Toxicity Of Intermediate Products Research Articles

Non-radical activation of peroxymonosulfate for degradation of antibiotics in saline environments by biochar flakes prepared with molten salt strategy

Due to the serious interference of inorganic salts, it is very important to develop a peroxymonosulfate (PMS) oxidation system that can operate normally and efficiently in saline environments. Herein, the Fe-N-doped biochar flakes (FSBC) derived from sesame powder were developed with the help of molten salt strategy for activating PMS to achieve efficient degradation of tetracycline in salt environment. The effect of calcination temperature on physical and chemical properties was studied to further optimize the performance of the catalyst. FSBC-800 showed the best activation performance for PMS, with a TC removal rate of ∼ 94 % within 10 min. Mechanism research shows that FSBC-800 activates PMS through singlet oxygen (1O2) and electron transfer, so the reaction system is extremely selective and can almost avoid interference from various inorganic ions. The FSBC-800/PMS system can operate efficiently in the coexistence of 8 common anions/cations (0–250 mM), and salinity of 0.1–5.0 wt% has almost no negative impact on the system. In addition, possible degradation pathways of tetracycline were proposed, and the toxicity of intermediate products during the degradation process was evaluated. This study provides a PMS oxidation system with strong selectivity that can cope with various complex saline environments.

Construction of rGO-Bi2Sn2O7-NiFe2O4 nanoheterojunction system for the enhanced photodegradation of doxycycline: A brief insight on degradation kinetics and toxicological evaluation on Allium cepa

In this study, the rGO-Bi2Sn2O7-NiFe2O4 nanocomposite (RBN NCs) was fabricated using an in-situ hydrothermal method and applied for the effective aqueous degradation of doxycycline (DOX). Various analytical techniques were employed to characterize the physicochemical properties of the fabricated nanoparticles, including TEM, UV–Vis, PL, FE-SEM, ESR, DRS, XPS, XRD, and N2 adsorption and desorption analysis. The efficiency of DOX degradation by the RBN system under different conditions was evaluated. Under optimal conditions (RBN concentration = 50 mg/L and pH = 7.0), the NCs removed 99.1% of DOX (10 mg/L) within 270 min under visible light irradiation. ESR and scavenging tests illustrated that the developed system produced O2⦁- radicals, which played a dominant role in the complete degradation of DOX. The mineralization of DOX was confirmed by total organic carbon results. The RBN system displayed exceptional reusability over six consecutive cycles and could be easily removed from treated water due to its magnetic properties. The toxicity of the end-product after degradation was assessed against Escherichia coli (gram-negative) and Bacillus subtilis (gram-positive). Additionally, GC-MS analysis was conducted to predict the possible photodegradation pathway of DOX, providing a better understanding of the degradation process. Toxicity of intermediate products was also estimated computationally using the ECOSAR software. The fabricated RBN was further investigated for genotoxicity towards Allium cepa. This study provides new insights into the RBN system for environmental remediation.

High-performance carbon@ metal oxide nanocomposites derived metal–organic framework-perovskite hybrid boosted microwave-induced catalytic degradation of norfloxacin: Performance, degradation pathway and mechanism

Herein, FeCo@C-LFCx (FeCo@C-xLaFeCoO3) materials were prepared by high-temperature carbonation based on the construction of Fe/Co metal–organic framework columns with LaCoO3 (FeCo-MOF-LFCx) by in-situ extraction and synchronous coordination growth strategy. This strategy could improve the defects of perovskite materials such as easy aggregation, poor stability and poor specific surface area. The results demonstrated that the degradation rate of FeCo@C-LFC1.0 for norfloxacin (NOR, 20 mg/L) was 93.81% within 15 min. Co-BTC column nanocolumns and spongy Fe-BTC were successfully formed. Compared with LaFeCoO3, the specific surface area (89.9 m2/g) and pore volume (0.101 cm3/g) of FeCo@C-LFC1.0 after carbonization were increased by 16.3 times and 9.2 times, respectively. FeCo@C-LFCx could produce more structural defects and coordination unsaturated sites, promote microwave absorption. Vo and C = O on the material surface were involved in the activation of PMS. Moreover, quenching experiments and EPR verified that 1O2, OH, and SO4− were the main reactive radicals in the degradation process. The FeCo@C-LFC1.0 showed excellent reusability and stability. After five experiments, the removal rate of NOR remained at 91.15%. The toxicity of intermediate products was reduced. This work provided new avenues for using FeCo@C-LFC1.0 for environmental remediation.

Efficient degradation of 2,4-dichlorophenol by heterogeneous electro-Fenton using bulk carbon aerogels modified in situ with FeCo-LDH as cathodes: Operational parameters and mechanism exploration

In this study, an in situ grown FeCo-Layered double hydroxide anchored to the surface of a bulk carbon aerogel (FeCo-LDH/CA) for contaminant degradation during the heterogeneous electro-Fenton (EF) process. The results exhibited that the FeCo-LDH/CA cathode achieved 100% of 2,4-dichlorophenol (2,4-DCP = 20 mg/L) degradation within 120 min at pH = 3, application current 20 mA, and Na2SO4 concentration 0.05 M. Moreover, the degradation efficiency was impressive in the range of pH = 2–9. The coexistence of the Fe (III)/Fe (II) and Co (III)/Co (II) as active sites on the cathode surface promoted the in-situ decomposition of H2O2 to form reactive oxygen species (ROS). •OH and O2- were confirmed to be the major degradation pollutants of ROS. Furthermore, density functional theory (DFT) was used to predict the reaction sites of 2,4-DCP, and its possible degradation pathways were proposed. The toxicity of intermediate products was evaluated and decreased after degradation. In addition, the eight cycle experiments and the degradation of other typical contaminants demonstrated the satisfactory stability and applicability of the synthetic cathode. This study presents the preparation of an efficient and stable EF cathode, further promoting the application of iron-based composites in wastewater treatment.

Efficient degradation of the refractory organic pollutant by underwater bubbling pulsed discharge plasma: performance, degradation pathway, and toxicity prediction.

It is essential to develop an efficient technology for the elimination of refractory contaminants due to their high toxicity. In this study, a novel underwater bubbling pulsed discharge plasma (UBPDP) system was proposed for the degradation of Orange II (OII). The degradation performance experiments showed that by enhancing the peak voltage and pulse frequency, the degradation efficiency of OII increased gradually. The removal efficiencies under different air flow rates were close. Reducing OII concentration and solution conductivity could promote the elimination of OII. Compared with neutral and alkaline conditions, acidic condition was more beneficial to OII degradation. The active species including ·OH, ·O2-, 1O2, and hydrated electrons were all involved in OII degradation. The concentrations of O3 and H2O2 in OII solution were lower than those in deionized water. During discharge, the solution pH increased while conductivity decreased. The variation of UV-vis spectra with treatment time indicated the effective decomposition of OII. Possible degradation pathways were speculated based on LC-MS. The toxicity of intermediate products was predicted by the Toxicity Estimation Software Tool. Coexisting constituents including Cl-, SO42-, HCO3-, and humic acid had a negative effect on OII removal. Finally, the comparison with other technology depicted the advantage of the UBPDP system.

S-doped core–shell heterojunction Fenton catalyst (Fe3O4-S@PVP@UIO-66-(SH)2) for enhanced activation of hydroxyl radicals: Synergistic enrichment and degradation mechanism

The design of catalysts for the rapid activation of H2O2 and synergistic enrichment of pollutants is an effective strategy to improve catalytic performance. Herein, an Fe3O4-S@PVP@UIO-66-(SH)2 (FPUSH) heterojunction was successfully synthesized to form a core–shell-doped multiphase Fenton catalyst with both internal doping and outer encapsulation structures, which had excellent mass and efficient electron transfer performance. Levofloxacin can be adsorbed (Qmax was 141.44 mg g−1) and degraded at a removal efficiency of 97.70% within 120 min. The recycled efficiency of FPUSH was maintained at more than 90% after five recycles. The experimental and DFT results showed that the introduction of S improved the electron density of Fe atomic orbitals, promoted the electron transfer of Fe(II)/Fe(III), and enhanced the catalytic performance of Fe active sites. The degradation pathway of LVFX and the toxicity of intermediate products were predicted. This work provides new ideas and insights for the application of nonmetals in high-performance multiphase Fenton systems.

Sulfur anchored on N-doped porous carbon as metal-free peroxymonosulfate activator for tetracycline hydrochloride degradation: Nonradical pathway mechanism, performance and biotoxicity

Dual heteroatoms doping is an efficient method to improve catalytic activity of carbon materials. In this research, N, S co-doped porous carbon material (S-NPC) was prepared by direct thermal reduction method of metal organic frameworks and proved to be an excellent metal-free heterogeneous Fenton-like catalyst for peroxymonosulfate (PMS) activation. Tetracycline hydrochloride (TC) could be completely degraded in a short time of 20 min with 20 mg S-NPC and 10 mg PMS at 25 °C, attributing that N, S co-doping provided more defects (ID/IG = 0.998) to produce more active sites for PMS activation. Based on the results from radical identification, scavenging tests, density functional theory (DFT) and electrochemical analysis, non-radical pathway based on singlet oxygen (1O2) and electron transfer was proposed to be the dominant way in the S-NPC/PMS system and the contribution rate was about 95.872 %. Three possible pathways of TC degradation were proposed by high resolution liquid chromatography-mass spectrometry (LC-MS) and the toxicity of intermediate products was lower than TC. This study provided a novel strategy to degrade pollutants by preparing efficient co-doping metal-free Fenton-like catalyst.

High stable photo-Fenton-like catalyst of FeP/Fe single atom-graphene oxide for long-term antibiotic tetracycline removal

The Fenton-like reaction has always suffered from the disadvantages of narrow pH and poor stability. Herein, a Fenton-like catalyst with dual-photo-functional sites of iron phosphide (FeP) and Fe single atom-graphene oxide (Fe1-GO) nanocomposite was constructed to activate H2O2 for antibiotic tetracycline (TC) pollutants removal. Under visible light irradiation, the degradation efficiency of TC reached 100 % within 30 min by FeP/Fe1-GO was 1.36 and 2.32 times than single component of FeP and Fe1-GO. Noteworthy, an extremely long-term stability with 100 times of recycling is achieved and the present system also bear a broad pH range with 3–11. The efficient charge separation and rich Fe single atoms active sites contribute the well Fe3+/Fe2+ cycles to support long-term multiple recycles. Finally, the TC degradation pathway and the toxicity of intermediate products were inferred. This work provides a way to construct high-stable Fenton-like catalyst via dual-photo-functional sites together with single atoms strategy.

Satisfactory degradation of tetracycline by a pH-universal MnFe-LDH@BC cathode in electric Fenton process: Performances, mechanisms and toxicity assessments

The ubiquitous and ineffective treatment of antibiotics in aquatic systems leads to serious environmental problems, threatening ecology and human health. Herein, layered double metal hydroxides (LDH) and biochar (BC) were successfully combined through a facile hydrothermal method to prepare a novel pH-universal electric Fenton (EF) cathode (MnFe-LDH@BC). The developed MnFe-LDH@BC-EF system exhibited superior performance in the degradation of tetracycline (TC) (94.2%) than both of MnFe-LDH-EF (64.1%) and BC-EF system (67.0%) and showed a well-pleasing performance in a wide pH range. It was proposed that the nanostructures of LDH favored the multivalent cycle of Fe and Mn, promoting the electron transfer of BC as well as the release of Fe2+, leading to continuously generation of extensive free radicals and non-radicals. The co-existing ions (Cl-, NO3-, CO32-, HCO3- and H2PO4-) had different impact on the removal of TC. The studied system exhibited satisfactory degradation of various selected contaminants as well as fantastic stability in successive cycles. The possible degradation pathways were proposed and the toxicity of intermediate products were assessed by the Estimation Program Interface (EPI) Suite analysis. This work demonstrated the great potential of the developed cathode in water treatment area and provided insights into the utilization of biomass waste resources.

Fabricating an oxygen-vacancy-rich urchin-like Co3O4 nanocatalyst to boost peroxymonosulfate activation to degrade high-concentration crystal violet

Due to the in-situ generation of reactive oxygen species (ROS), sulfate radical-based advanced oxidation processes (SR-AOPs) have emerged for the oxidative degradation of organic contaminants. Developing highly efficient heterogeneous catalysts is of great importance for SR-AOPs. In this work, an urchin-like Co3O4 nanocatalyst with oxygen vacancies (VO) was elaborately fabricated and employed for enhanced peroxymonosulfate (PMS) activation to degrade the high-concentration active dye crystal violet (CV). The obtained sample was characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and N2 adsorption/desorption isotherms. Characterization results indicated that this unique VO-rich urchin-like Co3O4 nanocatalyst was endowed with a larger surface area and abundant reactive sites for PMS adsorption and activation. The experimental results of CV degradation showed that nearly complete removal of 100 mg L−1 CV could be realized within 30 min of reaction time under neutral conditions at room temperature, and the degradation process followed retarded-first-order kinetics. Electron paramagnetic resonance (EPR) spectra accompanied by quenching experiments of radicals demonstrated that the contribution of ROS to CV degradation followed this sequence: 1O2 > ▪OH > SO4▪- > O2▪-. The degradation pathways of CV were proposed by a combination of density functional theory (DFT) calculations along with frontier orbit theory while the toxicity of intermediate products was evaluated by quantitative structure-activity relationship (QSAR) prediction.

High efficiently piezocatalysis degradation of tetracycline by few-layered MoS2/GDY: Mechanism and toxicity evaluation

A new strategy for the degradation of tetracycline in water by the piezo-catalysis of MoS2 doped with graphdiyne was proposed. The optimally doped MoS2/GDY-3 had a few and thin layer structure, and PFM characterization showed that the piezoelectric response of MoS2/GDY-3 was 35.29% higher than that of MoS2. MoS2/GDY-3 exhibited excellent catalytic activity, and the degradation rate of tetracycline reached 92.15% after 40 min by ball milling to trigger piezoelectric catalysis. After 5 cycles, the degradation rate reached 87.15%, which demonstrates the stability of the material. The influence of the MoS2/GDY-3 dosage, ball milling speed, TC concentration, pH, inorganic anions and water source on the degradation efficiency were investigated. ESR characterization showed that ∙OH and ∙O2– were the main active radicals of the piezoelectric catalysis. By analyzing the intermediate products, the possible degradation path of tetracycline was further analyzed, and a suitable mechanism of piezoelectric catalysis was proposed. The toxicity of intermediate products was evaluated to explore the toxicity changes in the degradation process. This work provides a new approach for changing the morphology of MoS2 to enhance its piezocatalytic performance and effectively degrade tetracycline in water.

Efficiency assessment of Cu and Al electrodes in the removal of anthraquinone based disperse dye aqueous solution in electrocoagulation–an analytical approach

ABSTRACT Anthraquinone dyes are tough to degrade compared to azo dyes, due to the resonance in the anthracene structure that leads to more difficulty in the removal and challenges the possibility of an effective decolouration/degradation process. The purpose of this study was to examine the effect of copper and aluminium electrodes in electrocoagulation process for the elimination of an anthraquinone based aqueous solution of Red BFL dye. The efficiency of the electrodes in the dye removal was studied using X-Ray Photoelectron Spectroscopy of the collected sludge, in terms of the respective M(OH)n formation which contributes in coagulation of the dispersed dye molecules and the results indicated that Al formed four types of hydroxides and Cu only one type. The maximum removal of the dye solution obtained with Al was 99.17% at the optimum conditions: pH 8, contact time 15 min, current density 40 A m−2, and 91.88% with Cu: pH 9, contact time 25 min and current density 60 A m−2. Phytotoxicity and ecotoxicity studies with Vigna radiata and Artemia salina was done to investigate the toxicity of intermediate products in the treated Red BFL dye solution, results showed that the Al used Red BFL dye solution was less toxic in comparison to copper. Abbreviation: EC: Electrocoagulation; AQ: Anthraquinone; CD: Current density; CT: Contact time; ECE%: Efficiency in Colour Elimination percentage; HPLC: High-performance liquid chromatography; XPS: X-ray photoelectron spectroscopy; V. radiata: Vigna radiata; A. salina: Artemia salina

Photodegradation of gemfibrozil in aqueous solution under UV irradiation: kinetics, mechanism, toxicity, and degradation pathways.

The lipid regulator gemfibrozil (GEM) has been reported to be persistent in conventional wastewater treatment plants. This study investigated the photolytic behavior, toxicity of intermediate products, and degradation pathways of GEM in aqueous solutions under UV irradiation. The results demonstrated that the photodegradation of GEM followed pseudo-first-order kinetics, and the pseudo-first-order rate constant was decreased markedly with increasing initial concentrations of GEM and initial pH. The photodegradation of GEM included direct photolysis via (3)GEM(*) and self-sensitization via ROS, where the contribution rates of degradation were 0.52, 90.05, and 8.38% for ·OH, (1)O2, and (3)GEM(*), respectively. Singlet oxygen ((1)O2) was evidenced by the molecular probe compound, furfuryl alcohol (FFA), and was identified as the primary reactive species in the photolytic process. The steady-state concentrations of (1)O2 increased from (0.324 ± 0.014) × 10(-12) to (1.021 ± 0.040) × 10(-12)molL(-1), as the initial concentrations of GEM were increased from 5 to 20mgL(-1). The second-order rate constant for the reaction of GEM with (1)O2 was calculated to be 2.55 × 10(6)M(-1)s(-1). The primary transformation products were identified using HPLC-MS/MS, and possible photodegradation pathways were proposed by hydroxylation, aldehydes reactions, as well as the cleavage of ether side chains. The toxicity of phototransformation product evaluation revealed that photolysis potentially provides a critical pathway for GEM toxicity reduction in potable water and wastewater treatment facilities.

Degradation of gas–liquid gliding arc discharge on Acid Orange II

The effects of pH value, initial concentration of dye solution and temperature on the degradation efficiency of Acid Orange II (AO7) using gas–liquid gliding arc discharge were investigated. The influences of pH value and temperature on degradation efficiency were not apparent. Increasing initial solution concentration caused the decrease of degradation rate and the increase of absolute degradation quantity. Considering energy efficiency and absolute degradation quantity, the gas–liquid gliding arc discharge is fit for treating high concentration organic wastewater. A possible mineralization pathway was proposed through the analysis of intermediate products detected by gas chromatograph coupled with mass spectrophotometer (GC–MS) and ion chromatograph (IC). Hydroxyl radicals reacted with the azo linkage-bearing carbon of a hydroxy-substituted ring, leading to the cleavage of C N and degradation of AO7. The solution biodegradability was significantly improved (BOD 5/COD from 0.02 to 0.43). The toxicity of intermediate products was lower than that of the initial Acid Orange II.