Degradation Of Sulfamethazine Research Articles

Fe3+/Fe2+ cycle promoted peroxymonosulfate activation with addition of boron for sulfamethazine degradation: Efficiency and the role of boron

Boron was used as an environmentally friendly and efficient reductant to accelerate the recycle of Fe2+ enhancing peroxymonosulfate (PMS) activation for sulfamethazine (SMT) degradation. The SMT removal was only 28.1% within 30 min in Fe2+/PMS system while SMT removal could reach to 98.9% within only 3 min in Boron/Fe2+/PMS (B/Fe2+/PMS). Electron paramagnetic resonance spectroscopy (EPR) tests, quantitative detection and radical quenching experiments illustrated that OH and SO4− played important role and Fe(IV), 1O2 and O2− also participated in SMT removal. The addition of boron could enhance the role of OH and SO4− in SMT removal in Fe2+/PMS system. X-ray photoelectron spectroscopy (XPS), electrochemical tests and density functional theory (DFT) calculation were conducted to confirm the mechanism of boron for accelerating the recycle of Fe2+. Possible SMT degradation pathway was proposed. B/Fe2+/PMS process could efficiently remove SMT at low Fe2+ dosage and neutral pH. B/Fe2+/PMS system also exhibited a superior resistance to inorganic ions and nature organic matters. Moreover, B/Fe2+/PMS system had good applicability to different pollutants, excellent reusability for antibiotics removal, and efficient performance for removing antibiotics in nature fresh water. The results compared with others’ works also demonstrated the present study process was a promising strategy for antibiotics removal.

Template-free hierarchical trimetallic oxide photocatalyst derived from organically modified ZnCuCo layered double hydroxide

High-performance photocatalysts have considerable potential to address energy and environmental issues. In this study, dodecylbenzenesulfonate (DBS) modified ZnCuCo layered double hydroxide (DBS-ZnCuCo LDH) microspheres were synthesized through the facile template-free hydrothermal method. Subsequently, ZnCuCo mixed-metal oxides (MMOs) with morphological features of the DBS modified LDH, enhanced surface area, increased light absorption and effective charge separation were prepared by the calcination of the as-synthesized LDH at 650 °C. Structural, morphological, and photoelectrochemical properties of ZnCuCo and DBS-ZnCuCo LDHs and the corresponding MMOs (ZnCuCo MMO1 and ZnCuCo MMO2) were investigated. SEM and TEM images revealed that DBS-ZnCuCo LDH and ZnCuCo MMO2 possess 3D flower-like hierarchical morphologies with interlaced petal-like nanosheets. Although ZnCuCo LDH was inactive for photocatalytic H2 production under visible light irradiation, ZnCuCo MMO2 exhibited a high H2 production rate (3700 μmol g−1 h−1), benefiting from the synergy of the ZnO, CuO, and Co3O4. Furthermore, 95% sulfamethazine (SMZ) degradation was obtained after 60 min of photocatalysis, which is considerably higher than the degradation efficiency of ZnCuCo LDH (24%) and ZnCuCo MMO1 (58%). Based on the photoelectrochemical tests, Z-scheme and double charge transfer mechanisms were proposed to explain the enhanced photocatalytic H2 production and degradation of SMZ. Scavenging tests revealed that O2•− radicals were the main reactive species in the photodegradation of SMZ. A possible degradation pathway was proposed based on the detection of intermediate products.

A comparative study on the activation of persulfate by mackinawite@biochar and pyrite@biochar for sulfamethazine degradation: The role of different natural iron-sulfur minerals doping

In this work, two novel heterogeneous catalysts were prepared by loading natural mackinawite (FeS) and pyrite (FeS2) particles into peanut shell-derived biochar (i.e., FeS@BC and FeS2@BC), and the persulfate (PS) activation processes by these two composites for sulfamethazine (SMT) degradation were systematically examined. After doping natural iron-sulfur ores, the catalytic removal performance of the above two composites were 37.2%–80.0% and 31.0%–35.2% higher than those of their respective original minerals and primitive biochar. Simultaneously, FeS@BC had better catalytic performance than FeS2@BC. The larger specific surface areas, abundant micropores, higher defect degree, better conductivity and FeS crystals favored the release of more iron, resulting in higher reaction stoichiometric efficiency (RSE) value, excellent catalytic activity, and enhanced SMT mineralization. In the FeS@BC/PS system, surface ketonic groups (C = O), Fe(II), and highly active S-thiophene groups all accounted for PS activation. In the FeS2@BC/PS system, C = O groups, Fe(II), highly reductive S2−/Sn2– species, and graphene structure participated in the catalytic reaction. The electron-rich S-thiophenic groups, S2−/Sn2– species, and ketonic moieties could act as electron donors, prompting the regeneration of Fe(II) in the lattice (≡Fe(II)) and solution (Fe2+) by direct or indirect electron transfer. In view of the higher catalytic activity of FeS@BC, we further investigated different influencing factors on SMT degradation, activation mechanism, and degradation pathway of SMT in the FeS@BC/system. Overall, this study would fill the gap in the research on the difference in the catalytic activity of catalysts prepared by loading different natural iron-sulfur minerals onto biochar for persulfate activation.

Copper exposure effects on antibiotic degradation in swine manure vary between mesophilic and thermophilic conditions

Antibiotic and heavy metal commonly coexist in manure. This study investigated the effect of Cu exposure on antibiotic dissipation in swine manure under two typical temperature (mesophilic and thermophilic) conditions in composting, focusing on biodegradation behaviors. The results showed that Cu promoted the dissipation of norfloxacin and sulfamethazine (SMZ) in solid swine manure under mesophilic conditions at initial concentrations ranging from 407.8 to 1353.0 mg·kg−1 but insignificantly influenced or even inhibited their dissipation under thermophilic conditions. A liquid manure suspension culture experiment was designed to elucidate the response of SMZ biodegradation to Cu. In this manure suspension, biodegradation was the major mechanism for SMZ removal, but SMZ biodegradation was decreased from 23.2 % to 5.5 % when the Cu concentration increased from 0 to 10 mg L−1. Mesophilic and heat-resistant SMZ-degrading bacterial inoculants were subsequently prepared using 21 SMZ-degrading bacteria that were isolated and identified from manure suspension cultures. Inoculating both mesophilic and heat-resistant SMZ-degrading bacterial inoculants enhanced SMZ degradation in sterilized manure suspensions without Cu addition, however only mesophilic SMZ-degrading inoculum improved SMZ degradation after Cu addition. In the presence of Cu, the heat-resistant SMZ-degrading inoculum failed to enhance SMZ removal in manure suspensions. Our findings can help to answer why Cu has varied effects on antibiotic degradation during manure composting.

Sulfur or nitrogen-doped rGO supported Fe-Mn bimetal – organic frameworks composite as an efficient heterogeneous catalyst for degradation of sulfamethazine via peroxydisulfate activation

In this work, sulfur/nitrogen modified reduced graphene oxide (S/N-rGO) was employed as both electron shuttle and support to fabricate Fe-Mn bimetallic organic framework@S/N-rGO hybrids (BOF@S/N-rGO) via a facile two-step solvothermal route. Compared with the transition metal ions (Fe2+/Mn2+), the classical metal oxide catalyst (Fe2O3 and Fe3O4) and nano zero-valent iron (nZVI), BOF@S/N-rGO catalyst can more effectively activate peroxydisulfate (PDS) with ultra-low concentration (0.05 mM) to degrade sulfamethazine (SMT). Quenching experiments, electron paramagnetic resonance (EPR) measurement and linear sweep voltammetry (LSV) showed that the activation pathways of PDS between the two catalysts were different. In BOF@N-rGO+PDS system, the degradation of SMT was mainly attributed to the oxidation of radicals including SO4•− and •OH, especially SO4•− . However, in BOF@S-rGO+PDS system, in addition to the radical pathway, there are also non-radical pathways, namely 1O2 and direct electron transfer. Furthermore, the applicability of BOF@S/N-rGO used in the PDS-mediated advanced oxidation processes (AOPs) was systematically investigated in terms of the effects of operating parameters and coexisting substance (anions and humic acid (HA)), the degradation of other pollutants, as well as the stability and reusability of the catalyst. This study proved that BOF@S/N-rGO was a promising activator of PDS with ultra-low concentration for the degradation of SMT.

Oxidation of sulfamethazine by a novel CuS/calcium peroxide/tetraacetylethylenediamine process: High efficiency and contribution of oxygen-centered radicals

Calcium peroxide (CP)-based advanced oxidation processes for water decontamination have stimulated considerable attention due to their inherent merits. Herein, a novel tetraacetylethylenediamine (TAED) coupled CuS/CP (i.e., CuS/TAED/CP) process was tentatively employed for the degradation of sulfamethazine (SMT) in water. Experimental results suggested that peracetic acid (PAA) could be efficiently generated and then activated by CuS in alkaline media, achieving 92.1% removal of SMT in 30 min. Identification of reactive oxygen species (ROS) revealed that the available ROS including hydroxyl radical (•OH), singlet oxygen (1O2), and oxygen-centered radicals (R − O•) together accounted for SMT degradation. Based on quantitative analysis of the relative contribution of involved ROS, R − O• were validated to be the primary reactive species that contributed to 75.2% of SMT removal. Additionally, the role of superoxide radical (O2•−), sulfur species, and calcium hydroxide (Ca(OH)2) were investigated. It was concluded that the O2•− and reductive sulfur species enabled the promoted redox cycle of Cu species, and the Ca(OH)2 generated from CP favored the efficient generation and activation of PAA. Influencing factors like CP dosage, initial pH, and nontarget matrix constituents were also evaluated. Moreover, degradation pathways of SMT were proposed, and the ecotoxicity of these intermediates was predicted. The present work provides a promising and simple approach for the rapid decontamination of antibiotic-polluted water.

An innovative S-scheme AgCl/MIL-100(Fe) heterojunction for visible-light-driven degradation of sulfamethazine and mechanism insight

The development of high efficient photocatalysts for antibiotics contamination in water remains a severe challenge. In this study, a novel step-scheme (S-scheme) photocatalytic heterojunction nanocomposites were fabricated from integrating AgCl nanoparticles on the MIL-100(Fe) octahedron surface through facile multi-stage stirring strategy. The S-scheme heterojunction structure in AgCl/MIL-100(Fe) (AM) nanocomposite provided a more rational utilization of electrons (e-) and holes (h+), accelerated the carrier transport at the junction interface, and enhanced the overall photocatalytic performance of nanomaterials. The visible-light-driven photocatalysts were used to degrade sulfamethazine (SMZ) which attained a high removal efficiency (99.9%). The reaction mechanisms of SMZ degradation in the AM photocatalytic system were explored by electron spin resonance (ESR) and active species capture experiments, which superoxide radical (•O2-), hydroxyl radical (•OH), and h+ performed as major roles. More importantly, the SMZ degradation pathway and toxicity assessment were proposed. There were four main pathways of SMZ degradation, including the processes of oxidation, hydroxylation, denitrification, and desulfonation. The toxicity of the final products in each pathway was lower than that of the parent according to the toxicity evaluation results. Therefore, this work might provide new insights into the environmentally-friendly photocatalytic processes of S-scheme AM nanocomposites for the efficient degradation of antibiotics pollutants.

Insights into transition metal encapsulated N-doped CNTs cathode for self-sufficient electrocatalytic degradation

In electrochemical advanced oxidation processes (EAOPs), a series of transition metal encapsulated nitrogen-doped carbon nanotubes (M@N-C, M=Fe, Co, Ni, Cu) as bifunctional cathodes were synthesized to compare and uncover their activity trends, fulfilling the self-sufficient electrocatalytic degradation. The sulfamethazine (SMT) degradation activity trends were follows: Co@N-C>Fe@N-C>Ni@N-C>Cu@N-C cathode at pH≤ 7, while the Fe@N-C cathode exhibited the highest activity at pH 9 due to the more 1O2 and atomic H*. In-situ Fourier transformed infrared (FTIR) spectroscopy and density functional theory (DFT) calculation suggested that the atomic H* was easier to generate under the action of pyridinic N on Fe@N-C cathode. Overall, various pollutants degradation on Fe@N-C cathode performed with good stability with low leaching iron (0.12 mg L−1) and low energy consumption (<0.3 kWh∙log−1∙m−3). This study sheds light on different mechanisms of reactive species production on M@N-C cathode, thus providing guidance for the selectivity between M@N-C via active species and pollutants.

Insights into a novel CuS/percarbonate/tetraacetylethylenediamine process for sulfamethazine degradation in alkaline medium

This work presents a novel CuS/percarbonate/tetraacetylethylenediamine (CuS/SPC/TAED) process for the degradation of sulfamethazine (SMT). Results indicated that the CuS/SPC/TAED process enabled the efficient generation of peracetic acid (PAA), which can be efficiently activated by CuS in alkaline reaction media, and 93.6% of SMT was degraded in 30 min. Mechanism study revealed that the available reactive oxygen species (ROS) including hydroxyl radical (•OH), carbonate radical (CO3•−), superoxide radical (O2•−), singlet oxygen (1O2), and organic radicals (R−O•). Among them, R−O• (acetyloxyl radical (CH3CO2•) and acetylperoxyl radical (CH3CO3•)) were confirmed to be the primary species that contributed to SMT degradation. Simultaneously, the role of sulfur species and carbonate ions were explored. It was found that the reductive O2•− and sulfur species rendered the efficient redox of Cu species. Besides, the effects of key influencing factors including SPC/TAED mole ratio, CuS dosage, initial pH, temperature, and nontarget matrix constituents on SMT degradation were examined. Finally, the degradation intermediates of SMT was identified, and the toxicity of these products was estimated by quantitative structure-activity relationship (QSAR) analysis. Overall, this work offers a new and simple strategy for antibiotic-polluted water remediation.

Efficient degradation of sulfamethazine in a silicified microscale zero-valent iron activated persulfate process

Microscale zero-valent iron (mZVI) is used as a catalyst for peroxide activation and, has attracted considerable attention for the degradation of organic contaminants. However, surface inherent oxide films impedes electron transfer in mZVI and decrease its activation efficiency. Herein, the mZVI surface was modified by sodium disilicate (Si-mZVIbm) using a mechanical ball-milling approach. The mechanochemically silicified mZVI enhanced the sulfamethazine removal rate by 2.9–23.8 fold in relation to unmodified ZVI; this rate increased with the Si/Fe molar ratio (0–8%). Reactive intermediates, including radicals and non-radicals, were efficiently generated via peroxydisulfate (PDS) activation over Si-mZVIbm both SO4•- and Fe(IV) contributed toward sulfamethazine removal. The excellent performance of PDS activation over Si-mZVIbm particles was attributed to the continuous generation of ferrous ions, which was due to the accelerated iron release and more effective Fe3+/Fe2+ cycles in the Si-mZVIbm/PDS system after silicification.

A novel Z-scheme NH2-MIL-125(Ti)/Ti3C2 QDs/ZnIn2S4 photocatalyst with fast interfacial electron transfer properties for visible light-driven antibiotic degradation and hydrogen evolution

Herein, a novel all-solid-state Z-scheme NH2-MIL-125(Ti)/Ti3C2 MXene quantum dots/ZnIn2S4 (Ti-MOF/QDs/ZIS) photocatalyst was prepared, then applied for photocatalytic antibiotic (tetracycline and sulfamethazine) degradation and hydrogen evolution under visible light. The Z-scheme Ti-MOF/QDs/ZIS photocatalyst afforded very efficient degradation of tetracycline (TC, 96% in 50 min) and sulfamethazine (SMZ, 98% in 40 min), as well as a high rate of hydrogen generation (2931.9 μmol g-1 h−1) under visible light irradiation. Trapping studies showed superoxide radicals (•O2−) to be the main active species for antibiotic degradation, with the intermediates formed during antibiotic photo-oxidation identified by liquid chromatography-mass spectrometry. Photocatalyst recycling studies showed the Z-scheme composite photocatalyst to be stable during both antibiotic photodegradation and hydrogen generation experiments. The Ti3C2 MXene quantum dots facilitated electron transfer between the semiconducting components of Z-scheme composite photocatalyst. This work identifies a promising new Z-scheme photocatalyst system for water purification and solar hydrogen production.

Effect of polystyrene microplastics on the degradation of sulfamethazine: The role of persistent free radicals

Microplastic (MPs) pollution is increasingly becoming a global environmental problem. MPs entering the environment are subjected to various aging processes, among which photoaging is the most important process leading to MPs oxidation. Persistent free radicals (EPFRs) are formed on the surface of MPs during photoaging, but it is not clear whether EPFRs on the surface of MPs can produce reactive oxygen species (ROS) and thus degrade organic pollutants. In this study, with polystyrene (PS) as the representative plastic and sulfamethazine (SMT) degradation as the target pollutant, the effect and mechanism of light-induced PS on SMT degradation were investigated by experiment and theoretical calculation. It was found that PS can stimulate the production of ROS under sunlight, which can significantly improve the degradation rate of SMT. Through quenching experiment and free radical trapping experiment, it was found that the mechanism of PS promoting the degradation of SMT was mainly due to the production of hydroxyl radical (·OH) in the system, and ·OH was the main ROS species affecting the oxidative degradation of SMT. The characterization results show that the high reactive oxygen generation ability of PS under solar irradiation was due to the abundant photoactive oxidation functional groups on its surface. In addition, the key reaction sites of SMT were predicted by density functional theory (DFT) calculation. The results of different calculations consistently showed that the sulfonamide group of SMT, the pyrimidine heterocycle and the amino group of aniline are the reaction sites of ·OH priority attack. The main intermediates were determined by UHPLC-HRMS/MS. Combined with theoretical calculation, it was proposed that the oxidative degradation pathway of SMT mainly includes SN bond cleavage, SMILES rearrangement and SO2 group removal. This study clarified the effect of PS on the degradation of organic pollutants under light, and provided theoretical guidance for the degradation mechanism.

High-efficient degradation of sulfamethazine by electro-enhanced peroxymonosulfate activation with bimetallic modified Mud sphere catalyst

Electrocatalytic oxidation and persulfate (PMS) advanced oxidation were widely favored by researchers, but their wide application has been limited due to poor mass transfer efficiency and poor mineralization rate. In this study, the codoping of rural mud and bimetallic oxides (copper and nickel) (Md-Cu-Ni) was prepared. Then, Md-Cu-Ni was used as a catalyst for electrocatalytic oxidation and PMS advanced oxidation to degrade sulfamethazine (SMT). The structure, surface morphology and catalytic performance of the Md-Cu-Ni were characterized by a series of instruments. The electron spin resonance spectroscopy test results confirmed that Md-Cu-Ni produced a large number of OH and SO4−. The electrochemical workstation confirmed that Md-Cu-Ni had strong electrocatalytic activity and repolarization ability. Then, the result shows that the removal efficiency and mineralization rate by three-dimensional electrocatalytic coupled PMS advanced oxidation technology were 99.56% and 88.63% in 90 min. The effect of the pH, voltage, aeration flow rate, plate spacing, Na2SO4 dosage, potassium peroxymonosulfate sulfate complex salt dosage on SMT degradation was investigated. Moreover, this method also has high degradation efficiency for other 13 organic pollutants. Cycling experiments demonstrated the good stability of Md-Cu-Ni. It was found that 16 intermediates appeared in the degradation process by LC-MS. It was believed that this work provides a new vision for water treatment.

One-step immobilization of tungsten oxide on microporous silica surface as a photocatalyst for water pollutant removal

Improving photocatalytic properties of semi-conductor materials and Band-gap engineering are a major challenge. Herein, we report, a successful immobilization of tungsten oxide and tungstite on the surface of microporous silica by simple one-step method. The surface area decreased from 607 to 588 m 2 /g after immobilization due to the loading of tungsten oxide species on silica pores. While, the band-gap energies were found to be 2.21, 2.41 eV for SiO 2 /WO 3 and SiO 2 /WO 3 –C, respectively. Thereafter, the photocatalytic activity of the composites was studied through the oxidative degradation of sulfamethazine under UV–visible light irradiation, SiO 2 /WO 3 exhibited relatively good stability and reusability after four cycles of photocatalytic experiment in respect to the calcinated sample. The high photocatalytic activity and recyclability of the non-calcinated sample are attributed to the presence of water molecules in tungstite structure, assuming that tungsten oxide species are bonded to microporous silica via hydrogen bond interaction. • One-step immobilization of Tungsten trioxide on the surface of mesoporous silica. • The effect of tungstite and tungsten trioxide structures on the photocatalytic activity. • The role of intercalated water on the stability and reusability of the photocatalyst.

A comparative study of activation of peroxymonosulfate and peroxydisulfate by greigite (Fe3S4) for the degradation of sulfamethazine in water

In this study, greigite (Fe3S4) was used to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) for sulfamethoazine (SMT) degradation in water. The possible influencing factors such as oxidant concentration, sulfur sources, iron sources and initial pH were investigated.Experimental results showed that SMT could be completely removed at 0.1 mM PMS in 15 min in Fe3S4/PMS system. 96.7% of SMT was removed at 1.0 mM PDS in 60 min in Fe3S4/PDS system.Both systems had good performance over a wide pH range of 3–9. In addition, different sulfur sources could affect the crystal structure, morphology and composition of the synthesized catalysts, while different iron sources had little influence. Quenching experiments and electron paramagnetic resonance (EPR) test evidenced that the activation of PMS and PDS by Fe3S4 was a multi-reactive oxygen species process with the coexistence of •OH, SO4•−, O2•− and 1O2. SO4•− was the main active species in the Fe3S4/PMS system, while SO4•− and •OH were the main free radicals in the Fe3S4/PDS system. X-ray photoelectron spectroscopy (XPS) experiments showed that Fe(II) on Fe3S4 surface effectively activated PMS and PDS, and S2− species were key factors controlling Fe(II) regeneration and subsequent activation of PMS and PDS.However, the consumption of Fe(II) and S2− in Fe3S4/PDS system was higher than that in Fe3S4/PMS system. In addition, in the two systems, the degradation intermediates of SMT and their practical application were also evaluated.This study provided a systematic evaluation of the performance of Fe3S4/PMS and Fe3S4/PDS systems for treatment of antibiotic contaminated water.

Degradation of sulfamethazine by amorphous zero-valent iron microspheres (A-mZVI) activated peroxydisulfate in groundwater

Amorphous zero-valent iron microspheres (A-mZVI) were synthesized by introduction of ethylenediamine (EDA) and used to activate peroxydisulfate (PDS) to eliminate sulfamethazine (SMT) in groundwater. Experimental results indicated that the A-mZVI/PDS system exhibited a much better performance in the removal of SMT (93.2%) than conventional crystalline nanoscale ZVI (C-nZVI) induced PDS activation system (45.3%). The A-mZVI/PDS system had a better performance under neutral and alkaline conditions than the acidic condition, showing excellent decontamination performance in actual groundwater. The co-existing groundwater components (Na+, Ca2+, Cl−, SO42−, humic acid) had no obvious impact on the removal of SMT except for HCO3−. Characterization of as-synthesized A-mZVI particles demonstrated that the addition of EDA resulted in the formation of amorphous structure of ZVI, and there is an optimum EDA/Fe(II) molar ratio. It was proposed that the amorphous structure favored the release of electrons from the iron core to the surface of A-mZVI to continuously generate ≡Fe(II), leading to the generation of abundant free radicals (both SO4•−and •OH) via the activation of PDS. The intermediates and possible degradation pathways of SMT were revealed, and the developmental toxicity and bioaccumulation factors of SMT and its intermediates were predicted by quantitative structure-activity relationship (QSAR) analysis.

Comparison of Four Tourmalines for PS Activation to Degrade Sulfamethazine: Efficiency, Kinetics and Mechanisms.

Four types of tourmalines (TMs, S1, S2, S3 and S4) for activating persulfate (PS) to degrade sulfamethazine (SMT) were compared to find the most efficient catalyst. The four TMs were mesoporous materials with abundant functional groups, but were different in terms of size, composition, specific surface area, contact angle, and zero potential point. The removal of SMT in S1, S2, S3 and S4 systems with PS at the optimum reaction conditions ([SMT]0 = 5 mg/L, [PS]0 = 4 mM, [TM]0 = 5 g/L, pH0 = 5, and T = 25 °C) were 99.0%, 25.5%, 26.0%, and 51.0%, respectively, which might be related to the metal content of TM. Although the degradation of SMT in the S1/PS/SMT system was not dominated by SO4•− and •OH, the radicals contributed to the SMT removal in the S2, S3, and S4 systems. 1O2 and holes both contributed to the degradation of SMT in the four systems. The metal at the X position might be related to the generation of 1O2 and holes, while Fe of TM was mainly related to the generation of free radicals, such as SO4•−. Electrochemical impedance spectroscopy tests confirmed that the separation of electrons and holes on the TM surface could be promoted by adding PS and SMT. S1 presented a higher electron-transfer rate than the other three TMs. The PS activation by TM with a high metal content at the X position provided an efficient and low-consumption treatment for antibiotic refractory wastewater.

Degradation of sulfamethazine in water by sulfite activated with zero-valent Fe-Cu bimetallic nanoparticles

In this work, zero-valent Fe-Cu bimetallic nanoparticles were synthesized using a facile method, and applied to activate sulfite for the degradation of sulfamethazine (SMT) from the aqueous solution. The key factors influencing SMT degradation were investigated, namely the theoretical loading of Cu, Fe-Cu catalyst dosage, sulfite concentration and initial solution pH. The experimental results showed that the Fe-Cu/sulfite system exhibited a much better performance in SMT degradation than the bare Fe0/sulfite system. The mechanism and possible degradation pathway of SMT in Fe-Cu/sulfite system were revealed. The reactive radicals that played a dominant role in the SMT degradation process were •OH and SO4•-, while the loading of Cu induced the synergistic effect between Fe and Cu. The redox cycle between Cu(I)/Cu(II) remarkably contributed to the conversion of Fe(III) to Fe(II), greatly enhancing the catalytic performance of Fe-Cu bimetal. In real groundwater applications, the Fe-Cu/sulfite system also exhibited satisfactory SMT degradation. The 30-day aging tests of Fe-Cu particles demonstrated that the aging of catalyst was not obviously affecting the removal of SMT. Furthermore, the reusability of catalyst was evidenced by the recycling experiments. This study provides a promising application of bimetal activated sulfite for enhanced contaminant degradation in groundwater.

Heterogeneous photoelectro-Fenton catalyzed by FeCu@PC for efficient degradation of sulfamethazine

To improve the mineralization efficiency of heterogeneous electro-Fenton (Hetero-EF), ultraviolet (UV) process and Hetero-EF process were coupled (Hetero-PEF) for degradation of sulfamethazine (SMT) by FeCu@PC (porous carbon) derived from metal-organic frameworks (MOFs). At 60 min, the total organic carbon (TOC) removal and mineralization current efficiency (MCE) of the Hetero-PEF process was 73.3% and 58.7%, which were both 2.23 times that of the Hetero-EF process due to the photoelectric synergy. Moreover, the Hetero-PEF process had wider pH applicability (3.0–7.0) than the Hetero-EF process. This process could also efficiently remove phenol, carbamazepine and 2, 4-D. Through process comparison, quenching and electron paramagnetic resonance (EPR) tests, the reasons for the improvement of mineralization efficiency by Hetero-EF process were disclosed, in which UV not only activated H2O2 to produce •OH but also excited FeCu@PC to form photo-generated electrons to catalyze H2O2 or O2 to •OH and O2•−, respectively. In addition, UV excitation of Fe(OH)2+ and Fe(OOCR)2+ promoted the regeneration of Fe2+, which also greatly enhanced the H2O2 conversion efficiency and mineralization current efficiency. In the five cycles of experiments, the removal efficiency of SMT still reached 97.0%. The FeCu@PC/Hetero-PEF process had the application prospect of highly effective removal of organic pollutants in water treatment.

One-step synthesis of F-TiO2/g-C3N4 heterojunction as highly efficient visible-light-active catalysts for tetrabromobisphenol A and sulfamethazine degradation

In order to achieve excellent visible light photoactivity of TiO2, it is still urgently required to extend their optical absorption ability and improve the potential of charge separation and migration. Here we synthesized highly efficient visible-light-active catalysts F-TiO2/g-C3N4 via a one-step-calcination method. Due to the synergic effect of ≡Ti−F, ≡Ti:F−H and the heterojunction, the obtained catalysts possess promising properties as highly efficient separation and migration of photoelectron-hole pairs. The prepared F-TiO2/g-C3N4 heterojunction can be successfully applied to degrade the widely used flame retardants and antibiotics. More than 95% of tetrabromobisphenol A (TBBPA) was decomposed after light illumination for 120 min, and 98% of sulfamethazine (SMZ) was degraded for 60 min by F-TiO2/g-C3N4. Furthermore, a reasonable catalytic mechanism for the F-TiO2/g-C3N4 catalysts was proposed. It could be seen that the active species •O2−, •OH, and h+ played important roles in the photocatalytic process under visible light illumination.