Degradation of veterinary antibiotics by the ozonation process: Product identification and ecotoxicity assessment.

The purpose of the study was to evaluate the effects of using of ozonation to remove antibiotics used, among others, in veterinary medicine, from the aqueous environment. The effect of this process on the degradation, mineralisation and ecotoxicity of aqueous solutions of ampicillin, doxycycline, tylosin, and sulfathiazole was investigated. Microbiological MARA® bioassay and two in silico methods were used for the ecotoxicity assessment. Ozonation was an effective method for the degradation of the antibiotics studied and the reduction in ecotoxicity of the solutions. However, after ozonation, the solutions contained large amounts of organic products, including compounds much less susceptible to ozonation than the initial antibiotics. Structures of 14, 12, 40 and 10 degradation products for ampicillin, doxycycline, tylosin, and sulfathiazole, respectively, were proposed. It was confirmed that ozone plays a greater role than hydroxyl radicals in the degradation of these antibiotics, with the exception of TYL. The use of ozonation to obtain a high degree of mineralisation is unfavourable and it is suggested to combine ozonation with biodegradation. The pre-ozonation will cause decomposition of antibiotic pharmacophores, which significantly reduces the risk of spread of antimicrobial resistance in the active biocenosis of wastewater treatment plants.

Photocatalytic degradation of sulfonamides in suspensions of coral-like graphene carbon nitride with nitrogen vacancies.

Sulfonamides (SNs) belong to a category of broad-spectrum antibiotics, which have attracted growing concerns owing to the adverse effects on ecosystem. In this paper, coral-like graphitic carbon nitrides with nitrogen vacancies were prepared by polymerization of melamine in the presence of NH4Cl, and the effect of NH4Cl amount on the structure and photocatalytic performance of g-C3N4 in degradation of sulfonamide antibiotics such as sulfamethoxazole (SMX), sulfadiazine (SDZ) and sulfathiazole (STZ) was systematically studied. It was found that the addition of NH4Cl results in the formation of coral-like g-C3N4 with nitrogen vacancies, and optimal photocatalyst (PCN-1 sample) prepared with a melamine to NH4Cl mass ratio of 1:1 showed the highest photocatalytic activity towards SNs degradation due to the quick electron-hole migration, efficient separation capacity and excellent photoelectric properties. The electron paramagnetic resonance (EPR) technique was used to determine the reactive oxygen species (ROSs) that are responsible for the degradation of SNs, and the detailed degradation pathway of STZ was proposed according to the identification of the intermediates by liguid chromatography-high resolution mass spectrometry (LC-HRMS).

Construction of a myoglobin scaffold-based biocatalyst for the biodegradation of sulfadiazine and sulfathiazole.

Sulfonamide antibiotics, a family of broad-spectrum antibiotic drugs, are increasingly used in aquaculture and are frequently detected in aquatic environments. This poses a potential threat to organisms and may cause the evolution of antimicrobial resistance. Therefore, it is important to develop an environmentally friendly and efficient biocatalyst to degrade sulfonamides (SAs) such as sulfadiazine (SD) and sulfathiazole (ST). Here, we realized the direct and efficient degradation of SD and ST using a hydrogen peroxide-dependent artificial catalytic system based on myoglobin (Mb). The arrangements of amino acids at positions 29, 43, 64, and 68 were found to influence catalytic activity. An L29H/H64D/V68I myoglobin mutant showed the best catalytic efficiency (i.e., kcat/Km = 720.42 M-1 s-1) against SD. Next, mutant H64D/V68I showed the best degradation rate against SD (i.e., 91.45 ± 0.16%). Moreover, L29H/H64D/V68I Mb was found to efficiently catalyze ST oxidation (kcat/Km = 670.08 M-1 s-1), while H64D/V68I had the best degradation rate against ST (i.e., 99.45 ± 0.23%). Our results demonstrate that SAs can be efficiently degraded by artificial peroxygenases constructed using a myoglobin scaffold. This therefore provides a simple and economical method for the biodegradation of SD and ST.

Synthesis and antibacterial activity of FST and its effects on inflammatory response and intestinal barrier function in mice infected with Escherichia coli O78.

Pathogenic Escherichia coli (E. coli) can cause intestinal diseases in humans and livestock, damage the intestinal barrier, increase systemic inflammation, and seriously threaten human health and the development of animal husbandry. In this study, we designed and synthesized a novel conjugate florfenicol sulfathiazole (FST) based on drug combination principles, and investigated its antibacterial activity in vitro and its protective effect on inflammatory response and intestinal barrier function in E. coli O78-infected mice in vivo. The results showed that FST had superior antibacterial properties and minimal cytotoxicity compared with its prodrugs as florfenicol and sulfathiazole. FST protected mice from lethal E. coli infection, reduced clinical signs of inflammation, reduced weight loss, alleviated intestinal structural damage. FST decreased the expression of inflammatory cytokines IL-1ß, IL-6, TNF-α, and increased the expression of claudin-1, Occludin, and ZO-1 in the jejunum, improved the intestinal barrier function, and promoted the absorption of nutrients. FST also inhibited the expression of TLR4, MyD88, p-p65, and p-p38 in the jejunum. The study may lay the foundation for the development of FST as new drugs for intestinal inflammation and injury in enteric pathogen infection.

Magnetized algae catalyst by endogenous N to effectively trigger peroxodisulfate activation for ultrafast degraded sulfathiazole: Radical evolution and electron transfer.

An innovative Fe-N co-coupled catalyst MN-2 was prepared from waste spirulina by co-pyrolysis as a highly active carbon-based catalyst for the activation of peroxydisulfate (PDS) for the degradation of sulfathiazole (ST). The protein-rich raw material Spirulina provided sufficient N during the pyrolysis process, thus achieving N doping without an additional nitrogen source, optimizing the interlayer structure of the biochar material and effectively inhibiting the leaching of the ligand metal Fe. MN-2 showed highly efficient catalytic activity for peroxydisulfate (PDS), with a degradation efficiency of 100% for ST within 30 min and a kinetic constant (kobs) reached 0.306 min-1, benefiting from the excellent adsorption ability of MN-2 forming MN-2-PDS* complexes and the electron transfer process generated by Fe3+ and Fe2+ cycling, oxygen-containing functional groups. The effects of PDS dosage, initial pH and coexisting anions on the oxidation process were also investigated. Free radical quenching, electron paramagnetic resonance and electrochemical measurements were employed to explain the hydroxyl (·OH) and sulfate (SO4·-) as the dominant active species and the electron transfer effect on the removal of ST. MN-2 maintained a ST removal rate of 84% after four recycling experiments, showing a high reusability performance. This work provides a simple way to prepare magnetized N-doped biochar, a novel catalyst (MN-2) for efficient activation of PDS for ST degradation, and a feasible method for removing sulfanilamide antibiotics in water environment.

Novel ternary Cu0-coupled core-shell Fe0/C nanoparticles micro-electrolysis system toward degradation of organic pollutants: Synergistic effects and removal mechanism.

A ternary micro-electrolysis system consisting of carbon-coated metallic iron with Cu nanoparticles (Fe0/C@Cu0) was synthesized for the degradation of sulfathiazole (STZ). Fe0/C@Cu0 catalysts exhibited excellent reusability and stability owing to the inner tailored Fe0 with persistent activity. The connection between Fe and Cu elements in the Fe0/C-3@Cu0 catalyst prepared with iron citrate as iron source exhibited a tighter contact than the catalysts prepared with FeSO4·7H2O and iron(II) oxalate as iron sources. Especially, unique core-shell structure of Fe0/C-3@Cu0 catalyst is more conducive to promoting the degradation of STZ. A two-stage reaction with rapidly degradation followed by gradual degradation was revealed. The mechanism of STZ degradation could be explained by the synergistic effects of Fe0/C@Cu0. Carbon layer with remarkable conductivity allowed electrons from Fe0 transferred freely to the Cu0. The electron-rich Cu0 releases electrons, facilitating the degradation of STZ. Furthermore, the high potential difference between cathode (C and Cu0) and anode (Fe0) accelerate the corrosion of Fe0. Importantly, Fe0/C@Cu0 catalysts exhibited excellent catalytic performance for sulfathiazole degradation in landfill leachate effluent. Results presented provide a new strategy for treatment of chemical wastes.

Microscopic insights into the variations of antibiotics sorption to clay minerals.

Understanding the adsorption behavior of antibiotic molecules on minerals is crucial for determining the environmental fate and transport of antibiotics in soils and waters. However, the microscopic mechanisms that govern the adsorption of common antibiotics, such as the molecular orientation during the adsorption process and the conformation of sorbate species, are not well understood. To address this gap, we conducted a series of molecular dynamics (MD) simulations and thermodynamics analyses to investigate the adsorption of two typical antibiotics, tetracycline (TET) and sulfathiazole (ST), on the surface of montmorillonite. The simulation results indicated that the adsorption free energy ranged from - 23 to - 32 kJ·mol-1, and - 9 to - 18 kJ·mol-1 for TET and ST, respectively, which was consistent with the measured difference of sorption coefficient (Kd) for TET-montmorillonite of 11.7 L·g-1 and ST-montmorillonite of 0.014 L·g-1. The simulations also found that TET was adsorbed through dimethylamino groups (85% in probability) with a molecular conformation vertical to the montmorillonite's surface, while ST was adsorbed through sulfonyl amide group (95% in probability) with vertical, tilted and parallel conformations on the surface. The results confirmed that molecular spatial orientations could affect the adsorption capacity between antibiotics and minerals. Overall, the microscopic adsorption mechanisms revealed in this study provide critical insights into the complexities of antibiotics adsorption to soil and facilitate the prediction of adsorption capacity of antibiotics on minerals and their environmental transport and fate. This study contributes to our understanding of the environmental impacts of antibiotic usage and highlights the importance of considering molecular-level processes when assessing the fate and transport of antibiotics in the environment.

An FeP/carbon composite derived from a phytic acid-Fe3+ complex for sulfathiazole degradation through peroxymonosulfate activation.

Peroxymonosulfate (PMS) activation-based advanced oxidation technology possesses great potential for antibiotic-containing wastewater treatment. Herein, we developed an iron phosphide/carbon composite and verified its capability and superiority towards a model antibiotic pollutant (sulfathiazole, STZ) degradation through PMS activation. Benefiting from the chelating ability of phytic acid (PA) with metal ions and its abundance on phosphorous element, a PA-Fe3+ complex was firstly formed and then served as sole precursor for iron phosphide formation by anoxic pyrolysis. Well crystalized FeP particle were found loading on the simultaneously formed thin layer carbon structure. Catalytic activity evaluation showed that FeP/carbon composite could remove over 99% of STZ (20 mg L-1) in 20 min adsorption and 30 min catalysis process under the reaction conditions of catalyst dosage 0.2 g L-1, PMS loading 0.15 g L-1. A pseudo-first-order reaction rate constant of 0.2193 min-1 was obtained, which was among the highest compared with reported studies. Further investigations indicated that the developed FeP/carbon composite worked well in a wide solution pH range of 3-9. Reaction mechanism study showed that reactive species of SO4-• and 1O2 generated from PMS activation played major roles for STZ degradation. Based on liquid chromatography-mass spectroscopy (LC-MS) analysis, a few STZ degradation intermediate products were identified, which facilitated the proposal of STZ degradation pathways. The possible ecological risk of STZ and related degradation intermediates were also considered by toxicity assessment using the Ecological Structure Activity Relationships (ECOSAR) Class Program. The obtained acute and chronic toxicity values implied the relatively low ecological risk of FeP/carbon-PMS reaction system for STZ treatment.

Generation of high-valent iron-oxo porphyrin cation radicals on hemin loaded carbon nanotubes for efficient degradation of sulfathiazole.

Hemin has attracted considerable interest as an efficient catalyst recently, however, its direct application is inefficient due to severe molecular aggregation. Immobilizing hemin on various supports is a feasible approach to address this issue. In this work, a CNTs-hemin catalyst was prepared by loading hemin onto multiwalled carbon nanotubes (CNTs) through ball milling. Compared with hemin, CNTs-hemin demonstrates remarkably enhanced performance in the peroxymonosulfate system, with a 650-fold improvement of apparent rate constant, reaching 97.8% degradation of sulfathiazole in 5 min. High-valent iron-oxo porphyrin cation ((Porp)+•FeIV=O) radicals are proposed as the dominant reactive species in the CNTs-hemin/peroxymonosulfate system instead of sulfate radicals (SO4•-), hydroxyl radicals (•OH), superoxide radicals (O2•-) and singlet oxygen (1O2). More in-depth mechanisms reveal that the strong electron transfer between CNTs and hemin promotes the generation of (Porp)+•FeIV=O radicals through a heterolysis pathway. This research enriches the understanding of the catalytic mechanism of supported biomimetic catalysts for PMS activation and provides a perspective on the role of support materials for catalytic activity.

Degradation of the Selected Antibiotic in an Aqueous Solution by the Fenton Process: Kinetics, Products and Ecotoxicity.

Sulfonamides used in veterinary medicine can be degraded via the Fenton processes. In the premise, the process should also remove the antimicrobial activity of wastewater containing antibiotics. The kinetics of sulfathiazole degradation and identification of the degradation products were investigated in the experiments. In addition, their toxicity against Vibrio fischeri, the MARA® assay, and unselected microorganisms from a wastewater treatment plant and the river was evaluated. It was found that in the Fenton process, the sulfathiazole degradation was described by the following kinetic equation: r0 = k CSTZ-1 or 0 CFe(II)3 CH2O20 or 1 CTOC-2, where r0 is the initial reaction rate, k is the reaction rate constant, C is the concentration of sulfathiazole, Fe(II) ions, hydrogen peroxide and total organic carbon, respectively. The reaction efficiency and the useful pH range (up to pH 5) could be increased by UVa irradiation of the reaction mixture. Eighteen organic degradation products of sulfathiazole were detected and identified, and a possible degradation mechanism was proposed. An increase in the H2O2 dose, to obtain a high degree of mineralization of sulfonamide, resulted in an increase in the ecotoxicity of the post-reaction mixture.

Remediation of sulfathiazole contaminated soil by peroxymonosulfate: Performance, mechanism and phytotoxicity.

Peroxymonosulfate (PMS) was successfully adopted to remove organic pollutants in water, but it was rarely applied to soil remediation. Sulfathiazole (STZ) is a widely used sulfonamide antibiotic, while its residues have negative impacts on soil. To the best of our knowledge, this is the first attempt to apply PMS for the treatment of STZ-contaminated soil. The results showed that 4 mM PMS can degrade 96.54% of STZ in the soil within 60 min. Quenching and probe experiments revealed that singlet oxygen rather than hydroxyl radical and sulfate radical was the predominant reactive oxygen species responsible for STZ removal. The presence of Cl-, SO42-, NO3-, Fe3+, and HA enhanced the degradation efficiency of STZ, while HCO3- and Mn2+ presented an obstructive effect on STZ elimination at high concentrations. Different chemical extraction procedures were used to determine the bioavailability of the heavy metals. PMS oxidation process caused an unnoticeable influence of the concentrations of heavy metals except for the increase of Mn concentration and the decrease of Ba concentration. Moreover, the germination rate and stem length of wheat and radish both increased, indicating PMS oxidation reduced the toxicity of STZ, and the increase of Mn concentration did not cause a negative impact on their growth. Besides, the results of XRD and FTIR tests showed oxidation processes have negligible impacts on soil structure and composition. Based on intermediates identified, STZ degradation pathways in the PMS system were proposed. According to the results of this study, using PMS alone to repair STZ-contaminated soil is a relatively feasible, safe, and environmentally friendly technology.

In-Vivo Analysis and Model-Based Prediction of Tensides' Influence on Drug Absorption.

Depending on their concentrations the surface-active substances, tensides (surfactants) can positively or negatively influence the drug absorption, which is widely used in the design of the dosage forms with controlled release. A problem is that the (in-vivo) rate of absorption cannot be directly measured and for that reason, it is frequently substituted by evaluation of the (in-vitro) dissolution. On other hand, a suitably designed pharmacokinetic model can directly predict virtually all pharmacokinetic quantities including both the rate of absorption and fraction of the dose reaching the blood circulation. The paper presents a new approach to the analysis of the rate of drug absorption and shows its superiority over traditional in-vivo approaches. Both the in-vivo analysis and model-based prediction of the tenside (monolaurin of sucrose) influence on the rate of absorption of the drug (sulfathiazole) after instantaneous per-oral administration to rats are discussed. It was found that 0.001% solution of tenside can increase the rate of absorption by cca 50% and a two-fold increase in absolute bioavailability can be reached. Attention is also devoted to the formal requirements laid on the model's structure and its identifiability. The systematic design, substantiation and validation of a parsimonious predictive model that confirms in-vivo results are presented. The match between in-vivo observations and model-based predictions is demonstrated. The frequently overlooked metaphysics lying behind the compartmental modelling is briefly explained.

Changes in the proportions of an active pharmaceutical through cocrystals.

In this study, the modulation of amounts sulfathiazolium cations in different 2,6-pyridinedicarboxylates is demonstrated. An uncommon monoionic sulfathiazolium zinc 2,6-pyridinedicarboxylate (1:1 electrolyte) complex was characterized. Conventional sulfathiazolium zinc-bis-2,6-pyridinedicarboxylate dianionic complexes (2:1 electrolyte) were formed when hydroxyaromatic compounds such as 1,3-dihydroxybenzene or 3-nitrophenol were used as guest components. Thus, with the aid of the hydroxyaromatic molecules the zinc-bis-2,6-pyridinedicarboxylate complexes were stabilized with the relatively large sized sulfathiazolium cations. It was a consequence of domain expansion by the phenolic compounds. Sandwiched aromatic guests between the 2,6-pyridinedicarboxylates provided appropriate packing to accommodate the two large cations in the self-assemblies, which helped to modulate the amounts of sulfathiazole in different formulations. Antibacterial activities with E. coli DH5α have shown that the salt and the complexes have lower g/ml antibacterial activity than the parent drug.

Nitrogen-doped porous carbon encapsulating iron nanoparticles for enhanced sulfathiazole removal via peroxymonosulfate activation.

Developing novel catalyst with both high efficiency and stability presents an enticing prospect for peroxymonosulfate (PMS) activation. In this paper, nitrogen-doped porous carbon encapsulating iron nanoparticles (CN-Fe) was fabricated by a facile carbothermal reduction process using polyaniline (PANI) and α-Fe2O3 as the precursors. The stubborn antibiotics, sulfathiazole (STZ), was employed as a target pollutant, demonstrating that CN-Fe coupled with PMS could achieve 96% removal efficiency and even 57% mineralization rate of STZ within 40 min. More importantly, the rate constant of CN-Fe was calculated to be 0.07665 min-1, which was 6 times higher than that of the commercial α-Fe2O3 catalyst. Furthermore, CN-Fe also presented a favorable catalytic performance for removing other organic pollutants including phenolic compounds and organic dyes. Interestingly, the catalytic activity of the used CN-Fe catalyst could be regenerated after thermal treatment (600 °C) and the as-synthesized CN-Fe catalyst exhibited excellent long-term stability with almost no loss of activity after storage for three months. The catalytic mechanism in the CN-Fe/PMS system was elucidated by electron paramagnetic resonance (EPR), linear sweep voltammetry (LSV), radical and electron trapping tests, which confirmed that sulfate radicals (SO4-), hydroxyl radicals (OH), superoxide radicals (O2-) and singlet oxygen (1O2) were generated in the oxidation process with the assistance of electron transfer between PMS and catalyst. To our knowledge, this was the first attempt for the application of PANI-derived CN-Fe hybrid materials as PMS activators and the findings would provide a simple and promising strategy to fabricate highly efficient and environment-benign catalysts for wastewater remediation.

Development and Validation of the Simple and Sensitive Spectrophotometric Method of Amoxicillin Determination in Tablets using Sulphanilamides.

A rapid, simple and sensitive spectrophotometric method for the determination of amoxicillin (AM) is described. The method is based on the previous sulphanilamide (SA) and sulphathiazole (STZ) diazotization in the medium of 0.6-0.7 M hydrochloric acid and their subsequent interaction with amoxicillin at pH = 10.5 with formation of yellow-colored azo compouds. Effective molar absorptivities at the absorbance maxima at 445 nm (SA) and 448 nm (STZ) for azo compounds were (1.74 ± 0,06)∆104 L×mol-1×cm-1 and (1.97 ± 0,05)∆104 L×mol-1×cm-1, respectively. Stoichiometric ratios of the components of azo compounds were determined using continuous variations method. Based on the optimum reaction conditions, new methods were developed. These methods allow to determine the amoxicillin in concentration range 1.3-32.9 mg×mL-1 with sulphanilamide and 0.7-27.4 mg×mL-1 with sulphathiazole. The methods were successfully validated for amoxicillin determination in tablets "Amoxil".

Sulfate radical-based oxidation of the antibiotics sulfamethoxazole, sulfisoxazole, sulfathiazole, and sulfamethizole: The role of five-membered heterocyclic rings.

The widespread occurrence of sulfonamides (SAs) in natural waters, wastewater, soil and sediment has raised increasing concerns about their potential risks to human health and ecological systems. Sulfate radical (SO4-)-based advanced oxidation processes (SR-AOPs) have become promising technologies to remove such contaminants in the environment. The present study systematically investigated the degradation of four selected SAs with different five-membered heterocyclic rings, namely, sulfamethoxazole (SMX), sulfisoxazole (SIX), sulfathiazole (STZ), and sulfamethizole (SMT), by thermo-activated persulfate (PS) process, and the role of heterocyclic rings was assessed particularly. The results revealed that all the selected SAs could be degraded efficiently by thermo-activated PS process and their decay rates were appreciably increased with increasing temperature. For instance, degradation rates of STZ increased from 0.3 × 10-3 to 19.5 × 10-3 min-1 as the temperature was increased from 30 to 60 °C. Under the same experimental conditions, the degradation rates of SAs followed the order of SIX > SMX ≈ STZ > SMT, which was in accordance with decay rates of their R-NH2 moieties. Kinetic results indicated that five-membered heterocyclic rings could serve as reactive moieties toward SO4- attack, which were confirmed by frontier electron density (FED) calculations. Based on the transformation products identified by high-resolution mass spectrometry (HR-MS), five different oxidation pathways, including hydroxylation, aniline moiety oxidation, dimerization, sulfonamide bond cleavage, and heterocyclic ring oxidation/cleavage were proposed. Moreover, the degradation efficiency in real surface water (RSW) was found to be slightly slower than that in artificial surface water (ASW), suggesting that SR-AOPs could be an efficient approach for remediation of soil and water contaminated by these SAs.

Hair removal and bioavailability of chemicals: Effect of physicochemical properties of drugs and surfactants on skin permeation ex vivo.

Cosmetic hair removal procedures are everyday routines in our society. However, it is unclear if such routines lead to increased uptake of applied substances such as drugs or formulation compounds, potentially resulting in skin irritation or sensitization. The aim of this study was to elucidate the effect of common depilation and epilation methods on skin penetration of two surfactants and four model drugs of different physicochemical properties using the porcine ear model. It should be elucidated whether the substances' skin penetration behavior would be affected by hair removal procedures and if potential effects would be related to their polarity. Confocal Raman spectroscopy revealed no effect of hair removal on total penetration depths of SDS and sulfathiazole. Significantly higher relative penetrated amounts within 0-6 µm of stratum corneum depth were found for SDS after dry shaving, depilatory cream and waxing and for sulfathiazole after all depilation methods and partly after epilation. ATR-FTIR spectroscopy revealed no effect of hair removal on the penetration depth of lecithin LPC80, but higher relative amounts at the skin surface after wet shaving and electric epilation. Diffusion cell experiments using a lecithin-based microemulsion as carrier system for fluconazole, fludrocortisone acetate and flufenamic acid showed higher cumulative amounts, higher drug fluxes and shorter lag times for the more lipophilic drugs for some of the methods, but only shorter lag times in some cases for fluconazole. In summary, the observed effects appeared to depend on drug polarity and experimental setup.

Parameters affecting LED photoreactor efficiency in a heterogeneous photo-Fenton process using iron mining residue as catalyst.

In this article, a light-emitting diode (LED)-based photoreactor was designed and evaluated for degradation of the antibiotic sulfathiazole (STZ), using heterogeneous photo-Fenton process with an iron ore residue as catalyst. The effects of the type of magnetic stirrer bar, use of baffles, rotation speed, and type and intensity of irradiation source were evaluated. The results showed that the degradation of STZ was strongly influenced by rotation speed (1100 rpm) and that the use of an octagonal stirrer bar favoured high dispersion and greater contact of the catalyst with the reaction medium. Although the presence of baffles had little influence on STZ degradation, their use enabled good dispersion of the catalyst (due to axial flow) and eliminated the vortex formed at high stirring speeds. It was found that the iron mining residue could be activated by UV LEDs, visible light LEDs, and black light irradiation, with similar degradation efficiencies achieved. Using the LEDs, STZ concentrations below the detection limit were obtained after 40 min, with power consumption 38-fold (UV LEDs) and 22-fold (visible light LEDs) lower than required for black light irradiation. The results demonstrated the advantages of the use of LED devices as irradiation systems in heterogeneous photo-Fenton processes.

Waste-wood-derived biochar cathode and its application in electro-Fenton for sulfathiazole treatment at alkaline pH with pyrophosphate electrolyte.

For the first time, a biomass-derived porous carbon cathode (WDC) was fabricated via a facile one-step pyrolysis of recovered wood-waste without any post-treatment. The WDC along with pyrophosphate (PP) as electrolyte were used in electro-Fenton (EF) at pH 8 for sulfathiazole (STZ) treatment. The H2O2 accumulation capacity of WDC was optimized via the following parameters: pyrolysis temperature, applied current and electrolyte. Results showed that the WDC cathode prepared at 900 °C achieved the highest H2O2 accumulation (13.80 mg L-1 in 3 h) due to its larger electroactive surface area (28.81 cm2). Interestingly, it was found that PP decreased the decomposition rate of H2O2 in solution as compared to conventional electrolyte, which resulted in higher H2O2 accumulation. PP allowed operating EF at pH of 8 due to the formation of Fe2+-PP complexes in solution. Moreover, Fe2+-PP was able to activate oxygen to produce OH. In this way, the degradation of STZ took place through four main pathways: 1) via OH from the Fe2+-PP complex, 2) via OH from EF reactions, 3) via surface OH at the boron doped diamond electrode (BDD) and 4) via SO4- from BDD activation. Finally, microtox tests revealed that some toxic intermediates were generated during WDC/BDD/PP EF treatment, but they were removed at the end of the process.

Removal of Sulfamethoxazole, Sulfathiazole and Sulfamethazine in their Mixed Solution by UV/H2O2 Process.

Sulfamethoxazole (SMZ), sulfathiazole (STZ) and sulfamethazine (SMT) are typical sulfonamides, which are widespread in aqueous environments and have aroused great concern in recent years. In this study, the photochemical oxidation of SMZ, STZ and SMT in their mixed solution using UV/H2O2 process was innovatively investigated. The result showed that the sulfonamides could be completely decomposed in the UV/H2O2 system, and each contaminant in the co-existence system fitted the pseudo-first-order kinetic model. The removal of sulfonamides was influenced by the initial concentration of the mixed solution, the intensity of UV light irradiation, the dosage of H2O2 and the initial pH of the solution. The increase of UV light intensity and H2O2 dosage substantially enhanced the decomposition efficiency, while a higher initial concentration of mixed solution heavily suppressed the decomposition rate. The decomposition of SMZ and SMT during the UV/H2O2 process was favorable under neutral and acidic conditions. Moreover, the generated intermediates of SMZ, STZ and SMT during the UV/H2O2 process were identified in depth, and a corresponding degradation pathway was proposed.