Electrochemical degradation of sulfonamides at BDD electrode: kinetics, reaction pathway and eco-toxicity evaluation

Robust Photocatalytic MICROSCAFS® with Interconnected Macropores for Sustainable Solar-Driven Water Purification

Advanced oxidation processes, including photocatalysis, have been proven effective at organic dye degradation. Tailored porous materials with regulated pore size, shape, and morphology offer a sustainable solution to the water pollution problem by acting as support materials to grafted photocatalytic nanoparticles (NPs). This research investigated the influence of pore and particle sizes of photocatalytic MICROSCAFS® on the degradation of methyl orange (MO) in aqueous solution (10 mg/L). Photocatalytic MICROSCAFS® are made of binder-less supported P25 TiO2 NPs within MICROSCAFS®, which are silica-titania microspheres with a controlled size and interconnected macroporosity, synthesized by an adapted sol-gel method that involves a polymerization-induced phase separation process. Photocatalytic experiments were performed both in batch and flow reactors, with this latter one targeting a proof of concept for continuous transformation processes and real-life conditions. Photocatalytic degradation of 87% in 2 h (batch) was achieved, using a calibrated solar light simulator (1 sun) and a photocatalyst/pollutant mass ratio of 23. This study introduces a novel flow kinetic model which provides the modeling and simulation of the photocatalytic MICROSCAFS® performance. A scavenger study was performed, enabling an in-depth mechanistic understanding. Finally, the transformation products resulting from the MO photocatalytic degradation were elucidated by high-resolution mass spectrometry experiments and subjected to an in silico toxicity assessment.

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).

Sustainable Electrochemical Activation of Self-Generated Persulfate for the Degradation of Endocrine Disruptors: Kinetics, Performances, and Mechanisms

This study presents an electrolysis system utilizing a novel self-circulation process of sulfate (SO42-) and persulfate (S2O82-) ions based on a boron-doped diamond (BDD) anode and an activated carbon fiber (ACF) cathode, which is designed to enable electrochemical remediation of environmental contaminants with reduced use of chemical reagents and minimized residues. The production of S2O82- and hydrogen peroxide (H2O2) on the BDD anode and ACF cathode, respectively, is identified as the source of active radicals for the contaminant degradation. The initiator, sulfate, is identified by comparing the degradation efficiency in NaSO4 and NaNO3 electrolytes. Quenching experiments and electron paramagnetic resonance (EPR) spectroscopy confirmed that the SO4-· and ·OH generated on the ACF cathode are the main reactive radicals. A comparison of the degradation efficiency and the generated S2O82-/H2O2 of the divided/undivided electrolysis system is used to demonstrate the superiority of the synergistic effect between the BDD anode and ACF cathode. This work provides evidence of the effectiveness of the philosophy of "catalysis in lieu of supplementary chemical agents" and sheds light on the mechanism of the generation and transmission of reactive species in the BDD and ACF electrolysis system, thereby offering new perspectives for the design and optimization of electrolysis systems.

Interactions between sulfonamide homologues and glycosyltransferase induced metabolic disorders in rice (Oryza sativa L.)

Sulfadiazine and its derivatives (sulfonamides, SAs) could induce distinct biotoxic, metabolic and physiological abnormalities, potentially due to their subtle structural differences. This study conducted an in-depth investigation on the interactions between SA homologues, i.e. sulfadiazine (SD), sulfamerazine (SD1), and sulfamethazine (SD2), and the key metabolic enzyme (glycosyltransferase, GT) in rice (Oryza sativa L.). Untargeted screening of SA metabolites revealed that GT-catalyzed glycosylation was the primary transformation pathway of SAs in rice. Molecular docking identified that the binding sites of SAs on GT (D0TZD6) were responsible for transferring sugar moiety to synthesize polysaccharides and detoxify SAs. Specifically, amino acids in the GT-binding cavity (e.g., GLY487 and CYS486) formed stable hydrogen bonds with SAs (e.g., the sulfonamide group of SD). Molecular dynamics simulations revealed that SAs induced conformational changes in GT ligand binding domain, which was supported by the significantly decreased GT activity and gene expression level. As evidenced by proteomics and metabolomics, SAs inhibited the transfer and synthesis of sugar but stimulated sugar decomposition in rice leaves, leading to the accumulation of mono- and disaccharides in rice leaves. While the differences in the increased sugar content by SD (24.3%, compared with control), SD1 (11.1%), and SD2 (6.24%) can be attributed to their number of methyl groups (0, 1, 2, respectively), which determined the steric hindrance and hydrogen bonds formation with GT. This study suggested that the disturbances on crop sugar metabolism by homologues contaminants are determined by the interaction between the contaminants and the target enzyme, and are greatly dependent on the steric hindrance effects contributed by their side chains. The results are of importance to identify priority pollutants and ensure crop quality in contaminated fields.

Removal of pharmaceuticals and personal care products from wastewater via anodic oxidation and electro-Fenton processes: current status and needs regarding their application

This review provides a current opinion on the most recent works that have been published toward the application of electrochemical advance oxidation processes (EAOPs) for the degradation of pharmaceutical and personal care products (PPCPs) in water streams. Advances in the application of anodic oxidation (AO)- and electro-Fenton (EF)-based processes are reported, including operational conditions, electrode performance, and removal. Although AO- and EF-based processes can easily reach 100% removal of PPCPs, mineralization is desirable to avoid the generation of potential toxic byproducts. The following section exploring some techno-economic aspects of the application of EAOPs is based on electrode selection, operational costs as well as their use as cotreatments, and their synergistic effects. Finally, this short review ends with perspectives about the emerging topics that are faced by these technologies applied for the degradation of PPCPs in research and practice.

Reactive species conversion into 1O2 promotes substantial inhibition of chlorinated byproduct formation during electrooxidation of phenols in Cl--laden wastewater

The generation of chlorinated byproducts during the electrochemical oxidation (EO) of Cl^--laden wastewater is a significant concern. We aim to propose a concept of converting reactive species (e.g., reactive chlorines and HO^• resulting from electrolysis) into ¹O₂ via the addition of H₂O₂, which substantially alleviates chlorinated organic formation. When phenol was used as a model organic compound, the results showed that the H₂O₂-involving EO system outperformed the H₂O₂-absent system in terms of higher rate constants (5.95 × 10^-2 min^-1vs. 2.97 × 10^-2 min^-1) and a much lower accumulation of total organic chlorinated products (1.42 mg L^-1vs. 8.18 mg L^-1) during a 60 min operation. The rate constants of disappearance of a variety of phenolic compounds were positively correlated with the Hammett constants (σ), suggesting that the reactive species preferred oxidizing phenols with electron-rich groups. After the identification of ¹O₂ that was abundant in the bulk solution with the use of electron paramagnetic resonance and computational kinetic simulation, the routes of ¹O₂ generation were revealed. Despite the consensus as to the contribution of reaction between H₂O₂ and ClO^- to ¹O₂ formation, we conclude that the predominant pathway is through H₂O₂ reaction with electrogenerated HO^• or chlorine radicals (Cl^• and Cl₂^•-) to produce O₂^•-, followed by self-combination. Density functional theory calculations theoretically showed the difficulty in forming chlorinated byproducts for the ¹O₂-initiated phenol oxidation in the presence of Cl^-, which, by contrast, easily occurred for the Cl^•-or HO^•-initiated phenol reaction. The experiments run with real coking wastewater containing high-concentration phenols further demonstrated the superiority of the H₂O₂-involving EO system. The findings imply that this unique method for treating Cl^--laden organic wastewater is expected to be widely adopted for generalizing EO technology for environmental applications.

Molar absorption coefficients and acid dissociation constants for fluoroquinolone, sulfonamide, and tetracycline antibiotics of environmental concern

Antibiotics are priority contaminants of emerging concern due to their pseudo-persistence in the environment and contribution to the development of antimicrobial resistance. In solution, antibiotics undergo (de)protonation reactions that affect their UV absorbance and, therefore, photolytic fate in natural and engineered systems. This study employed enhanced spectrophotometric methods to determine the acid dissociation constants (as pK_a values) and molar absorption coefficients for 12 fluoroquinolone, 9 sulfonamide, and 7 tetracycline antibiotics of environmental relevance. Molar absorption coefficient heatmaps were generated for all 28 antibiotics at 200-500 nm and pH 1.8-12.2. The data in the heatmaps were deconvoluted to calculate pK_a values and specific molar absorption coefficients at each wavelength. All antibiotics had at least one pK_a value in the environmentally relevant range of 5.5-8.5, and pK_a values were reported for methacycline, moxifloxacin, nadifloxacin, rolitetracycline, sulfadoxine, and sulfapyridine for the first time. Deprotonation of the carboxylic acid associated with pK_a,1 (5.5-6.7) exerted the strongest effects on the UV absorbance of fluoroquinolones. For tetracyclines, deprotonation of the tertiary amine at pK_a,3 (7.8-10.2) was responsible for major shifts in UV absorbance. Although sulfonamides have conserved pK_a sites, no general trends were observed for the molar absorption coefficients. The structural similarity of fluoroquinolones and tetracyclines supported the potential for a class-based approach to identifying molar absorbance as a function of pH. Overall, the reported pK_a values and specific molar absorption coefficients will serve as important resources for future studies on antibiotic fate in natural and engineered systems.

Pharmaceuticals and personal care products in water streams: Occurrence, detection, and removal by electrochemical advanced oxidation processes

Pharmaceutical and personal care products (PPCPs) are part of the emerging contaminants (ECs) in the environment due to their known or suspected adverse effects in aquatic and terrestrial organisms, as well as in human health. Presence of PPCPs in aquatic and terrestrial ecosystems has been mainly attributed to the effluents of wastewater treatment plants (WWTPs). Although several PPCPs have been detected in wastewater, their removal from wastewater via biological processes is limited. Removal of PPCPs depends on their chemical structure, concentration, solubility, and technology used to treat the wastewater. Electrochemical Advanced Oxidation Processes (EAOPs) are some of the most sought-after methods for dealing with organic pollutants in water including PPCPs, due to generation of strong oxidants such as •OH, H₂O₂ and O₃^- by using directly or indirectly electrochemical technology. This review is focused on the removal of main PPCPs via EAOPs such as, anodic oxidation, electro-Fenton, photoelectron-Fenton, solar photoelectron-Fenton, photoelectrocatalysis and sonoelectrochemical processes. Although more than 40 PPCPs have been identified through different analytical approaches, antibiotics, anti-inflammatory and antifungal are the main categories of PPCPs detected in different water matrices. Application of EAOPs has been centered in the removal of antibiotics and analgesics of high consumption by using model media, e.g. Na₂SO_4. Photoelectrocatalysis and Electro-Fenton processes have been the most versatile EAOPs applied for PPCPs removal under a wide range of operating conditions and a variety of electrodes. Although EAOPs have gained significant scientific interest due to their effectiveness, low environmental impact, and simplicity, further research about the removal of PPCPs and their by-products under realistic concentrations and media is needed. Moreover, mid-, and long-term experiments that evaluate EAOPs performance will provide knowledge about key parameters that allow these technologies to be scaled and reduce the potential risk of PPCPs in aquatic and terrestrial ecosystem.

In situ scrutinize the adsorption of sulfamethoxazole in water using AFM force spectroscopy: Molecular adhesion force determination and fractionation

The interaction force of a typical antibiotic molecule during adsorption has never been experimentally determined and fractionated, which hindered the evolution of removal strategies. In this study, sulfamethoxazole (SMX) as a typical antibiotic was stably immobilized onto an atomic force microscopy (AFM) tip without affecting original properties. The SMX modified AFM tip visualized the potential adsorption sites on a graphene oxide (GO) nanosheet for the first time by mapping the SMX adhesion force distribution. Moreover, the interaction force of a single SMX molecule to GO was determined at 38.6 pN which was subsequently fractionated into the hydrophobic (17.9 pN) and π-π (160.0 pN) attractions as well as the electrostatic repulsion (- 139.3 pN) at pH: 5.7. As compared with highly-ordered pyrolytic graphite (HOPG), the introduced oxygen containing groups on GO not only reduced the hydrophobic interaction but also generated an opposite electrostatic repulsion force to SMX. This study experimentally and theoretically revealed the adhesion mechanisms of SMX and potentially other sulfonamide antibiotics in molecular level, which may contribute to the study of antibiotic environmental transportation and the development of next-generation antibiotic remediation protocols.

Comparison of chemical and biological degradation of sulfonamides: Solving the mystery of sulfonamide transformation

Sulfonamides (SAs) are widespread in aquatic environments and pose serious environmental risks. The removal efficiencies and degradation mechanisms of SAs in both chemical and biological degradation systems were comprehensively reviewed. Density functional theory (DFT) was utilized to decipher the reaction types and reactive sites of both degradation mechanisms at the electron level. In chemical degradation, the rate of the reactive oxidants to degrade SAs follows the order SO₄•^- ≈ •OH > O₃ > ¹O₂ > ClO₂ ≈ Fe(VI) ≈ HOCl > peroxymonosulfate. pH affects the oxidation-reduction potentials of oxidants, the reactivity of SAs, and the intermolecular force between oxidants and SAs, thereby affecting the chemical degradation efficiencies and mechanisms. In biological degradation, oxidoreductase produced by bacteria, fungi, algae, and plants can degrade SAs. The catalytic activity of the enzyme is affected by the enzyme system, reaction conditions, and type of SAs. Despite the different reaction modes and removal efficiencies of SAs in chemical degradation and biological degradation, the transformation pathways and products show commonalities. Modification of the amino (N¹H₂-) moiety and destruction of sulfonamide bridge (-SO₂-N¹¹H-) moiety are the main pathways for both chemical and biological degradation of SAs. Most oxidants or enzymes can react with the N¹H₂- moiety. Reactions of the -SO₂-N¹¹H- moiety are mainly initiated by the cleavage of S-N bonds for five-membered heterocyclic ring-substituted SAs, and by SO₂ extrusion for six-membered heterocyclic ring-substituted SAs. Chlorine substitution and coupling on the N¹H₂- moiety, hydroxylation of the benzene moiety, oxidation of methyl, and isomerization of the R substituents are the transformation pathways unique to chemical degradation. Formylation/acetylation, glycosylation, pterin conjugation, and deamination of the N¹H₂- moiety are the transformation pathways unique to biological degradation. DFT studies revealed the same reaction types and the same reactive sites of SAs in chemical and biological degradation. Electrophiles are mostly prone to attack the N¹ atom on the amino moiety of neutral SAs and the N¹¹ atom on the sulfonamide bridge moiety of anionic SAs, leading to nitration or electrophilic substitution of the amino moiety and the cleavage of S-N bonds or SO₂ extrusion of the sulfonamide bridge moiety. Reactions on the -SO₂-N¹¹H- moiety eliminate antibacterial activity in the SA degradation process. This review elucidated SA transformation by comparing the chemical and biological degradation of SAs. This could provide theoretical guidance for the development of more efficient and economical treatment technologies for SAs.

Enhanced perfluorooctane acid mineralization by electrochemical oxidation using Ti3+ self-doping TiO2 nanotube arrays anode

Perfluorooctanoic acid (PFOA) is of increasing concern due to its worldwide application and extremely environmental persistence. Herein, we demonstrated the electrochemical degradation of PFOA with high efficiency using the Ti³⁺ self-doping TiO₂ nanotube arrays (Ti³⁺/TiO₂-NTA) anode. The fabricated Ti³⁺/TiO₂-NTA anode exhibited vertically aligned uniform nanotubes structure, and was demonstrated good performance on the electrochemical degradation of PFOA in water. The degradation rate, total organic carbon (TOC) removal rate and defluorination rate of PFOA reached 98.1 %, 93.3 % and 74.8 %, respectively, after electrolysis for 90 min at low current density of 2 mA cm^-2. The energy consumption (7.6 Wh L^-1) of this electrochemical oxidation system using Ti³⁺/TiO₂-NTA anode for PFOA degradation was about 1 order of magnitude lower than using traditional PbO₂ anodes. Cathodic polarization could effectively prolong the electrocatalytic activity of the anode by regenerating Ti³⁺ sites. PFOA molecular was underwent a rapidly mineralization to CO₂ and F^-, with only low concentration of short-chain perflfluorocarboxylic acids (PFCAs) intermediates identified. A possible electrochemical degradation mechanism of PFOA was proposed, in which the initial direct electron transfer (DET) on the anode to yield PFOA free radicals (C₇F₁₅COO•) and hydroxyl radicals (•OH) oxidation were greatly enhanced. This presented study provides a novel approach for the purification of the recalcitrant PFOA from wastewaters.

Synergetic metronidazole removal from aqueous solutions using combination of electro-persulfate process with magnetic Fe3O4@AC nanocomposites: nonlinear fitting of isotherms and kinetic models

The removal of metronidazole (MNZ) from aqueous solutions by the electro-persulfate (EC–PS) process was performed in combination with magnetic Fe3O4@activated carbon (AC) nanocomposite. In the first step, the Fe3O4@AC nanocomposites were synthesized and characterized using energy-dispersive X-ray spectroscopy (XRD), vibrating-sample magnetometer (VSM) and field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), mapping, and Fourier-transform infrared spectroscopy (FTIR) analysis. The effect of Fe3O4@AC, PS and EC processes were studied separately and in combination and finally, the appropriate process for MNZ removal was selected. The effect of key parameters on the EC–Fe3O4@AC–PS process including pH, Fe3O4@AC dosage, initial MNZ concentration, and PS concentration were investigated. Based on the results obtained, the Fe3O4@AC had a good structure. The MNZ removal in EC, PS, Fe3O4@AC, EC–Fe3O4@AC, EC–PS, EC–Fe3O4@AC–NaCl, EC–Fe3O4@AC–PS, and EC–Fe3O4@AC–PS–NaCl processes were 0, 0, 59.68, 62, 68.94, 67.71, 87.23 and 88%, respectively. Due to the low effect of NaCl insertion on the EC–Fe3O4@AC–PS process, it was not added into the reactor and optimum conditions for the EC–Fe3O4@AC–PS process were determined. Under ideal conditions, including MNZ = 40 mg/L, Fe3O4@AC dose = 1 g/L, pH = 3, PS concentration = 1.68 mM, current density (CD) = 0.6 mA/cm2 and time = 80 min, the MNZ removal was 92%. Kinetic study showed that the pseudo-second-order model was compatible with the obtained results. In the isotherm studies, the Langmuir model was the most consistent for the data of the present study, and the Q max for Fe3O4@AC dose from 0.25 to 1 g/L was 332 to 125 mg/g, respectively.

High adsorption of sodium diclofenac on post-synthetic modified zirconium-based metal-organic frameworks: Experimental and theoretical studies

Water pollution by pharmaceuticals is currently a great concern due to their ecological risks. In this study, zirconium-based metal-organic frameworks (UiO-66-(COOH)₂) were used for removal of the nonsteroidal anti-inflammatory drug (NSAID) diclofenac sodium (DCF). They have been synthesized using a hydrothermal method. Copper and iron metal ions were incorporated in the framework using post-synthetic modification techniques to produce UiO-66-(COOCu)₂ and UiO-66-(COOFe)₂. The resulted MOFs were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning/transmission electron microscopy, and Brunauer-Emmett-Teller. The effects of the pH, initial concentration, and adsorption time on the adsorption process of diclofenac were studied. The maximum adsorption capacities obtained on UiO-66-(COOH)₂, UiO-66-(COOCu)₂, and UiO-66-(COOFe)₂ were 480.5, 624.3, and 769.1 mg/g, respectively. The adsorption of diclofenac was found to be better fitted with Langmuir isotherm and pseudo-second-order kinetic models. The adsorption mechanism was investigated using XRD, FT-IR, density functional theory and Monte Carlo simulation, in which the latter method was used to calculate the adsorption energies and determine the possible interactions between diclofenac and the adsorbents. UiO-66-(COOH)₂, UiO-66-(COOCu)₂, and UiO-66-(COOFe)₂ exhibited good recyclability for diclofenac removal, which confirms the sustainability of these materials.

A tubular electrode assembly reactor for enhanced electrochemical wastewater treatment with a Magnéli-phase titanium suboxide (M-TiSO) anode and in situ utilization

The electrochemical oxidation technology has been widely used for the waste water treatment and water reuse because of its easy-to-operate nature, an effective removal of pollutants and non-secondary pollution. However, the price of electrode materials, the limitation of mass transfer and the associated effects on contaminant degradation hamper its application. Within this context, an in situ utilization tubular electrode assembly reactor (TEAR) was proposed, in which a stainless steel pipe (SSP) was used as the cathode, and a tubular Magnéli-phase titanium suboxide (M-TiSO) anode was posited in the center of that pipe. Besides the cathode and anode, an integral electrochemical system to treat water pollutants was constituted with a spiral static mixer made from three-dimensional (3D) printing. A spiral static mixer was pushed into the interspace of electrodes to minimize the adverse effect caused by inhomogeneous distribution of pollutants. Here, the effects of current density and resident time on the removal of methylene blue (MB) and total organic carbon (TOC) were investigated, the corresponding hydrodynamics was studied using computational fluid dynamics (CFD), and the long-term stability of removing MB by the reactor was discussed. The results indicated that the MB and TOC removal rate was enhanced at specific current density with a static mixer and the velocity distribution tended to be more homogeneous. Moreover, the anode surface shear force and heat transfer were increased by improving the fluid state. This study proposed an in situ utilization concept and provided a potential value for feasible and efficient water treatment.

A stainless steel pipe (SSP) was used as a cathode. A tubular Magnéli-phase titanium suboxide (M-TiSO) anode was posited in the center. A spiral static mixer was used to process intensification.

Preparation of Ce0.9Zr0.1O2/SnIn4S8 composite photocatalyst and its degradation of typical antibiotic pollutants

Considering the high environmental risk, the remediation of antibiotic pollutants attracted numerous attentions. In this work, a novel photocatalyst, Ce0.9Zr0.1O2/SnIn4S8, was fabricated by in situ precipitation and hydrothermal method and then applied to the degradation of norfloxacin under the irritation of visible light. The SEM, TEM, XRD, XPS, and electrochemical results clearly showed that the n-type heterojunction between Ce0.9Zr0.1O2 and SnIn4S8 was successfully constructed, which greatly reduces the recombination of the photogenic electron and holes, leading to the improvement of photocatalytic performance and stability (recycled over eight times). Besides, the Ce0.9Zr0.1O2/SnIn4S8 composite also exhibited good ability to mineralize norfloxacin. Under the optimal condition (pH 3, 1 g L-1 of 10% Ce0.9Zr0.1O2/SnIn4S8, and 8 mg L-1 of initial norfloxacin concentration), norfloxacin could be fully and rapidly degraded in 60 min, and completely mineralized in 4 h (99.3 ± 1.7%). LC-QTOF-MS results evidently displayed eight intermediates during norfloxacin degradation. In addition, with the attack of the reactive oxygen species (h+, •OH, and •O2-), norfloxacin could be effectively decomposed via deoxygenation, hydroxylation, and carboxylation reactions. Notably, compared to photodegradation, the photocatalytic process could completely eliminate the norfloxacin from water because it could avoid the accumulation of toxic byproducts.

Efficient mineralization of sulfanilamide over oxygen vacancy-rich NiFe-LDH nanosheets array during electro-fenton process

Electrochemical degradation of toxic sulfanilamide with inexpensive approach is in urgent demand due to the harmful effects of sulfanilamide for both humans and aquatic environments. Here, we reported an efficient mineralization of sulfanilamide by using NiFe-layered double hydroxide (NiFe-LDH) nanosheets array with abundant oxygen vacancies that was in situ grown on exfoliated graphene (EG) by a simple hydrothermal treatment at different temperatures. The hydrothermal temperature was carefully analyzed for control synthesis of oxygen vacancy-rich NiFe-LDH/EG nanosheets array (NiFe-LDH/EG-OVr) for sulfanilamide degradation. Owing to the abundant oxygen vacancies, NiFe-LDH/EG-OVr rapidly generated hydrogen peroxide (H₂O₂) and hydroxyl radical (•OH) during electro-Fenton (EF) process_, which resulted in the 98% mineralization of sulfanilamide in first 80 min. The radicals trapping experiments revealed that the •OH radicals was participated as the main active oxidation species in the efficient mineralization of sulfanilamide. The present results indicated that the oxidative attack by •OH radicals initiated the degradation process of sulfanilamide. During the total degradation of sulfanilamide, several organic compounds including aminophenol, hydroquinone, and oxalic acid, were identified as main intermediates by using gas chromatography-mass spectroscopy (GC-MS) and high-performance liquid chromatography-mass spectroscopy (HPLC-MS).

The remediation of sulfonamides from the environment by Pleurotus eryngii mycelium. Efficiency, products and mechanisms of mycodegradation

The objective of the study was to assess the applicability of the mycelium obtained from the in vitro cultures of nontoxic bracket fungus, Pleurotus eryngii, to sulfonamides mycodegradation. Samples containing one of the six selected sulfonamides, sulfanilamide derivatives, were incubated with the mycelium of P. eryngii for 7 and 14 days in vitro. Subsequently, change in the sulfonamide concentration was assessed in the samples using the UPLC-QTof. The transformation products were identified based on monoisotopic molecular mass and fragmentation spectra. The studied sulfonamides did not inhibit the growth of P. eryngii mycelium in the in vitro cultures. In addition, a considerable reduction of sulfonamide concentration was observed in all the incubated samples (from 73.7 ± 8.3% to 99.8 ± 0.3%). In the case of three sulfonamides, the reduction in concentration >90% occurred after 7 days of incubation. However, the transformation of sulfonamides was partially caused by their degradation to simpler organic compounds. After incubation, the products of condensation of sulfonamides with formyl, acyl, and sugar groups, and amino acid-derived compounds were identified in the samples. This indicated the partially reversible nature of the mycodegradation process.

Recent advancement in remediation of synthetic organic antibiotics from environmental matrices: Challenges and perspective

Continuous discharge and persistence of antibiotics in aquatic ecosystem is identified as emerging environment health hazard. Partial degradation and inappropriate disposal induce appearance of diverse antibiotic resistant genes (ARGs) and bacteria, hence their execution is imperative. Conventional methods including waste water treatment plants (WWTPs) are found ineffective for the removal of recalcitrant antibiotics. Therefore, constructive removal of antibiotics from environmental matrices and other alternatives have been discussed. This review summarizes present scenario and removal of micro-pollutants, antibiotics from environment. Various strategies including physicochemical, bioremediation, use of bioreactor, and biocatalysts are recognized as potent antibiotic removal strategies. Microbial Fuel Cells (MFCs) and biochar have emerged as promising biodegradation processes due to low cost, energy efficient and environmental benignity. With higher removal rate (20-50%) combined/ hybrid processes seems to be more efficient for permanent and sustainable elimination of reluctant antibiotics.

Boron-doped diamond (BDD) electro-oxidation coupled with nanofiltration for secondary wastewater treatment: Antibiotics degradation and biofouling

In this study, a boron-doped diamond (BDD) electro-oxidation technology coupled with nanofiltration membrane (EO-NF) technology was investigated for its effectiveness in removing antibiotics (i.e., sulfamethazine:SMZ) and mitigating biofouling during secondary wastewater treatment. The result showed that EO obtained an effective SMZ removal, owing to the ·OH generation observed by Electron paramagnetic resonance (EPR) analysis; complete elimination of SMZ was found under the high current density (30 mA/cm²) and long Electrolysis Time (ET = 60 min). Meanwhile, EO-NF process enabled to reduce COD content from 60 mg/L to nearly 5 mg/L. Furthermore, regardless of the effect of EO process, NF could retain most NH₃-N because of the excellent performance of NF for ions rejection, and its permeate concentration was below 0.5 mg/L. EO was able to reduce membrane fouling notably, increasing the final flux (15 L/(m²·h)) of NF by 25.1% during long-term operation (240 h). Scanning electron microscopy-Energy dispersive spectrometry (SEM-EDS) showed that a porous layer formed on the vicinity of NF membrane in the case of filtrating EO effluent, in contrast to a uniform and dense biofouling layer generated during the direct NF. Besides, the content of adenosine triphosphate (ATP) and the number of bacterial colonies in the retentate of the EO-NF process were greater than those of the direct NF process. This resulted in a smaller amount of extracellular polymeric substances (EPS) attaching to the membrane surface, decreasing the tightness and hardness of the fouling layer in the case of EO, as indicated by CLSM analysis. Overall, considering its ability to effectively eliminate persistent contaminants and reduce membrane fouling, BDD-based EO is considered a promising pre-treatment option for future NF applications.

Electrochemical oxidation of butyl paraben on boron doped diamond in environmental matrices and comparison with sulfate radical-AOP

The electrochemical oxidation (EO) of butyl paraben (BP) over boron-doped diamond (BDD) anode was studied in this work. Emphasis was put on degradation performance in various actual water matrices, including secondary treated wastewater (WW), bottled water (BW), surface water (SW), ultrapure water (UW), and ultrapure water spiked with humic acid (HA). Experiments were performed utilizing 0.1 M Na₂SO₄ as the electrolyte. Interestingly, matrix complexity was found to favor BP degradation, i.e. in the order WW ~ BW > SW > UW, thus implying some kind of synergy between the water matrix constituents, the reactive oxygen species (ROS) and the anode surface. The occurrence of chloride in water matrices favors reaction presumably due to the formation of chlorine-based oxidative species, and this can partially offset the need to work at increased current densities in the case of chlorine-free electrolytes. No pH effect in the range 3-8 on degradation was recorded. EO oxidation was also compared with a sulfate radical process using carbon black as activator of sodium persulfate. The matrix effect was, in this case, detrimental (i.e. UW > BW > WW), pinpointing the different behavior of different processes in similar environments.

Enhanced Sulfamerazine Removal via Adsorption–Photocatalysis Using Bi2O3–TiO2/PAC Ternary Nanoparticles

The presence of sulfonamides (SAs) in water has received increasing attention due to the risk to ecosystems. The adsorption and photocatalysis performance for sulfamerazine (SMZ) of Bi2O3–TiO2 supported on powdered activated carbon (Bi2O3–TiO2/PAC) nanoparticles was evaluated. The amount of doped Bi2O3 not only influenced the photocatalytic performance but also impacted the adsorption capacity. The adsorption mass transfer mechanism of Bi2O3–TiO2/PAC was elucidated and is further discussed in combination with the photocatalytic mechanism. It was indicated that Bi2O3–TiO2/PAC(10%–700 °C) performed best, and the SMZ removal by the adsorption–photocatalysis of Bi2O3–TiO2/PAC(10%–700 °C) reached 95.5%. Adsorption onto active sites was a major adsorption step, and external diffusion was assisted. Superoxide radical (●O2−) and hole (h+) were identified as the major reactive oxygen species (ROS) for SMZ removal. Benzene ring fracture, SO2 extrusion and nitrogenated SMZ were proposed as the main pathways for photocatalysis. Meanwhile, alkaline conditions enhanced photocatalytic performance, while contrary effects were observed for adsorption. The adsorption–photocatalysis removal performance for SMZ in lake water was better than that for river water. It can be generalized for the potential application of photocatalysis coupling with adsorption to remove refractory antibiotics in water.

Abiotic and biotic transformation of torasemide - Occurrence of degradation products in the aquatic environment

The pharmaceutical torasemide is an important loop diuretic and was 2017 one of the ten most prescribed drugs in Germany. Despite its detection in different compartments of the urban water cycle including drinking water, no studies were so far performed to elucidate its fate in the environment and the occurrence of transformation products (TPs). Therefore, we investigated the phototransformation, microbial degradation, transformation with human liver microsomes and anodic oxidation of torasemide to obtain good coverage of environmentally relevant degradation products. Overall sixteen products were identified, covering the following reaction mechanisms: aromatic and aliphatic hydroxylation, including further oxidation to carboxylic acids and quinone imines, amide cleavage, N-dealkylation, N-dearylation, and sulfonamide hydrolysis to sulfonic acids. Especially the formation of quinone imines could be of concern as they are highly reactive electrophiles. Torasemide itself was observed in all investigated wastewater treatment plant (WWTP) samples and wastewater-impacted surface waters. The maximum detected concentration was about 350 ng L^-1. Only three of the sixteen transformation products were generally observed in at least one of the samples and the most frequently detected TPs were the human metabolites hydroxytorasemide (TP 364a) and carboxytorasemide (TP 378a). The complete removal of TP 364a during wastewater treatment was in agreement with the results of microbial degradation experiments. TP 364a was most likely transformed into TP 378a, which was microbially less degraded in lab experiments. Based on estimated concentrations, TP 378a could reach about 1 μg L^-1 in the investigated wastewater matrices.

Synthesis, characterization and electrochemical properties of some biologically important indole-based-sulfonamide derivatives

A new series of indole-based-sulfonamide derivatives (A1–A8) was synthesized by treating 5-fluoro-1H-indole-3-carbohydrazide with different aryl-sulfonyl chloride in the presence of pyridine. All synthesized derivatives (A1–A8) were characterized by different analytical methods. The electrochemical behavior of these compounds (A1–A8) was investigated in detail using cyclic voltammetry (CV) and square wave voltammetry (SWV) at the pencil graphite electrode (PGE). In the present study, the redox behavior of all derivatives varies due to the nature of substitutions in the indole sulfonamide moiety. Various fundamental electrochemical parameters, including the standard heterogeneous rate constants (k_s), and the electroactive surface coverage (Г) were calculated from the obtained CVs. The obtained results shed light on the understanding of structure–activity relationships of this class of compounds.

Fabrication of graphene oxide wrapped Ti/Co3O4 nanowire photoanode and its superior photoelectrocatalytic performance

Here, we successfully fabricated graphene oxide (GO) wrapped Ti/Co₃O₄ nanowires (NWs) by electrophoretic deposition based on the good dispersibility of GO in an aqueous solution. Interestingly, GO can adhere to the surface of Co₃O₄ NWs via an ultrathin gossamer-like sheet, and the coverage and wrapping of GO on the surface of Co₃O₄ NWs can be controlled by tuning the electrochemical deposition time and voltage. Our results also demonstrate that GO wrapped Co₃O₄ NWs had superior photoelectrochemical activity for the decolorization of dye (reactive brilliant blue KN-R) in wastewater, mainly because the introduction of GO can tune the oxygen evolution behavior, the transportation of reactant and induced carriers, electrochemical active areas, and the light-harvesting capability of Co₃O₄ NWs. Therefore, we anticipate that GO wrapped Ti/Co₃O₄ NWs could be considered as a promising photoanode for the treatment of organic pollutants in wastewater.

Catalytic ozonation of the antibiotic sulfadiazine: Reaction kinetics and transformation mechanisms

In this work, ozone has been used to study the transformation of the antibiotic sulfadiazine (SDZ). SDZ and its transformation products was investigated using liquid chromatography coupled to mass spectrometry and using NMR. The results revealed that 6% of SDZ is transformed into 2-aminopyrimidine. A significant amount of SDZ undergoes a rearrangement reaction followed by ring-closing reactions. One of these products, SDZ-P15, is the main product after 240 min of ozonation. Almost 30% of SDZ transforms into SDZ-P15. SDZ was also transformed via the addition of one or more hydroxyl groups, via the oxidation of an amine group to a nitro group as well as via a bond cleavage reaction. Most of the intermediate products presented in this study have not previously been reported as SDZ transformation products formed using ozonation technology.

Molecular characteristics of leonardite humic acid and the effect of its fractionations on sulfamethoxazole photodegradation

The widespread occurrence of synthetic antibiotic sulfamethoxazole (SMX)- poses a potential risk to aquatic ecosystems where dissolved organic matter (DOM) may affect its photolysis. In this study, the elimination of SMX by solar photolysis was investigated in the presence of leonardite humic acid (LHA) and its fractions. Fourier transform ion cyclotron resonance mass (FT-ICR-MS) spectra showed that LHA has high aromaticity. van Krevelen diagrams demonstrated highly unsaturated and phenolic compounds. The photolytic degradation of SMX was impeded by all DOM, mainly due to the competition of photons and scavenging or quenching of reactive oxygen species (ROS). The evaluation of isolated fractions of LHA suggested that fractions with MW < 3500, 14000-25,000 and > 100,000 had the greatest negative effects on sulfamethoxazole photodegradation; their inhibitory activities could reach up to 56.2%, 52.9% and 50.5%, respectively. The characterization of DOM at the molecular level will provide further insights into the assessment of photolysis for antibiotic elimination in natural waters where DOM exists ubiquitously.

Recent Trends in Removal Pharmaceuticals and Personal Care Products by Electrochemical Oxidation and Combined Systems

Due to various potential toxicological threats to living organisms even at low concentrations, pharmaceuticals and personal care products in natural water are seen as an emerging environmental issue. The low efficiency of removal of pharmaceuticals and personal care products by conventional wastewater treatment plants calls for more efficient technology. Research on advanced oxidation processes has recently become a hot topic as it has been shown that these technologies can effectively oxidize most organic contaminants to inorganic carbon through mineralization. Among the advanced oxidation processes, the electrochemical advanced oxidation processes and, in general, electrochemical oxidation or anodic oxidation have shown good prospects at the lab-scale for the elimination of contamination caused by the presence of residual pharmaceuticals and personal care products in aqueous systems. This paper reviewed the effectiveness of electrochemical oxidation in removing pharmaceuticals and personal care products from liquid solutions, alone or in combination with other treatment processes, in the last 10 years. Reactor designs and configurations, electrode materials, operational factors (initial concentration, supporting electrolytes, current density, temperature, pH, stirring rate, electrode spacing, and fluid velocity) were also investigated.

Formation and Inhibition of Calcium Carbonate Crystals under Cathodic Polarization Conditions

The formation of CaCO3 crystals on the cathode surface and the scale-inhibition performance of scale inhibitor 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) on the cathode surface were studied by methods of solution analysis, gravimetric analysis, SEM, FTIR, and XRD techniques. They were then compared with the results of the formation and suppression of CaCO3 crystals in aqueous solution. PBTCA had a good solution-scale-inhibition performance and good lattice-distortion effects on CaCO3 crystals in solution, which could change the CaCO3 from calcite to vaterite and aragonite crystals. The solution-scale-inhibition efficiency exceeded 97% when the PBTCA concentration reached 8 mg/L. Under cathodic polarization conditions, the surface-scale-inhibition efficiency of the cathode and solution-scale-inhibition efficiency near the cathode surface both exceed 97% at polarization potential of −1V. The addition of PBTCA significantly reduced the amount of CaCO3 crystals formed on the cathode surface and had good surface and solution-scale-inhibition effect. However, the lattice-distortion effect of PBTCA on CaCO3 crystals disappeared on the cathode surface, and the resulting CaCO3 contained only calcite crystals. The high-scale-inhibition effect of PBTCA under cathodic polarization was mainly due to the inhibition of the formation of calcium carbonate crystals by PBTCA, and not because of the lattice distortion of CaCO3 crystals.

UVC-assisted electrochemical degradation of novel bisphenol analogues with boron-doped diamond electrodes: kinetics, pathways and eco-toxicity removal

In the present study, the UVC-assisted electrochemical degradation ofthree novel bisphenol analogues (BPs; including bisphenol F, S, and B, i.e., BPF, BPS and BPB, respectively), along with bisphenol A (BPA), was investigated using boron-doped diamond (BDD) electrode. At first, this study demonstrated a significant influence ofcurrent density on the degradation rates of BPF by the BDD anode. The pseudo-first order rate constants for BPF were calculated as 0.012, 0.028 and 0.029 min^-1 at the applied current densities of 10, 20 and 30 mA/cm², respectively. UVC irradiation significantly enhanced the electrochemical degradation of BPF in the concentration range from 5 to 30 mg/L, with synergistic effects in the range of 32.0%-40.9%. The UVC-BDD electrolysisshowed comparable or even lower electric energy per order (E_EO) than single BDD electrolysis. The UVC-assisted degradation of the investigated BPs showed decreased pseudo-first order rate constants in the following order: BPF > BPA > BPB > BPS. Based on the identifiedtransformation products, UVC-assisted electrochemical degradation pathways of the novel BPs were proposed to be mainly hydroxylation and bond-cleavage. UVC irradiation has been proved to promote the formation of hydroxyl radicals by BDD electrode to facilitate the degradation process. For these BPs, nearly 100% mineralization can be achieved by a modified strategy using a short-time UVC-assisted BDD electrolysis (120 min) that is followed by UVC photolysis (360 min). Finally, the eco-toxicity of the BPs solutions towardsVibrio Fischeri was significantly removed after 120 min of the electrochemical degradation period. Based on these results, the UVC-assisted electrochemical treatment using a BDD electrode can be considered a promising technology for the removal of novel BPs and the reduction of their hazardous effects to aqueous environments.

Photocatalytic degradation of sulfamethazine using a direct Z-Scheme AgI/Bi4V2O11 photocatalyst: Mineralization activity, degradation pathways and promoted charge separation mechanism

Z-scheme heterojunction can not only promote the separation of photogenerated carriers, but also retain the strong redox potential of the system, which would greatly improve the photocatalytic performance of catalyst. Herein, a Z-scheme AgI/Bi₄V₂O₁₁ heterojunction photocatalyst was prepared by a hydrothermal process combined with in situ coprecipitation process. Multiple techniques were employed to investigate the morphology, composition, chemical and electronic properties of the as-prepared samples. The obtained Z-scheme AgI/Bi₄V₂O₁₁ heterojunction photocatalyst exhibited remarkably enhanced photocatalytic performance towards sulfamethazine (SMZ) degradation under visible light irradiation. Especially, the 20 wt% AgI/Bi₄V₂O₁₁ composites exhibited the highest photocatalytic activity for sulfamethazine (SMZ) degradation and 91.47% SMZ would be eliminated within 60 min. In comparison with NO₃^- and SO₄^2-, the presence of Cl^- and HCO₃^- presented more obviously inhibition effects on SMZ degradation. The possible degradation pathways of SMZ were speculated by identifying degradation intermediates. O₂^-, h⁺ and OH all involved in the photocatalytic degradation SMZ. The highly enhanced photocatalytic performance might be attributed to form Z-scheme junction between AgI and BVO, which are conducive to the efficient charges separation and maintain high redox potential. This work enriches Bi₄V₂O₁₁-based Z-scheme heterojunction photocatalytic system and provides a reference for the preparation of effective Z-scheme junction photocatalysts.

Modeling electrochemical oxidation and reduction of sulfamethoxazole using electrocatalytic reactive electrochemical membranes

In this research, degradation of the antibiotic sulfamethoxazole (SMX) was studied using electrochemical reduction and oxidation in single pass, flow-through mode using porous titanium suboxide (Ti₄O₇) reactive electrochemical membranes (REMs) and Pd-Cu doped Ti₄O₇ REMs (Pd-Cu/Ti₄O₇ REMs). Electrochemical reduction of SMX increased from 3.8 ± 0.3% for the Ti₄O₇ REM to 96.1 ± 3.9% for the Pd-Cu/Ti₄O₇ REM at -1.14 V/SHE and at a permeate flux of 300 L m^-2 h^-1 (LMH) (liquid residence time: ∼1.8 s). By contrast, electrochemical oxidation using Ti₄O₇ REMs achieved 95.7 ± 1.0% removal of SMX at 2.03 V/SHE and a permeate flux of 300 LMH (liquid residence time: ∼9.0 s) without the catalyst addition. We developed a reactive transport mathematical model and calibrated it to the SMX experimental data. The calibrated model predicted SMX permeate concentrations at fixed potentials and as a function of permeate flux. Based on products from SMX reduction, we proposed that SMX was reduced by a hydrogen atom transfer reaction that was mediated by the Pd-Cu/Ti₄O₇ REM. Toxicity tests indicated that electrochemical oxidation/reduction lowered solution toxicity. The results of this work indicate that a tandem electrochemical reduction/oxidation approach using the REM-based technology is a potential treatment strategy for sulfonamide-contaminated pharmaceutical wastewater.

Electrochemical Oxidation of Sulfonamides with Boron-Doped Diamond and Pt Anodes

Electrochemical oxidation processes usually favored specific degradation pathways depending on anode materials. In this work, a series of sulfonamides (SNs) were degraded by electrochemical oxidation. Compared to Pt anodes (0.1567–0.1795 h⁻¹), degradation rates of SNs were much higher at boron‐doped diamond (BDD) anodes (2.4290–13.1950 h⁻¹). However, the same intermediates were detected in the two anode systems. Due to the strong oxidizing ability of BDD anodes, a large amount of intermediates with high toxicities were initially generated and then finally reduced in the BDD anode systems, while the amount of intermediates continuously increased in the Pt anode systems. Additionally, SNs were degraded faster in Na₂SO₄ than NaH₂PO₄ electrolytes at BDD anodes, while they were similar at Pt anodes. This study demonstrated that the degradation pathways of SNs at BDD and Pt anodes were similar, but the evolutions of intermediate amounts and toxicities were different due to their varied oxidizing abilities.

Development of a 3D ordered macroporous RuO2 electrode for efficient pyrazole removal from water

Inability to remove biologically toxic and persistent contaminants is a critical issue in traditional water treatment processes. In this study, a novel 3D macroporous RuO₂ (3D-RuO₂) electrode with uniform and interconnected cavities has been fabricated via templated electrodeposition approach for treatment of persistent pyrazole. The physicochemical properties of the electrodes are characterized by means of SEM, BET, XRD, LSV and CV measurements. The results show that structural features of the 3D-RuO₂ play important roles in the electrocatalysis performance. Thanks to the abundant crystal defect sites, 3D-RuO₂ electrode possesses more mesopores within the skeleton, resulting in 17.9 and 2.2 times larger specific surface area compared to traditional flat thermal-deposited (TF-RuO₂) and electrodeposited RuO₂ (EF-RuO₂) respectively. At a current density of 5 mA cm^-2, the pyrazole removal rate on 3D-RuO₂ is 1.7 times and 1.3 times that of TF-RuO₂ and EF-RuO₂. The energy consumption for 50% of pyrazole removal on 3D-RuO₂ is 0.05 kWh g^-1pyrazole, much lower than that of TF-RuO₂ (0.11 kWh g^-1pyrazole) and EF-RuO₂ (0.075 kWh g^-1pyrazole). The improved removal performance of 3D-RuO₂ electrode is attributed to its strong electro-adsorption capacity (270.3 μg cm^-2), leading to enhanced mass transfer of pollutants to the electrode surface. The mass transfer coefficient (κ_m) is estimated as 2.4 × 10^-6 m s^-1 for 3D-RuO₂, which is 3.9 and 2.3 times as much as that of TF-RuO₂ and EF-RuO₂. Finally, contribution of different electron transfer approaches to pyrazole degradation under anodic polarization was investigated by ROS scavenging experiments.

Hospital wastewaters treatment: Fenton reaction vs. BDDE vs. ferrate(VI)

Various types of micropollutants, e.g., pharmaceuticals and their metabolites and resistant strains of pathogenic microorganisms, are usually found in hospital wastewaters. The aim of this paper was to study the presence of 74 frequently used pharmaceuticals, legal and illegal drugs, and antibiotic-resistant bacteria in 5 hospital wastewaters in Slovakia and Czechia and to compare the efficiency of several advanced oxidations processes (AOPs) for sanitation and treatment of such highly polluted wastewaters. The occurrence of micropollutants and antibiotic-resistant bacteria was investigated by in-line SPE-LC-MS/MS technique and cultivation on antibiotic and antibiotic-free selective diagnostic media, respectively. The highest maximum concentrations were found for cotinine (6700 ng/L), bisoprolol (5200 ng/L), metoprolol (2600 ng/L), tramadol (2400 ng/L), sulfamethoxazole (1500 ng/L), and ranitidine (1400 ng/L). In the second part of the study, different advanced oxidation processes, modified Fenton reaction, ferrate(VI), and oxidation by boron-doped diamond electrode were tested in order to eliminate the abovementioned pollutants. Obtained results indicate that the modified Fenton reaction and application of boron-doped diamond electrode were able to eliminate almost the whole spectrum of selected micropollutants with efficiency higher than 90%. All studied methods achieved complete removal of the antibiotic-resistant bacteria present in hospital wastewaters.

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.

Effects of sulfamethoxazole and sulfamethoxazole-degrading bacteria on water quality and microbial communities in milkfish ponds

Intensive farming practices are typically used for aquaculture. To prevent disease outbreaks, antibiotics are often used to reduce pathogenic bacteria in aquaculture animals. However, the effects of antibiotics on water quality and microbial communities in euryhaline fish culture ponds are largely unknown. The aim of this study was to investigate the interactions between sulfamethoxazole (SMX), water quality and microbial communities in milkfish (Chanos chanos) culture ponds. The results of small-scale milkfish pond experiments indicated that the addition of SMX decreased the abundance of ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB) and photosynthetic bacteria. Consequently, the levels of ammonia and total phosphorus in the fish pond water increased, causing algal and cyanobacterial blooms to occur. In contrast, the addition of the SMX-degrading bacterial strains A12 and L effectively degraded SMX and reduced the levels of ammonia and total phosphorus in fish pond water. Furthermore, the abundances of AOB, NOB and photosynthetic bacteria were restored, and algal and cyanobacterial blooms were inhibited. This study demonstrate the influences of SMX on water quality and microbial community composition in milkfish culture ponds. Moreover, the use of the bacterial strains A12 and L as dual function (bioaugmentation and water quality maintenance) beneficial bacteria was shown to provide an effective approach for the bioremediation of SMX-contaminated euryhaline milkfish culture ponds.

Electro-oxidation of amoxicillin trihydrate in continuous reactor by Ti/RuO2 anode

Electro-oxidation (EO) of synthetic wastewater containing amoxicillin (AMT) antibiotic as a model pollutant was performed using dimensionally stable Ti/RuO₂ electrodes in a continuous reactor set-up. Response surface methodology (RSM) was used for optimization of continuous EO process. Individual and interactive effects of initial pH of synthetic wastewater (2-10), applied current, I (0.25-1.25 A), elapsed time, t (20-180 min) and retention time, R_T (15-195 min) on AMT removal, total organic carbon (TOC) removal and specific energy consumption (SEC, kWh (g TOC removed)^-1) were investigated. At optimum conditions (pH = 7.53, I = 0.7 A, R_T = 175.6 min, t = 128.89 min), 51.64% and 37.82% AMT and TOC removal was achieved, with SEC value of 0.408 kWh (g TOC removed)^-1. AMT and TOC removal at optimum conditions was found to follow pseudo-first order kinetics. Mineralization current efficiency for optimum run of continuous EO came out to be 9.81%. Furthermore, 8 transformation products/reaction intermediates of AMT (ARIs) were determined by UPLC-Q-TOF-MS analysis, and subsequently, a plausible degradation scheme of AMT by anodic oxidation and cathodic reduction using Ti/RuO₂ electrodes was proposed.

Removal of 5-fluorouracil by solar-driven photoelectrocatalytic oxidation using Ti/TiO2(NT) photoelectrodes

The efficient and safe degradation of drugs present in wastewater requires the design of a new material possessing high activity for that process. In addition to other methods, photoelectrocatalysis (PEC) merges the strengths of both photocatalytic and electrochemical methods, and the efficiency could be enhanced by the type of photoelectrode material. To address this challenge, three Ti/TiO₂ nanotube-based photoelectrodes, differing in their tube morphology, were prepared by anodic oxidation and employed for the degradation of the 5-fluorouracil (5-FU) drug by the PEC process. The highest efficiency for 5-fluorouracil (5-FU) degradation by PEC was observed for the photoelectrode with a 1.7 μm length, 65 nm diameter and 8 nm wall thickness of TiO₂ nanotubes, which were prepared by Ti foil anodization at 30 V. The effects of applied potential, irradiation intensity, initial pH and 5-FU concentration on PEC were investigated. Furthermore, our findings showed that the mechanism of photoelectrocatalysis in the presence of TiO₂ nanotubes is based on ∙OH and h⁺ activity. To determine the 5-FU degradation pathway, the organic byproducts were identified by LC-MS analysis. Furthermore, the ecotoxicity evaluated during PEC dropped with decreasing 5-FU concentration.

Electrospun spongy zero-valent iron as excellent electro-Fenton catalyst for enhanced sulfathiazole removal by a combination of adsorption and electro-catalytic oxidation

In this study, a highly active electro-Fenton catalyst, spongy zero-valent iron (ZVI), has been developed at first via in-situ synthesis of ZVI nanoparticles (NPs) on an electrospun three-dimensional (3D) nanofiber network. The spongy ZVI effectively overcame the defects of easy aggregation of ZVI NPs and ferric sludge accumulation during the electro-catalytic process. Then, a three-dimensional electro-Fenton (3D-EF) system using the as-fabricated spongy ZVI as particle catalytic electrodes was designed, which presented a significant synergistic effect of adsorption and electro-catalytic oxidation on the enhanced removal of a widely used antibiotic, sulfathiazole (STZ) from water. Adsorption experiments demonstrated that the spongy ZVI had a relative high adsorption affinity towards STZ with about 50% of the total removal within 240 min, and the adsorption equilibrium was reached in 570 min. Hydroxyl radical (OH) was produced in the 3D-EF system with spongy ZVI catalyst, and almost 100% STZ was removed within 5 min. Reactive oxygen species analysis verified that OH was mainly responsible for the STZ degradation. Based on intermediates identified by a liquid chromatography-tandem mass spectrometry (LC-MS/MS), three pathways for the electro-Fenton oxidative degradation of STZ were proposed.