Sulfamethazine Research Articles

Veterinary antimicrobials in cattle feedlot environs and irrigation conveyances in a high-intensity agroecosystem in southern Alberta, Canada

The South Saskatchewan River Basin (SSRB) is considered one of the most intensively farmed regions in Canada, with high densities of livestock and expansive areas of irrigated cropland. We measured concentrations of seven veterinary antimicrobials (VAs) in 114 surface water samples from feedlot environs and 219 samples from irrigation conveyances in the SSRB. Overall, detection frequencies in feedlot environs were 100% for chlortetracycline (CTC) and tetracycline (TC), 94% for monensin (MON), 84% for tylosin (TYL), 72% for lincomycin (LIN), 66% for erythromycin (ERY), and 23% for sulfamethazine (SMZ). For irrigation conveyances, detection frequencies for CTC and TC remained high (94–100%), but dropped to 18% for ERY, 15% for TYL, 10% for MON, and 4% for SMZ. Lincomycin was not detected in irrigation conveyance water. Maximum concentrations of VAs ranged from 1384 µg L−1 (TC) to 17 ng L−1 (SMZ) in feedlot environs while those in irrigation conveyances were 155 ng L−1 (TC) to 29 ng L−1 (ERY). High detection frequencies and median concentrations of VAs in both feedlot environs and irrigation conveyances were associated with high amounts of precipitation. However, an irrigation district (ID) with high livestock density (Lethbridge Northern) did not exhibit higher concentrations of VAs compared to IDs with less livestock, while levels of VAs in irrigation conveyances were less influenced by the degree of surface runoff. The ubiquity of CTC and TC in our study is likely a reflection of its widespread use in intensive livestock operations. Additional investigation is required to link environmental concentrations of VAs with livestock densities and increase our understanding of potential antimicrobial resistance in high-intensity agroecosystems.

High-Sensitive FAM Labeled Aptasensor Based on Fe3O4/Au/g-C3N4 for the Detection of Sulfamethazine in Food Matrix.

In this study, we developed a fluorescent aptasensor based on Fe3O4/Au/g-C3N4 and a FAM-labeled aptamer (FAM-SMZ1S) against sulfamethazine (SMZ) for the specific and sensitive detection of SMZ in food matrix. The FAM-SMZ1S was adsorbed by the Fe3O4/Au/g-C3N4 via π–π stacking and electrostatic adsorption, serving as a basis for the ultrasensitive detection of SMZ. Molecular dynamics was used to explain the reasons why SMZ1S and SMZ were combined. This aptasensor presented sensitive recognition performance, with a limit of detection of 0.16 ng/mL and a linear range of 1–100 ng/mL. The recovery rate ranged from 91.6% to 106.8%, and the coefficient of variation (CV) ranged from 2.8% to 13.4%. In addition, we tested the aptasensor for the monitoring of SMZ in various matrix samples, and the results were well-correlated (R2 ≥ 0.9153) with those obtained for HPLC detection. According to these results, the aptasensor was sensitive and accurate, representing a potentially useful tool for the detection of SMZ in food matrix.

Oxidation of sulfamethazine by peracetic acid activated with biochar: Reactive oxygen species contribution and toxicity change

Peracetic acid (PAA) as an emerging oxidative has been concerned increasingly due to its high oxidation capacity and low byproducts formation potential. This study was to investigate the oxidation of sulfamethazine (SMZ) by PAA activated with activated biochar (ABC) after thermal modification. The results demonstrated that PAA could be effectively activated by ABC to degrade SMZ in a wide pH range (3–9), which followed the pseudo-second-order kinetics (R2 > 0.99). Both non-radicals (singlet oxygen) and free radicals (alkoxy radicals, hydroxyl radicals) existed in the ABC/PAA system, and the degradation of SMZ was dominated by singlet oxygen. Humic acid (HA), SO42− and HCO3− slightly inhibited the degradation of SMZ in the ABC/PAA process, while Cl− and Br− promoted the degradation of SMZ. The cleavage of S–N, S–C bond, and SO2 extraction reaction rearrangement was the main oxidation process of SMZ. Meanwhile, the results of the ECOSAR program showed that the acute toxicity of most by-products was significantly reduced compared to SMZ, which revealed the potential applicability of the ABC/PAA process in the treatment of antibiotics pollution and their detoxification.

Influence of co-exposure to sulfamethazine on the toxicity and bioaccumulation kinetics of chlorpyrifos in zebrafish (Danio rerio)

Pesticides and antibiotics are frequently present in aquatic environment which may pose potential risks to aquatic organisms. However, the interaction of pesticides and antibiotics in co-exposure model remains unclear. Here, the effects of the co-exposure of sulfamethazine (SMZ) on the toxicity and bioaccumulation of the organophosphorus insecticide chlorpyrifos (CPF) in zebrafish (Danio rerio) were explored. The 96-h LC50 of chlorpyrifos to zebrafish was 1.36 mg/L and sulfamethazine at 1 mg/L slightly increased the acute toxicity with the 96-h LC50 of 1.20 mg/L which was not significant. The 30-day co-exposure of chlorpyrifos with sulfamethazine at 1 mg/L aggravated the oxidative stress, decreased CarE and AChE activity, and increased CYP450 activity significantly. Furthermore, the co-exposure reduced the accumulation of chlorpyrifos and sulfamethazine while prolonged their depuration duration. The results demonstrated the exposure risk of chlorpyrifos to zebrafish may be enhanced in the presence of sulfamethazine.

Graphene shell-encapsulated copper-based nanoparticles (G@Cu-NPs) effectively activate peracetic acid for elimination of sulfamethazine in water under neutral condition

In this study, a graphene shell-encapsulated copper-based nanoparticles (G@Cu-NPs) was prepared and employed for peracetic acid (PAA) activation. The characterization of G@Cu-NPs confirmed that the as-prepared material was composed of Cu0 and Cu2O inside and encapsulated by a graphene shell. Experimental results suggested that the synthesized G@Cu-NPs could activate PAA to generate free radicals for efficiently removing sulfamethazine (SMT) under neutral condition. The formation of graphene shells could strongly facilitated electron transfer from the core to the surface. Radical quenching experiments and electron spin resonance (ESR) analysis confirmed that organic radicals (R-O•) and hydroxyl radicals (•OH) were generated in the G@Cu-NPs/PAA system, and R-O• (including CH3CO3• and CH3CO2•) was the main contributor to the elimination of SMT. The possible SMT degradation pathways and mechanisms were proposed, and the toxicity of SMT and its intermediates was predicted with the quantitative structure-activity relationship (QSAR) analysis. Besides, the effects of some key parameters, common anions, and humic acid (HA) on the removal of SMT in the G@Cu-NPs/PAA system were also investigated. Finally, the applicability of G@Cu-NPs/PAA system was explored, showing that the G@Cu-NPs/PAA system possessed satisfactory adaptability to treat different water bodies with admirable reusability and stability.

Removal of sulfamethazine by a flow-Fenton reactor with H2O2 supplied with a two-compartment electrochemical generator

A novel continuous-flow H2O2 electrochemical generator using a natural air diffusion electrode (NADE) as the cathode was designed and the two compartments of the generator were separated by a cation exchange membrane. The reactor did not require aeration, which saved aeration energy consumption. The reactor showed good performance in generating H2O2 up to 50.8 mg/h/cm2 with the energy consumption of 25.2 kWh/kg H2O2, and maintained a high current efficiency of about 70–94% in the current density range of 20 to 100 mA/cm2. The yield of H2O2 and current efficiency remained high and stable in a wide pH range of 3 ∼ 9. H2O2 produced in the generator was delivered to a flow-Fenton reactor for the occurrence of the Fenton reaction and the degradation of sulfamethazine (SMT), which avoided the problem of excessive generation and ineffective consumption of H2O2 in the electro-Fenton process and improved the utilization rate of H2O2. Moreover, due to the introduction of H2O2 solution with low pH to the flow-Fenton reactor, the pH of the working solution did not need adjustment. The flow-Fenton process achieved 99% of SMT removal, 90% of H2O2 utilization rate, and 54% of TOC removal within 20 min under the optimum conditions. The degradation of several other contaminants (2,4-dichlorophenoxyacetic acid, tetracycline and carbamazepine) was investigated and all of the removals were maintained above 97%. The study is promising for the practical electrochemical production of H2O2 and application of flow-Fenton for contaminants degradation.

Ti-based robust MOFs in the combined photocatalytic degradation of emerging organic contaminants

Photocatalysis process is a promising technology for environmental remediation. In the continuous search of new heterogeneous photocatalysts, metal–organic frameworks (MOFs) have recently emerged as a new type of photoactive materials for water remediation. Particularly, titanium-based MOFs (Ti-MOFs) are considered one of the most appealing subclass of MOFs due to their promising optoelectronic and photocatalytic properties, high chemical stability, and unique structural features. However, considering the limited information of the reported studies, it is a hard task to determine if real-world water treatment is attainable using Ti-MOF photocatalysts. In this paper, via a screening with several Ti-MOFs, we originally selected and described the potential of a Ti-MOF in the photodegradation of a mixture of relevant Emerging Organic Contaminants (EOCs) in real water. Initially, two challenging drugs (i.e., the β-blocker atenolol (At) and the veterinary antibiotic sulfamethazine (SMT)) and four water stable and photoactive Ti-MOF structures have been rationally selected. From this initial screening, the mesoporous Ti-trimesate MIL-100(Ti) was chosen as the most promising photocatalyst, with higher At or SMT individual photodegradation (100% of At and SMT photodegradation in 2 and 4 h, respectively). Importantly, the safety of the formed by-products from the At and SMT photodegradation was confirmed. Finally, the At and SMT photodegradation capacity of MIL-100(Ti) was confirmed under realistic conditions, by using a mixture of contaminants in tap drinking water (100% of At and SMT photodegradation in 4 h), proven in addition its potential recyclability, which reinforces the potential of MIL-100(Ti) in water remediation.

Comparison of disinfection by-products formed by preoxidation of sulfamethazine by K2FeO4 and O3 and the influence on cytotoxicity and biological toxicity.

This study researched the formation of disinfection by-products (DBPs) in sulfamethazine (SMZ) chlorination after preoxidation by K2FeO4 and O3 and the influence of preoxidation on cytotoxicity and biological toxicity. Then, the study emphatically analyzed the influencing factors such as NaClO dosage, pH value, reaction temperature, fulvic acid (FA), and bromide and iodide ions. The results showed that preoxidation by K2FeO4 effectively inhibited the formation of DBPs of haloketones (HKS) and trihalomethanes (THMs), with an average inhibition rate of over 60%. The formation of DBPs after preoxidation by O3 was higher than that by K2FeO4; preoxidation by K2FeO4 reduced the influence of NaClO dosage, temperature, and pH value on the production of DBPs after SMZ chlorination. The cytotoxicity and biological toxicity of SMZ chlorination after preoxidation were evaluated and compared by calculating the LC50 value of DBPs and the luminescent bacteria method. The results of both calculation methods showed that the toxicity of DBPs after preoxidation by K2FeO4 was lower than that by O3 preoxidation. K2FeO4 and O3 preoxidation improved the SMZ removal efficiency by 8.41 and 10.49%, respectively, and inhibited the formation of most DBPs, but the preoxidation promoted the formation of highly toxic DBPs (HANs). The toxicity of DBPs formed in SMZ chlorination after preoxidation by K2FeO4 and O3 was slightly higher than that of chlorination disinfection alone, but it was still within the safe range. This study provides more new details about the formation and toxicity changes of DBPs in the process of SMZ chlorination after preoxidation.

Bimetallic PtNi nanozyme-driven dual-amplified photoelectrochemical aptasensor for ultrasensitive detection of sulfamethazine based on Z-scheme heterostructured Co9S8@In-CdS nanotubes

Antibiotics residues are still an important and noticeable issue, and realizing the ultra-sensitive, sample, and rapid detection of residual antibiotics in the environment is the basis for evaluating and monitoring the pollution status. Herein, a new bimetallic PtNi nanozyme-driven dual-amplified photoelectrochemical (PEC) aptasensor was developed for sulfamethazine (SMZ) assay based on the superior photosensitive material of Z-scheme heterostructured Co9S8@ In doped CdS nanotubes (Co9S8@In-CdS NTs). In this protocol, bimetallic alloyed nanotube PtNi was introduced as the mimic enzyme to instead of bio-enzyme for constructing of signal amplification strategy. On the basis of the outstanding photosensitivity of Co9S8@In-CdS NTs and highly catalytic property of PtNi nanozyme, the proposed PEC aptasensor exhibits a wide linear range of 0.05 pg mL–1 ~ 1.0 ng mL–1, and a low detection limit of 37.2 fg mL–1. This work put forwards a novel approach for the accurate analysis of antibiotics in the environment.

Green, Sustainable Synthesis of γ-Fe2O3/MWCNT/Ag Nano-Composites Using the Viscum album Leaf Extract and Waste Car Tire for Removal of Sulfamethazine and Bacteria from Wastewater Streams.

Multi-walled carbon nanotubes (MWCNTs) decorated with Ag nanoparticles (NPs) are bifunctional adsorbent nanomaterials with antibacterial activity. They can be magnetically recovered from wastewater in case of coupling with γ-Fe2O3. In this study, for the first time, an environmentally friendly technique was applied to prepare a nanocomposite (NC) material composed of γ-Fe2O3/MWCNT/Ag by using Bridgestone disposable tires and Viscum album leaves extract. γ-Fe2O3/MWCNTs/Ag NC was employed for the removal of sulfamethazine (SMT) from aqueous solutions. Under the optimized conditions determined via the Taguchi method, the highest SMT adsorption capacity of the γ-Fe2O3/MWCNT/Ag NC was measured to be 47.6 mg/g. The experimental data fitted well with the pseudo-second-order kinetic model and the Langmuir isotherm. The thermodynamic parameters implied that the adsorption process was endothermic. In addition to adsorption of the drug pollutant, the NC demonstrated a superior antibacterial activity against Gram-positive bacteria. The reusability test also showed that over 79% SMT can be removed using γ-Fe2O3/MWCNTs/Ag NC even after four adsorption cycles. Taken together, γ-Fe2O3/MWCNTs/Ag NC was proven to be a promising antibacterial nano-adsorbent for wastewater treatment.

Iron-tungsten oxides modified oxygen-rich carbon nitride with defects S-scheme heterojunction for boosting photo-Fenton like removal of pollutants

Owning to excellence of photocatalytic persulfate (PS)-based oxidation processes in pollutant removal, the iron-tungsten oxides modified oxygen-rich carbon nitride with defects (ITOs/OCNv) S-scheme heterojunction composites were successfully prepared, and the photo-Fenton like system (Vis/ITOs/OCNv/PS) was constructed to degrade antibiotic pollutants. Results indicated that the ITOs/OCNv composites exhibited large specific surface area and rich porous structure. In addition, the in-situ introduction of oxygen-rich functional groups and lots of N and O vacancy defects in the composites enhanced the absorption of visible light (Vis) and the electron transfer. Importantly, the formed S-scheme heterojunction improved the separation of photogenerated carriers. The degradation efficiencies of sulfamethazine (SMZ) and ciprofloxacin (CIP) in the optimal Vis/5% ITOs/OCNv/PS system were 99.6 % and 99.5 %, which were 1.69 and 2.34 times that of Vis/5% ITOs/OCNv system (SMZ 58.9 % and CIP 42.6 %) after 40 min, respectively. Results of quenching experiments showed that the main active species were h+, 1O2 and O2− for SMZ and CIP degradation. Moreover, this system exhibited better anti-interference of water substrates and applicability in actual water body. The degradation pathways of CIP were proposed by combining density functional theory calculation with intermediate analysis. Moreover, the ecotoxicities of CIP and its products were evaluated comprehensively. The system showed better broad-spectrum degradation of pollutants, including sulfamethoxazole, atrazine, sulfadimethoxine and bisphenol A, which would provide a new insight for persistent pollutant removal.

Bioaccessibility of Microplastic-Associated Antibiotics in Freshwater Organisms: Highlighting the Impacts of Biofilm Colonization via an In Vitro Protocol.

Microplastics in the environment can be colonized by microbes capable of forming biofilms, which may act as reactive coatings to affect the bioaccessibility of pollutants in organisms. This study investigated the dynamic evolution of biofilm colonization on microplastics and its impacts and mechanisms on the bioaccessibility of microplastic-associated sulfamethazine (SMT) via microcosm incubation in surface water and sediment. After 60 days of incubation, the microbial communities formed in microplastics were distinct and more diverse than those untethered in surroundings, and photoaging treatment decreased the affinity of biofilms on microplastics due to decreased hydrophobicity. Biofilm formation further enhanced the desorption and bioaccessibility of microplastic-sorbed SMT in organisms. In vitro experiments indicated that the critical effects were mainly related to the stronger interaction of gastrointestinal components (i.e., pepsin, bovine serum albumin (BSA), and NaT) with biofilm components (e.g., extracellular polymer substances) than with the pure surface of microplastics, which competed for binding sites in microplastics for SMT more significantly. Photoaging decreased the enhancing effects of biofilms due to their lower accumulation in aged microplastics. This study is the first attempt to reveal the role of biofilms in the bioaccessibility of microplastics with associated antibiotics and provide insights into the combined risk of microplastics in the environment.

Hydrogen Peroxide Activated by Biochar-Supported Sulfidated Nano Zerovalent Iron for Removal of Sulfamethazine: Response Surface Method Approach.

Biochar (BC)-supported sulfide-modified nanoscale zerovalent iron (S-nZVI/BC) was prepared using the liquid-phase reduction method for the application of the removal of sulfamethazine (SMZ) from water. The reaction conditions were optimized by the Box–Behnken response surface method (RSM). A model was constructed based on the influence factors of the removal rate, i.e., the carbon-to-iron ratio (C/Fe), iron-sulfur ratio (Fe/S), pH, and hydrogen peroxide (H2O2) concentration, and the influence of each factor on the removal efficiency was investigated. The optimal removal process parameters were determined based on theoretical and experimental results. The results showed that the removal efficiency was significantly affected by the C/Fe ratio and pH (p < 0.0001) but relatively weakly affected by the Fe/S ratio (p = 0.0973) and H2O2 concentration (p = 0.022). The optimal removal process parameters were as follows: 0.1 mol/L H2O2, a pH of 3.18, a C/Fe ratio of 0.411, and a Fe/S ratio of 59.75. The removal rate of SMZ by S-nZVI/BC was 100% under these conditions. Therefore, it is feasible to use the Box–Behnken RSM to optimize the removal of emerging pollutants in water bodies by S-nZVI/BC.

Preparation and characterisation of photoresponsive molecularly imprinted polymer based on 5-[(4-(methacryloyloxy) phenyl) diazenyl] isophthalic acid for the determination of sulfamethazine

Combining with the surface imprinting technique, a novel molecularly imprinted polymer with core–shell structure was designed and successfully synthesised, coated on the surface of SiO2 with functionalised photoresponsive monomer, 5-[(4-(methacryloyloxy) phenyl) diazenyl] isophthalic acid. It is worth noting that through a series of absorption experiments, the prepared polymer can be controlled by light to selectively absorb (irradiation of 365 nm) and release (irradiation of 440 nm or under darkness) sulfamethazine (SMZ) with a maximal absorption quantity of 28.8 mg⋅g−1 and prominent selectivity (imprinting factor = 2.01). Moreover, the polymer presented prominent recyclability, with negligible attenuation in performance after four loops of light-actuated absorption and discharge of SMZ. Finally, the polymer was successfully applied as the solid-phase extractant in determining the SMZ content in tap water, with a maximum recovery rate of 96.7 %.

Assessment of safety and quality aspects of boiling treatment of quail eggs.

A total of 300 quail eggs were collected randomly from different markets in Cairo and Giza Governorates. Five eggs were represented as one egg sample. Shell and content of each egg were examined for their microbiological contents, sensory evaluation and study of Escherichia coli O157 survival in artificially contaminated eggs. Moreover, qualitative detection of antimicrobial residues by seven plates microbiologically bioassay and confirmed by validated high-performance liquid chromatography (HPLC) methods for positively reacted antimicrobials in raw and boiled samples. There was a significant difference (P < 0·05) between the grading score of eggs after the boiling at 2-, 4-, 5- and 7-min. Based on the survival results, the refrigeration storage and boiling for 5 min of quail eggs was confirmed that such eggs are without E.coli O157. After the boil, the concentrations of oxytetracycline (OTC) and 4-Epi-OTC residues were significantly reduced, and there was no effect on the concentration of sulphadimidine (SDD), amoxicillin (AMO) and Diketo residues. Samples that exceeded the maximum residual limits (MRLs) were 17·0%, 12·0%, 10·0%, 16·0% and 14·0% for SDD, OTC, 4-Epi-OTC, AMO and Diketo, respectively. After boiling, no significant change was noted for SDD, AMO and Diketo, but all OTC and 4-Epi-OTC were completely below MRLs. Therefore, SDD and AMO with their metabolite (Diketo) are heat-stable antimicrobial residues with multiple human health hazards.

Visible LED photocatalysis combined with ultrafiltration driven by metal-free oxygen-doped graphitic carbon nitride for sulfamethazine degradation

A novel visible light emitting diode (LED) photocatalysis combined ultrafiltration (UF) system driven by metal-free O-doped C3N4 was established for sulfamethazine (SMZ) removal in environmental remediation. Among different O-doping ratios, 8%O-C3N4 exhibited the optimal SMZ degradation efficiency (89.36%) and the flux of 8%O-C3N4/LED/UF system could reach up to 38.92 L/m2/h. Benefitting from the O-doping, the synergetic effect of the expansion of visible-light absorption, enhancement of electron redox capacity, and improvement of e--h+ separation efficiency could produce the intensified photoactivity. Superoxide radical (O2•-) and single oxygen (1O2) were proved to be the primary active species by EPR and quenching tests. Moreover, the influence of several parameters such as photocatalyst dosage, SMZ concentration, raw turbidity and humic acid concentration in 8%O-C3N4/LED/UF system on SMZ removal were systematically studied. Under simulated surface water matrix, 8%O-C3N4/LED/UF system could also remove 96.88% SMZ and stable membrane flux stabilized as high as 33.36 L/m2/h. This study makes a demonstration for applying highly-effective powdery photocatalysts in the actual wastewater treatment and designing future photocatalytic reactors.

Efficient degradation of Health-threatening organic pollutants in water by atomically dispersed Cobalt-Activated peroxymonosulfate

Degrading health-threatening organic pollutants (HTOPs) in water systems through advanced oxidation processes (AOPs) is an effective way to treat environmental wastewater; however, such processes require advanced catalysts. This study combined complexation effects and structural confinement strategies to rapidly prepare Co2+-isolated metal–organic framework polymers and utilized a thermal treatment process to achieve the efficient anchoring of atom-dispersed Co in a boron–carbon-nitrogen matrix (denoted as SACoN/BCN), which can improve the utilization of Co catalytic sites. SACoN/BCN effectively activated peroxymonosulfate (PMS), with the ratio and mineralization rate of sulfamethazine (SMT) removed by degradation within 40 min reached 95.2 % and 70.0 %, respectively. Radical inhibition experiments and electron paramagnetic resonance (EPR) tests showed that 1O2 generated from SACoN/BCN-activated PMS was the key reactive oxygen species that promoted HTOP degradation. Density functional theory calculations revealed that, following the introduction of electron-deficient B heteroatoms, electrons in PMS will be injected into SACoN/BCN, thereby realizing strong adsorption and further activation of PMS. The cytotoxicity of SACoN/BCN is almost negligible because of the chemical bonding (or entrapment) of Co atoms in the inorganic boron–carbon-nitrogen matrix, thereby preventing Co from forming mobile CoII ions in the aqueous system. This research provides information for advanced catalysts for the removal of HTOPs and experimental and theoretical inspiration for the preparation of single-atom catalysts for advanced oxidation processes and the mechanism of PMS activation.

Amorphous Co@TiO2 heterojunctions: A high-performance and stable catalyst for the efficient degradation of sulfamethazine via peroxymonosulfate activation

Persulfate-based advanced oxidation processes (AOPs) cannot easily achieve the efficient degradation of persistent organic pollutants (POPs) with high stability. In this study, a simple in situ precipitation method was used to prepare an amorphous Co@TiO2 heterojunction catalyst. The deposition of Co oxide on TiO2, which is relatively nontoxic, efficiently activated peroxymonosulfate (PMS) to degrade sulfamethazine (SMT) and reduce the leaching of Co ions (0.915%). A catalytic system prepared using 0.3 g L−1 Co@TiO2 and 0.5 g L−1 PMS could degrade SMT within 30 min with a degradation rate of 95.8%. Co@TiO2 could activate PMS over a wide pH range (5.00–9.00) to efficiently degrade other antibiotics and dyes. Radical-capture experiments and electron paramagnetic resonance analysis suggested that SMT degradation occurs through a combination of the free radical and non-radical pathways, in which singlet 1O2 played a major role. Owing to the novelty of the proposed composite materials, the degradation path of SMT, which was determined through liquid chromatography–mass spectrometry, differed from that reported previously. This study provides not only an advanced and renewable catalyst for SMT degradation but also a feasible strategy for designing materials for AOPs.

Photo-Fenton degradation of sulfamethazine using self-assembled CdS nanorods with in-situ production of H2O2 at wide pH range

The large-scale application of the conventional Fenton process is restricted by the strict acidic working pH and the demand for externally supplying hydrogen peroxide (H2O2). To conquer these disadvantages, an efficient visible-light-driven photo-Fenton system which can in-situ produce and apply H2O2 was investigated and developed, based on self-assembled CdS nanorods capable of converting dissolved O2 to H2O2. The self-assembled CdS nanorods had high purity and good crystallinity with a pine-leaf-like structure. Highly effective degradation of sulfamethazine (SMT) was achieved by the CdS/Fe2+ photo-Fenton system under visible light irradiation and 20 mg/L SMT was almost completely degraded within 90 min over a broad pH range from 4 to 8. It was attributed that self-assembled CdS nanorods with excellent photocatalytic activity could produce numerous photoelectrons, which could not only reduce dissolved O2 to H2O2 via a direct two-electron reduction route but also accelerate the conversion of Fe3+ to Fe2+. Moreover, the self-assembled CdS nanorods possessed excellent reusability and the constructed photo-Fenton system exhibited widespread suitability for degradation of different pollutants, demonstrating potential applications in wastewater treatment. It is expected that this study can provide new ideas for improving the conventional Fenton process.

FeMo@porous carbon derived from MIL-53(Fe)@MoO3 as excellent heterogeneous electro-Fenton catalyst: Co-catalysis of Mo

An ultra-efficient electro-Fenton catalyst with porous carbon coated Fe-Mo metal (FeMo@PC), was prepared by calcining MIL-53(Fe)@MoO3. This FeMo@PC-2 exhibited impressive catalytic performance for sulfamethazine (SMT) degradation with a high turnover frequency value (7.89 L/(g·min)), much better than most of reported catalysts. The mineralization current efficiency and electric energy consumption were 83.2% and 0.03 kWh/gTOC, respectively, at low current (5 mA) and small dosage of catalyst (25.0 mg/L). The removal rate of heterogeneous electro-Fenton (Hetero-EF) process catalyzed by FeMo@PC-2 was 4.58 times that of Fe@PC/Hetero-EF process. Because the internal-micro-electrolysis occurred between PC and Fe0, while the co-catalysis of Mo accelerated the rate-limiting step of the Fe3+/Fe2+ cycle and greatly improved the H2O2 utilization efficiency. The results of radical scavenger experiments and electron paramagnetic resonance confirmed the main role of surface-bound hydroxyl radical oxidation. This process was feasible to remove diverse organic contaminants such as phenol, 2,4-dichlorophenoxyacetic acid, carbamazepine and SMT. This paper enlightened the importance of the doped Mo, which could greatly improve the activity of the iron-carbon heterogeneous catalyst derived from metal-organic frameworks in EF process for efficient removal of organic contaminants.