Atrazine Degradation Efficiency Research Articles

Constructing a CeFeO3/LaFeO3/ZnIn2S4 double Z-scheme heterojunction for photocatalytic atrazine degradation under visible light irradiation

The limited light absorption range and rapid recombination of interfacial charges were deemed to be the main restriction of the photocatalysts for atrazine (ATZ) degradation, and the construction of Z-scheme heterojunction was an effective strategy. Herein, a CeFeO3/LaFeO3/ZnIn2S4 (CFO/LFO/ZIS) double Z-scheme ternary heterojunction photocatalyst was fabricated by the in-situ precipitation and hydrothermal method. The photocatalytic ATZ degradation efficiency of optimized heterojunction reached 52% within 175 min under visible light irradiation, which was 3.1, 3.7 and 1.7 times higher than that of CFO, LFO and ZIS, respectively. The enhanced photocatalytic activity was due to the excellent light capture capacity and improved photogenerated charge separation in CFO/LFO/ZIS double Z-scheme heterojunction photocatalyst. Meanwhile, some environmental factors on the influence of photocatalytic ATZ degradation performance were systematically investigated. Quenching experiments confirmed that ·OH, h+ and 1O2 were the main active species during the photocatalytic ATZ degradation process. The possible photogenerated charge separation route was proposed via the analysis of the IEF effects between CFO, LFO and ZIS. Finaly, the possible ATZ degradation pathway was deduced by LC-MS measurement and toxicity assessment of the intermediates were also evaluated by the Toxicity Estimation Software Tool (TEST). This work not only provided a potential magnetic recyclable ferrate based double Z-scheme heterojunction photocatalyst for enhancing photogenerated charge separation and light absorption, but also evaluated the intermediate toxicity and related environmental factors on the activity of photocatalyst, which was facilitating the practical application for the degradation of ATZ.

Design of a multi-electrode dielectric barrier discharge reactor and experimental study on the degradation of atrazine in water.

Atrazine (ATZ) is widely used in agriculture as a triazine herbicide, and its long-term use can cause serious environmental pollution. This paper independently designed a multi-electrode reactor, explored the output power and energy utilization efficiency of the dielectric barrier discharge reactor, and used the dielectric barrier discharge reactor to treat ATZ solution. The results showed that the degradation efficiency of ATZ was 96.39% at 30 min at an initial ATZ concentration of 14 mg/L, an input voltage of 34 kV, an input current of 1.38 mA, an aeration rate of 100 L/h, and a treatment water volume of 150 mL. The degradation of ATZ was significantly increased by the addition of persulfate (PS), Fe2+, and H2O2. After adding radical quenchers (EtOH, p-BQ, and FFA), the degradation efficiency of ATZ decreased, indicating that free radicals (•OH, •O2-, and 1O2) played a key role in the degradation process of ATZ.

Prediction of atrazine degradation in soil based on XGBoost model.

We established the optimal model by using the automatic machine learning method to predict the degradation efficiency of herbicide atrazine in soil, which could be used to assess the residual risk of atrazine in soil. We collected 494 pairs of data from 49 published articles, and selected seven factors as input features, including soil pH, organic matter content, saturated hydraulic conductivity, soil moisture, initial concentration of atrazine, incubation time, and inoculation dose. Using the first-order reaction rate constant of atrazine in soil as the output feature, we established six models to predict the degradation efficiency of atrazine in soil, and conducted comprehensive analysis of model performance through linear regression and related evaluation indicators. The results showed that the XGBoost model had the best performance in predicting the first-order reaction rate constant (k). Based on the prediction model, the feature importance ranking of each factor was in an order of soil moisture > incubation time > pH > organic matter > initial concentration of atrazine > saturated hydraulic conductivity > inoculation dose. We used SHAP to explain the potential relationship between each feature and the degradation ability of atrazine in soil, as well as the relative contribution of each feature. Results of SHAP showed that time had a negative contribution and saturated hydraulic conductivity had a positive contribution. High values of soil moisture, initial concentration of atrazine, pH, inoculation dose and organic matter content were generally distributed on both sides of SHAP=0, indicating their complex contributions to the degradation of atrazine in soil. The XGBoost model method combined with the SHAP method had high accuracy in predicting the performance and interpretability of the k model. By using machine learning method to fully explore the value of historical experimental data and predict the degradation efficiency of atrazine using environmental parameters, it is of great significance to set the threshold for atrazine application, reduce the residual and diffusion risks of atrazine in soil, and ensure the safety of soil environment.

Understanding atrazine elimination via treatment of the enzyme-based Fenton reaction: Kinetics, mechanism, reaction pathway, and metabolites toxicity

The degradation kinetics and mechanism of atrazine (ATZ) via an enzyme-based Fenton reaction were investigated at various substrate concentrations and pH values. Toxicological assessment was conducted on ATZ and its degradation products, and the associated reaction pathway was examined. The in situ production of hydrogen peroxide (H2O2) was monitored within the range of 3–15 mM, depending on the increase in glucose concentration, while decreasing the pH to 3.2–5.1 (initial pH of 5.8) or 6.5–7.4 (initial pH of 7.7). The degradation efficiency of ATZ was approximately 2–3 times higher at an initial pH of 5.8 with lower glucose concentrations than at an initial pH of 7.7 with higher substrate concentrations during the enzyme-based Fenton reaction. The apparent pseudo-first-order rate constant for H2O2 decomposition under various conditions in the presence of ferric citrate was 1.9–6.3 × 10−5 s−1. The •OH concentration ([•OH]ss) during the enzyme-based Fenton reaction was 0.5–4.1 × 10−14 M, and the second-order rate constant for ATZ degradation was 1.5–3.3 × 109 M−1 s−1. ATZ intrinsically hinders the growth and development of Arabidopsis thaliana, and its inhibitory effect is marginal, depending on the reaction time of the enzyme-based Fenton process. The ATZ transformation during this process occurs through dealkylation, hydroxylation, and dechlorination via •OH-mediated reactions. The degradation kinetics, mechanism, and toxicological assessment in the present study could contribute to the development and application of enzyme-based Fenton reactions for in situ pollutant abatement. Moreover, the enzyme-based Fenton reaction could be an environmentally benign and applicable approach for eliminating persistent organic matter, such as herbicides, using diverse H2O2-producing microbes and ubiquitous ferric iron with organic complexes.

Valorization of soybean plant wastes in preparation of N-doped biochar for catalytic ozonation of organic contaminants: Atrazine degradation performance and mechanistic considerations

Selecting the biomass source is critical because different plants or tissues may exhibit varying textures and chemical properties. However, few researchers have compared the catalytic activity of different tissues from the same plant after carbonization. Soybean is widely cultivated worldwide and always suffers from pests and diseases. The inappropriate storage of harvested soybeans leads to mildew and its wastage. Herein, soybean biochar (SB), soybean shell biochar (SBS), and soy straw biochar (SS) catalysts were prepared using waste soybean plant tissues as precursors, which drastically improved the degradation efficiency of atrazine in catalytic ozonation. The specific reaction rate constant normalized by the surface area (kobs/SBET) of SB during catalytic ozonation indicated the catalytic performance of biochar was not affected just by SBET. The characterization results showed that the delocalized π-electrons, nitrogen-, and oxygen-containing functional groups played key roles in catalytic ozonation, and contributions of these active sites to the generation of both radical and nonradical reactive oxygen species (ROS) including hydroxyl radicals (•OH), superoxide radicals (O2•−), and singlet oxygen (1O2) contributed to atrazine degradation. Compared with SBS and SS, SB contained the highest pyridine N content, the highest carbonyl group (–C = O) content, the strongest delocalized electron density, and electron donor ability, which was responsible for its superior catalytic performance. Such active sites on biochar enhanced the ozone adsorption and decomposition, accelerated the electron transfer process to produce more ROS, and achieved efficient pollutant elimination. Overall, guided by the “waste treating waste” concept, this study provided a valuable alternative in the recycling and reuse of agricultural waste soybean plants, proving that the derived biochar could be potentially used as a catalyst for advanced oxidation processes-based applications.

Experimental degradation of atrazine in soil by dielectric barrier discharge and optimization

In this study, a self-made rotating double-media barrier reactor was used for remediation of atrazine contaminated soil, aiming to provide a reference for industrial application of low-temperature plasma treatment of organic contaminated soil. The effects of applied voltage and reactor state on the reactor discharge performance were investigated. When the applied voltage was increased, the energy efficiency of low-temperature plasma increased; the effect of reactor state was not significant. The effects of input voltage, reactor rotational speed and soil water content on the degradation efficiency of atrazine were investigated, and the results showed that the degradation rate of atrazine increased when the input voltage was 35 kV and the treatment time was 25 min, and the degradation rate of atrazine was 71.12%; when the reactor rotational speed and soil water content were 18.7 r/min and 0.8%, the degradation rates were 73.25% and 65.41%. The response surface method was applied to optimize the selection. The results showed that the significance degree of each factor was input voltage > soil water content > rotating motor speed, and the optimal conditions were 0.6% soil water content, 37 kV input voltage, 18 r/min reactor speed, and 51.93% atrazine degradation rate.

Promotion Mechanism of Atrazine Removal from Soil Microbial Fuel Cells by Semiconductor Minerals

In recent years, soil microbial fuel cells (Soil-MFCs) have attracted attention due to their simultaneous electricity production and contaminant removal functions, but soil electron transfer resistance limits their contaminant removal effectiveness. To overcome the above-mentioned drawbacks, in this study, a dual-chamber Soil-MFC was constructed using atrazine (ATR) as the target contaminant, and the electrochemical performance of Soil-MFC and ATR removal were enhanced by semiconductor mineral addition. Analysis of atrazine was performed in soil using HPLC and GC-MS, and analysis of metallic minerals using XPS. Anodic microorganisms were determined using high-throughput sequencing technology. The results showed that the addition of Fe3O4 increased the maximum output voltage of the device by 2.56 times, and the degradation efficiency of atrazine in the soil to 63.35%, while the addition of MnO2 increased the internal resistance of the device and affected the current output, and these changes were closely related to the ion dissolution rate of the semiconductor minerals. In addition, the addition of both minerals significantly increased the relative abundance of both Proteobacteria and Bacteroidota, and Fe3O4 simultaneously promoted the significant enrichment of Firmicutes, indicating that the semiconductor minerals significantly enhanced the enrichment of electroactive microorganisms near the anode. The structural equation modeling indicated that the semiconductor minerals achieved efficient degradation of ATR in the soil through a synergistic mechanism of metal ion leaching and microbial community structure changes. The detection of ATR and its degradation products in soil revealed that the degradation of ATR mainly included: (1) hydrolysis of atrazine by microorganisms to generate dehydroxylated atrazine (HYA); (2) reduced to diethyl atrazine (DEA) and diisopropyl atrazine (DIA) by extracellular electron reduction and re-dechlorination and hydrolysis to HYA. Semiconductor minerals make an important contribution to promoting microbial activity and extracellular electron reduction processes. The results of this study strengthen the power production and ATR removal efficiency of the Soil-MFC system and provide important theoretical support for the on-site removal of organic pollutants and the sustainable application of converting biomass energy into electricity.

A novel solar-activated chlorine dioxide process for atrazine degradation in drinking water

New technologies using advanced oxidation processes (AOPs) with low energy-input to address the presence of micro-contaminants and the formation of disinfection byproducts (DBPs) are required for drinking water safety. In this work, the activation of chlorine dioxide with solar (solar/ClO2 process), a type of renewable and inexhaustible energy, was developed to degrade atrazine (ATZ) and control the formation of DBPs. Results revealed that solar/ClO2 process was effective in degrading ATZ. Hydroxyl radicals (•OH) and chlorine radicals (Cl•) produced in solar/ClO2 process were found to be the predominant agents for ATZ degradation with contribution rates of 55.9% and 44.1%, respectively, based on radical quenching tests and competition kinetics. Reaction pH did not affect the total amount of Cl• and •OH (i.e., [•OH]exp) and [Cl•]exp), while the conversion of Cl• to •OH was responsible for the depressed ATZ degradation efficiency with the increasing pH in solar/ClO2 process. The presence of bicarbonate (HCO3−), chloride (Cl−) and humic acid (HA) retarded the ATZ degradation mainly due to they decreased [•OH]exp) and [Cl•]exp. Using the UPLC-MS/MS analysis, six degradation intermediates of ATZ were tentatively identified, and the three-stage degradation pathway as well as the stepwise detoxification of ATZ were confirmed by the condensed Fukui function (CFF) calculation and ECOSAR prediction. Applying solar/ClO2 as a pretreatment of HA-containing water, the formation of DBPs during post-chlorination was significantly reduced. However, the presence of ATZ during solar/ClO2 pretreatment of HA significantly lowered the control efficiency of DBPs. The major degradation intermediate, i.e., deethyldeisopropylhydroxyatrazine (DEIHA), of ATZ could incorporate into HA and therefore providing more precursors for DBPs. The acute toxicity recorded by the behavior of zebrafish larvae revealed that using chloramine instead of chlorine downstream the solar/ClO2 pretreatment of ATZ and HA could significantly reduce the acute toxicity by decreasing the formation of total DBPs. This study demonstrated the great potential of applying solar/ClO2 process followed by chloramination to simultaneously degrade micro-contaminants and reduce DBPs formation as well as toxic risk in practical applications.

Degradation of atrazine in river sediment by dielectric barrier discharge plasma (DBDP) combined with a persulfate (PS) oxidation system: response surface methodology, degradation mechanisms, and pathways.

Single degradation systems based on dielectric barrier discharge plasma (DBDP) or persulfate (PS) oxidation cannot achieve the desired goals (high degradation efficiency, high mineralization rate, and low product toxicity) of degrading atrazine (ATZ) in river sediment. In this study, DBDP was combined with a PS oxidation system (DBDP/PS synergistic system) to degrade ATZ in river sediment. A Box-Behnken design (BBD) including five factors (discharge voltage, air flow, initial concentration, oxidizer dose, and activator dose) and three levels (- 1, 0, and 1) was established to test a mathematical model by response surface methodology (RSM). The results confirmed that the degradation efficiency of ATZ in river sediment was 96.5% in the DBDP/PS synergistic system after 10min of degradation. The experimental total organic carbon (TOC) removal efficiency results indicated that 85.3% of ATZ is mineralized into CO2, H2O, and NH4+, which effectively reduces the possible biological toxicity of the intermediate products. Active species (sulfate (SO4•-), hydroxy (•OH), and superoxide (•O2-) radicals) were found to exert positive effects in the DBDP/PS synergistic system and illustrated the degradation mechanism of ATZ. The ATZ degradation pathway, composed of 7 main intermediates, was clarified by Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS). This study indicates that the DBDP/PS synergistic system is a highly efficient, environmentally friendly, novel method for the remediation of river sediment containing ATZ pollution.

Immobilization of bacterial mixture of Klebsiella variicola FH-1 and Arthrobacter sp. NJ-1 enhances the bioremediation of atrazine-polluted soil environments.

In this study, the effects of the immobilized bacterial mixture (IM-FN) of Arthrobacter sp. NJ-1 and Klebsiella variicola strain FH-1 using sodium alginate-CaCl2 on the degradation of atrazine were investigated. The results showed that the optimal ratio of three types of carrier materials (i.e., rice straw powder, rice husk, and wheat bran) was 1:1:1 with the highest adsorption capacity for atrazine (i.e., 3774.47 mg/kg) obtained at 30°C. On day 9, the degradation efficiency of atrazine (50 mg/L) reached 98.23% with cell concentration of 1.6 × 108 cfu/ml at pH 9 and 30°C. The Box-Behnken method was used to further optimize the culture conditions for the degradation of atrazine by the immobilized bacterial mixture. The IM-FN could be reused for 2-3 times with the degradation efficiency of atrazine maintained at 73.0% after being stored for 80 days at 25°C. The population dynamics of IM-FN was explored with the total soil DNA samples specifically analyzed by real-time PCR. In 7 days, the copy numbers of both PydC and estD genes in the IM-FN were significantly higher than those of bacterial suspensions in the soil. Compared with bacterial suspensions, the IM-FN significantly accelerated the degradation of atrazine (20 mg/kg) in soil with the half-life shortened from 19.80 to 7.96 days. The plant heights of two atrazine-sensitive crops (wheat and soybean) were increased by 14.99 and 64.74%, respectively, in the soil restored by immobilized bacterial mixture, indicating that the IM-FN significantly reduced the phytotoxicity of atrazine on the plants. Our study evidently demonstrated that the IM-FN could significantly increase the degradation of atrazine, providing a potentially effective bioremediation technique for the treatment of atrazine-polluted soil environment and providing experimental support for the wide application of immobilized microorganism technology in agriculture.

Efficient atrazine degradation via photoactivated SR-AOP over S-BUC-21(Fe): The formation and contribution of different reactive oxygen species

Fe-based metal organic frameworks (MOFs) as catalysts exhibited great potential in peroxymonosulfate (PMS) activation for organic pollutant decontamination. In this work, a Fe-based MOF S-BUC-21(Fe) with superior catalytic activity in PMS activation to remove atrazine (ATZ) is reported, in which ATZ was completely degraded within 20.0 min in the presence of 0.1 g/L S-BUC-21(Fe), 0.4 mM PMS and LED UV light irradiation. Both the active species capturing experiments and electron spin resonance (ESR) revealed that reactive species like SO4•-, •OH, •O2–, and 1O2 could be generated continuously via ≡Fe2+/≡Fe3+ cycle along with direct or indirect photo-induced electron transfer. According to the reactive oxygen species (ROSs) contribution calculation, SO4•- and 1O2 were found to play major roles in the ATZ degradation process. Furthermore, quantification and the generation pathways of 1O2 were revealed. After 5-runs experiments, S-BUC-21(Fe) exhibited outstanding stability and reusability, maintaining the morphology and structure of used S-BUC-21(Fe) along with 100.0 % ATZ degradation efficiency.

Heterogeneous catalytic ozonation by amorphous boron for degradation of atrazine in water

As one of the most promising and practical advanced oxidation processes (AOPs), the catalytic ozonation is triggered by the active components of catalyst, which are usually derived from metals or metal oxides. To avoid the metal pollution from catalyst, here the amorphous boron (A-boron) is used as a metal-free catalyst for catalytic ozonation to produce free radicals for effective degradation of atrazine (ATZ), the world-widely used herbicide and also a widespread pollutant in environment. A-boron exhibits an outstanding performance for catalytic ozonation to remove ATZ from water. As A-boron is introduced into ozonation, the degradation efficiency in 10 min is promoted to 97.1%, much higher than that of 15.1% under ozonation. The mechanism is that the B–B bonds and internal suboxide B in A-boron serve as the main active sites to donate electrons to accelerate ozone decomposition to produce reactive oxygen species (ROS), including •O2− and 1O2, and further enhance ATZ degradation via ROS reactions. Moreover, the A-boron is still highly active with a degradation efficiency of ATZ over 95% in 10 min even after four successive cycles. This work shows A-boron could be an alternative for the active components of metal or metal oxide in catalytic ozonation.

UV activated sodium percarbonate to accelerate degradation of atrazine: Mechanism, intermediates, and evaluation on residual toxicity by metabolomics.

Efficient and safe removal of widely used herbicides such as atrazine has become a recent hotspot. Herein, UV driven sodium percarbonate system (UV/SPC) was established to have many advantages in remediation of atrazine contamination. The mechanism and environmental risk of intermediates were explored, which provided information for the feasibility of UV/SPC. The degradation efficiency of atrazine was significantly enhanced as the increasing dosage of SPC. Quenching assay identified that •OH and CO3•- were committed to degrading atrazine. Humic acid and HPO42- remarkably inhibited atrazine degradation. Several intermediates were generated through the dealkylation, dechlorination-hydroxylation, alkylic-hydroxylation, alkyl oxidation and olefination reactions. Toxicity prediction proved that acute toxicity and bioaccumulation of intermediates were mitigated comparing with atrazine. Based on metabolomics results, the alteration of key metabolites such as citrate, L-kynurenine, malic acid, putrescine, glutamine, spermine, ethanolamine and phytosphingosine in various metabolic pathways of E.coli verified that the toxicity of atrazine was weakened after UV/SPC treatment. The application of UV/SPC on atrazine removal in real waters was influenced by environmental factors, and might be improved through coupling with other treatment technologies.

Triboelectric nanogenerator enhanced radical generation in a photoelectric catalysis system via pulsed direct-current

Traditional photoelectric catalysis technologies are limited by the needs for large external energy input. In this study, the self-powered photoelectric catalysis was established by a spherical triboelectric nanogenerator (S-TENG) under a pulsed direct-current electric field to improve the removal rate of Atrazine (ATZ). Also, the electrical output performance of S-TENG was tested. To further improve the utilization of light and degradation efficiency of ATZ, the photoelectrode (TiO2 nanotube) and photocatalyst (6HF-TiO2 nanosheets) were both used to degrade ATZ. The removal rate of ATZ was enhanced by 8.53%, and the mineralization was increased by 27.2% within 30 min in the photoelectric catalysis system with pulse direct-current electric field by S-TENG. The degradation mechanism of ATZ was also demonstrated by the EPR tests and free radicals quenching experiments. The result showed that the photogenerated free radicals were increased by triboelectric pulsed direct-current during the photoelectric catalysis degradation. The hydroxyl radical (•OH) played an essential role in the degradation of ATZ in the self-powered photoelectric catalysis system. In addition, the degradation pathway of ATZ was proposed in detail based on LC-MS/MS test and density functional theory (DFT) calculation. Furthermore, the toxicity of ATZ and its degradation intermediates were evaluated by the ECOSAR program. Overall, this research provides a novel strategy for enhancing the performance of self-powered photoelectric catalysis processes for wastewater treatment.

Rapid degradation of atrazine by a novel advanced oxidation process of bisulfite/chlorine dioxide: Efficiency, mechanism, pathway

Recently, (bi)sulfite as the precursor of SOx− generation has drawn significant attention in advance oxidation process based on SO4− (SR-AOP) due to its low cost and conforming to waste utilization. The current activation on (bi)sulfite mainly employs the transition metals and their composite materials, which limited its application. In this study, chlorine dioxide (ClO2) was employed to activate bisulfite (BS). It was found that the dominant radicals in BS/ClO2 process were ClO and SO4− according to scavenger experiments and ESR detection. To investigate the performance of the established BS/ClO2 system, atrazine (ATZ) was used as target pollutant. The degradation efficiency of ATZ reached 86.8% within 3 min and nearly half of the degradation occurred at the first 10 s. The optimum ClO2 dosage for the ATZ degradation was 100 μM when the BS dosage was 200 μM. The effects of pH, temperature and coexisting substances including halide ions, bicarbonate ion and humic acid on ATZ degradation by BS/ClO2 were investigated. It is predicted that the degradation pathway of ATZ in this study involved olefination, dealkylation and the combination of dichlorination with hydroxylation according to the final products identified after degradation. The system has also shown the ability on degradation of four pharmaceuticals and personal care products (PPCPs) including ibuprofen, bisphenol A, sulfamethoxazole and carbamazepine. This study reveals that ClO2 is capable of activating BS and provides a method for effectively degrading refractory organic contaminants.

Effective peroxymonosulfate activation by natural molybdenite for enhanced atrazine degradation: Role of sulfur vacancy, degradation pathways and mechanism

In this study, natural molybdenite (MoS2) was applied to activate peroxymonosulfate (PMS) for the removal of atrazine (ATZ) and its degradation mechanism was investigated. Molybdenite exhibits superior catalytic performance. The best condition for atrazine degradation efficiency (>99%) was obtained with molybdenite concentration of 0.4 g/L, PMS concentration of 0.1 mM, and ATZ concentration of 12 μM within 10 min under experimental conditions. Electron paramagnetic resonance (EPR) test and chemical probe test further proved that HO• and SO4•− played important roles in the molybdenite/PMS system, and SO4•− was dominant. Meanwhile, Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) tests showed that sulfur vacancies and edge sulfur played important roles in the system. Edge sulfur was conducive to Mo4+ exposure, while sulfur vacancy facilitated electron transfer and reduced Mo6+ back to Mo4+. Combined with DFT calculation, the role of sulfur in the degradation process was verified. Besides, five ATZ degradation pathways were proposed. Finally, the degradation ability of the molybdenite/PMS system for different pollutants and in actual water bodies was also explored. This work provided ideas for exploring the degradation of organic contaminants by natural minerals.

Growth and degradation characteristics of an efficient and broad-spectrum atrazine-degrading strain SB5

In this study, triazine-degrading strain SB5 was isolated and screened from the activated sludge contaminated with atrazine by enrichment culture technology. Based on its morphology and 16S rRNA gene analysis, strain SB5 was initially identified as Paenarthrobacter sp. It contained the atrazine-degrading genes trzN, atzB, and atzC. The addition of glucose, sucrose, sodium citrate, yeast extract and peptone to the culture medium significantly increased the biomass and atrazine degradation efficiency of strain SB5. The addition of (NH4)2SO4 and NH4Cl inhibited the biomass of strain SB5, but did not affect its degradation efficiency for atrazine. The addition of starch did not affect the biomass of strain SB5, but significantly inhibited its degradation for atrazine. Strain SB5 showed good atrazine tolerance and atrazine degradation ability in the temperature range of 4-42 ℃, initial pH of 4-10 and initial concentration of 50-1000 mg·L-1. Using 100 mg·L-1 atrazine as the sole carbon source, the strain SB5 degraded 100% of atrazine within 36 h under the optimal conditions of 37 ℃ and initial pH 8.0. The results of degradation spectrum analysis showed that strain SB5 had a good degradation effect on the six triazine herbicides (simazine, terbuthylazine, propazine, cyanazine, ametryn and prometryn) at an initial concentration of 100 mg·L-1, and the degradation rates were 86.4%, 92%, 98.6%, 95.6%, 100% and 99.2% after 48 h of incubation, respectively. The results demonstrated that SB5 was an efficient and broad-spectrum degradation strain. The strain SB5 further enriched the strain resources for atrazine biodegradation, and its high-efficient and broad-spectrum degradation characteristics for triazine herbicides showed a potential application value in the development of bioremediation technology for the pollution of triazine herbicides.

Facilitated catalytic ozonation of atrazine over highly stabilized Zn-Al layered double oxides composites: efficacy and mechanism

ABSTRACT A series of Zn-Al Layered Double Oxides (ZnAl-LDO) composites were prepared by the hydrothermal and calcination method via employing the Zn-Al Layered Double Hydroxide (ZnAl-LDH) as the precursors in the present study. The structural properties and the catalytic ozonation activity of ZnrAl-T composites synthesized with different Zn/Al molar ratios and calcination temperatures were systematically investigated. Diversified characterizations were applied to analyze the phase structure and chemical composition of ZnrAl-T composites. As the calcination temperature increased, the layered ZnAl-LDH structure could be entirely destroyed and the crystallinity gradually improved. With the Zn/Al mole ratio of 4.0 and calcination temperature of 500°C, the Zn4Al-500 composite obtained the outstanding catalytic ozonation performance for atrazine (ATZ) degradation with the pseudo-first-order constant of 0.5080 min−1, which was 5 times more than that in O3 alone. Meanwhile, the ATZ degradation efficiency was gradually enhanced from 44.1% to 99.9% within 3.0 min when the solution pH ranged from 3.0 to 10.0. Besides, the Zn4Al-500 composite exhibited splendid stability over multiple reaction cycles. In addition, the radical scavenging test and electron spin resonance measurement demonstrated that superoxide radical and hydroxyl radical are the dominant reactive species in O3/Zn4Al-500 process. Moreover, nineteen and ten transformation products were detected in O3 alone and O3/Zn4Al-500 process, and possible degradation pathways of ATZ were further elucidated. Overall, the Zn4Al-500 composite would provide a potential alternative for pollutants removal due to its high catalytic ozonation efficiency, stability, and reusability.

Core-shell P-laden biochar/ZnO/g-C3N4 composite for enhanced photocatalytic degradation of atrazine and improved P slow-release performance

Technologies that can effectively address the environmental issues arisen from the use of agrochemicals and P fertilizers are needed for the development of green agriculture. Here, we reporta new core–shell P-laden biochar/ZnO/g-C3N4 composite (Pbi-ZnO-g-C3N4) used both as an efficient photocatalyst for degrading atrazine and a promising slow-release fertilizer for improving the P utilization efficiency. In comparison with P-laden biochar/ZnO (Pbi-ZnO), Pbi-ZnO-g-C3N4 exhibits enhanced photocatalytic activity with the maximum atrazine degradation efficiency of 85.3% after 260 min. Pbi-ZnO-g-C3N4 also shows superior P slow-release performance with the cumulative P release concentration of 216.40 g/L in 260 min. Besides, it is found that the coating of g-C3N4 on the surface of Pbi-ZnO improves the utilization of visible light and separation of photoinduced electron-hole pairs, producing more radicals (•OH and •O2–) under visible light irradiation. The mechanistic study reveals that Z-shaped heterojunction is formed between ZnO and g-C3N4 in Pbi-ZnO-g-C3N4, and biochar serves as an electron-transfer bridge that promotes the separation of electron-hole pairs. Finally, pot experiments reveal that the P utilization efficiency for pepper seedlings fertilized by Pbi-ZnO-g-C3N4 is higher than that by Pbi-ZnO. The application of Pbi-ZnO-g-C3N4 is beneficial for the growth of native soil microorganism.

Enhanced atrazine degradation in the Fe(III)/peroxymonosulfate system via accelerating Fe(II) regeneration by benzoquinone

Fe(II)-involved advanced oxidation processes could effectively degrade refractory contaminants, but the slow transformation of Fe(III) to Fe(II) limits their wide application. Herein we reported that p-benzoquinone (BQ) could accelerate Fe(III)/Fe(II) cycle and promote atrazine (ATZ) degradation in the Fe(III)/peroxymonosulfate (Fe(III)/PMS) system through reconstructing active Fe(II)/PMS system. Under the identical experimental conditions, ATZ degradation efficiency in the BQ/Fe(III)/PMS system (99.8%) was superior to that in the Fe(III)/PMS system (23.2%), suggesting the indispensable role of BQ in Fe(II) regeneration and PMS activation. Reactive species sulfate radical (SO4•−), hydroxyl radical (•OH) and ferryl ion (Fe(IV)) were involved in the BQ/Fe(III)/PMS system based on alcohol quenching experiments, ESR tests and the selective transformation from methyl phenyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO2). ATZ degradation mechanism was proposed based on LC-MS detection, among which dealkylation and dechlorination-hydroxylation were the dominant transformation pathways. The BQ/Fe(III)/PMS system showed satisfactory catalytic performance at pH 2.5–7.0 and low Fe(III) concentration, which expanded the pH range and avoided the addition of a large amount of Fe. More importantly, the increase of PMS concentration not only enhanced the oxidative degradation of ATZ and its two main chlorinated byproducts (atrazine-desethyl (DEA) and atrazine-desisopropyl (DIA)), but also facilitated the removal of toxic BQ. Cl− inhibited the degradation of ATZ and caused the accumulation of DEA and DIA, and the higher Cl−, the more obvious this effect. This study provided a new approach to improve the Fe(III)/PMS system by boosting Fe(III)/Fe(II) cycle with quinons.