Degradation Of Sulfadiazine Research Articles

Magnetic porous carbon materials derived from metal-organic framework in-situ growth on natural cellulose of wood for sulfadiazine degradation: Role of delignification and mechanisms

Magnetic porous carbon materials as peroxymonosulfate (PMS) activators for sulfadiazine degradation were derived from metal-organic frameworks (MOFs) grown in-situ on the cellulose of wood through the one-step pyrolysis method. The cellulose was obtained by treating wood powder with sodium chlorite to remove lignin, and Fe-MOFs (MIL-101(Fe)) nanoparticles were in-situ grown on the cellulose through hydrothermal reaction. The delignification of wood effectively enhanced the in-situ growth of MIL-101(Fe) on the wood tracheid skeleton, increased the specific surface area of magnetic porous carbon material (Fe@PC-50) after pyrolysis, and improved the performance of Fe@PC-50 as a PMS activator for the degradation of sulfadiazine. With the presence of 0.04 g L−1 Fe@PC-50 and 0.12 g L−1 PMS, the degradation percentage of sulfadiazine (20 mg L−1) could reach 100 % within 15 min, indicating excellent catalytic activity. Quenching tests and electron paramagnetic resonance (EPR) indicated that both free and non-free radicals played important roles in PMS activation. X-ray photoelectron spectroscopy (XPS) suggested that Fe0 and Fe3C were the possible important active sites for sulfadiazine degradation. This work offered an effective method to synthesize PMS activators from biomass/MOF materials for water treatment.

Perborate accelerated copper-immobilized carbon nanofibers activating peroxymonosulfate process for sulfadiazine degradation: Performance and mechanisms understanding

In this work, perborate (BO3−) was applied to promote the degradation of sulfadiazine (SDZ) in copper-immobilized carbon nanofibers (Cu-CNF-x) activated peroxymonosulfate (PMS) system. Results showed that in BO3−/Cu-CNF-3/PMS ternary system, 100% of SDZ (40 μM) could be efficiently eliminated in 5 min with 0.1 g/L Cu-CNF-3, 1 mM BO3− and 1 mM PMS; while Cu-CNF-3/PMS and BO3−/PMS systems only achieved 58.4% and 47.3% degradation in 30 min. In initial pH range of 5.0–9.0, the ternary system removed over 92.6% of SDZ, and the treated solution pH maintained neutral, effectively relieving the water acidification introduced by PMS. Electron paramagnetic resonance analysis and radical scavenger tests evidenced the production of SO4−•, •OH, 1O2 and H2O2BO•O•−. Mechanisms analysis proposed the activation process as follows: initially, BO3− promptly activated PMS to generate H2O2BO•O•− via electrophilic substitution reaction, and H2O2 was produced due to the decomposition of BO3−; thereafter, PMS was activated by Cu-CNF-x to yield SO4−•, •OH and 1O2; the obtained H2O2 was then utilized by Cu-CNF-x to produce •OH and 1O2 as well. Density functional theory (DFT) calculations showed that the adsorption energy (Ead) between PMS and Cu-CNF-x was 0.43 eV. BO3− greatly increased the Ead of PMS on Cu-CNF-x by ten times to 4.75 eV, which extremely promoted the PMS activation. This work provided a novel strategy of BO3−/Cu-CNF-3/PMS for the efficient degradation of refractory organic pollutants, and managed to understand the synergistic role of BO3− to PMS based heterogeneous catalytic processes.

Periodate activation by atomically dispersed Mn on carbon nanotubes for the production of iodate radicals and rapid degradation of sulfadiazine

Sulfonamides, such as sulfadiazine (SDZ), are widely used antibiotics that pose a significant threat to the environment due to their poor biodegradability and potential to induce antibiotic resistance. In this study, a new catalyst with atomically dispersed Mn on carbon nanotubes (MnN@CNT) was applied for the first time to activate periodate (PI) for rapid degradation of SDZ. MnN@CNT/PI system achieved 100% SDZ removal in 15 min, and the kinetic rate constant (knor) reaches 406.1 min−1·g−2·L2, higher than those of the reported catalytic PI systems. Multiple reactive oxygen species (ROS), including IO3•, O2–•, 1O2, high-valent Mn-oxo complexes, and •OH, were detected, with IO3• being the most predominant. The Mn atom bridged the electron from the carbon support to IO4- via the Mn-O bond, which induced the prolonged I-O bond and thus the generation of IO3•. SDZ was degraded through S-N bond cleavage, pyrimidine destruction, SO2 extrusion, and N-N coupling. The intermediate products of the SDZ degradation process showed little antibacterial activity, indicating the greatly reduced risk of the treated water to induce antibiotic resistance in the environment. The superior performance of MnN@CNT/PI in the environmental water samples suggests its high application potential for selective degradation of SDZ in complex waters. The research presents a novel advanced catalytic oxidation technology for efficiently removing sulfonamides and similar antibiotics from water for adequate environmental and ecological protection.

Boosted persulfate activation by hierarchically porous carbonaceous materials: Pivotal role of pore structure and electron-accepting capacity

Porous carbonaceous materials (CMs) have been praised as superior candidates in activating persulfate for antibiotic wastewater decontamination. Whereas, as one of the frequently reported nonradical pathways, the formation mechanism of the reactive complexes and their correlation with physicochemical properties of CMs have not been comprehensively unveiled. Herein, a series of carbonaceous materials (CMs) with different specific surface area (SSA) and defect structures were fabricated by using KCl, MgCl2, KHCO3 and K2C2O4 as porogenic agents to activate peroxydisulfate (PDS) for sulfadiazine (SDZ) degradation. Results showed that the total pore volume of CMs exhibited a good linearity with degradation rate, attributing to the combined effect of SSA, defect degree and oxygen-containing functional groups according to multiple regression model. The reactive complexes (CM/PDS*) were proved as the foremost active species for SDZ oxidation via a suite of solid evidences. Compared with that after PS addition, the current direction was reversed after SDZ addition in i-t curves shedding light on the sharp enhanced potential of CM/PDS* and much low potential of SDZ. Furthermore, the inner-sphere CM/PDS* originating from the formation of new covalent bonds between CMs and PDS was inferred due to the poor dependence between electron-donating capacity and SDZ degradation result. The CM/PDS* with considerably higher potential can extract electron from SDZ based on the excellent positive relationship between electron-accepting capacity of CMs and SDZ degradation effect. This study advances the mechanistic comprehension of nonradical PDS activation, and provides a multiple regression model to predict degradation effects of carbon materials.

Sulfadiazine Elimination from Wastewater Effluents under Ozone-Based Catalysis Processes

The presence of antibiotic sulfadiazine (SFD) poses threats to the ecosystem and human health, and traditional wastewater treatment processes are not ideal for sulfadiazine removal. Therefore, it is urgent to develop treatment processes with high efficiency targeting sulfadiazine. This study investigated the degradation and mineralization mechanisms of SFD by ozone-based catalysis processes including ozone/persulfate (PS) and ozone/peroxymonosulfate (PMS). The degradation, mineralization and byproducts of SFD were monitored by HPLC, TOC and LC/MS, respectively. SFD was efficiently removed by two ozone-based catalysis processes. Ozone/PMS showed high efficiency for SFD removal of 97.5% after treatment for 1 min and TOC reduction of 29.4% after treatment for 20 min from wastewater effluents. SFD degradation was affected by pH, oxidant dosage, SFD concentration and anions. In the two ozone-based catalysis processes, hydroxyl radicals (OH•) and sulfate radicals (SO4•−) contributed to the degradation of SFD. The degradation pathways of SFD under the two processes included hydroxylation, the opening of the pyrimidine ring and SO2 extrusion. The results of this study demonstrate that the two ozone-based catalysis processes have good potential for the elimination of antibiotics from water/wastewater effluents.

Peroxymonosulfate activation by iron-nickel nanoalloys anchored on nitrogen-doped biochar for efficient sulfadiazine degradation

Biochar-based transition metals have been intensively studied as promising catalysts for peroxymonosulfate (PMS) activation towards the degradation of recalcitrant organic contaminants, but their catalytic activities and stabilities remain to be improved. Herein, Fe-Ni nanoalloys anchored on nitrogen-doped biochar (FeNi-NBC) was developed for PMS activation towards sulfadiazine (SDZ) degradation. The results show that SDZ (10 mg/L) is completely degraded by the PMS/FeNi-NBC system within 60 min under optimum conditions, and the SDZ degradation rate constant (0.266 min−1) outperforms most reported catalysts. Besides, the prepared FeNi-NBC has a high stability with a SDZ removal efficiency of around 86% after twenty cycles. Electron paramagnetic resonance measurements and quenching tests fully demonstrate the nonradical PMS activation by FeNi-NBC. Combined with the results of electrochemical tests and DFT calculations, the formation of activated surface-PMS complexes is found to be the dominant pathway for PMS activation by FeNi-NBC. DFT calculations further reveal that the adsorption of PMS on the FeNi-N-C sites to form the surface-PMS complex is thermally spontaneous, and the FeNi-N-C sites in FeNi-NBC are dominant active sites for PMS activation.

Efficient purification of aqueous solutions contaminated with sulfadiazine by coupling electro-Fenton/ultrasound process: optimization, DFT calculation, and innovative study of human health risk assessment.

In the current work, the hybrid process potential of ultrasound (US) and electro-Fenton (EF), named sono-electro-Fenton (SEF), was fully investigated for sulfadiazine (SDZ) degradation. The decontamination in the integration approach was revealed to be greater than in individual procedures, i.e., EF process (roughly 66%) and US process (roughly 15%). The key operating process factors (i.e., applied voltage, H2O2 content, pH, initial concentration of SDZ, and reaction time) affecting SDZ removal were evaluated and optimized using Box-Behnken Design (BBD). In addition, an adaptive neuro-fuzzy inference system (ANFIS) as an efficient predictive model was applied to forecast the decontamination efficiency of SDZ through the SEF process based on the same findings produced from BBD. The results revealed that the predictability of SDZ elimination by the ANFIS and BBD approaches exhibited an excellent agreement (a greater R2 of 0.99%) among the both models. Density functional theory was also employed to forecast the plausible decomposition elucidation by the bond-breaking mechanism of organic substances. Plus, the main side products of SDZ degradation during the SEF process were tracked. Eventually, the non-carcinogenic risk assessment of different samples of natural water containing SDZ that was treated by adopting US, EF, and SEF processes was examined for the first time. The findings indicated that the non-carcinogenic risk (HQ) values of all the purified water sources were computed in the permissible range.

Nitrogen doped magnetic porous carbon derived from starch of oatmeal for efficient activation peroxymonosulfate to degradation sulfadiazine

Nitrogen doped magnetic porous carbon catalyst based on starch of oatmeal was obtained by mixing and pyrolysis process, and its catalytic activity of peroxymonosulfate activation for sulfadiazine degradation was evaluated. When ratio of oatmeal/urea/iron was 1: 2: 0.1, CN@Fe-10 had the best catalytic activity to degrade sulfadiazine. Around 97.8 % removal of 20 mg L−1 sulfadiazine was achieved under incorporating of 0.05 g L−1 catalyst and 0.20 g L−1 peroxymonosulfate. Good adaptability, stability and universality of CN@Fe-10 were verified under different conditions. Electron paramagnetic resonance and radical quenching test suggested that surface-bound reactive oxides species and singlet oxygen were the main reactive oxides species in this reaction. Electrochemical analysis indicated that CN@Fe-10 had a good electrical conductivity and electron transferred did occur among CN@Fe-10 surface, peroxymonosulfate and sulfadiazine. X-ray photoelectron spectroscopy suggested that Fe0, Fe3C, pyridine nitrogen and graphite nitrogen were the potential active sites for peroxymonosulfate activation. Therefore, the work provided a practical approach for recycling biomass.

Understanding the cometabolic degradation of sulfadiazine by an enriched ammonia oxidizing bacteria culture from both extracellular and intracellular perspectives

Antibiotics are widely used drugs in the world and pose serious threats to ecosystems and human health. Although it has been reported that ammonia oxidizing bacteria (AOB) can cometabolize antibiotics, little has been reported on how AOB would respond to the exposure of antibiotics on extracellular and enzymatic levels, as well as the impact of antibiotics on the bioactivity of AOB. Therefore, in this study, a typical antibiotic, sulfadiazine (SDZ), was selected, and a series short-term batch tests using enriched AOB sludge were conducted to investigate the intracellular and extracellular responses of AOB along the cometabolic degradation process of SDZ. The results showed the cometabolic degradation of AOB made the main contribution to SDZ removal. When the enriched AOB sludge was exposed to SDZ, ammonium oxidation rate, ammonia monooxygenase activity, adenosine triphosphate concentration and dehydrogenases activity were negatively affected. The amoA gene abundance increased 1.5 folds within 24 h, which may enhance the uptake and utilization of substrates and maintain stable metabolic activity. In the tests with and without ammonium, the concentration of total EPS increased from 264.9 to 231.1 mg/gVSS to 607.7 and 538.2 mg/gVSS, respectively, under the exposure to SDZ, which was mainly contributed by the increase of proteins in tightly bound extracellular polymeric substances (EPS) and polysacharides in tightly bound EPS and soluble microbial products. The proportion of tryptophan-like protein and humic acid-like organics in EPS also increased. Moreover, SDZ stress stimulated the secretion of three quorum sensing signal molecules, C4-HSL (from 140.3 to 164.9 ng/L), 3OC6-HSL (from 17.8 to 42.4 ng/L) and C8-HSL (from 35.8 to 95.9 ng/L) in the enriched AOB sludge. Among them, C8-HSL may be a key signal molecule that promoted the secretion of EPS. The findings of this study could shed more light on the cometabolic degradation of antibiotics by AOB.

Low concentration of bromide ions improves sulfadiazine phytoremoval and attenuates its phytotoxicity

Sulfonamide antibiotics (SAs) are ubiquitous in surface water and soil environments, raising considerable concerns about their risk and removal. However, the impacts of various bromide ion (Br−) concentrations on the phytotoxicity, uptake and fate of SAs in plant growth and physiological metabolism of plants have not been well understood. Our research demonstrated that low concentrations of Br− (0.1, 0.5 mM) promoted the uptake and degradation of sulfadiazine (SDZ) in wheat and attenuated the phytotoxicity of SDZ. Additionally, we proposed a degradation pathway and identified the brominated product of SDZ (SDZBr), which attenuated the dihydrofolate synthesis inhibition by SDZ. The primary mechanism was that Br− reduced the level of reactive oxygen radicals (ROS) and alleviated oxidative damage. The production of SDZBr and the high consumption of H2O2 suggest the potential generation of reactive bromine species, contributing to the degradation of the electron-rich SDZ and thus reducing its toxicity. Moreover, metabolome analysis of wheat roots indicated that low concentrations of Br− stimulated the production of indoleacetic acid under SDZ stress, promoting growth and enhancing the uptake and degradation of SDZ. Conversely, high Br− (1 mM) concentration produced a deleterious effect. These findings provide valuable insights into the mechanisms of antibiotic removal, suggesting a potentially novel approach to plant-based antibiotic remediation.

CoFe2O4/MWCNTs as peroxymonosulfate activator for sulfadiazine degradation in wastewater: Performance, mechanisms, degradation pathway, and products toxicity assessment

Bimetal oxide-based compounds have potential in the degradation of antibiotics in wastewater. In this study, cobalt-ferrite-coated multi-walled carbon nanotubes (CoFe2O4/MWCNTs) have been synthesized by solvothermal method and characterized. Then, the degradation of sulfadiazine (SDZ) by CoFe2O4/MWCNTs activated peroxymonosulfate (PMS) system was determined, mainly including the effects of CoFe2O4/MWCNTs dosage, PMS concentration, solution pH, initial SDZ concentration, and co-existing anions on the degradation of SDZ. Based on reactive oxygen species identification and XPS analysis, the possible reaction mechanisms were investigated. In addition, the potential degradation pathways of SDZ were discussed. The results showed that CoFe2O4/MWCNTs exhibited superior catalytic activity and stability toward SDZ removal, and 97.5% of SDZ was degraded within 30 min under the condition of CoFe2O4/MWCNTs dosage 0.3 g/L, PMS concentration 0.5 mM and solution pH 7. The possible mechanism of PMS activation by CoFe2O4/MWCNTs involved both free-radical and non-radical pathways, and the generated reactive species (SO4•−, •OH, O2•− and 1O2) were responsible for the degradation of SDZ. In addition, four potential degradation pathways were proposed and 15 intermediates were identified. In view of the ecotoxicity assessment, it was found that the toxicity of the degradation intermediates was lower than that of SDZ. Overall, this study established an effective strategy for PMS activation to remove recalcitrant organic pollutants in wastewater.

Adsorbed copper on urea modified activated biochar catalyzed H2O2 for oxidative degradation of sulfadiazine：Degradation mechanism and toxicity assessment

The combined pollution of heavy metals and organic compounds usually occurs simultaneously and induces high toxicity. The technology of simultaneous removal of combined pollution is lacking and the removal mechanism is not clear. Sulfadiazine (SD), a widely used antibiotic, was used as a model contaminant. Urea modified sludge-based biochar (USBC) was prepared and used to catalyze H2O2 to remove the combined pollution of Cu2+ and sulfadiazine (SD) without causing secondary pollution. After 2 h, the removal rates of SD and Cu2+ were 100 and 64.8%, respectively. Cu2+ adsorbed on the surface of USBC accelerated the activation of H2O2 by the USBC catalyzed by CO bond to produce hydroxyl radical (•OH) and single oxygen (1O2) to degrade SD. Twenty-three intermediate products were detected, most of which were completely decomposed into CO2 and H2O. The toxicity was significantly reduced in the combined polluted system. This study highlights the potential of the low-cost technology based on sludge reuse and its inherent significance in reducing the toxic risk of combined pollution in the environment.

Cu doped Fe2O3 growing a nickel foam for sulfadiazine degradation in peroxymonosulfate assisting photo-electrochemical system: Performance, mechanism and degradation pathway

In this study, cost-effective and easily recovery Cu doped Fe2O3 in-situ growing on a nickel foam (Cu-Fe2O3/NF) was successfully fabricated and employed in peroxymonosulfate (PMS) assisting visible-light photoelectrochemical oxidation (VL + EC + catalyst + PMS) system for sulfadiazine (SD) removal. The optimum 2Cu-Fe2O3/NF exhibited excellent catalytic efficiency toward SD degradation in the VL + EC + catalyst + PMS system, 100% of SD being removed in 10 min and the firs-order reaction kinetic constant being 41.30 × 10-2 min−1. The excellent catalytic efficiency of 2Cu-Fe2O3/NF was due to the depressed recombination of photoinduced electron and hole, the enhanced electron transfer efficiency, more Fe2+, Cu+ and Ni2+ in sample resulting from Cu doping, and more active sites owing to the bulk thick petals-like of Fe2O3 being changed to thinner flakes after Cu doping. Therefore, a large number of reactive oxygen species including •OH, •O2− and h+ in the VL + EC + 2Cu-Fe2O3/NF + PMS system were produced to degrade SD. The mechanism of SD degradation in the system was explored in detail. The 2Cu-Fe2O3/NF displayed adaptation ability for a wide range, good anti-interference ability toward ions in real water. More inspiring, benefiting from the in-situ growth of Cu-Fe2O3 on NF surface, 2Cu-Fe2O3/NF exhibited good durability and recycle ability. This study provides a worthy reference for designing efficient and easily recycled catalysts and promotes the practical application possibility of low-cost Fe2O3 in antibiotics removal.

Theoretical investigation on the degradation of sulfadiazine in water environments: Oxidation of •OH, SO4•−and CO3•− and reactivity of (TiO2)n clusters (n = 1–6)

This study reported the degradation of micro pollutants through reactive radicals like •OH, SO4•−and CO3•−. Sulfadiazine (SDZ) is widely used antibiotic and emerging water pollutant. The synergistic degradation of sulfadiazine by •OH, SO4•−and CO3•− was investigated through quantum chemistry methods. The degradation of SDZ by •OH radicals was dependent on radical adduct formation (RAF) reactions while degradation of SDZ by SO4•− radical was caused by RAF, hydrogen atom transfer (HAT) and also single electron transfer (SET). The degradation of SDZ by CO3•− radical mainly caused by RAF and HAT. The degradation rate constants of SDZ initiated through •OH, SO4•−and CO3•− radicals were calculated separately: kSDZ-SO4•− (5.29 × 1010 M−1 s−1) > kSDZ-•OH (1.38 × 1010 M−1 s−1) > kSDZ-CO3•− (1.28 × 108 M−1 s−1). The degradation mechanism of SDZ by (TiO2)n (n = 1–6) cluster was investigated. The conformation between benzene ring and heterocyclic ring of SDZ has a lower adsorption energy and the (TiO2)n cluster (n = 5) is the most stable adsorption conformation with SDZ. The toxicity assessment showed that most of the degradation products were less toxic and eco-friendly. However, O-P1, P4 and P9 exhibited more severe aquatic toxicity.

A Novel Strategy of Combined Pulsed Electro-Oxidation and Electrolysis for Degradation of Sulfadiazine.

A combination of the peroxymonosulfate (PMS) electro-activation process and the electro-oxidation process driven by a pulsed electric field (PEF) was used to degrade sulfadiazine (SND) wastewater. Mass transfer is the limiting step of electrochemical processes. The PEF could enhance mass transfer efficiency by reducing the polarization effect and increasing the instantaneous limiting current compared with the constant electric field (CEF), which could benefit the electro-generation of active radicals. The degradation rate of SND after 2 h was 73.08%. The experiments investigated the effects of operating parameters of pulsed power supply, PMS dosage, pH value and electrode inter distance on the degradation rate of SND. The predicted response value of single-factor performance experiments was obtained as 72.26% after 2 h, which was basically consistent with the experimental value. According to the quenching experiments and EPR tests, both SO4•- and •OH were present in the electrochemical processes. The generation of active species were significantly greater in the PEF system than that in the CEF system. Moreover, four kinds of intermediate products were detected during the degradation by LC-MS. This paper presents a new aspect for electrochemical degradation of sulfonamide antibiotics.

Investigating the Effect of Bi2MoO6/g-C3N4 Ratio on Photocatalytic Degradation of Sulfadiazine under Visible Light

In this study, a series of Bi2MoO6/g-C3N4 composites were prepared through a wet-impregnation method, and their photocatalytic properties were investigated for the degradation of sulfadiazine (SDZ) under visible light irradiation. Physical and chemical characterizations were carried out using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), UV-vis diffuse reflectance spectra (UV-vis), and electrochemical impedance spectra (EIS). Compared to pure g-C3N4, the introduction of Bi2MoO6 significantly enhanced the visible light responsive photocatalytic activity, with the 1:32 Bi2MoO6/g-C3N4 composite exhibiting the highest photodegradation efficiency towards SDZ under visible light irradiation with a photocatalytic efficiency of 93.88% after 120 min of visible light irradiation. The improved photocatalytic activity can be attributed to the formation of a heterojunction between Bi2MoO6 and g-C3N4, which promotes the transfer of photogenerated electron-hole pairs, thereby elevating its photocatalytic activity. The results suggest that Bi2MoO6/g-C3N4 composites have potential application for the degradation of sulfonamides in aquatic environments.

Novel dual-photoelectrode photoelectrocatalytic system based on TiO2 nanoneedle arrays photoanode and nitrogen-doped carbon dots/Co3O4 photocathode for efficient water purification at low/no applied voltage

A novel tandem photoelectrocatalysis (PEC) cell consisting of TiO2 nanoneedle arrays (TiO2 NNs/Ti mesh) photoanode and nitrogen-doped carbon dots (NCDs) modified Co3O4 photocathode (NCDs/Co3O4/Ti mesh) is designed to work at low/no applied voltage. Electrochemical impedance spectroscopy, incident photo-to-current conversion efficiency, and open-circuit voltage confirmed enhancement in the photogenerated charge transfer efficiency and internal photovoltage, which is due to synergistic effect in combination of two photoelectrodes. Under light-emitting diode (LED) light irradiation and cell voltage of 0.4 V, the system represented high activity and stability (0.0527 min−1 after 20 cycles) and energy efficiency (2.09 kWh m−3 order−1) for sulfadiazine removal. Based on the main •OH-induced reaction, the cooperative operation mechanism of TiO2 NNs/Ti mesh and NCDs/Co3O4/Ti mesh for sulfadiazine degradation was elaborated. Finally, the high performance under real water matrices or real sunlight irradiation without external voltage confirmed the feasibility of this PEC system in practical application for efficient water purification.

The enhancing energy efficiency of sulfadiazine degradation using a DBD-contact plasma treatment process

Nonthermal plasma has attracted extensive attention because of its ability to remove emerging organic micropollutants. However, its high amount of energy consumption severely limits its economic feasibility. In this study, sulfadiazine degradation was achieved in an optimized dielectric barrier discharge (DBD)-Contact system. The sulfadiazine removal in the DBD-Contact/peroxymonosulfate (PMS) system reached 91.8% within 15 min. Compared to a conventional DBD system, the energy efficiency (G50) of the DBD-Contact/PMS system was 4.37 times greater, which meant a saving of 77.17% in electricity consumption. The reactive species generated by discharge plasma were identified as mostly excited nitrogen species in the gas phase, and after transferred to the water phase, OH and SO4− played an important role in the sulfadiazine removal. The hydroxylation of the S-N bond and the nucleophilic reaction of the pyrimidine ring were proposed as mechanisms for the sulfadiazine degradation, and the developmental and acute toxicity was significantly reduced after treatment. Furthermore, the DBD-Contact/PMS system showed good applicability in a wide pH range and complex practical water samples. This study finds that the DBD-Contact/PMS system can degrade antibiotics with high efficiency and low energy consumption and provides new insights for the practical application of DBD technology in water treatment.

UV-induced degradation of contaminants of emerging concern in the presence of monobromoamine: Role of N-Br bond and degradation mechanisms

The N-Br bond in monobromoamine (NH2Br) can be cleaved by UV irradiation to generate Br• and subsequently HO•, resulting in an advanced oxidation condition (i.e., UV/NH2Br). This study investigated the degradation of six contaminants of emerging concern (CECs) in the UV/NH2Br process, including the phenolic hydrocarbons phenol and bisphenol A (BPA), the amines aniline and sulfadiazine (SDZ), and the persistent organic pollutants ibuprofen (IBP) and carbamazepine (CBZ). The results showed that UV/NH2Br process significantly improved the degradation of CECs following pseudo-first order kinetics, and the degradation of CECs was enhanced with the increase of NH2Br dosage. UV/NH2Br was more efficient in degrading CECs containing phenolic hydroxyl groups (100 %), followed by those containing amine groups (> 95 %). The degradation efficiency was influenced by the pH value and was highest at pH 7. It was found that low concentrations of Cl− (< 0.5 mM) and HCO3− (< 0.5 mM) promoted the degradation of SDZ and IBP, but further increases in Cl− and HCO3− (0.5 ∼ 5.0 mM) resulted in inhibition. SDZ and IBP degradation was inhibited by photo absorption competition and free radical depletion in natural organic matter and actual water. Probe experiments showed that reactive bromine species (RBS), reactive nitrogen species (RNS), and hydroxyl radical (HO•) played a dominant role in CEC degradation. During the degradation of IBP by UV/NH2Br, hydroxylation, bromination, and quinylation were proposed as the primary reaction mechanisms. As compared to HOCl disinfection, NH2Cl disinfection after the UV/NH2Br process produced lower concentrations of disinfection by-products (DBPs).

2D defect-engineered Ag-doped γ-Fe2O3/BiVO4: The effect of noble metal doping and oxygen vacancies on exciton-triggering photocatalysis production of singlet oxygen

The selectivity of singlet oxygen (1O2) holds promising applications in complex environmental systems due to its ability to preferentially oxidize target pollutants. Usually, 1O2 in photocatalytic systems is generated via the electron transfer pathway and •O2− plays an important role as an intermediate, while the exciton-based energy transfer pathway for 1O2 generation has been less studied. Here, a 2D Ag-γ-Fe2O3/BiVO4 with oxygen vacancies was designed which was capable of generating 1O2 by an exciton-based energy transfer-dominated approach, as strongly demonstrated by the results of steady-state fluorescence spectroscopy and phosphorescence spectroscopy. In the Z-type heterojunction photocatalyst system, Ag acted as an electron mediator to promote not only the generation of free carriers but also the generation of singlet excitons, while the appropriate concentration of oxygen vacancies further promotes the exciton-triggering photocatalysis production of 1O2. The Ag-γ-Fe2O3/BiVO4 could degrade 99.4% of sulfadiazine within 90 min, and 1O2 played an important role in the degradation of sulfadiazine, as shown by EPR and active species capture experiments. Ecotoxicity predictions indicated that the main byproducts of sulfadiazine degradation by Ag-γ-Fe2O3/BiVO4 were low in toxicity. The prepared photocatalysts provide a new idea for obtaining 1O2 and designing photocatalysts with selectivity.