Removal of atrazine in water by combination of activated carbon and dielectric barrier discharge

Efficient degradation and mineralization of aniline in aqueous solution by new dielectric barrier discharge non-thermal plasma

Aniline is a priority pollutant that is unfavorable to the environment and human health due to its carcinogenic and mutagenic nature. The performance of the dielectric barrier discharge reactor was examined based on the aniline degradation efficiency. Different parameters were studied and optimized to treat various wastewater conditions. Role of active species for aniline degradation was investigated by the addition of inhibitors and promoters. The optimum conditions were 20 mg/L initial concentration, 1.8 kV applied voltage, 4 L/min gas flow rate and a pH of 8.82. It was observed that 87% of aniline was degraded in 60 min of dielectric barrier discharge treatment at optimum conditions. UV-Vis spectra showed gradual increase in the treatment efficiency of aniline with the propagation of treatment time. Mineralization of AN was confirmed by TOC measurement and a decrease in pH during the process. To elicit the aniline degradation route, HPLC and LC-MS techniques were used to detect the intermediates and byproducts. It was identified that aniline degraded into different organic byproducts and was dissociated into carbon dioxide and water. Comparison of the current system with existing advanced oxidation processes showed that DBD has a remarkable potential for the elimination of organic pollutants.

Degradation of micropollutants in secondary wastewater effluent using nonthermal plasma-based AOPs: The roles of free radicals and molecular oxidants

Emerging micropollutants (µPs) appearing in water bodies endanger aquatic animals, plants, microorganisms and humans. The nonthermal plasma-based advanced oxidation process is a promising technology for eliminating µPs in wastewater but still needs further development in view of full-scale industrial application. A novel cascade reactor design which consists of an ozonation chamber preceding a dielectric barrier discharge (DBD) plasma reactor with a falling water film on an activated carbon textile (Zorflex®) was used to remove a selection of µPs from secondary municipal wastewater effluent. Compare to previous plasma reactor, molecular oxidants degraded micropollutants again in an ozonation chamber in this study, and the utilization of different reactive oxygen species (ROS) was improved. A gas flow rate of 0.4 standard liter per minute (SLM), a water flow rate of 100 mL min^-1, and a discharge power of 25 W are identified as the optimal plasma reactor parameters, and the µP degradation efficiency and electrical energy per order value (EE/O) are 84-98% and 2.4-5.3 kW/m³, respectively. The presence of ROS during plasma treatment was determined in view of the µPs removal mechanisms. The degradation of diuron (DIU), bisphenol A (BPA) and 2-n-octyl-4-isothiazolin-3-one (OIT) was mainly performed in ozonation chamber, while the degradation of atrazine (ATZ), alachlor (ALA) and primidone (PRD) occurred in entire cascade system. The ROS not only degrade the µPs, but also remove nitrite (90.5%), nitrate (69.6%), ammonium (39.6%) and bulk organics (11.4%). This study provides insights and optimal settings for an energy-efficient removal of µPs from secondary effluent using both free radicals and molecular oxidants generated by the plasma in view of full-scale application.

Degradation of carbamazepine by high-voltage direct current gas-liquid plasma with the addition of H2O2 and Fe2

Carbamazepine (CBZ) is a typical psychotropic pharmaceutical which is one of the most commonly detected persistent pharmaceuticals in the environment. The degradation of CBZ in the aqueous solution was studied by a direct current (DC) gas-liquid phase discharge plasma combined with different catalysts (H₂O₂ or Fe²⁺) in this study. The concentrations of reactive species (H₂O₂, O₃, and NO₃^-) and •OH radical yield in the liquid were measured during the discharge process. The various parameters that affect the degradation of CBZ, such as discharge powers, initial concentrations, initial pH values, and addition of catalysts, were investigated. The energy efficiency was 25.2 mg·kW^-1·h^-1 at 35.7 W, and the discharge power at 35.7 W was selected to achieve the optimal balance on the degradation effect and energy efficiency. Both acidic and alkaline solution conditions were conducive to promoting the degradation of CBZ. Both H₂O₂ and Fe²⁺ at low concentration (10-100 mg/L of Fe²⁺, 0.05-2.0 mmol/L of H₂O₂) were observed contributing to the improvement of the CBZ degradation rate, while the promotional effect of CBZ degradation was weakened even inhibition would occur at high concentrations (100-200 mg/L of Fe²⁺, 2.0-5.0 mmol/L of H₂O₂). The degradation rate of CBZ was up to 99.1%, and the total organic carbon (TOC) removal efficiency of CBZ was up to 67.1% in the plasma/Fe²⁺ (100 mg/L) system at 48 min, which suggested that high degradation rate and mineralization efficiency on CBZ could be achieved by employing Fe²⁺ as a catalyst. Based on the intermediate products identified by Ultra Performance Liquid Chromatography Tandem Mass Spectrometry (UPLC-MS), the possible degradation pathways were proposed. Finally, the growth inhibition assay with Escherichia coli (E. coli) showed that the toxicity of plasma/Fe²⁺-treated CBZ solution decreased and a relatively low solution toxicity could be achieved. Thus, the plasma/catalyst could be an effective technology for the degradation of pharmaceuticals in aqueous solutions.

Degradation of Residual Herbicide Atrazine in Agri-Food and Washing Water

Atrazine, an herbicide used to control grassy and broadleaf weed, has become an essential part of agricultural crop protection tools. It is widely sprayed on corn, sorghum and sugar cane, with the attendant problems of its residues in agri-food and washing water. If ingested into humans, this residual atrazine can cause reproductive harm, developmental toxicity and carcinogenicity. It is therefore important to find clean and economical degradation processes for atrazine. In recent years, many physical, chemical and biological methods have been proposed to remove atrazine from the aquatic environment. This review introduces the research works of atrazine degradation in aqueous solutions by method classification. These methods are then compared by their advantages, disadvantages, and different degradation pathways of atrazine. Moreover, the existing toxicological experimental data for atrazine and its metabolites are summarized. Finally, the review concludes with directions for future research and major challenges to be addressed.

Emerging Pollutants in Moroccan Wastewater: Occurrence, Impact, and Removal Technologies

The rapid growth of anthropogenic activities in recent decades has resulted in the appearance of numerous new chemical compounds in the environment, known as “emerging pollutants” (EPs) or “contaminants of emerging concern” (CECs). Although partially or not yet regulated or monitored, there is growing research interest in these EPs among the scientific community because of their bioaccumulation, persistence, and adverse effects. Among these, endocrine disruptors, pesticides, and pharmaceuticals can have harmful impacts on human health and the ecosystem. Conventional wastewater treatment technologies are not effective in removing these contaminants, allowing them to be released into the receiving environment. In order to improve the understanding of emerging pollutants, this review discusses the source, occurrence, and impacts of bisphenol A, atrazine, amoxicillin, and paracetamol as model molecules of emerging environmental pollutants, an issue that remains underrepresented in Morocco. Then, treatment methods for EPs are reviewed, including adsorption, advanced oxidation processes, biodegradation, and hybrid treatment. It is proposed that adsorption and photocatalysis can be used as simple, effective, and environmentally friendly technologies for their removal. Thus, we summarize some of the adsorbent and photocatalyst materials applied in recent work to control these pollutants. Towards the end of this paper, the development of inexpensive and locally available (Morocco) materials to remove these compounds from wastewater is considered.

Review on the treatment of organic wastewater by discharge plasma combined with oxidants and catalysts

Discharge plasma technology is a new advanced oxidation technology for water treatment, which includes the effects of free radical oxidation, high energy electron radiation, ultraviolet light hydrolysis, and pyrolysis. In order to improve the energy efficiency in the plasma discharge processes, many efforts have been made to combine catalysts with discharge plasma technology. Some heterogeneous catalysts (e.g., activated carbon, zeolite, TiO₂) and homogeneous catalysts (e.g., Fe²⁺/Fe³⁺, etc.) have been used to enhance the removal of pollutants by discharge plasma. In addition, some reagents of in situ chemical oxidation (ISCO) such as persulfate and percarbonate are also discussed. This article introduces the research progress of the combined systems of discharge plasma and catalysts/oxidants, and explains the different reaction mechanisms. In addition, physical and chemical changes in the plasma catalytic oxidation system, such as the effect of the discharge process on the catalyst, and the changes in the discharge state and solution conditions caused by the catalysts/oxidants, were also investigated. At the same time, the potential advantages of this system in the treatment of different organic wastewater were briefly reviewed, covering the degradation of phenolic pollutants, dyes, and pharmaceuticals and personal care products. Finally, some suggestions for future water treatment technology of discharge plasma are put forward. This review aims to provide researchers with a deeper understanding of plasma catalytic oxidation system and looks forward to further development of its application in water treatment.

Degradation of antibiotic resistance contaminants in wastewater by atmospheric cold plasma: kinetics and mechanisms

This work employed the atmospheric cold plasma technology to efficiently control the antibiotic resistance contaminants in the wastewater effluent. We found that the plasma inactivated the antibiotic-resistant Escherichia coli through multiple damages on the cell membranes and intracellular components (enzymes and DNA). Plasma treatment at an influence of 0.71 kJ/cm² resulted in a more than 3 log₁₀ CFU/ml reduction (>99.999%) of E. coli in an actual wastewater system. We further estimated the effect of plasma on the ampicillin (bla_TEM ) and tetracycline (tet) resistance genes. The results demonstrated that an applied plasma dose of 1.06 kJ/cm² could significantly (P < .05) eliminate the extracellular (e-) bla_TEM and tet genes by 3.26 and 3.14 log₁₀ copies/ml, respectively. Higher plasma intensity was required for the efficient reduction of intracellular (i-)antibiotic resistance genes (ARGs) than extracellular (e-)ARGs due to the shielding effect of the outer envelopes or intracellular components. The inactivation of E. coli and the degradation of e- and i-ARGs can be well described by the Weibull models. The results here provide the evidence for the potential of the plasma technology as a water/wastewater treatment technology.

Non-Thermal Plasma Coupled with Catalyst for the Degradation of Water Pollutants: A Review

Non-thermal plasma is one of the most promising technologies used for the degradation of hazardous pollutants in wastewater. Recent studies evidenced that various operating parameters influence the yield of the Non-Thermal Plasma (NTP)-based processes. In particular, the presence of a catalyst, suitably placed in the NTP reactor, induces a significant increase in process performance with respect to NTP alone. For this purpose, several researchers have studied the ability of NTP coupled to catalysts for the removal of different kind of pollutants in aqueous solution. It is clear that it is still complicated to define an optimal condition that can be suitable for all types of contaminants as well as for the various types of catalysts used in this context. However, it was highlighted that the operational parameters play a fundamental role. However, it is often difficult to understand the effect that plasma can induce on the catalyst and on the production of the oxidizing species most responsible for the degradation of contaminants. For this reason, the aim of this review is to summarize catalytic formulations coupled with non-thermal plasma technology for water pollutants removal. In particular, the reactor configuration to be adopted when NTP was coupled with a catalyst was presented, as well as the position of the catalyst in the reactor and the role of the main oxidizing species. Furthermore, in this review, a comparison in terms of degradation and mineralization efficiency was made for the different cases studied.

Catalytic degradation of clothianidin with graphene/TiO2 using a dielectric barrier discharge (DBD) plasma system

Clothianidin served as the model pollutant to investigate the performance and mechanism of pollutant removal by dielectric barrier discharge plasma (DBD) combined with the titanium dioxide-reduced graphene oxide (rGO-TiO₂) composite catalyst. In this study, different ratios of titanium dioxide-graphene catalysts were loaded onto honeycomb ceramic plates via the sol-gel method, and the modified catalytic ceramic plates were characterized by XRD, SEM, FTIR, DRS, and energy dispersive X-ray. The results suggested that the rGO-TiO₂ was well loaded on the surface of the honeycomb ceramic plates. According to the results of the characterization experiments and the degradation of the clothianidin solution with different proportions of the catalyst, 8 wt% rGO-TiO₂ was selected as the optimum ratio for degradation. Clothianidin degradation efficiency was significantly influenced by input power, clothianidin concentration, pH value, liquid conductivity, free radical quencher. Finally, six degradation products of clothianidin were identified by HPLC-MS, and the possible transformation pathways of clothianidin degradation were identified. Graphical abstract.

Degradation of aniline in aqueous solution by dielectric barrier discharge plasma: Mechanism and degradation pathways

The degradation of aniline solution using the dielectric barrier discharge (DBD) plasma was studied in this paper. The results indicated that the initial concentration of aniline, applied voltage and initial pH value affected the removal efficiency of aniline significantly. After 12 min with DBD plasma treatment, 90.2% removal efficiency was achieved at aniline concentration of 100 mg L^-1 with an applied voltage of 3.0 kV and pH 8.43. The removal efficiency decreased with the presence of radical scavengers, indicating that hydroxyl radical plays a key role in the degradation process. The removal efficiency increased obviously when Fe²⁺ was added. Additionally, the intermediate products generated in the degradation process of aniline were analyzed by some analytical techniques, including total organic carbon analysis, ultraviolet-visible spectroscopy, Fourier Transform Infrared spectroscopy, Gas Chromatography-Mass Spectrometer, etc. The results showed that the degradation of aniline was mainly due to the strong oxidizing capacity of hydroxyl radical produced by the DBD plasma system. Based on the intermediate products identified in the study, the possible degradation mechanism and pathways were proposed.

Degradation of atrazine by catalytic ozonation in the presence of iron scraps: performance, transformation pathway, and acute toxicity

Degradation of atrazine by catalytic ozonation in the presence of iron scraps (ZVI/O₃) was carried out. The key operational parameters (i.e., initial pH, ZVI dosage, and ozone dosage) were optimized by the batch experiments, respectively. This ZVI/O₃ system exhibited much higher degradation efficiency of atrazine than the single ozonation, ZVI, and traditional ZVI/O₂ systems. The result shows that the pseudo-first-order constant (0.0927 min^-1) and TOC removal rate (86.6%) obtained by the ZVI/O₃ process were much higher than those of the three control experiments. In addition, X-ray diffraction (XRD) analysis indicates that slight of γ-FeOOH and Fe₂O₃ were formed on the surface of iron scrap after ZVI/O₃ treatment. These corrosion products exhibit high catalytic ability for ozone decomposition, which could generate more hydroxyl radical (HO^•) to degrade atrazine. Six transformation intermediates were identified by liquid chromatography-mass spectrometry (LC-MS) analysis in ZVI/O₃ system, and the degradation pathway of atrazine was proposed. Toxicity tests based on the inhibition of the luminescence emitted by Photobacterium phosphoreum and Vibrio fischeri indicate the detoxification of atrazine by ZVI/O₃ system. Finally, reused experiments indicate the approving recyclability of iron scraps. Consequently, the ZVI/O₃ system could be as an effective and promising technology for pesticide wastewater treatment.

Removal of micropollutants from water in a continuous-flow electrical discharge reactor

The emergence of micropollutants into our aquatic resources is regarded as an issue of increasing environmental concern. To protect the aquatic environment against further contamination with micropollutants, treatment with advanced oxidation processes (AOPs) is put forward as a promising technique. In this work, an innovative AOP based on electrical discharges in a continuous-flow pulsed dielectric barrier discharge (DBD) reactor with falling water film over activated carbon textile is examined for its potential application in water treatment. The effect of various operational parameters including feed gas type, gas flow rate, water flow rate and power on removal and energy efficiency has been studied. To this end, a synthetic micropollutant mixture containing five pesticides (atrazine, alachlor, diuron, dichlorvos and pentachlorophenol), two pharmaceuticals (carbamazepine and 1,7-α-ethinylestradiol), and 1 plasticizer (bisphenol A) is used. While working under optimal conditions, energy consumption was situated in the range 2.42-4.25 kW h/m³, which is about two times lower than the economically viable energy cost of AOPs (5 kW h/m³). Hence, the application of non-thermal plasma could be regarded as a promising alternative AOP for (industrial) wastewater remediation.

Removal of alachlor, diuron and isoproturon in water in a falling film dielectric barrier discharge (DBD) reactor combined with adsorption on activated carbon textile: Reaction mechanisms and oxidation by-products

A falling film dielectric barrier discharge (DBD) plasma reactor combined with adsorption on activated carbon textile material was optimized to minimize the formation of hazardous oxidation by-products from the treatment of persistent pesticides (alachlor, diuron and isoproturon) in water. The formation of by-products and the reaction mechanism was investigated by HPLC-TOF-MS. The maximum concentration of each by-product was at least two orders of magnitude below the initial pesticide concentration, during the first 10 min of treatment. After 30 min of treatment, the individual by-product concentrations had decreased to values of at least three orders of magnitude below the initial pesticide concentration. The proposed oxidation pathways revealed five main oxidation steps: dechlorination, dealkylation, hydroxylation, addition of a double-bonded oxygen and nitrification. The latter is one of the main oxidation mechanisms of diuron and isoproturon for air plasma treatment. To our knowledge, this is the first time that the formation of nitrificated intermediates is reported for the plasma treatment of non-phenolic compounds.

Efficient degradation of atrazine by BiOBr/UiO-66 composite photocatalyst under visible light irradiation: Environmental factors, mechanisms and degradation pathways

Atrazine, a typical herbicide, has caused extensive concern due to its wide application and persistance. In this work, a visible light responsive photocatalyst BiOBr/UiO-66 was synthesized and applied to the degradation of atrazine. The BiOBr/UiO-66 materials exhibited significantly enhanced photocatalytic performance on the degradation of atrazine under visible light irradiation compared to pure BiOBr. Moreover, the effects of typical environment factors (i.e. pH, common anions, inorganic cations and water matrix) on the degradation of atrazine were investigated extensively. Results showed that atrazine was degraded with the fastest rate at the strong acidity conditions of pH = 3.1 in the investigated pH region (3.1-9.4). The photocatalytic degradation of atrazine was obviously inhibited by HCO₃^- and SO₄^2-. However, Cl^- had negligible influence on the degradation of atrazine. Inorganic cations had little influence on the degradation of atrazine. Futhermore, the water matrix showed apparent impacts on the photocatalytic degradation of atrazine by BiOBr/UiO-66. In mineral water, tap water and river water, the removal efficiency of atrazine was evidently lower than that in pure water. The main active species that responsible for the degradation of atrazine by BiOBr/UiO-66 were determined to be ·O₂^- and h⁺. Ultimately, the degradation pathways of atrazine were proposed based on the intermediates detected by LC-MS/MS.

Preparation, performances and mechanisms of magnetic Saccharomyces cerevisiae bionanocomposites for atrazine removal

Saccharomyces cerevisiae and nanoparticles of iron oxide (Fe₃O₄) which were linked with chitosan (CS) through epichlorohydrin (ECH) were encapsulated in calcium alginate to prepare a novel type of bionanocomposites. Characterization results showed that the Fe₃O₄-ECH-CS nanoparticles were quasi-spherical with an average diameter of 30 nm to which chitosan was successfully attached through epichlorohydrin. The saturation magnetization value of the nanoparticles was 21.88 emu/g, and ferrous and ferric irons were simultaneously observed in the magnetic nanoparticles. Data of atrazine removal by yeasts showed that both inactivated and live yeasts could decrease the concentration of atrazine effectively. The inactivated yeasts achieved 20% removal rate, which indicated that adsorption by the yeasts also played a role in the removal. Removal efficiency of atrazine was maximized at 88% under 25 °C, pH of 7 and an initial atrazine concentration of 2 mg/L. When the magnetic bionanocomposite was recycled and reused twice, only 12% and 20% drop in removal efficiency was observed at the first time and the second time severally. So, atrazine could be used by the yeasts as the sole carbon source for growth and multiplication, and both adsorption and biodegradation by the bionanocomposite contributed to atrazine removal.

Imprinted silica nanofiber formation via sol–gel-electrospinning for selective micro solid phase extraction

Molecular imprinted silica nanofibers were implemented for atrazine recognition via an on-line micro-SPE-HPLC set up.

Degradation of the chlorophenoxyacetic herbicide 2,4-D by plasma-ozonation system

A novel advanced oxidation process based on the combination of ozonation with non-thermal plasma generated in a pulsed corona discharge was developed for the oxidative degradation of recalcitrant organic pollutants in water. The pulsed corona discharge in contact with liquid, operated in oxygen, produced 3.5mgL^-1 ozone, which was subsequently introduced in the ozonation reactor. The solution to be treated was continuously circulated between the plasma reactor and the ozonation reactor. The system was tested for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and considerably improved performance as compared to ozonation alone, both with respect to the removal of the target compound and to mineralization. The apparent reaction rate constant for 2,4-D removal was 0.195min^-1, more than two times higher than the value obtained in ozonation experiments. The mineralization reached more than 90% after 60min treatment and the chlorine balance confirms the absence of quantifiable amounts of chlorinated by-products. The energy efficiency was considerably enhanced by shortening the duration of the discharge pulses, which opens the way for further optimization of the electrical circuit design.

Removal of several pesticides in a falling water film DBD reactor with activated carbon textile: Energy efficiency

Bio-recalcitrant micropollutants are often insufficiently removed by modern wastewater treatment plants to meet the future demands worldwide. Therefore, several advanced oxidation techniques, including cold plasma technology, are being investigated as effective complementary water treatment methods. In order to permit industrial implementation, energy demand of these techniques needs to be minimized. To this end, we have developed an electrical discharge reactor where water treatment by dielectric barrier discharge (DBD) is combined with adsorption on activated carbon textile and additional ozonation. The reactor consists of a DBD plasma chamber, including the adsorptive textile, and an ozonation chamber, where the DBD generated plasma gas is bubbled. In the present paper, this reactor is further characterized and optimized in terms of its energy efficiency for removal of the five pesticides α-HCH, pentachlorobenzene, alachlor, diuron and isoproturon, with initial concentrations ranging between 22 and 430 μg/L. Energy efficiency of the reactor is found to increase significantly when initial micropollutant concentration is decreased, when duty cycle is decreased and when oxygen is used as feed gas as compared to air and argon. Overall reactor performance is improved as well by making it work in single-pass operation, where water is flowing through the system only once. The results are explained with insights found in literature and practical implications are discussed. For the used operational conditions and settings, α-HCH is the most persistent pesticide in the reactor, with a minimal achieved electrical energy per order of 8 kWh/m³, while a most efficient removal of 3 kWh/m³ or lower was reached for the four other pesticides.

Pseudomonas sp. ZXY-1, a newly isolated and highly efficient atrazine-degrading bacterium, and optimization of biodegradation using response surface methodology

Atrazine, a widely used herbicide, is increasing the agricultural production effectively, while also causing great environmental concern. Efficient atrazine-degrading bacterium is necessary to removal atrazine rapidly to keep a safe environment. In the present study, a new atrazine-degrading strain ZXY-1, identified as Pseudomonas, was isolated. This new isolated strain has a strong ability to biodegrade atrazine with a high efficiency of 9.09mg/L/hr. Temperature, pH, inoculum size and initial atrazine concentration were examined to further optimize the degradation of atrazine, and the synthetic effect of these factors were investigated by the response surface methodology. With a high quadratic polynomial mathematical model (R²=0.9821) being obtained, the highest biodegradation efficiency of 19.03mg/L/hr was reached compared to previous reports under the optimal conditions (30.71°C, pH7.14, 4.23% (V/V) inoculum size and 157.1mg/L initial atrazine concentration). Overall, this study provided an efficient bacterium and approach that could be potentially useful for the bioremediation of wastewater containing atrazine.

Complete genome sequence of Arthrobacter sp. ZXY-2 associated with effective atrazine degradation and salt adaptation

An atrazine-degrading strain Arthrobacter sp. ZXY-2 was originally isolated from Jilin Pesticide Plant (China). Strain ZXY-2 demonstrated excellent atrazine degradation performance and saline tolerance. Here we report the complete genome sequence of strain ZXY-2 contained a circular chromosome and five circular plasmids encoding for the mechanism of salt adaptation and pollutant degradation.