Removal Of Sulfamethazine Research Articles

Simulation removal of sulfamethazine, ciprofloxacin, sulfathiazole and amoxicillin via photo-Fenton process in by Monte Carlo modeling

Kinetic Monte Carlo modeling was employed as a powerful tool to kinetically investigate of antibiotics removal by photo-Fenton process (iron(III) citrate/ hydrogen peroxide in the presence of UV irradiation). Sulfamethazine, ciprofloxacin, sulfathiazole and amoxicillin are the antibiotics which were studied in this investigation. The kinetic mechanism of the photo-Fenton degradation was found by Monte Carlo simulation for several studied antibiotics including sulfamethazine, ciprofloxacin, sulfathiazole and amoxicillin. Also the rate constants values of each step in the suggested mechanism were acquired for these antibiotics through the simulation. Optimized values of Fe(III) citrate and hydrogen peroxide were attained through obtaining the effect of their initial amounts on the rate of antibiotics elimination by utilizing kinetic Monte Carlo simulation. The perfect agreement is observed between the simulation results and the experimental photo-Fenton data for the systems above.

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.

Degradation of sulfamethazine using sludge-derived photocatalysts from dyeing industry and livestock farm: preparation and mechanism

Excess sludge disposal and management has become a global issue of scientific and public concern owing to its high yield and toxicity. In this study, for the first time, we prepared industrial and livestock sludge-derived photocatalysts using dyeing sludge and swine sludge as raw materials, respectively, using a facile pyrolysis coupled ball-milling process without additives. The photocatalytic performances of the two types of photocatalysts were evaluated using sulfamethazine as the target contaminant. The surface morphology and functional groups of the catalysts were analyzed using field-emission scanning electron microscopy combined with energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The sulfamethazine removal rate was 91.5 % under optimal conditions. Degradation intermediates were detected, and a possible degradation pathway was proposed. Major reactive oxygen species in the photocatalytic systems were investigated using electron spin resonance spectroscopy and radical trapping experiments. The results revealed that·O2– and h+ played main roles in the degradation of SMZ. Furthermore, a pilot-scale experimental setup was designed and manufactured to realize pilot-scale production. Economic analysis of the pilot-scale experiment suggested that the developed photocatalysts are comparatively suitable for practical applications.

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.

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.

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.

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.

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.

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.

Activation of sulfite via zero-valent iron-manganese bimetallic nanomaterials for enhanced sulfamethazine removal in aqueous solution:Key roles of Fe/Mn molar ratio and solution pH

In this study, the nano zero-valent iron-manganese (NZVIM) bimetallic materials with different Fe/Mn molar ratios were synthesized by one-step liquid-phase reduction method and utilized to activate sulfite for the elimination of sulfamethazine (SMT) at different pH (3.0, 6.0, and 8.0). It was found the optimum Fe/Mn molar ratio was different under different solution pH conditions. The sulfite could be efficiently activated by nano zero-valent iron (NZVI) and NZVIM with Fe/Mn = 2:1 and 1:1 to remove SMT with a high removal efficiency at pH 3.0. While the NZVIM/sulfite system corresponding to Fe/Mn ratios of 1:1 and 2:1, respectively, could degrade SMT more efficiently than the NZVI/sulfite system at neutral and alkaline conditions. The improvement of degradation efficiency of SMT may result from the addition of Mn element. On the one hand, the ability of direct electron transfer inside the NZVIM particles might be enhanced, and on the other hand, Mn(II) promoted the conversion of Fe(III) to Fe(II), thereby enhancing the ability of free radical generation. Besides, electron spin resonance (ESR) analysis and the radical quenching experiments confirmed that •OH was the primary radicals that responsible for SMT elimination. Then the intermediates of SMT were identified by high-performance liquid chromatography mass spectrometry (LC-MS) and possible degradation pathways were proposed. Additionally, the developmental toxicity and bioaccumulation factors of SMT and its possible intermediates were predicted by quantitative structure–activity relationship (QSAR) analysis. In addition, the effect of some typical coexisting components (Cl−, HCO3−, HA) in water was examined. The effectiveness of NZVIM/sulfite system for SMT removal in two actual water matrices (i.e., tap water and river water) was investigated. These results indicated that the NZVIM/sulfite system is viable and effective for the elimination of SMT in water, and the Fe/Mn molar ratio and solution pH are two critical factors influencing the performance of the NZVIM/sulfite system.

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H 2 O 2

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H ₂ O ₂

Efficient removal of sulfamethazine from irrigation water using an ultra-stable magnetic carbon composite catalyst

Antibiotics accumulated in ecosystem can easily enter the agricultural cycle with irrigation water, which brings a huge potential threat to food security. Transition metals are widely utilized in advanced oxidation processes to degrade pollutants, but the poor stability has significantly impeded their application in irrigation water. To solve these problems, the harmless tetrasodium iminodisuccinate is selected to pyrolysis with ferrite and cobalt resources to obtain a composite heterogeneous catalyst composed of porous carbon and Co3Fe7, CoFe2O4 (IDC@Co3Fe7/CFO). The catalyst exhibits excellent catalytic performance in peroxydisulfate (PDS) activation and shows a high removal efficiency of sulfamethazine up to 100%. The ESR analysis proves SO4•−, •OH and •O2– are the main active substances, and sulfamethazine can be gradually degraded until mineralization. More importantly, with the formation of Metal-Metal/Metal-Oxygen bonds and the protection of the IDS derived carbon, the dispersion and stability of the metal can be greatly promoted. The composite can maintain the rate of degrading sulfamethazine above 93.44% after 10 times catalytic reactions, with extremely low detection of Fe or Co leaching. This study not only give a super-stable material for the removal of antibiotics in irrigation water, but also provides a novel stratagem for obtaining stable catalytic structures.

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.

Advanced removal of pesticides, herbicides, and pharmaceutical residues from surface water

ABSTRACT This work is interested in studying the removal of 27 harmful pollutants from drinking water in the Rosetta branch of the River Nile by advanced treatment processes (i.e. photo-catalysis under natural conditions and normal pH of surface water). The concentration levels of the selected pesticides (11 compounds) in raw water by the spiking method ranged from 1.57–0.40 µg/L, while the concentration of pharmaceuticals (10 compounds) ranged from 41.56–5.95 µg/L and the herbicides (6 compounds) in the range of 1.89–1.37 µg/L. For this purpose, TiO2-Hombikat/alumina (T/A) was prepared by a two-step method; sonication followed by the hydrothermal method. Cu/TiO2-Hombikat/alumina was prepared hydrothermally (H-Cu/T/Al) and by the wet impregnation method (Ma-Cu/T/Al). The prepared materials were characterized by XRD and SEM. The use of advanced treatment could successfully remove selected pollutants. In the case of pharmaceutical residues, the prepared catalysts showed a powerful efficiency in the complete removal of sulfamethazine, while only (T/A) and (H-Cu/T/Al) showed such an efficiency in the complete removal of diclofenac sodium. On the other hand, lower efficiencies were observed with caffeine (17.99% (T/A) and 24.05% (H-Cu/T/Al)). In the case of pesticides, a high removal of pendimethalin (93.77%) using (H-Cu/T/Al) and 86.03% by using (Mb-Cu/T/Al), whereas lower efficiencies were observed for T/A toward the degradation of aldicarb (15.6%) (l) and H-Cu/T/Al (26.07%). In the case of herbicides, the catalysts showed no more than 57% efficiency in the removal of these pollutants.

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.

Response of fungi-microalgae pellets to copper regulation in the removal of sulfonamides and release of dissolved organic matters

Both sulfonamides (SAs) and copper (Cu(II)) were frequently detected together in swine wastewater. In this study, the regulation of Cu(II) on SAs adsorption and release of dissolved organic matters (DOMs) by fungi-microalgae pellets (FM-pellets) were investigated. Aspergillus oryzae pellets were prepared for combination with Chlorella vulgaris and the optimal conditions were at agitation speed of 130 rpm, fungi to microalgae ratio of 10:1 and the combined time of 3 h with the highest combination efficiency of 98.65%. The results showed that adsorption was the main mechanism for SAs removal. FM-pellets exhibited a high SAs adsorption potential within 6 h, and the adsorption capacity of sulfamethazine (SMZ), sulfamonomethoxine (SMM) and sulfamethoxazole (SMX) was 1.07, 0.94 and 1.67 mg/g, respectively. Furthermore, the removal of SMX, SMZ and SMM was greatly promoted from 62.31% to 85.21%, 58.71–67.91% and 64.17–80.31%, respectively, under the presence of 2 mg/L Cu(II) through ion exchange and adsorption bridging. DOMs were analyzed by the parallel factor (PARAFAC) to demonstrate the response mechanism of FM-pellets to Cu(II). Protein-like substances and NADH in DOMs released by FM-pellets formed complexes with Cu(II) to alleviate the damage on the organism. These findings provide new insights into the mechanism and response of Cu(II) in the removal of SAs by FM-pellets.

Hydroxylamine enables rapid heterogeneous-homogeneous coupled Fenton sulfamethazine degradation on ferric phosphate

Heterogeneous-homogeneous coupled Fenton (HHCF) processes compromise the merits of rapid degradation and catalyst reusability, thus are very attractive for environmental remediation and water treatment. However, the development of HHCF processes suffers from the lack of desirable catalysts and Fe(III)/Fe(II) redox cycle (iron cycle) mediators. Herein we demonstrate the combination of hydrogen peroxide, ferric phosphate and hydroxylamine offers a promising HHCF process, where ferric phosphate and hydroxylamine serve as the catalyst and iron cycle mediator, respectively. Hydroxylamine can realize suitable iron release from ferric phosphate, effective iron cycle, and •OH consumption, resulting in efficient conversion of H2O2 to •OH for sulfamethazine removal. More importantly, the phosphorus release from ferric phosphate and nitrogen residual during this HHCF process are limited to reduce the risk of secondary pollution. This study clarifies the importance of iron dissolution and iron cycle on highly efficient Fenton processes, and also provides a promising antibiotic pollutant removal strategy.

Pd/MIL-100(Fe) as Hydrogen Activator for FeIII/FeII Cycle: Fenton Removal of Sulfamethazine

Masses of iron sludge generated from engineering practice of classic Fenton reaction constraints its further promotion. Accelerating the FeIII/FeII cycle may be conducive to reducing the initial ferrous slat dosage and the final iron sludge. Based on the reduction of Pd/MIL-100(Fe)-activated hydrogen, an improved Fenton system named MHACF-MIL-100(Fe) was developed at ambient temperature and pressure. 97.8% of sulfamethazine, the target pollutant in this work, could be degraded in 5 min under the conditions of 20 mM H2O2, 25 μM ferrous chloride, initial pH 3.0, 2 g·L-1 composite catalyst Pd/MIL-100(Fe), and hydrogen gas 60 mL·min-1. Combining density functional theory (DFT) calculation and intermediate detection, the degradation of this antibiotic was inferred to start from the cleavage of N-S bond. The catalytic of Pd/MIL-100(Fe), demonstrated by removal efficiency of SMT and the catalyst morphology, remained intact after 6 reaction cycles. The present study provides an insight for the promotion of Fenton reaction.

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.