Sulfamethoxypyridazine Research Articles

Boron and nitrogen hydrothermal co-doped sludge biochar towards efficiently activate peroxymonosulfate for sulfamethoxazole degradation

Designing efficient catalyst for peroxymonosulfate (PMS) activation is beneficial for eliminating the adverse effects of sulfamethoxazole (SMX) on human health. A novel boron (B) and nitrogen (N) co-doped sludge biochar (BNSBC) was synthesized by one-pot hydrothermal activation, and its remarkable PMS activation performance facilitated the rapid elimination of SMX from water. The degradation rate of SMX by BNSBC/PMS system could reach 92.1% within 60 min ([SMX]0 = 10 mg/L, [BNSBC]0 = 0.4 g/L, [PMS]0 = 1 mM). B and N exhibited the synergistic enhancement effects on the physico-chemical characteristics of SBC, and abundant pores, defects, CO, -O-B-O-, graphitic-N and pyridinic N were confirmed as the main active sites of BNSBC for PMS activation. Characterization, quenching, electron paramagnetic resonance (EPR) and electrochemical tests proved that non-radicals of surface-bound, 1O2 and electron transfer were the main contributors to SMX degradation. The high anti-interference of BNSBC/PMS system to pH range, co-existing inorganic anions and organic matter guaranteed its outstanding purification performance for SMX in diverse environmental waters. Four potential degradation pathways of SMX in BNSBC/PMS system were proposed by its intermediates identification and density functional theory (DFT) calculation, and pathway Ⅳ was the main one. The toxicity levels of its intermediates were lower than that of SMX regardless of chronic and acute toxicity. Also, BNSBC/PMS system exhibited the board-spectrum removal performance for other typical antibiotics (e.g., sulfadiazine (SDZ), sulfamethoxypyridazine (SMP), ciprofloxacin (CIP), tetracycline (TC)). BNSBC/PMS has great application potential for eliminating diverse antibiotics in actual wastewater due to its high tolerance to complex environmental conditions and outstanding detoxification ability, also it offers a harmless disposal approach for sludge.

Novel insights into ferrate (VI) activation by Mn-modified sludge biochar for sulfamethoxazole degradation: Dominance of hydroxyl group and Mn-O bond in the non-radical pathway

Ferrate (Fe (VI)), as a versatile oxidizer, has been widely employed for water treatment. However, the rapid self-decomposition of Fe (VI) diminishes its practical application efficiency. In this study, a novel Mn-modified sludge biochar (MSBC) was synthesized for the first time to activate Fe (VI) and generate highly reactive Fe (IV)/Fe (V) for the rapid removal of sulfamethoxazole (SMX). The results showed that MSBC (0.10 g/L) effectively activated Fe (VI) (100 μM), and 87.39 % of SMX (10 μM) and 40.26 % of total organic carbon (TOC) were removed within 10 min. Notably, raising the solution pH (e.g., from 6.0 to 11.0) would result in decreasing the reactivity of Fe (VI) and a lower removal efficiency of SMX. The quenching, electron paramagnetic resonance and probe experiments suggested that •O2– and high-valent iron species (Fe (V)/Fe (IV)) were identified as the major contributions to the removal of SMX. The detailed activation sites of MSBC were –OH and Mn-O, as corroborated by density functional theory (DFT) calculation and characterization. These activation sites facilitated activation of Fe (VI) through efficient electron transfer. The Fukui index indicated that the N, S, and O atom of SMX were the primary attacked sites. Subsequently, five potential degradation pathways were proposed, with the cleavage of the S-N bond being the predominant one. The toxicity of these products was examined using ECOSAR program, revealing that main products showed low toxicity or non-toxicity. The Cl-, SO42-, and NO3– had negligible effect on SMX degradation, although excessive concentrations of HCO3– and humic acid (HA) showed slightly inhibition. Additionally, the Fe (VI)/MSBC system also effectively removed 87.34 % of sulfadiazine (SDZ) and 93.91 % of sulfamethoxypyridazine (SMP). Overall, this study offered a practical and cost-effective approach for the activation of Fe (VI) and provided new insights to the degradation mechanism.

Biological Activities, DFT and Molecular Docking Studies of Novel Schiff Bases Derived from Sulfamethoxypyridazine

AbstractThe present study reported the synthesis and biological activities of sulfamethoxypyridazine (SMPR) Schiff bases (SBs) with different aromatic aldehydes. The antimicrobial potential of SBs against various pathogenic strains (S. epidermidis, E. coli, S. agalactiae, S. aureus, S. typhi, K. pneumoniae, C. albicans, and C. tropicalis) was explored by disc diffusion method. The antidiabetic potential was monitored by inhibition of α‐amylase, α‐glucosidase, and anti‐inflammatory activity was studied by protein denaturation assay. The binding of protein with SBs was determined by MOE docking. The synthesized SBs reveal significant antimicrobial potential against all strains (p values<0.0001) better than the parent drug SMPR but less than amoxicillin. The synthesized SBs exhibited reasonable inhibition potential against α‐glucosidase, α‐amylase, and anti‐inflammatory activity. The derivative 10 a depicted antioxidant (IC50 value 12.18 μg/mL) and anti‐inflammatory (IC50 value 49.37 μg/mL) even better than standard ascorbic acid and diclofenac sodium (IC50 values 49.92 and 123.81 μg/mL), respectively. Molecular docking results revealed that synthesized SBs have good binding affinities towards different receptor proteins and results support our experimental results. The electronic properties have been calculated using density function theory (DFT) to determine the chemical reactivity of studied compounds. The low energy gap between Frontier Molecular Orbitals (FMOs) revealed the significant chemical reactivity of compounds 8 a and 10 a, among other compounds.

Comparison of the effectiveness of UV, UV/VUV photolysis, ozonation, and ozone/UV processes for the removal of sulfonamide antibiotics

UV (254 nm) and UV/VUV (254/185 nm) photolysis, ozonation, and O3/UV combination were investigated and compared for the transformation of two sulfonamide (SAs) antibiotics, sulfamethazine (SMT) and sulfamethoxypyridazine (SMP). Change in toxicity, the effect of bacteria growth inhibition of the treated solutions, and the cost-efficiency of the methods were studied. In UV/VUV radiated solutions, the formation of •OH results in the doubled transformation rate. The relative contribution of various ROS (•OH, 1O2, O2•−) to the transformations were also investigated in the case of UV and UV/VUV photolysis. Both SAs can be eliminated ten times faster during ozonation than UV photolysis; but conversion via ozonation is associated with the formation of products with low reactivity to ozone and has biological effects. The O3/UV process did not enhance the transformation rate but positively affected mineralization and significantly decreased the ecotoxicity of the treated solutions. Ozonation was cost-effective, but O3/UV is a much safer technology to minimize environmental impacts because it effectively reduces the ecotoxicity and the bacterial growth inhibition effect of the treated solution. The observed differences between SMT and SMP are primarily related to the transformation of the N-containing rings. Our results showed a correlation between the reactivity of the N-containing groups of SAs, the rate of mineralization, and the change in ecotoxicity and antibacterial effect and emphasized the need for toxicological characterization of the treated samples. The removal of parent compounds is not sufficient to avoid the release of toxic substances into the environment.

UV-LED cocatalytic Fe3+/peroxymonosulfate process for the degradation of sulfamethoxypyridazine: Performance, mechanism and DBP formation during postchlorination

Herein, a UV-LED-catalytic Fe3+/peroxymonosulfate homogeneous advanced oxidation process (UV-LED/Fe3+/PMS) was adopted for the removal of sulfamethoxypyridazine (SMP), a commonly used sulfonamide antibiotic (SA), in water. Quenching experiments showed that SO4●–, •OH and Fe(IV) were generated in this system and contributed to the rapid removal of SMP. Generally, acidic media favored SMP degradation, and the contribution rate of active species to SMP removal was highly pH dependent. Higher light intensity and an equal Fe3+/PMS ratio (1:1) were appropriate for SMP removal. The introduction of HCO3−, NO3− and humic acid suppressed the degradation of SMP to different extents, but obvious acceleration was observed in the presence of halide ions. The transformation products were investigated, and their toxicity was also assessed. UV-LED/Fe3+/PMS was capable of controlling trichloromethane (TCM) during postchlorination while increasing the formation of dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM) owing to the generation of precursors having certain functional groups. Prolonging pretreatment time had a positive effect on reducing DBP formation. The presence of humic acid increased the formation of both TCM and DCAN. Furthermore, total trihalomethanes and dihaloacetonitriles increased with increasing bromide concentration, which needs to be considered when adopting the UV-LED/Fe3+/PMS as pretreatment for the abatement of SMP.

A Paper-Based Multicolor Colorimetric Aptasensor for the Visual Determination of Multiple Sulfonamides Based on Aptamer-Functionalized Magnetic Beads and NADH–Ascorbic Acid-Mediated Gold Nanobipyramids

It is crucial that simple and high-throughput methods for determining multiple, or groups of, sulfonamides (SAs) be developed since they are widely used in animal husbandry and aquaculture. We developed a paper-based multicolor colorimetric aptasensor to detect 3 SAs: sulfaquinoxaline (SQ), sulfamethoxypyridazine (SMP) and sulfamethoxydiazine (SMD). Using a broad-specificity aptamer as a bioreceptor, we reduced the growth of nicotinamide adenine dinucleotide I (NADH)–ascorbic acid (AA)-mediated gold nanobipyramids (AuNBPs) to generate a multicolor signal. We also used a paper-based analytical device (PAD) system to deposit AuNBPs for a sensitive color signal read out. The aptasensor can detect more color changes corresponding to the concentrations of SQ, SMP and SMD and has higher sensitivity, better specificity and stability. It can also be used to determine SQ, SMP and SDM individually, or collectively, or any two together with a visual detection limit of 0.3–1.0 µM, a spectrometry quantification limit (LOQ) of 0.3–0.5 µM and a spectrometry detection limits (LOD) of 0.09–0.15 µM. The aptasensor was successfully used to determine SQ, SMP and SDM in fish muscle with a recovery of 89–94% and a RSD n = 5) < 8%, making it a promising method for the rapid screening of total SQ, SMP and SDM residue in seafood.

Application of BiOX Photocatalyst to Activate Peroxydisulfate Ion-Investigation of a Combined Process for the Removal of Organic Pollutants from Water

The persulfate-based advanced oxidation processes employing heterogeneous photocatalysts to generate sulfate radicals (SO4•−) from peroxydisulfate ion (PDS, S2O82−) have been extensively investigated to remove organic pollutants. In this work, BiOX (X = Cl, Br, and I) photocatalysts were investigated to activate PDS and enhance the transformation rate of various organic substances under UV (398 nm) and Vis (400–700 nm) radiation. For BiOCl and BiOBr, in addition to excitability, the light-induced oxygen vacancies are decisive in the activity. Although without organic substances, the BiOI efficiency highly exceeds that of BiOBr and BiOCl for PDS activation (for BiOI, 15–20%, while for BiOBr and BiOCl, only 3–4% of the PDS transformed); each BiOX catalyst showed enhanced activity for 1,4-hydroquinone (HQ) transformation due to the semiquinone radical-initiated PDS activation. For sulfamethoxypyridazine (SMP), the transformation is driven by direct charge transfer, and the effect of PDS was less manifested. BiOI proved efficient for transforming various organic substances even under Vis radiation. The efficiency was enhanced by PDS addition (HQ is wholly transformed within 20 min, and SMP conversion increased from 40% to 90%) without damaging the catalyst; its activity did change over three consecutive cycles. Results related to the well-adsorbed trimethoprim (TRIM) and application of biologically treated domestic wastewater as a matrix highlighted the limiting factors of the method and visible light active photocatalyst, BiOI.

Broad-Specificity Aptamer of Sulfonamides: Isolation and Its Application in Simultaneous Detection of Multiple Sulfonamides in Fish Sample.

Sulfonamide antibiotics (SAs) are widely used in animal husbandry and aquaculture, and the excess residues of SAs in animal-derived foods will harm the health of consumers. In reality, various SAs were alternately used in animal husbandry and aquaculture, and thus, it is urgent need to develop simple and high-throughput methods for simultaneously detecting multiple SAs or groups of SAs in order to realize rapid screening of total SAs residues in animal-derived foods. We herein isolated a broad-specificity aptamer for SAs by using a multi-SAs systematic evolution of ligands by exponential enrichment (SELEX) strategy. The isolated broad-specificity aptamer has a higher binding affinity to five different SAs including sulfaquinoxaline (SQ), sulfamethoxypyridazine (SMPZ), sulfametoxydiazine (SMD), sulfachloropyridazine (SCP), and sulfapyridine (SPD) and, thus, can be used as a bioreceptor for developing various high-throughput methods for the simultaneous detection or rapid screening of above five SAs. Based on the isolated broad-specificity aptamer and Cy7 (diethylthiatricarbocyanine) displacement strategy, a colorimetric aptasensor was developed for the simultaneous detection of SQ, SMPZ, SMD, SCP, and SPD with a visual detection limit of 2.0-5.0 μM and a spectrometry detection limit of 0.2-0.5 μM. The colorimetric aptasensor was successfully used to detect SQ, SMPZ, SMD, SCP, and SPD in fish muscle with a recovery of 82%-92% and a RSD (n = 5) < 7%. The success of this study provided a promising bioreceptor for developing various high-throughput methods for on-site rapid screening of multiple SAs residues, as well as a simple method for the rapid and cost-effective screening of total SQ, SMPZ, SMD, SCP, and SPD in seafood.

Degradation of Doxycycline, Enrofloxacin, and Sulfamethoxypyridazine under Simulated Sunlight at Different pH Values and Chemical Environments

In this work, the dissipation of the antibiotics doxycycline (DC) (from the group of tetracyclines), enrofloxacin (ENR) (a fluoroquinolone), and sulfamethoxypyridazine (SMP) (a sulfonamide) is investigated both under simulated sunlight and in the dark, at three different pH (4.0, 5.5, and 7.2), and in the presence of different salts and humic acids. The results indicate that all three antibiotics are very sensitive to photodegradation, and this sensitivity increased with rising pH values, from 4.0 to 7.2. The rise in pH also caused an increase in the degradation kinetic constants and a decrease in the half-lives of antibiotics. In general, the half-lives ranged from a few minutes to 6 h, depending on the pH conditions and the specific antibiotic, and followed the sequence DC &gt; SMP &gt; ENR, although at pH 5.5 the sequence changed to SMP &gt; DC &gt; ENR. After 24 h of simulated sunlight, mineralization was always lower than 10%, although the antibiotic was not quantifiable after the same time of exposure to light (24 h), which indicates that intermediate compounds were generated. The effect of the presence of salts on the dissipation of the three antibiotics was negligible for NaCl and NaNO3, while NaHCO3 did favor the dissipation of DC and ENR. The presence of humic acids showed no effect on the dissipation of SMP, and it only slightly increased the dissipation of DC and ENR. These results may be useful in the assessment of the persistence/degradation of the antibiotics studied when they reach different environmental compartments and may suffer exposure to light under different physicochemical conditions.

Wavelength Dependence of the Transformation Mechanism of Sulfonamides Using Different LED Light Sources and TiO2 and ZnO Photocatalysts.

The comparison of the efficiency of the commercially available photocatalysts, TiO2 and ZnO, irradiated with 365 nm and 398 nm light, is presented for the removal of two antibiotics, sulfamethazine (SMT) and sulfamethoxypyridazine (SMP). The •OH formation rate was compared using coumarin, and higher efficiency was proved for TiO2 than ZnO, while for 1,4-benzoquinone in O2-free suspensions, the higher contribution of the photogenerated electrons to the conversion was observed for ZnO than TiO2, especially at 398 nm irradiation. An extremely fast transformation and high quantum yield of SMP in the TiO2/LED398nm process were observed. The transformation was fast in both O2 containing and O2-free suspensions and takes place via desulfonation, while in other cases, mainly hydroxylated products form. The effect of reaction parameters (methanol, dissolved O2 content, HCO3− and Cl−) confirmed that a quite rarely observed energy transfer between the excited state P25 and SMP might be responsible for this unique behavior. In our opinion, these results highlight that “non-conventional” mechanisms could occur even in the case of the well-known TiO2 photocatalyst, and the effect of wavelength is also worth investigating.

Photodegradation of Sulfamethoxypyridazine in UV/Co(II)/Peroxymonosulfate System: Kinetics, Influencing Factors, Degradation Pathways, and Toxicity Assessment.

Sulfonamides (SAs) including sulfamethoxypyridazine (SMP) are regarded as a new type of persistent pollutant at present due to their abuse. In this work, the direct photodegradation behavior of 11 SAs under simulated sunlight was first investigated, and the results indicated that the direct photolysis of SMP is the slowest among these SAs. Then the oxidation degradation of SMP in UV/Co(II)/peroxymonosulfate (PMS) system was systematically explored. Up to 95.2% removal of 0.071 mM SMP was observed after 20 min of reaction under the optimal condition with a molar ratio of 1:150:5 between SMP, PMS, and Co(II). The effects of some coexisting anions on degradation of SMP were investigated. It was found that Cl− and high concentrations of CO32− and HCO3− have a significant inhibitory effect, while HPO42− has only a slight positive effect. Radical scavenger experiments indicated that hydroxyl radicals (HO•) are prevailing active species responsible for SMP removal in UV/Co(II)/PMS system. The degradation of SMP in UV/Co(II)/PMS system was accomplished mainly by hydroxylation of the aromatic ring, extrusion of SO2, oxidation of NH2 group, and N − S bond cleavage. Eight intermediates for SMP degradation were identified, and their toxicities to aquatic organisms were predicted by using the ECOSAR program based on the structure − activity relationships (SARs), which suggested that the chronic toxicities of SMP and its degradation intermediates are more significant than their acute toxicities. The present research indicates that UV/Co(II)/PMS system is applicable for SMP degradation in aqueous solutions and may be helpful to understand the transformation behavior of SAs.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11270-021-05351-5.

Investigation of the efficiency of BiOI/BiOCl composite photocatalysts using UV, cool and warm white LED light sources - Photon efficiency, toxicity, reusability, matrix effect, and energy consumption

BiOI, BiOCl, and their composites (BiOI:BiOCl) with molar ratios from 95:5 to 5:95 were synthesized and tested in the transformation of methyl orange (MO) and sulfamethoxypyridazine (SMP) antibiotic, using three various LED light sources: UV LEDs (398 nm), cool and warm white LEDs (400–700 nm). The 80:20 BiOI:BiOCl photocatalyst showed the best adsorption capacity for MO and enhanced activity compared to BiOI and BiOCl. The apparent quantum yield (Φapp) of the MO and SMP transformation for cool and warm white light was slightly lower than for 398 nm UV radiation. The effect of methanol and 1,4-benzoquinone proved that the transformation is initiated mainly via direct charge transfer, resulting in the demethylation of MO and SO2 extrusion from SMP. The change of photocatalytic efficiency was followed during three cycles. After the first one, the transformation rates decreased, but there was no significant difference between the second and third cycles. The decreased efficiency is most probably caused by the intermediates, whose continuous accumulation was observed during the cycles. Ecotoxicity measurements confirmed that no toxic substances were leached from the catalyst, but the transformation of both MO and SMP results in toxic intermediates. Using 80:20 BiOI:BiOCl and LED light source, the energy requirement of the removal is about half of the value determined using TiO2 and a mercury vapor lamp. The effect of some components of wastewater (Cl−, HCO3− and humic acids), pH, and two matrices on the composite photocatalysts' efficiency and stability were also investigated.

Environmental relevance of adsorption of doxycycline, enrofloxacin, and sulfamethoxypyridazine before and after the removal of organic matter from soils

In this work batch-type experiments were used to study the adsorption of the antibiotics doxycycline (DC), enrofloxacin (ENR), and sulfamethoxypyridazine (SMP) in cultivation soils, before and after the removal of soil organic matter. Organic matter removal by calcination resulted not only in C and N removal, but also in increased soil pH, exchangeable basic cations and surface area values. The results indicate a very different behavior depending on the type of antibiotic, showing the adsorption sequence DC > ENR > SMP. Specifically, DC adsorption was very high in untreated soil samples (with organic matter), and was still high (although decreased) after the removal of soil organic matter. Furthermore, the adsorption behavior of DC was clearly dependent on the pH of the medium. Regarding ENR, it also showed high adsorption, although to a lesser extent than DC. However, when soil organic matter was removed, ENR adsorption significantly decreased in all soil samples. As regards SMP, it was adsorbed to a much lesser extent, and the removal of soil organic matter caused an additional drastic decrease in adsorption, reaching negligible values in some samples. Desorption followed the reverse sequence of adsorption, specifically in the order DC < ENR < SMP. In the case of DC, desorption was negligible, both in samples with and without organic matter, while for ENR and SMP, desorption clearly increased for soil samples where organic matter was removed. These results may be of relevance as regards environmental quality and public health, especially to facilitate a correct use of soils and organic amendments in areas that receive the application of substances containing the investigated antibiotics.

Development of sulfonamide-based Schiff bases targeting urease inhibition: Synthesis, characterization, inhibitory activity assessment, molecular docking and ADME studies

A series of Sulfonamide-based Schiff bases (E)-4-(benzylideneamino)-N-(6-methoxypyridazin-3-yl) benzenesulfonamide (3a-r) targeting Urease Inhibition was synthesized from sulphamethoxy pyridazine and substituted aldehydes. The prepared compounds were characterized by various spectroscopic techniques including FTIR, 1HNMR, 13CNMR, and spectrometric HRMS analysis. The most active agent (3g) bearing halogens and OH groups gave IC50 value of 2.20 µM for urease inhibition against the standard Thiourea (IC50 = 20.03 ± 2.06) and the overall trend within the series was 3g > 3n > 3p > 3j > 3q > 3h, 3o > 3l, 3r > 3k, 3m > 3a > 3d > 3e > 3f. Structure-activity relationship study established that the nature as well as the position of varying groups attached to aryl group had crucial roles in defining the urease inhibition activity. Additionally, in silico investigation was carried out which demonstrated that the compounds exhibit polar and apolar contacts with the crucial residues in the binding site of urease. The ADME analysis suggested all the synthesized compounds to be non-toxic, and likely to undergo passive gastrointestinal absorption. Taken together, the study suggests that the synthesized Sulfonamide-based Schiff bases derivatives may serve as potential hits as urease inhibitors.

Adsorption/desorption of sulfamethoxypyridazine and enrofloxacin in agricultural soils

Adsorption and desorption processes were studied for the antibiotics sulfamethoxypyridazine (SMP) and enrofloxacin (ENR) in 20 agricultural soils devoted to wheat-potato and vine cultivation. Batch experiments were used to conduct kinetic studies, as well as to evaluate adsorption and desorption for different concentrations of antibiotics. The results indicated that adsorption curves were linear for SMP, while presented a certain curvature in the case of ENR. The adsorption of both antibiotics was fitted to a linear equation and to the Freundlich model. In the case of the linear equation, the values of the distribution coefficient Kd were lower for SMP (0.9–26.0 L kg−1) than for ENR (121–2345 L kg−1). In the Freundlich model, the values of the adsorption constant KF ranged between 1.7 and 34.0 Ln μmol1−n kg−1 for SMP, and between 829 and 3019 Ln μmol1−n kg−1 for ENR. A multiple regression analysis showed that, in the case of SMP, 78% of the variance of the adsorption parameter Kd was explained by soil organic carbon (SOC) and exchangeable magnesium (Mge) contents, while for ENR no significant relation was found. In addition, for SMP, 66% of the variance of KF was explained by SOC, and for ENR 45% of the variability of KF was explained by nitrogen content. Desorption rates were higher for SMP (reaching up to 24%) than for ENR (which reached up to 7%). Desorption percentages showed a potential relation with the adsorption parameter Kd for both SMP and ENR. These results could be useful to elucidate the evolution and dynamics of these emerging pollutants in soils and other environmental compartments, which could be of aid in controlling public health risks associated to them.

Occurrence and Risk Assessment of Antibiotics in Manure, Soil, Wastewater, Groundwater from Livestock and Poultry Farms in Xuzhou, China.

Antibiotics in manure, soil, wastewater, and groundwater samples from the livestock and poultry farms in Xuzhou City were investigated in the present study. The concentrations of antibiotics in all matrices varied greatly among farms. Total concentrations of fluoroquinolones and macrolides were much higher than those of sulfonamides in manures and soil samples. Total concentrations of antibiotics in wastewater of livestock farms were higher than those of poultry farm. Josamycin (JM) and tilmicosin (TIL) accounted for more than 74% of the nine macrolides in all groundwater samples. Sulfamethizole (SMT), fleroxacin (FLE), cinoxacin (CIN) and JM were the main antibiotics detected in manure and soil samples, while sulfamethoxypyridazine (SMP), sulfameter (SME), SMT, FLE, JM and TIL accounted for a large proportion of antibiotics in surface and groundwater. The risk assessment of target antibiotics revealed that JM in wastewater showed relatively high RQs for aquatic organisms.

UV-activated persulfate oxidation of sulfamethoxypyridazine: Kinetics, degradation pathways and impact on DBP formation during subsequent chlorination

The kinetics and mechanisms of the degradation of sulfamethoxypyridazine (SMP) by an ultraviolet-activated persulfate (UV/PS) advanced oxidation process (AOP) and the formation of disinfection byproducts (DBPs) during subsequent chlorination were investigated in this study. The UV/PS process can significantly remove SMP through pseudo-first-order reaction kinetics. In a competitive kinetic experiment, the second-order rate constant of SMP with sulfate radical was determined to be 2.73 × 1010 M−1 s−1, while that with hydroxyl radical was 2.22 × 1010 M−1 s−1. Six major transformation products in SMP degradation were recognized by LC/MS/MS analysis. It was assumed that the degradation pathway of SMP involves the hydroxylation of the aromatic ring, cleavage of the sulfonamide bond, oxidation of the aniline moiety and elimination of SO2. The impacts of persulfate dose, pH, anions (HCO3–, SO42−, and Br−) and humic acid (HA) concentration on SMP degradation efficiency and DBP formation during subsequent chlorination were also examined. SMP degradation was accelerated with increasing persulfate dose, HCO3– and Br- concentration as well as decreasing pH and HA concentration. However, the amount of chloroform (CF) formed was reduced under a higher persulfate dosage and lower pH. In contrast, the amount of dichloroacetonitrile (DCAN) formed was enhanced under a higher persulfate dose and lower pH. Adding HA also increased the formation of both CF and DCAN. While, both HCO3– and SO42– had little effects on the formation of CF and DCAN. The presence of Br– had no significant effects on the bromine incorporation factors (BIFs) of trihalomethanes (THMs) and dihaloacetonitriles (DHANs). Raw water experiments showed that the UV/PS process could destroy SMP in natural water as well as control the formation of DBPs.

Aqueous chlorination of sulfamethazine and sulfamethoxypyridazine: Kinetics and transformation products identification.

Sulfonamides (SNs) are synthetic antimicrobial agents. These substances are continually introduced into the environment, and they may spread and maintain bacterial resistance in the different compartments. The chlorination of 2 SNs, namely, sulfamethazine (SMT) and sulfamethoxypyridazine (SMP), was investigated to study their reactivity with chlorine at typical concentrations for water treatment conditions. Experiments conducted in purified water show an acceleration of SMT and SMP degradation of a factor 1.5 by comparison to drinking water matrix. This difference is due to pH variation and competitive reactions between SNs and mineral and organic compounds, with chlorine in drinking water. In the presence of an excess of chlorine (6.7μmol·L-1 ) in ultrapure water at pH7.2, second-order degradation rate constants were equal to 4.5×102 M-1 ·s-1 and 5.2×102 M-1 ·s-1 for SMT and SMP, respectively. The structures of transformation products were investigated by liquid chromatography tandem mass spectrometry analyses with equimolar concentrations between chlorine and SNs. SO2 elimination, cyclization, and electrophilic substitutions were the main pathways of by-products formation. Moreover, the toxicity of the proposed structures was predicted by using toxicity estimation software tool program. The results indicated that most by-products may present developmental toxicity.

Antibiotics pollution in Gonghu Bay in the period of water diversion from Yangtze River to Taihu Lake

As a famous project in China, the water diversion from Yangtze River to Taihu Lake Project has impacts on the water quality of Taihu Lake, especially Gonghu Bay, which is the entrance of the diversion water and the drinking water source for Wuxi and Suzhou. To investigate contamination of the antibiotics in Gonghu Bay in the period of water diversion, 16 antibiotics in 14 water samples collected from Wangyu River and Gonghu Bay in China were analyzed by liquid chromatography–tandem mass spectrometry. The results indicated that the concentration of total antibiotics in Wangyu River and Gonghu Bay ranged from 1320 to 17,209 ng/L (mean: 3920 ± 3841 ng/L). The average level of different antibiotics was tetracyclines (range 1082–15,310 ng/L, mean 3161 ± 3479 ng/L) > quinolones (range 225–1325 ng/L, mean 463 ± 276 ng/L) > sulfonamides (range n.d.–888 ng/L, mean 402 ± 248 ng/L) > macrolides (range 12–17 ng/L, mean 14 ± 2 ng/L), and levels of the detected antibiotics in Gonghu Bay were higher than that in Wangyu River, indicating that the antibiotics pollution in Gonghu Bay were much severer than Wangyu River. Ecological risk evaluation showed that in the Wangyu and Gonghu water, trimethoprim (TMP), sulfacetamide (SAAM), sulfamethoxypyridazine (SMP), and sulfamerazine (SMRZ) presented low ecological risk levels, chlortetracycline (CTC), tetracycline (TC), roxithromycin (ROM), and sulfamethoxazole (SMX) had medium level of risk, and oxytetracycline (OTC), norfloxacin (NOR), ofloxacin (OFL), ciprofloxacin (CIP), and enrofloxacin (ENR) had high level of ecological risk. The total hazard quotient of antibiotic mixtures for each sample site indicated high risk of antibiotics in Wangyu River and Gonghu Bay. In summary, the water diversion could mitigate antibiotic pollution in Gonghu Bay to a certain degree. However, the risk of antibiotics in the Wangyu River and Gonghu Bay is still high.

Transformation of aqueous sulfonamides under horseradish peroxidase and characterization of sulfur dioxide extrusion products from sulfadiazine

The potential of horseradish peroxidase (HRP) to catalyze the removal of sulfonamides from water and the effects of different H2O2 and HRP concentrations were investigated. Six sulfonamides, each with a five- or six-membered heterocyclic group, including sulfamethoxazole (SMX), sulfathiazole (STZ), sulfapyridine (SPD), sulfadiazine (SDZ), sulfamerazine (SMR) and sulfamethoxypyridazine (SMP) were selected as target compounds. All sulfonamides exhibit a pseudo-first-order dependence of the concentration versus the reaction time. The decay rate (k, h−1) of the six sulfonamides spiked individually exhibit a trend following the order of STZ > SMP, SPD > SMR > SDZ » SMX. When spiked together, the coexistent sulfonamides might act as mediators for the enhancement of SMX removal and as competitors for the decreased removal of most sulfonamides. Moreover, six transformation products of SDZ are identified by the Thermo Scientific LTQ Orbitrap Elite technique. SDZ transformation involves two steps: one is the Smiles re-arrangement of the structure, and the other is oxidation and sulfur dioxide extrusion. This study is the first to report the removal dynamics of sulfonamides in HRP-catalyzed reactions and the identified products of SDZ.