Oxidation Of Sulfamethoxazole Research Articles

Insights into the degradation of sulfamethoxazole in UV/nitrite system: Mechanism, transformation process and disinfection by-products formation

Antibiotics removal from wastewater by conventional methods is limited, and their lingering presence in the environment can be hazardous to both human health and the ecosystem. Sulfamethoxazole (SMX) is one of the primary study subjects for antibiotic contamination, the degradation behavior, mechanism, transformation pathway, disinfection byproducts (DBPs) formation and variations about toxicity in UV/nitrite (NO2−) system were examined in this study. Compared with UV irradiation, the first-order reaction rate of SMX in UV/NO2− system rose from 0.0397 to 0.0528 min−1. This enhancement was linked to the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), which promoted the degradation. SMX removal was more favorable under high dissolved oxygen (DO) levels and acidic conditions. When NO2− concentrations ranged from 0.1 to 1.0 mM, the higher concentration was more favorable to the degradation. The addition of 10 mM of HA and HCO3− hindered the oxidation of SMX by 48.46 % and 26.85 %, respectively, while the addition of Cl− slightly accelerated the decay of SMX at certain concentrations (5, 10 mM). The results of HPLC-ESI-MS and DFT computation suggested three possible SMX degradation pathways, including nitrification, hydroxylation, and bond breaking (such as sulfonamide cleavage). The primary DBPs produced by the post-chlorination of SMX in UV/NO2− system were TCM (87.02 % of the total detected DBPs) with a minor quantity of DBPs containing nitrogen. The presence of bromide ions (Br−) can lead to the production of highly toxic bromine containing disinfection by-products (Br-DBPs). After adding Br− in UV/NO2− system, 100 % of N-DBPs (TCNM, DCAN) and 93.43 % of C-DBPs (TCM, DCAA, TCAA) were converted to Br-DBPs (TBM, DBAA, TBAA, BDCM, DBCM), with the production of Br-DBPs accounting for 82.63 % of the detected DBPs.

Hydroxylamine-induced activation of permanganate for enhanced oxidation of sulfamethoxazole: Mechanism and products

Recently, many reagents have been introduced to accelerate the formation of highly reactive intermediate Mn species from permanganate (KMnO4), thereby improving the oxidation activity of KMnO4 towards pollutants. However, most studies have mainly focused on sulfur-containing reducing agents (e.g., bisulfite and sodium sulfite), with little attention paid to nitrogen-containing reducing agents. This study found that hydroxylamine (HA) and hydroxylamine derivatives (HAs) can facilitate KMnO4 in pollutant removal. Taking sulfamethoxazole (SMX) as a target contaminant, the effect of pH, SMX concentration, KMnO4 and HA dosages, and the molar ratio of HA and KMnO4 on the degradation of SMX in the KMnO4/HA process was systematically investigated. Quenching experiments and probe analysis revealed MnO2-catalyzed KMnO4 oxidation, Mn(III) and reactive nitrogen species as the primary active species responsible for SMX oxidation in the KMnO4/HA system. Proposed transformation pathways of SMX in the KMnO4/HA system mainly involve hydroxylation and cleavage reactions. The KMnO4/HA system was more conducive to selective oxidation of SMX, 2,4-dichlorophenol, and several other pollutants, but reluctant to bisphenol S (BPS). Overall, this study proposed an effective system for eliminating pollutants, while providing mechanistic insight into HA-driven KMnO4 activation for environmental remediation.

Homogeneous to heterogeneous redox mediator enhancing ferrate(VI) oxidation of sulfamethoxazole: Role of ferrate(VI) activation and electron shuttle

Ferrate (Fe(VI)) is a promising oxidant for water remediation, yet it has limited reactivity towards certain recalcitrant but important emerging contaminants, such as sulfamethoxazole. Here, this study demonstrates that nitroxide redox mediators, specifically 9-azabicyclo[3.3.1]nonasne N-oxyl (ABNO), can catalyze Fe(VI) reaction with sulfamethoxazole by functioning both as Fe(VI) activator and electron shuttle. The underlying mechanism is explained as: (i) Fe(VI) activation: a series of one-electron transfers between Fe(VI) and ABNO produces highly reactive Fe(V)/Fe(IV) and ABNO+; (ii) electron shuttle: the newly formed active ABNO+ reacts with the sulfamethoxazole, contributing to its removal. Concurrently, ABNOH is generated and subsequently converted back to ABNO by reactive species, thereby completing the redox cycle. The as-developed heterogeneous redox mediator, ABNO@SiO2, retained its catalytic properties and effectively catalyzed Fe(VI) to remove sulfamethoxazole at environmentally relevant pH levels.

A sustainable electrochemical strategy utilizing pulsed alternating current and dual carbon felt electrodes for enhanced degradation of organic pollutants: Oxidation performance and mechanisms

In this work, a novel electrochemical (EC) oxidation system utilizing pulsed alternating current (PAC) and dual carbon felt (CF) electrodes has been established for sustainable degradation of sulfamethoxazole (SMX) with no addition of extra oxidant. The EC/PAC system showed high degradation efficiency and energy efficiency compared to the pulsed direct current (PDC) and direct current (DC) systems. The EC/PAC process was effective across a wide pH range of 3–11 for SMX removal. The results showed that the 1O2 confined to the CF electrode surface was the dominant oxidative specie that was generated from dissolved oxygen in the system. Under PAC conditions, the cathode and anode were rapidly switched on the same CF electrode, increasing the generation of 1O2 for enhanced SMX oxidation. Furthermore, the EC/PAC system demonstrated resistance to interference from various anions of different concentration levels found in natural environment. In contrast to the EC/PDC system, the EC/PAC system emerged as a promising option for more efficient H2O2 production. High-resolution mass spectrometry results revealed the SMX degradation pathways and byproducts, which were then evaluated for toxicity removal. Overall, the EC/PAC system offers a green and sustainable solution to future wastewater treatment, with high degradation rates, energy efficiency, and sustainability.

Synergistic oxidative removal of sulfamethoxazole using Ferrate(VI) and peroxymonosulfate

The synergic effect of Ferrate(VI) (Fe(VI)) and peroxymonosulfate (PMS) on sulfamethoxazole (SMX) oxidative removal was investigated in this study. The sulfate radicals (SO4−), generated through Fe(VI)-mediated activation of PMS, have been demonstrated as an effective oxidant for the removal of SMX. However, the scavenging experiments have suggested that various iron species, i.e., Fe(VI), Fe(V), and Fe(IV) play a vital role in facilitating efficient SMX oxidation. pH is a crucial parameter in this system because the involved species, including Fe(VI), PMS, and SMX, have acid-base dissociation points. Accordingly, the optimal pH value for the SMX removal was achieved at pH = 6, and the addition of PMS enhanced the degradation efficiency of Fe(VI) at all pH-operating conditions. Several oxidation products of SMX were identified, including sulfanilamide (SAM), 3-amino-5-methylisoxazole (AMI), and other potentially hydroxylated byproducts. Characterization studies on solid particles collected after the Fe(VI)/PMS treatment revealed structural changes during SMX oxidation, and the potential contributions of Fe2O3 or Fe(OH)3 to the oxidation mechanism were evaluated accordingly. While the removal efficiency in a river matrix was slightly reduced, the presence of inorganic ions had minimal impact on SMX removal, which confirms the high potential of the Fe(VI)/PMS technology to operate in environmentally relevant conditions.

Mn-Cu bimetallic electro-spun catalytic membrane coupled Fenton-like scheme for sulfamethoxazole destruction under ambient pH

Heterogeneous catalyst reuse and the effectiveness of hydrogen peroxide (H2O2)-based advanced oxidation processes under near-neutral conditions remain an obstacle in wastewater remediation. Herein, we put forward a versatile catalytic membrane with Cu-doped MnO active layer anchoring on the polydopamine-modified electrospinning polyvinylidene fluoride (PDA@PVDF) base. The Cu-MnO@PDA@PVDF membrane was conferred admirable sulfamethoxazole (SMX) reduction (over 90% within 90 min) and clogging alleviation (relative flux recovery to 0.98) capabilities via in situ H2O2 activation at pH 8, which was slightly affected by actual water background. Electron paramagnetic resonance (EPR) and trapping tests unveiled the joint contribution of •OH, O2•− and 1O2, with •OH exerting the supreme role in SMX oxidation. The inherent characteristics of dual Mn-Cu centers on the membrane surface for facilitation of electron transfer, H2O2 adsorption and barrierless dissociation to •OH were further elucidated by electrochemical measurements and density functional theory (DFT) computation. Comprehensively, this study proposes a facile procedure and insights into engineering catalytic membrane coupled H2O2 strategy for refractory organic treatment at ambient conditions.

Insights into the potential applications of permanganate/peroxymonosulfate systems: enhancement via amorphous MnO2, effects of water matrices, and optimization using response surface methodology.

In this study, we developed a novel self-catalytic oxidation system involving peroxymonosulfate (PMS) and permanganate (KMnO4), named as CUPP, to efficiently mineralize sulfamethoxazole (SMX) in groundwater. It was found that amorphous MnO2 derived from the in situ reduction of KMnO4 can directly adsorb HSO5-, a complex hydroxyl group, mediate the internal disproportionation reaction of HSO5- with the manganese complex, and effectively activate PMS, thereby promoting the oxidation of SMX and its degradation intermediates through sulfonate radiation. Furthermore, by using electron spin resonance (EPR), HPLC/MS full scan, and response surface methodology, the coexistence of HO˙, SO4-˙, O2-˙, 1O2, and active chlorine (Cl2, HOCl) in the CUPP system was confirmed. A total of 24 intermediate products were detected, and four possible degradation pathways were identified for SMX. In addition, it was found that the CUPP system has a strong impact resistance to pH variations, groundwater anions, and natural organic matter stress. Undoubtedly, the CUPP system presents an innovative approach for the degradation of various emerging organic pollutants in groundwater.

Plastic wastes-derived N-doped carbon nanotubes for efficient removal of sulfamethoxazole in high salinity wastewater via nonradical peroxymonosulfate activation

Peroxymonosulfate (PMS) catalytic activation is effective to eliminate organic pollutants from water, thus the development of low-cost and efficient catalysts is significant in applications. The resource conversion of plastic wastes (PWs) into carbon nanotubes (CNTs) is a promising candidate for PMS-based advanced oxidation processes (AOPs), and also a sustainable strategy to realize plastic management and reutilization. Herein, cost-effective PWs-derived N-doped CNTs (N-pCNTs) were synthesized, which displayed efficient activity for PMS activation through an electron transfer pathway (ETP) for sulfamethoxazole (SMX) degradation in high salinity water. The pyrrolic N induced the positively charged surface of N-pCNTs, favoring the electrostatic adsorption of PMS and subsequent generation of active PMS* . A galvanic oxidation process was developed to prove the electron-shuttle dominated ETP for SMX oxidation. Combined with theoretical calculations, the efficiency of ETP was determined by the potential difference between HOMO of SMX and LUMO of N-pCNTs. Such oxidation produced low-toxicity intermediates and resulted in selective degradation of specific sulfonamide antibiotics. This work reveals the feasibility of low-cost N-pCNTs catalysts from PWs serving as an appealing candidate for PMS-AOPs in water remediation, providing a new solution to alleviate environmental issues caused by PWs and also advances the understanding of ETP during PMS activation.

Iron electrocoagulation activated peracetic acid for efficient degradation of sulfamethoxazole

Activation of peracetic acid (PAA) by Fe species is the attractive advanced oxidation processes for the removal of antibiotics. However, achieving optimal performance in many of these processes often requires acidic pH conditions, which impedes practical application. In this study, an iron electrocoagulation (EC) system was devised to for activate PAA and oxidate sulfamethoxazole (SMX). Under optimal conditions, the degradation of SMX by the EC/PAA system reached 96.2% within 15 min, with a pseudo-first order reaction constant of 0.241 min−1, but only consuming 0.044 kW·h/m3. Interestingly, the EC/PAA system showed a high buffering capacity in the initial pH range of 4–8 to maintain the final pH of around 7. The quenching experiments revealed both free radical and non-free radical pathways involved in the oxidation of SMX in the EC/PAA system. Specifically, the active species, including •OH, organic radicals (CH3COO• and CH3COOO•) and 1O2, contribute 86.77%, 5.53% and 7.70%, respectively. These findings suggest that the EC/PAA system has unique advantages and potential for the degradation of antibiotic organics such as SMX in aquatic environments due to its strong oxidative capacity, wide pH range and high buffering capacity.

Enhanced Oxidation of Organic Compounds by the Ferrihydrite-Ferrate System: The Role of Intramolecular Electron Transfer and Intermediate Iron Species.

Previous studies mostly held that the oxidation capacity of ferrate depends on the involvement of intermediate iron species (i.e., FeIV/FeV), however, the potential role of the metastable complex was disregarded in ferrate-based heterogeneous catalytic oxidation processes. Herein, we reported a complexation-mediated electron transfer mechanism in the ferrihydrite-ferrate system toward sulfamethoxazole (SMX) degradation. A synergy between intermediate FeIV/FeV oxidation and the intramolecular electron transfer step was proposed. Specifically, the conversion of phenyl methyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO2) suggested that FeIV/FeV was involved in the oxidation of SMX. Moreover, based on the in situ Raman test and chronopotentiometry analysis, the formation of the metastable complex of ferrihydrite/ferrate was found, which possesses higher oxidation potential than free ferrate and could achieve the preliminary oxidation of organics via the electron transfer step. In addition, the amino group of SMX could complex with ferrate, and the resulting metastable complex of ferrihydrite/ferrate would combine further with SMX molecules, leading to intramolecular electron transfer and SMX degradation. The ferrate loss experiments suggested that ferrihydrite could accelerate the decomposition of ferrate. Finally, the effects of pH value, anions, humic acid, and actual water on the degradation of SMX by ferrihydrite-ferrate were also revealed. Overall, ferrihydrite demonstrated high catalytic capacity, good reusability, and nontoxic performance for ferrate activation. The ferrihydrite-ferrate process may be a green and promising method for organic removal in wastewater treatment.

Efficient removal of sulfamethoxazole by biomass phosphorus-derived Cu3P/biochar catalyst combined with persulfate

Sulfamethoxazole (SMX) is ubiquitous in environments with concentrations ranging from nano-gram per liter to milli-gram per liter in practice, especially in water matrices (surface water and wastewater), posing a grave threat to ecosystems for its antibacterial and persistent characteristics. Efficient SMX removal is critical for water purification. Herein, the nano and micron Cu3P particles are synthesized on biochar utilizing phytic acid (PA) doped rice brans. PA facilitates the transformation of Cu-containing precursors to Cu3P on biochar, promoting catalytic performance. Under the conditions of 0.15 g/L catalyst (6PA-Cu11), 3.0 mM persulfate (PS), and pH 7.00, sulfamethoxazole (SMX) at a concentration of 0.25, 0.50, 1.00, and 10.00 mg/L can be completely removed within 30, 60, and 180 min, respectively. Moreover, the combination of Cu3P/biochar and persulfate exhibits preferable catalytic performances for SMX removal in sodium humate solution and surface water matrices, demonstrating the broad applicability of such a catalytic system for water purification. Sulfate radical (SO4−•) and hydroxy radical (•OH) play vital roles in the oxidation of SMX, with 1O2 assisting in. Except for cuprous ion (≡Cu+), partially charged copper ions (≡Cuδ+) and phosphorus ions (≡Pγ−) in Cu3P, owning the electron-donating ability, are found to participate in the activation of PS or the reduction of high-valent copper ions depending on density functional theory (DFT) calculations. Biochar carrier enhances the catalytic role of copper ions in Cu3P and facilitates the recovery of active sites by improving the desorption of the activation product (SO42−) from the Cu3P surface. This research promotes the practicability of the Cu3P/biochar catalyst in the advanced oxidation process for refractory organic pollutant removal and deepens the perception of its catalytic mechanisms.

Voltammetric determination of sulfamethoxazole using commercial screen-printed carbon electrodes

A differential pulse voltammetric (DPV) method using commercial screen-printed carbon electrodes (SPCE) is developed for a fast and cost-effective determination of the antibiotic sulfamethoxazole (SMX). Optimal measurements are carried out at pH 5.5 in acetate buffer and yield a detection limit of 15 µg/L and a linearity range of 50 – 600 µg/L with good repeatability (1.1%) and reproducibility (2.5%). The method is successfully applied to the analysis of a spiked tap water sample with very high reproducibility (0.4%) and good trueness (Recovery 95.2%).Additional considerations are made about the irreversible electrochemical oxidation of SMX, which is notoriously pH-dependent according to a process involving 2e- and 2H+, in agreement with several reported mechanisms in the literature. Besides, the analysis of other sulfonamide antibiotics is discussed, showing the key role of the free terminal amino group in oxidation, which makes almost undistinguishable voltammetric signals from different molecules sharing this moiety. In contrast, the acetylation of the mentioned group (e.g., in sulfonamide metabolites) drastically reduces the sensitivity of voltammetric measurements.

Activation of peroxymonosulfate by Fe–Mn-modified MWCNTs for selective decontamination: Formation of high-valent metal-oxo species and superoxide anion radicals

The extensive presence of organic micropollutants in complex water matrices requires the development of selective oxidation technologies. In this study, a novel selective oxidation process was developed via the conjunction of FeMn/CNTs with peroxymonosulfate and successfully used to remove micropollutants such as sulfamethoxazole (SMX) and bisphenol A from aqueous solutions. FeMn/CNTs were prepared using a facile co-precipitation method, characterized using a series of surface characterization techniques, and then tested for pollutant removal. The results showed that the FeMn/CNTs had much greater reactivity than CNTs, manganese oxide, and iron oxide. The pseudo-first-order rate constant with FeMn/CNTs was more than 2.9–5.7 times that of the other tested materials. The FeMn/CNTs had great reactivity in a wide range of pH values from 3.0 to 9.0, with the best reactivity found at pH values of 5.0 and 7.0. High-valent metal-oxo species such as Fe(IV)O and Mn(IV)O and superoxide anion radicals were determined to be the reactive species and were responsible for the oxidation of SMX. These reactive species were selective; therefore, the overall removal performance of SMX was not obviously influenced by high levels of water components including chloride ions, bicarbonates, and natural organic matters. The results from this study may promote the design and application of selective oxidation technologies for micropollutant abatement.

An in-depth insight into the simultaneous oxidation of sulfamethoxazole and reduction of Cr (VI) by one system of water film DBD plasma: The interaction effect, role of active species, and their dominant to pathways

This study aims to deeply investigate the simultaneous elimination of sulfamethoxazole (SMZ) and Cr (VI) through one system of water film dielectric barrier discharge (WFDBD) plasma. The interaction effect of SMZ degradation and Cr (VI) reduction and dominant effect of active species were highlighted. Results showed that the oxidation of SMZ and the reduction of Cr (VI) directly promote each other. When the concentration of Cr (VI) raised from 0 to 2 mg L−1, the degradation rate of SMZ enhanced from 75.6% to 88.6%, respectively. Similarly, when the concentration of SMZ improved from 0 to 15 mg L−1, the removal efficiency of Cr (VI) improved from 70.8% to 84.3%, respectively. ·OH, 1O2 and ·O2− play crical roles for SMZ degradation, and e−, ·O2−, ·H and H2O2 dominated to the Cr (VI) reduction. The variations of pH, conductivity and TOC during the removal process were also explored. The removal process was studied by UV–vis spectroscopy and a three-dimensional excitation-emission matrix. Based on DFT calculation and LC-MS analysis, free radicals dominated SMZ degradation pathways in the WFDBD plasma system were clarified. Besides, the influence of Cr (VI) on SMZ degradation pathway was clarified. The ecotoxicity of SMZ and the toxicity of Cr (VI) into Cr (III) were greatly reduced. This study provides a significant reference value for the application and mechanism of plasma simultaneous removal of organic pollutants and heavy metals in wastewater.

Dual role of soil-derived dissolved organic matter in the sulfamethoxazole oxidation by manganese dioxide

Manganese dioxide (MnO2) can mediate organic pollutant oxidation in aquatic environments, which has been reported to be inhibited or promoted by dissolved organic matter (DOM) in different studies. It remains unresolved why conflicting results have been observed and whether such results depend on the type and concentration of DOM. Here, we used three types of well-characterized DOM derived from soil heated at 50, 250, or 400°C (DOM_50, DOM_250, and DOM_400, respectively) to evaluate the impacts of DOM type and concentration and environmental pH on MnO2-mediated oxidation of sulfamethoxazole, a widely detected and ecotoxic emerging pollutant. We observed that the degradation rate of sulfamethoxazole was possibly promoted by DOM_250 (pH 6‒8), while it was generally inhibited by DOM_50 and DOM_400. Furthermore, it was initially inhibited and then promoted with increasing DOM concentrations and was consistently less inhibited at a higher pH. The inter-DOM variations of sulfamethoxazole degradation could be explained by the more enriched polyphenolics in DOM_250 than in DOM_50 and DOM_400, whereas the weak promoting effect of DOM_400 indicates that high DOM aromaticity may not necessarily promote pollutant degradation. Our results reconcile the debate on the role of DOM in the oxidation of sulfamethoxazole by MnO2 and highlight the decisiveness of the molecular composition and concentration of DOM and the reaction pH in the overall promoting or inhibiting role of DOM.

Biochar from Lemon Stalks: A Highly Active and Selective Carbocatalyst for the Oxidation of Sulfamethoxazole with Persulfate

Pyrolysis of lemon stalks at 850 °C under a limited oxygen atmosphere yields a highly active and selective biochar for the activation of persulfate ion and the oxidation of sulfamethoxazole (SMX). The biochar mainly consists of C and O atoms, with Ca and K being the most abundant minerals. It has a moderate specific surface area of 154 m2 g−1 and carbonate species, probably in the form of calcium carbonate. Complete degradation of 0.5 mg L−1 SMX can be achieved within 20 min using 500 mg L−1 sodium persulfate (SPS) and 100 mg L−1 biochar in ultrapure water (UPW). The acidic environment positively influences the degradation and adsorption processes, while the complexity of the water matrices usually has a negative impact on the degradation. The presence of chloride accelerates the oxidation of SMX, whose mechanism follows radical and non-radical pathways. Hydroxyl radicals seem to have the dominant contribution, while the electron transfer pathway was proven with electrochemical characterization. The biochar is stable for at least five cycles, and this makes it a good candidate for a sustainable, metal-free catalyst.

Peroxymonosulfate activation by iron-carbon composite derived from coal gasification slag for sulfamethoxazole removal: Performance evaluation and mechanism insight

A novel iron-carbon (Fe-C) composite was fabricated using coal gasification slag (CGS) as the feedstocks and applied in sulfamethoxazole (SMX) degradation via peroxymonosulfate (PMS) activation. The optimized Fe-C composite (CGS-1000) had excellent catalytic ability among the reported metal-C catalysts, showing a superior SMX degradation capacity (91.1 %) and kinetic reaction rate (0.0177 min−1) within 90 min under the condition of 0.2 g·L−1 CGS-1000, 2.0 mM PMS at ambient pH (6.3). Characterization results illustrated that the relatively larger surface area (102.50 m2·g−1), pore size (3.93 nm), and higher carbon defectiveness (ID/IG = 1.48) of CGS-1000 promoted its SMX degradation performance. XPS and FTIR spectrum revealed that PMS was mainly activated by Fe species and oxygen-containing functional groups (CO, C-OH) on the carbon matrix for the generation of reactive oxygen species (ROS). Notably, surface-bounded radicals (SO4−, OH), singlet oxygen (1O2), and direct electron transfer were primarily involved in the CGS-1000/PMS system, of which the relative contributions to SMX oxidation were calculated to be 25.8 %, 49.5 %, and 12.5 %, respectively. The excellent degradation efficiency should be attributed to the simultaneous SMX oxidation both in solution and on the surface of CGS-1000 through these three oxidation pathways. Finally, four SMX degradation pathways were proposed based on the twelve intermediates detected by LC-MS. The toxicity of the by-products of SMX was alleviated according to the quantitative structure–activity relationship analysis. Overall, these results suggested that CGS-1000 was a high-efficiency PMS catalyst for SMX degradation and provided new insights into the design of other solid waste-derived catalysts.

Electric field-enhanced coupled with metal-free peroxymonosulfate activactor: The selective oxidation of nonradical species-dominated system

Nowadays metal-free persulfate-based advanced oxidation processes (AOPs) have been intensively investigated, however, the catalysts are often too complex to fully consider their application potential. Conventional AOPs usually suffer from severe interference in real water matrix, thus, selective oxidation is practically and scientifically challenging as it could avoid unnecessary inputs of energy and possible secondary pollutants. In this study, a remarkably synergistic effect was achieved when conventional amorphous boron/peroxymonosulfate (Boron/PMS, 0.67 × 10−2 min−1) system was combined with electrolysis (E-Boron/PMS, 1.54 × 10−2 min−1) to degrade sulfamethoxazole (SMX). Evidenced by selectively quenching tests with kinetic evaluation, electron paramagnetic resonance (EPR), solvent-exchange experiment and electrochemical analysis, the dominated reactive oxygen species in E-Boron/PMS system tended to be 1O2, instead of the •OH and SO4•−. Mechanistic study unveiled that 1O2 was generated via accelerated PMS self-decomposition, triggered by interface alkalization and hydroxyl radicals transfer at the cathode interface. 1O2 is considered to be selective to the electron-rich organic compounds, thus E-Boron/PMS system was superior to conventional radical-dominated system (Boron/PMS) for SMX removal in the co-presence of common inorganic anions, showing the great merits of selective oxidation in nonradical system. These findings provided new insights into effective and selective oxidation of SMX via E-Boron/PMS system, which shed new light on the development of nonradical system.

One-step synthesis of ultrafine silver-decorated polyaniline nanowire arrays for trace analysis of sulfamethoxazole

Sulfamethoxazole (SMX), a broad-spectrum antibiotic, has potential risk of ecological damage and human health, due to its over-dosage utilization and wanton discharge. It is desirable to develop a highly sensitive sensor for the rapid and accurate determination of SMX to evaluate the environmental risk of antibiotics. Herein, an ultrafine Ag nanoparticles-decorated polyaniline nanowire arrays (AgNPs-PANI-NAs) were successfully formed on the carbon nanofibers (AgNPs-PANI-NAs@CNF) by in-situ one-step redox reaction. The PANI wire length around CNFs and the AgNPs amount were conveniently tuned by adjusting Ag+ concentration. The conductivity and electrochemical activity of the AgNPs-PANI-NAs@CNF were significantly improved. With AgNPs-PANI-NAs@CNF as sensing material, the resultant AgNPs-PANI-NAs@CNF modified glassy carbon electrode (AgNPs-PANI-NAs@CNF/GCE) presented a super-high electrochemical response to the oxidation of SMX by strong interaction of SMX with the sensing interface. A wide linear range (1 nM ∼ 10 μM) was achieved with an ultra-low detection limit (80 pM, S/N>3). The chronocoulometry measurement proved that the adsorption capacity of SMX at AgNPs-PANI-NAs@CNF/GCE was significantly enhanced, thus improving the sensitivity of SMX detection. The related reaction mechanism and strong interaction of SMX with AgNPs-PANI-NAs were demonstrated by X-ray photo spectroscopy and ultraviolet-visible spectroscopy characterization. This work provides a novel strategy of constructing high-performance sensing materials for pollutants analysis in environmental waters.

Electrochemical determination of sulfamethoxazole in biological and drug samples using Ce (III)-doped CuO modified electrode

This study aimed to fabricate Ce (III)-doped CuO via a simple participation technique. The produced nanocomposite as an effective modifier was applied at the surface of screen-printed electrode (SPE) to evaluate the electro-oxidation of sulfamethoxazole (SMX). Using K3Fe(CN)6 and related equation, electro-active area of electrodes was calculated that were 0.041, 0.111 and 0.123 cm2 for SPE, CuO/SPE and Ce (III)-doped CuO/SPE, respectively. The results of scan rate investigation revealed the diffusion-controlled mechanism of SMX on Ce (III)-doped CuO/SPE. The developed electrode displayed good electrocatalytic activity toward oxidation of SMX and had a broad linear range of 0.03–360 µM, a low limit of detection (LOD) of 0.01 µM, acceptable reproducibility and excellent selectivity under optimized conditions. Moreover, diffusion coefficient was calculated 1.44 × 10−5 cm2 s−1 using chronoamperometry technique. The successful applicability of the sensor was confirmed to detect SMX in real samples, with suitable recoveries.