturized quick, easy, cheap, effective, rugged, and safe method before the separation of analytes on an IonPac^® AS11-HC column by pumping 40 mM NaOH having minuscule content of acetonitrile (5%, v/v) as an eluent. Both intrinsically nonfluorescent analytes were turned-on by online postcolumn photoinduced derivatization, avoiding the need for complex chemical derivatization or addition of a postcolumn extra pump. The developed method was appraised for the analysis of environmental samples, exhibiting excellent linearity (0.050-10 μg/mL) with a correlation coefficient greater than 0.9993 for both analytes. Whereas, obtained limit of detection (0.025-0.0072 μg/mL), recoveries (98.02-116.00%), and inter- and intraday precision (≤3.02 %) were satisfactory for both compounds in environmental samples.

Porous Activated Carbon from Lignocellulosic Agricultural Waste for the Removal of Acetampirid Pesticide from Aqueous Solutions

A facile eco-friendly approach for acetampirid pesticide removal is presented. The method is based on the use of micro- and mesoporous activated carbon (TPAC) as a natural adsorbent. TPAC was synthesized via chemical treatment of tangerine peels with phosphoric acid. The prepared activated carbon was characterized before and after the adsorption process using Fourier- transform infrared (FTIR), X-ray diffraction (XRD), particle size and surface area. The effects of various parameters on the adsorption of acetampirid including adsorbent dose (0.02–0.2 g), pH 2–8, initial adsorbate concentration (10–100 mg/L), contact time (10–300 min) and temperature (25–50 °C) were studied. Batch adsorption features were evaluated using Langmuir and Freundlich isotherms. The adsorption process followed the Langmuir isotherm model with a maximum adsorption capacity of 35.7 mg/g and an equilibration time within 240 min. The adsorption kinetics of acetamiprid was fitted to the pseudo-second-order kinetics model. From the thermodynamics perspective, the adsorption was found to be exothermic and spontaneous in nature. TPAC was successfully regenerated and reused for three consecutive cycles. The results of the presented study show that TPAC may be used as an effective eco-friendly, low cost and highly efficient adsorbent for the removal of acetamiprid pesticides from aqueous solutions.

Priority pesticides abatement by advanced water technologies: The case of acetamiprid removal by ozonation

With the aim of exploring treatment alternatives for priority insecticide acetamiprid (ACMP) abatement, the removal of this compound from water by ozonation was studied for the first time, paying special attention to the kinetic, mechanistic and toxicological aspects of the process. The second order rate constants of reactions between ACMP and both molecular ozone (O₃) and hydroxyl radicals (OH) were determined to be 0.25M^-1s^-1 and 2.1·10⁹M^-1s^-1, respectively. On the basis of kinetic results, the degradation of ACMP during ozonation could be well-explained by the reactivity of this pesticide with OH. HPLC/MS analysis of the ozonated ACMP showed ACMP-N-desmethyl, 6-chloronicotinic acid, N'cyano-N-methyl acetamidine and N'-cyano acetamidine as the major transformation products (TPs), all of them formed through amine α carbon oxidation in combination with hydrolysis. Microtox bioassays revealed an increase in the toxicity of the medium during ACMP ozonation process, followed by a decrease to relatively low values. These changes could be attributed to the synergistic effects between TPs as well as to the presence of toxic intermediate aldehydes. Even though adopting strategies to further promote ozone decomposition to hydroxyl radicals appears to be essential, ozonation can be an effective treatment process for ACMP removal and associated toxicity abatement.

Photodegradation of neonicotinoid insecticides in water by semiconductor oxides

The photocatalytic degradation of three neonicotinoid insecticides (NIs), thiamethoxam (TH), imidacloprid (IM) and acetamiprid (AC), in pure water has been studied using zinc oxide (ZnO) and titanium dioxide (TiO2) as photocatalysts under natural sunlight and artificial light irradiation. Photocatalytic experiments showed that the addition of these chalcogenide oxides in tandem with the electron acceptor (Na2S2O8) strongly enhances the degradation rate of these compounds in comparison with those carried out with ZnO and TiO2 alone and photolytic tests. Comparison of catalysts showed that ZnO is the most efficient for the removal of such insecticides in optimal conditions and at constant volumetric rate of photon absorption. Thus, the complete disappearance of all the studied compounds was achieved after 10 and 30 min of artificial light irradiation, in the ZnO/Na2S2O8 and TiO2/Na2S2O8 systems, respectively. The highest degradation rate was noticed for IM, while the lowest rate constant was obtained for AC under artificial light irradiation. In addition, solar irradiation was more efficient compared to artificial light for the removal of these insecticides from water. The main photocatalytic intermediates detected during the degradation of NIs were identified.

A novel sensor for the detection of acetamiprid in vegetables based on its photocatalytic degradation compound

An electrochemical method for the indirect determination of acetamiprid was studied, using titanium dioxide photocatalysts coupled with a carbon paste electrode. The cyclic voltammetric results indicated that the photocatalytic degradation compound of acetamiprid had electroactivity in neutral solutions. The amount of acetamiprid was further indirectly determined by differential pulse anodic stripping voltammetric analysis as a sensitive detection technique. The experimental parameters were optimized with regard to the photocatalytic degradation time, pH of buffer solution, accumulation potential and accumulation time. Under optimal conditions, the proposed electrochemical method could detect acetamiprid concentrations ranging from 0.01 to 2.0μM, with a detection limit (3S/N) of 0.2nM. Moreover, the proposed method displays excellent selectivity, good reproducibility, and acceptable operational stability and can be successfully applied to acetamiprid determination in vegetable samples with satisfying results.

Removal of 1,4-dioxane from industrial wastewaters: routes of decomposition under different operational conditions to determine the ozone oxidation capacity

This paper denotes the importance of operational parameters for the feasibility of ozone (O3) oxidation for the treatment of wastewaters containing 1,4-dioxane. Results show that O3 process, which has formerly been considered insufficient as a sole treatment for such wastewaters, could be a viable treatment for the degradation of 1,4-dioxane at the adequate operation conditions. The treatment of both synthetic solution of 1,4-dioxane and industrial wastewaters, containing 1,4-dioxane and 2-methyl-1,3-dioxolane (MDO), showed that about 90% of chemical oxygen demand can be removed and almost a total removal of 1,4-dioxane and MDO is reached by O3 at optimal process conditions. Data from on-line Fourier transform infrared spectroscopy provides a good insight to its different decomposition routes that eventually determine the viability of degrading this toxic and hazardous compound from industrial waters. The degradation at pH>9 occurs faster through the formation of ethylene glycol as a primary intermediate; whereas the decomposition in acidic conditions (pH<5.7) consists in the formation and slower degradation of ethylene glycol diformate.

Optimization of the Fenton treatment of 1,4-dioxane and on-line FTIR monitoring of the reaction

1,4-Dioxane is a non-biodegradable, toxic, hazardous, and priority pollutant widely used in the chemical industry as a solvent; as well as it is a resulting by-product of many industrial processes. The optimization of the Fenton treatment of 1,4-dioxane, and the on-line FTIR monitoring of its degradation route, including the assessment of the enhancement of the biodegradability of the solution along treatment are herein addressed. Besides the full removal of 1,4-dioxane, an 80% reduction of the chemical oxygen demand (COD) was achieved at the best tested treatment conditions. Whether the used concentration of H2O2 was expectedly addressed as the reaction factor most influencing the achieved COD removal at the end of the process; the performance of the treatment under acid pH conditions showed to have just a slight influence, thus supporting this process may suitably be performed at neutral pH value. On-line FTIR monitoring of the process novelly provided the degradation route of 1,4-dioxane along its oxidation treatment, as well as a comprehensive optimization of the Fenton process based on the increase of the biodegradability of the solution and the reduction of the consumption of reagents.