Degradation Of Bentazone Research Articles

Effective degradation of bentazone by two-dimensional and three-phase, three-dimensional electro-oxidation system: kinetic studies and optimization using ANN.

Bentazone is a broad-leaved weed-specific herbicide in the pesticide industry. This study focused on removing bentazone from water using three different methods: a two and three-dimensional electro-oxidation process (2D/EOP and 3D/EOP) with a fluid-type reactor arrangement using tetraethylenepentamine-loaded particle electrodes and an adsorption method. Additionally, we analysed the effects of two types of supporting electrolytes (Na2SO4 and NaCl) on the degradation process. The energy consumption amounts were calculated to evaluate the obtained results. The degradation reaction occurs 3.5 times faster in 3D/EOP than in 2D/EOP at 6 V in Na2SO4. Similarly, the degradation reaction of bentazone in NaCl occurs 2.5 times faster in 3D/EOP than in 2D/EOP at a value of 7.2 mA/cm2. Removal of bentazone is significantly better in 3D/EOPs than in 2D/EOPs. The use of particle electrodes can significantly enhance the degradation efficiency. The study further assessed the prediction abilities of the machine learning model (ANN). The ANN presented reasonable accuracy in bentazone degradation with high R2 values of 0.97953, 0.98561, 0.98563, and 0.99649 for 2D with Na2SO4, 2D with NaCl, 3D with Na2SO4, and 3D with NaCl, respectively.

Removal of Bentazone Pesticide from Aqueous Solutions by Electro-oxidation Method

The kinetics of the electro-oxidation degradation of prepared aqueous solutions containing bentazone as a model compound of the thiadiazine group of pesticides was studied in the lab. The oxidation process was conducted under galvanostatic polarization in natural model media using boron-doped diamond (BDD) cathode and anode. Chemical oxygen demand (COD) estimation along the electro-oxidation treatment processing allowed the assessment of kinetic of organic compounds decay as well as the instantaneous current efficiency. The obtained data reflected that the degradation of bentazone pesticide is significantly dependent on initial amount of bentazone pesticide, current density and electrolytes concentration. COD removal follows a pseudo first-order kinetic and the electro-oxidation process was under the control of mass transport within the range studied, regardless the conditions of experimental. The COD removal rate increases with applied current density until 20 mA/cm2 and decreases for higher values. Two different concentrations supporting electrolyte (5mM, 10mM) were used. The rate of degradation increased significantly with increasing electrolyte concentration. The best obtained conditions for COD removal efficiency on the BDD electrode to degrade bentazone solutions (COD= 91.18 %) include operating at 20 mA/cm2 and 10 mM Na2SO4 as supporting electrolyte. This arrangement and condition allow to approximately complete degradation of bentazone in just 80 min. A decrease in the relative toxicity index value along the electro-oxidation indicate toxic compounds disappearance. The initial toxicity EC50 (5 min) and (15min) were decrease by 81% and 94% The kinetics of the electrooxidation degradation of prepared aqueous solutions containing bentazone as a model compound of the thiadiazine group of pesticides were studied in the lab. The oxidation process was conducted under galvanostatic polarization in natural model media using boron-doped diamond (BDD) cathodes and anode. Chemical oxygen demand (COD) estimation along the electro-oxidation treatment processing allowed the assessment of kinetic of organic compounds decay as well as the instantaneous current efficiency. The obtained data reflected that the degradation of bentazone pesticide is significantly dependent on initial amount of bentazone pesticide, current density and electrolytes concentration. COD removal follows a pseudo first-order kinetic and the electrooxidation process was under the control of mass transport within the range studied, regardless the conditions of experimental. The COD removal rate increases with applied current density until 20 mA/cm2 and decreases for higher values. Two different concentration (5mM, 10mM) were used. The rate of degradation increased significantly with increasing electrolyte concentration. The best obtained conditions for COD removal efficiency on the BDD electrode to degrade bentazone solutions (COD= 91.18 %) include operating at 20 mA/cm2 and 10 mM. This arrangement and condition allow to approximately complete degradation of bentazone in just 80 min. A decrease in the value of  relative toxicity index along the electrolysis indicate the disappearance of toxic compounds. The initial toxicity EC50 (5min) and (15min) were reduced by 81% and94% respectively after 80 minutes.

Photocatalytic removal of bentazon by copper doped zinc oxide nanorods: Reaction pathways and toxicity studies

In this study, bentazon herbicide was degraded photocatalytically by copper doped zinc oxide nanorods fabricated by using a facile co-precipitation method. The crystal structure, morphology, surface composition, functional groups on the surface and valence state of the nanorods were investigated by XRD, SEM-EDX, FTIR, and XPS material characterization techniques. Environmental parameters including solution pH, catalyst dose, bentazon concentration, purging gases, H2O2 content, organic compound type and reusability affecting the rate of photocatalytic degradation of bentazon were evaluated. Under the optimal conditions, [Bentazon]0 = 20 mg L−1, Cu–ZnO loading = 0.5 g L−1, H2O2 = 2 mM, pH = 7 and in the presence of oxygen gas, 100% of the herbicide was removed within 60 min. By raising bentazon concentration (10–50 mg L−1), kobs decreased to values between 0.14 and 0.006 min−1 and the calculated electrical energy per order (EEo) increased from 38.16 to 727.27 (kWh m−3), respectively. The degradation removal of the herbicide using the UV/Cu–ZnO method (98.28%) was higher than that of the UV/ZnO method (32.14%) process. Interestingly, the photocatalytic performances in the first and fifth reuse cycles during catalyst recyclability tests were found to be similar. Generally, the efficacy of the method in the decomposition of bentazon in drinking water (78.95%) and actual sewage (46.77%) declined because of the presence of other anions due to their role as a scavenger of photogenerated reactive species. Intermediate products in the photocatalytic degradation of bentazon identified by gas chromatography/mass spectrometry (GC/MS) analysis were 2-amino-N-isopropyl-benzamide, 2-amino-benzoic acid, N-isopropyl-2-nitro-benzamide, and acids such as pentenedioic acid, oxalic acid and propenoic acid. Furthermore, the main mechanism for the photocatalytic removal of bentazon was determined to be via attack by hydroxyl radicals (•OH). The results of toxicity in the photocatalytic removal of bentazon by D. magna showed LC50 and toxicity unit (TU) 48 h equal to 46.10 and 9.56 vol percent.

RNA-Seq Transcriptome Analysis of Potato with Differential Tolerance to Bentazone Herbicide

Potato (Solanum tuberosum), an important food crop worldwide, is threatened by broadleaf weeds. Bentazone is an effective herbicide for controlling weeds; however, as a photosynthesis inhibitor, it can also affect potato plants. Therefore, screening potato seedlings for bentazone resistance and determining the genes involved is essential. Herein, we selected potato varieties with tolerance and sensitivity to bentazone. The photosynthetic rate of sensitive plants was notably affected by bentazone application, whereas the tolerant plants showed a significantly higher photosynthetic rate. We observed 95.7% bentazone degradation within 24 d after application in the tolerant plants. Transcriptome sequencing revealed that the numbers of differentially expressed genes (DEGs) between the tolerant and sensitive potato seedlings were 2703 and 11,024 before and after bentazone application, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that the majority of DEGs were enriched in metabolic pathways, biosynthesis of secondary metals, carbon metabolism, glutathione metabolism, and photosynthesis. Polyphenol oxidase (PPO), flavonoid 3′,5′-methyltransferase-like (AOMT3), ribulose bisphosphate carboxylase small chain C (RBCS-C), and chalcone synthase 2 (CHS2) were identified as candidates contributing to bentazone tolerance. These results provide a theoretical basis for selecting potato stress-resistant resources in the future.

Remediation of bentazone contaminated water by Trametes versicolor: Characterization, identification of transformation products, and implementation in a trickle-bed reactor under non-sterile conditions

Bentazone, an herbicide widely applied in rice and cereal crops, is widespread in the aquatic environment. This study evaluated the capacity of Trametes versicolor to remove bentazone from water. The fungus was able to completely remove bentazone after three days at Erlenmeyer-scale incubation. Both laccase and cytochrome P450 enzymatic systems were involved in bentazone degradation. A total of 19 transformation products (TPs) were identified to be formed during the process. The reactions involved in their formation included hydroxylations, oxidations, methylations, N-nitrosation, and dimerization. A laccase mediated radical mechanism was proposed for TP formation. In light of the results obtained at the Erlenmeyer scale, a trickle-bed reactor with T. versicolor immobilized on pine wood chips was set up to evaluate its stability during bentazone removal under non-sterile conditions. After 30 days of sequencing batch operation, an average bentazone removal of 48% was obtained, with a considerable contribution of adsorption onto the lignocellulosic support material. Bacterial contamination, which is the bottleneck in the implementation of fungal bioreactors, was successfully addressed by this particular system according to its maintained performance. This research is a pioneering step forward to the implementation of fungal bioremediation on a real scale.

Oxidative degradation and mineralization of bentazone from water

Bentazone degradation efficiency and mineralization in water solutions using chlorine dioxide treatment were evaluated. Double distilled water and a river water sample spiked with bentazone were studied and compared after chlorine dioxide treatment. Degradation efficiency was determined using high-performance liquid chromatography (HPLC). Daphnia magna toxicity testing and total organic carbon (TOC) analysis were used to ascertain the toxicity of the degraded solutions and mineralization degree. Bentazone degradation products were identified using gas chromatography with a triple quadrupole mass detector (GC-MS-MS). A simple mechanistic scheme for oxidative degradation of bentazone was proposed based on the degradation products that were identified. Decrease in D. magna mortality, high degradation efficiency and partial bentazone mineralization were achieved by waters containing bentazone degradation products, which indicate the formation of less toxic compounds than the parent bentazone and effective removal of bentazone from the waters. Bentazone degraded into four main degradation products. Humic acid from Sava River water influenced bentazone degradation, resulting in a lower degradation efficiency in this matrix (about 10% lower than in distilled water). Chlorine dioxide treatment of water to degrade bentazone is efficient and offers a novel approach in the development of new technology for removal of this herbicide from contaminated water.

Efficient degradation of bentazone via peroxymonosulfate activation by 1D/2D γ-MnOOH-rGO under simulated sunlight: Performance and mechanism insight

An innovative 1D/2D γ-MnOOH-rGO catalyst was successfully synthesized by anchoring γ-MnOOH nanowires on rGO nanosheets. Its catalytic activity was comprehensively evaluated by bentazone degradation in PMS/simulated sunlight system. Results showed that the γ-MnOOH-rGO catalyst achieved 96.1% decomposition of bentazone within 90 min in the coupled system, improving by 26.7% compared to that obtained in the γ-MnOOH mediated system. Moreover, the newly-designed γ-MnOOH-rGO exhibited stability, recyclability and practicability for bentazone elimination. Mechanism insight highlighted that more active sites exposed on γ-MnOOH-rGO surface, providing more opportunities for PMS activation and bentazone degradation. Besides, the rGO could transfer photo-induced electrons, accelerating radical-based reactions. More importantly, ∙OH and 1O2 appeared in γ-MnOOH-rGO/PMS/simulated sunlight system, which played an overwhelming role in bentazone removal. In prospect, the γ-MnOOH-rGO showed promising potential for refractory contaminants remediation from aquatic environment in PMS/photocatalytic system.

Importance of Methane Oxidation for Microbial Degradation of the Herbicide Bentazone in Drinking Water Production

Bentazone is a herbicide, which is frequently detected in groundwater due to its mobility and persistence in aquifers. Groundwater is used as a drinking water source all over the world, and sustainable methods to remove pesticides at low concentrations are urgently needed since pesticide contaminations can adversely affect human health. The aim of this study was to investigate whether microbial bentazone degradation was associated with methane oxidation in full-scale drinking water treatment plants. To this end, we investigated bentazone biodegradation in microcosms with water and filter material from rapid sand filters, or biomass from aeration systems, and we investigated the statistical relation between the presence of methane and bentazone in groundwater abstraction wells. An array of evidence supported an association between bentazone degradation and methane oxidation in the biological treatment process. The biodegradation potential of bentazone was associated with the presence of methane in the raw water at 14 different water works. In contrast, no association was observed with any of the other investigated inorganic energy sources, e.g. ammonium. Addition of acetylene inhibited methane oxidation and the bentazone degradation in filter material from two investigated waterworks. Biomass from the aeration tanks degraded bentazone, but only while oxidizing methane. Bentazone removal rates and methane removal rates correlated significantly across all the experiments with biomass or filter material, with an overall transformation yield of 15×10-5 moleBTZ/moleCH4. This demonstrated that the bentazone degradation was conducted by the same type of process in all the investigated communities, governed by methane oxidation. Furthermore, based on more than 10.000 water analyses from waterworks abstraction wells in Denmark, bentazone was detected significantly less frequent in wells with high methane concentrations (> 1 mg/L) than in wells without methane. This suggests that biological treatment of bentazone contamination in drinking water may be achieved using methanotrophs.

Highly efficient and mild electrochemical degradation of bentazon by nano-diamond doped PbO2 anode with reduced Ti nanotube as the interlayer

Anodic oxidation based on PbO2 anode has been demonstrated as the feasible approach for the decontamination of organic pollutants; however, the performance of this process is hindered by its ordinary electrochemical activity and relatively low stability. In this study, we fabricated an efficient Ti/TiO2-RNTs/Sb-SnO2/PbO2-ND electrode with electrochemically reduced TiO2 nanotubes as the interlayer and nano-diamond as the dopant. As compared with other electrodes, the constructed Ti/TiO2-RNTs/Sb-SnO2/PbO2-ND exhibited higher oxygen evolution overpotential, larger active area and less charge transfer resistance. Thus, the average current efficiency of 30% could be attained at 120 min with TiO2-NTs/Sb-SnO2/PbO2, which was 1.5 times higher in comparison with the typical Ti/Sb-SnO2/PbO2 electrode. It was found that the removal efficiency of COD could be increased from 49% to 69% after 120 min treatment in the presence of 10 mM Cl−1 in the electrolyte. After 6 h of electrolysis, 74% of TOC was removed and 31% and 22% of initial N was transformed into NH4+ and NO3− ions, respectively. And oxalic acid, glyoxylic acid, malonic acid and acetic acid were identified quantitatively as the intermediate products. Finally, it was estimated that the accelerated service life of Ti/TiO2-RNTs/Sb-SnO2/PbO2-ND electrode was approximately three times of Ti/Sb-SnO2/PbO2 electrode. Generally, this study is of great interest for the engineering community to design an efficient electrode material for the wastewater treatment.

Preparation and Characterization of ZnO & TiO2 Nanocatalysts For Photo Degradation of Bentazon existing in Polluted water

One of the most important scientific research activities in both of energy and environmental sectors is synthesizing of composites such as nanocatalyst powders of zinc oxide and titanium oxide. The reason why is the best to use this combination of composites, as they are available in the market, with low cost, they have powerful optical,electric properties, high stability, and nontoxicity,these composites are classified as one of the best promising photocatalysts. They show high level of light absorption range and wide range of charge transfer from ZnO to TiO2 their composite has a superior photocatalytic activity. The goal of this investigation is to prove the applicability of ZnO–TiO2 composite as a photocatalyst for degradation of Bentazon in polluted water. Many various parameters will be studied, to see their effects on the process of the degradation of the Bentazon, examples of that are the initial catalyst dosage, pH level, initial Bentazon concentration, purging of oxygen gas, adding of hydrogen peroxide of a multiple concentration and total organic compounds on the removal efficiency of Bentazon.The best guaranteed removal of Bentazon is at neutral pH,and the reason for that could be due to the photo-corrosion of ZnO composite for both acidic and basic conditions. While it is noticeable that degradation of the Bentazon decreased in the presence of organic compounds. Removing the Bentazon by UV/ZnO/TiO2 process shows greater Efficiency than that by UV/TiO2 process, UV/ZnO, and UV alone.

Degradation and leaching of bentazone, terbuthylazine and S-metolachlor and some of their metabolites: A long-term lysimeter experiment

The degradation and leaching of bentazone, terbuthylazine and S-metolachlor and their metabolites N-methyl-bentazone, desethyl-terbuthylazine, 2-hydroxy-terbuthylazine, metolachlor ethane sulfonic acid (ESA) and metolachlor oxanilic acid (OA) were investigated using the plant protection products Artett (bentazone/terbuthylazine), Gardo Gold (S-metolachlor/terbuthylazine) and Dual Gold (S-metolachlor) applied to a weighable, monolithic, high precision lysimeter with a loamy, sandy soil. Artett and Gardo Gold were applied at higher doses than recommended according to good agricultural practice. In leachate, S-metolachlor was detected at concentrations of up to 0.15 µg/L, whereas metolachlor-ESA and metolachlor-OA were present at higher concentrations of up to 37 µg/L and 8.4 µg/L, respectively. In a second terbuthylazine application, concentrations of desethyl-terbuthylazine of up to 0.1 µg/L were detected. In soil, bentazone degraded faster than terbuthylazine and S-metolachlor, whereas the metabolization of terbuthylazine after the second application resulted in an enhanced formation of desethyl-terbuthylazine and a highly increased hydroxylation of terbuthylazine. The importance of analysing both parent compounds and metabolites on a long-term scale was demonstrated to better understand the environmental fate and transport.

Hydrolysis and photolysis of bentazone in aqueous abiotic solutions and identification of its degradation products using quadrupole time-of-flight mass spectrometry.

Hydrolysis and photolysis of bentazone in abiotic aqueous solutions were examined under laboratory conditions. Hydrolysis was studied in different buffer solutions (pH 4.0 ± 0.1, 7.0 ± 0.1, and 9.0 ± 0.1), at different temperatures (15 °C ± 2 °C, 25 °C ± 2 °C, 35 °C ± 2 °C, and 45 °C ± 2 °C), and at different Fe3+ concentrations (1, 5, and 10 mg/L). Photolysis was assessed in different buffer solutions and at different solvent (methanol and ethyl acetate) concentrations (10%, 20%, and 30%) or Fe3+ (1, 5, and 10 mg/L) concentrations and under mercury or xenon light irradiation. Hydrolysis half-lives ranged 46-99 days at three different conditions. Photolysis half-lives ranged 2.3-7.5 h in three different conditions under mercury and xenon irradiation. Hydrolysis and photolysis of bentazone were accelerated by both alkaline conditions and elevated temperatures, and solvents and Fe3+ strongly enhanced bentazone degradation. Photodecomposition was much faster under a mercury lamp than under a xenon lamp. N-methyl bentazone and 6-OH bentazone/8-OH bentazone were identified as degradation products using UPLC-Q-TOF-MS. The data generated from this study could be useful for risk assessment of pesticides in the environment.

Influence of electrolysis conditions on the treatment of herbicide bentazon using artificial UVA radiation and sunlight. Identification of oxidation products

The main objective of this work is to demonstrate the viability of solar photoelectro-Fenton (SPEF) process to degrade pesticides in urban wastewater matrix, selecting the herbicide bentazon as a model molecule. In order to provide a correct assessment of the role of the different oxidants and catalysts involved, bentazon was comparatively treated by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and UVA-assisted EF (i.e., PEF) processes as well, either in sulfate or chloride media. Trials were made in a stirred tank reactor with an air-diffusion cathode and a boron-doped diamond (BDD), RuO2-based or Pt anode. In chlorinated matrices, the herbicide disappeared more rapidly using a RuO2-based anode because of the generated active chlorine. The best mineralization performance was always obtained using BDD due to its higher oxidation power, which allowed the complete destruction of refractory chloroderivatives. A concentration of 0.50 mM Fe2+ was found optimal to catalyze Fenton's reaction, largely enhancing the mineralization process under the action of OH. Among photo-assisted treatments, sunlight was proven superior to a UVA lamp to promote the photolysis of intermediates, owing to its greater UV irradiance and contribution of visible photons, although PEF also allowed achieving a large mineralization. In all cases, bentazon decay obeyed a pseudo-first-order kinetics. SPEF treatment in urban wastewater using BDD at only 16.6 mA cm−2 yielded 63.2% mineralization. A thorough, original reaction pathway for bentazon degradation is proposed, including seven non-chlorinated aromatics, sixteen chloroaromatics and two chloroaliphatics identified by GC-MS, most of them not previously reported in literature. Ion-exclusion HPLC allowed the detection of seven short-chain linear carboxylic acids.

Assessment of the Photocatalytic Efficiency of TiO<sub>2</sub> in the Presence of Sulphate

The use of salts on the degradation of toxic substances may cause the acceleration or delay of radicals production originating from the degradation process. This work had as its objective to investigate the presence and absence of potassium sulphate salt on the photocatalysis of Bentazone using TiO2 as a catalyzer. The effect of the sulphate ion on the photodegradation of the Bentazone herbicide was studied using concentrations of 0,05; 0,10 and 0,20 g L-1 with 0,5 g L-1 of TiO2, in suspension of 180 mL from bentazone solution (3,0x10-5 mol L-1). The samples were analyzed through UV-Vis spectroscopy. The presence of sulphate ions presented a difference of 3,3% on the degradation of bentazone in comparison to TiO2 alone.

Evidence of co-metabolic bentazone transformation by methanotrophic enrichment from a groundwater-fed rapid sand filter

The herbicide bentazone is recalcitrant in aquifers and is therefore frequently detected in wells used for drinking water production. However, bentazone degradation has been observed in filter sand from a rapid sand filter at a waterworks with methane-rich groundwater. Here, the association between methane oxidation and removal of bentazone was investigated with a methanotrophic enrichment culture derived from methane-fed column reactors inoculated with that filter sand. Several independent lines of evidence obtained from microcosm experiments with the methanotrophic enrichment culture, tap water and bentazone at concentrations below 2 mg/L showed methanotrophic co-metabolic bentazone transformation: The culture removed 53% of the bentazone in 21 days in presence of 5 mg/L of methane, while only 31% was removed in absence of methane. Addition of acetylene inhibited methane oxidation and stopped bentazone removal. The presence of bentazone partly inhibited methane oxidation since the methane consumption rate was significantly lower at high (1 mg/L) than at low (1 μg/L) bentazone concentrations. The transformation yield of methane relative to bentazone normalized by their concentration ratio ranged from 58 to 158, well within the range for methanotrophic co-metabolic degradation of trace contaminants calculated from the literature, with normalized substrate preferences varying from 3 to 400. High-resolution mass spectrometry revealed formation of the transformation products (TPs) 6-OH, 8-OH, isopropyl-OH and di-OH-bentazone, with higher abundances of all TPs in the presence of methane. Overall, we found a suite of evidence all showing that bentazone was co-metabolically transformed to hydroxy-bentazone by a methanotrophic culture enriched from a rapid sand filter at a waterworks.

Preparation of photo-catalytic copolymer grafted asymmetric membranes (N-TiO2-PMAA-g-PVDF/PAN) and their application on the degradation of bentazon in water

Nitrogen-doped titanium dioxide (N–TiO2) was prepared and supported on a novel copolymer grafted membrane matrix to avoid the problems associated with the removal of spent photocatalyst from treated water. Membranes of poly (methacrylic acid) grafted onto poly (vinylidene difluoride) and blended with poly (acrylonitrile) (PMAA-g-PVDF/PAN) were prepared through a dry–wet phase inversion technique. Methacrylic acid side chains were grafted onto an activated PVDF backbone by the method of reversible addition fragmentation chain transfer polymerization and then the novel photocatalytic asymmetric membranes of N–TiO2–PMAA-g-PVDF/PAN were prepared. The casting solutions were blended with 1–5 % N–TiO2 before immersion into the coagulation bath. PVDF and PAN offer several advantages which include: mechanical strength and toughness, chemical resistance, unaffected by long-term exposure to UV radiation, low weight, and thermal stability. N–TiO2 was prepared through sol-gel synthesis. The photocatalytic membranes were evaluated by degradation process of herbicide bentazon in water. Photodegradation studies revealed that the optimum photocatalyst loading was 3 % N–TiO2 and the optimum pH was 7 for the degradation of bentazon in water. UV–Vis, TOC and LC–MS analyses confirmed the successful photodegradation of bentazon. A bentazon removal efficiency of 90.1 % was achieved at pH 7. N–TiO2–PMAA-g-PVDF/PAN membranes were successfully prepared and characterized. These photocatalytic membranes showed great potential as a technology for the effective removal of pesticides from water. According to literature, N–TiO2–PMAA-g-PVDF/PAN asymmetric photocatalytic membranes have not been prepared before for the purpose of treating agricultural wastewater.

Zero-valent iron (ZVI) activation of persulfate (PS) for oxidation of bentazon in water

Bentazon (BTZ) in water, a broadly used herbicide in agriculture, is toxic to human beings and has a negative impact on ecosystem. In this study, zero-valent iron (ZVI) activation of persulfate (PS) for the oxidation of BTZ was investigated. More active sulfate radicals produced from the system were principally responsible for the BTZ degradation. The BTZ removal well followed a pseudo-first-order (PFO) kinetics pattern. Key factors affecting the treatment were tested, including ZVI concentration, PS dose, initial BTZ concentration, initial solution pH, temperature and common coexisting ions in water. Under the optimal ZVI (4.477mM) and PS (0.262mM) concentrations, 0.021mM BTZ was totally removed at an initial pH⩽7.Generally, lower BTZ concentration, lower pH and higher temperature favored the treatment. Different coexisting ions exhibited different effects. Al3+, Cl− and NO3− improved the treatment; NH4+, Ca2+, and Mg2+ did not significantly influence the BTZ removal; and, Mn2+, Cu2+, CO32−, HCO3−, PO43−, HPO42− and H2PO4− inhibited the BTZ degradation. Most of BTZ were not mineralized, and instead degraded into three major degradation products including 2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide (P1, C7H6N2O3S), 2-aminobenzoic acid (anthranilic acid) (P3, C7H7NO2), and 2-amino-2-sulfobenzoic acid (P5, C7H7NO5S). This study demonstrates that ZVI/PS is a viable alternative for controlling BTZ-induced water pollution.

Synthesis, characterization, and application of ZnO/TiO2 nanocomposite for photocatalysis of a herbicide (Bentazon)

The purpose of this investigation was to study the applicability of ZnO–TiO2 composite as a photocatalyst for degradation of Bentazon. Effects of various parameters such as catalyst dosage, pH, initial Bentazon concentration, oxygen purging gas, hydrogen peroxide concentration and type of organic compounds on the removal efficiency of Bentazon were studied. The results of SEM and FT-IR analysis demonstrated favorable immobilization of zinc oxide nanoparticles onto TiO2. The greatest removal of Bentazon was observed at neutral pH due to photo-corrosion of ZnO on composite in acidic and basic conditions. The pseudo-first-order rate constant (kobs) and electrical energy per order (EEo) were greatly dependent on the Bentazon concentration. Removal efficiency of Bentazon was increased with O2 purging and addition of H2O2, while it was decreased in the presence of organic compounds. Removal efficiency of Bentazon by UV/ZnO/TiO2 process was greater than that by UV/TiO2 process, UV/ZnO, and UV alone. Photocatalytic activity was maintained even after five successive cycles.

Stimulation of aerobic degradation of bentazone, mecoprop and dichlorprop by oxygen addition to aquifer sediment

In order to investigate aerobic degradation potential for the herbicides bentazone, mecoprop and dichlorprop, anaerobic groundwater samples from two monitoring and three drinking water wells near a drinking water abstraction field in Nybølle, Denmark, were screened for their degradation potential for the herbicides. In the presence of oxygen 14C-labelled bentazone and mecoprop were removed significantly from the two monitoring wells' groundwater samples. Oxygen was added to microcosms in order to investigate whether different oxygen concentrations stimulate the biodegradation of the three herbicides in microcosms using groundwater and sandy aquifer materials. To maintain a certain oxygen concentration this level was measured from the outside of the bottles with a fibre oxygen meter using oxygen-sensitive luminescent sensor foil mounted inside the microcosm, to which supplementary oxygen was added. The highest oxygen concentrations (corresponding to 4–11mgL−1) stimulated degradation (a 14–27% increase for mecoprop, 3–9% for dichlorprop and 15–20% for bentazone) over an experimental period of 200days. Oxygen was required to biodegrade the herbicides, since no degradation was observed under anaerobic conditions. This is the first time bentazone degradation has been observed in aquifer material at low oxygen concentrations (2mgL−1). The sediment had substantial oxygen consumption (0.92–1.45O2g-1dw over 200days) and oxygen was depleted rapidly in most incubations soon after its addition, which might be due to the oxidation of organic matter and other reduced species such as Fe2+, S2− and Mn in sediment before the biodegradation of herbicides takes place. This study suggests that oxygen enhancement around a drinking water abstraction field could stimulate the bioremediation of diffuse source contamination.

Photocatalytic degradation of herbicide Bentazone in aqueous suspension of TiO2: mineralization, identification of intermediates and reaction pathways

Semiconductor-mediated hydrogen peroxide-assisted photocatalytic degradation of a selected herbicide, Bentazone (1) has been investigated in aqueous suspensions of TiO2 under a variety of conditions. The degradation was studied by monitoring the depletion in total organic carbon content as a function of irradiation time. The degradation kinetics was investigated under different conditions such as type of TiO2 (Anatase/Anatase-Rutile mixture), reaction pH, catalyst dosage and hydrogen peroxide (H2O2) concentration. The degradation rates were found to be strongly influenced by all the above parameters. Titanium dioxide Degussa P25 was found to be more efficient as compared with other two commercially available TiO2 powders like Hombikat UV100 and PC500 from Millennium Inorganic Chemicals. Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the irradiated mixture of Bentazone (1) indicates the formation of several intermediate products which have been characterized on the basis of molecular ion/mass fragmentation pattern and also on comparison with the National Institute of Standards and Technology (NIST) library. Plausible mechanism for the formation of different products during photocatalytic treatment of Bentazone in the presence of TiO2 has been proposed. The use of H2O2 substantially increased the efficiency of TiO2 photocatalytic degradation.