Sulfonamide Antibiotics Research Articles

Analysis of the Comparative Growth Kinetics of Paenarthrobacter ureafaciens YL1 in the Biodegradation of Sulfonamide Antibiotics Based on Substituent Structures and Substrate Toxicity

The high consumption and emission of sulfonamide antibiotics (SAs) have a considerable threat to humans and ecosystems, so there is a need to develop safer and more effective methods than conventional strategies for the optimal removal of these compounds. In this study, four SAs with different substituents, sulfadiazine (SDZ), sulfamerazine (SMR), sulfamethoxazole (SMX), and sulfamethazine (SMZ) were removed by a pure culture of Paenarthrobacter ureafaciens YL1. The effect of the initial SAs concentration on the growth rate of strain YL1 was investigated. The results showed that the strain YL1 effectively removed various SAs in the concentration range of 0.05–2.4 mmol·L−1. The Haldane model was used to perform simulations of the experimental data, and the regression coefficient of the model indicated that the model had a good predictive ability. During SAs degradation, the maximum specific growth rate of strain YL1 was ranked as SMX > SDZ > SMR > SMZ with constants of 0.311, 0.304, 0.302, and 0.285 h−1, respectively. In addition, the biodegradation of sulfamethoxazole (SMX) with a five-membered substituent was the fastest, while the six-membered substituent of SMZ was the slowest based on the parameters of the kinetic equation. Also, density functional theory (DFT) calculations such as frontier molecular orbitals (FMOs), and molecular electrostatic potential map analysis were performed. It was evidenced that different substituents in SAs can affect the molecular orbital distribution and their stability, which led to the differences in the growth rate of strain YL1 and the degradation rate of SAs. Furthermore, the toxicity of P. ureafaciens is one of the crucial factors affecting the biodegradation rate: the more toxic the substrate and the degradation product are, the slower the microorganism grows. This study provides a theoretical basis for effective bioremediation using microorganisms in SAs-contaminated environments.

Hierarchically porous zirconium-based metal–organic frameworks for rapid adsorption and enrichment of sulfonamide antibiotics

Due to serious risk to human health and eco-environmental security, antibiotics in water and foods received considerable concern. Herein, a series of stable hierarchically porous zirconium-based metal–organic frameworks (MOFs) namely HP-NU-902-X were prepared via modulator-induced defect-guided formation strategy for the first time and functioned as sorbents to removal and preconcentration of sulfonamide antibiotics (SAs). The pore size and specific surface area of HP-NU-902-X were systematically adjusted by changing concentration of monocarboxylic acid modulator. The adsorption performance of HP-NU-902-X were greatly improved by forming defects. Experiments demonstrated that HP-NU-902-80 possessed the highest adsorption efficiency to SAs. The limits of detection (S/N = 3) were achieved ranging 0.08 to 0.25 ng/mL. The spiked recoveries of water and milk samples were obtained in the range of 70.34–103.4 % and 73.83–100.5 %. Enrichment factors were calculated between 203 and 358. The SAs can be completely removed within 10 min, and adsorption kinetic data was best consistent with pseudo-second-order model. Using Langmuir isotherm model, maximum adsorption capacities for sulfadiazine, sulfapyridine, sulfametoxydiazine, sulfachloropyridazine, sulfabenzamide and sulfamethazine were calculated as 279.9, 467.7, 414.4, 433.1, 415.5 and 336.6 mg/g, respectively. The improved adsorption capacity was mainly owing to high surface area and extra defect sites. This synthetic strategy provides a way to prepare stable defective MOFs and enhance their potential applications in removal and extraction of environmental pollutants.

New Models for Estimating the Sorption of Sulfonamide and Tetracycline Antibiotics in Soils.

Sulfonamides (SAs) and tetracyclines (TCs) are two classes of widely used antibiotics. There is a lack of easy models for estimating the parameters of antibiotic sorption in soils. In this work, a dataset of affinity coefficients (Kf and Kd) of seven SA/TC antibiotics (i.e., sulfachlorpyridazine, sulfamethazine, sulfadiazine, sulfamethoxazole, oxytetracycline, tetracycline, and chlortetracycline) and associated soil properties was generated. Correlation analysis of these data showed that the affinity coefficients of the SAs were predominantly affected by soil organic matter and cation exchange capacity, while those of the TCs were largely affected by soil organic matter and pH. Pedotransfer functions for estimating Kf and Kd were built by multiple linear regression analysis and were satisfactorily validated. Their performances would be better for soils having higher organic matter content and lower pH. These pedotransfer functions can be used to aid environmental risk assessment, prioritization of antibiotics and identification of vulnerable soils.

Spherical Ni/Ni3Se2 Heterostructure for Efficient Electrochemical Oxidation Reactions

AbstractA Ni/Ni3Se2 metal‐semiconductor heterojunction catalyst with a sphere structure was prepared by a hydrothermal and hydrogen reduction method. The results showed that the heterostructure Ni/Ni3Se2 exhibits better performance than Ni3Se2 and Ni counterparts for electrochemical oxidation reactions. During electrocatalytic water oxidation, the overpotential is 340 mV to reach a catalytic current density of 10 mA cm−2 in 1.0 M KOH solution. The heterogeneous interface formed between the metal Ni and Ni3Se2 in the Ni/Ni3Se2 catalyst can accelerate the electron transfer in the electrochemical oxidation process. Moreover, the as‐prepared material is also applied for sulfonamide degradation, with the aid from hydroxyl radicals generated during water oxidation. This application is meaningful since the product from water oxidation is not desired in hydrogen production from water electrolysis. The material with heterojunctions delivered degradation efficiency up to 80% of sulfonamide antibiotics within 2 h. Therefore, the Ni/Ni3Se2 material might have application prospects in electrochemical sustainability research.

Integrated phycoremediation and ultrasonic-irradiation treatment (iPUT) for the enhanced removal of pharmaceutical contaminants in wastewater

Ultrasonication using low frequencies of sound can increase cell organogenesis, which is beneficial for various industrial applications. This study demonstrates a novel approach of integrated phycoremediation and ultrasonication-irradiation treatment (iPUT) used for improving the degradation of sulfonamide antibiotics via a cumulative effect of combined treatments. Variable ultrasonication treatment (UT) (20 %-2 min to 40 %-10 min) was given to a model microalga, Chlamydomonas mexicana in two ways, 1) single ultrasonic treatment (SUT) and 2) multiple-intermittent ultrasonic treatments (IUT). The microalgal growth was slightly affected by SUT, while it significantly inhibited by IUT. The removal of sulfacetamide and sulfapyridine was significantly improved by >1.7-fold and >1.95-fold at 20 % of SUT and IUT treatment, respectively, compared to control. In the case of sulfamethazine, the SUT showed maximum removal (33.5 %) at 20 %, whereas IUT could achieve 27.5 % removal at the same ultrasonication conditions compared to 9.5 % removal in control. The IUT accelerated the degradation of sulfamethoxazole and sulfadimethoxine more than SUT showing a 9- fold and 12- fold increase in the removal of sulfamethoxazole and sulfadimethoxine with 20 % and 40 % treatments, respectively. The changes in microalgal cell morphology due to ultrasonication treatment were the main cause of enforced uptake and subsequent degradation of these ECs.

Selective photocatalytic removal of sulfonamide antibiotics: The performance differences in molecularly imprinted TiO2 synthesized using four template molecules

Four types of molecularly imprinted TiO2 photocatalysts named MIP-TiO2/sulfadiazine (SD), MIP-TiO2/sulfamethoxazole (SMX), MIP-TiO2/sulfonamide (SN) and MIP-TiO2/aniline (AN), were synthesized. The five catalysts exhibited different degrees of selectivity for two types of sulfonamide antibiotics (SAs), SD and SMX. In the systems of NIP–TiO2, MIP-TiO2/SD, MIP-TiO2/SMX, MIP-TiO2/SN and MIP-TiO2/AN, the degradation rate constants of SD were 0.0789, 0.1031, 0.0859, 0.1034 and 0.1051 min−1, respectively. Moreover, the removal rate constants of SMX on the mentioned catalysts were 0.1076, 0.3250, 0.4260, 0.3885 and 0.5848 min−1, correspondingly. The single bond cleavage (C–S, C–N, and S–N bonds), hydroxylation, ring-opening, oxidation, and deamination were the major transformation pathways of SAs. With the presence of MIP-TiO2/SN and MIP-TiO2/AN, more low molecular weight products were generated, and the intermediates preferred to go through further hydroxylation and oxidation reactions. Therefore, besides MIP-TiO2/SD and MIP-TiO2/SMX, the novel MIP-TiO2/SN and MIP-TiO2/AN, which were prepared by using substances with the similar main functional groups as SAs as template molecules, had excellent catalytic abilities and less byproducts formed in the situation. The results may provide an effective idea to level up the SAs degradation rates, control the generation of intermediates, and reduce environmental risks.

Co–Mn spinel oxides trigger peracetic acid activation for ultrafast degradation of sulfonamide antibiotics: Unveiling critical role of Mn species in boosting Co activity

Activation of peracetic acid (PAA) to generate powerful oxidizing species has become a promising advanced oxidation processes (AOPs) in wastewater treatment, yet the development of low-cost and high-performance activators is still a primary challenge. Herein, a range of Co–Mn spinel oxides (Co3-xMnxO4) with varying levels of Co and Mn were successfully elaborated, in which Co1.1Mn1.9O4 exhibited remarkable performance in PAA activation, outperforming most reported heterogeneous catalysts. Extensive quenching experiments and electron spin resonance (ESR) analysis indicated that acetylperoxyl radical (CH3C(O)OO●) was the predominated oxidizing species responsible for sulfamethoxazole (SMX) degradation. Density functional theory (DFT) calculations revealed that doping with Mn not only promoted the electron transfer and accelerated reduction of Co(III) to Co(II), but also lowered the energy barrier for PAA activation. Moreover, the prominent chemisorption and activation of PAA with Co1.1Mn1.9O4 was also benefitted from the significant role of Mn in optimizing the distribution of bonding and antibonding states on Co 3d orbitals. Unexpectedly, high levels of Cl−greatly facilitated SMX degradation due to the mass production of HOCl from the chain reactions of various radicals with Cl−. This work provides new insights into bimetallic activation of PAA, and the knowledge obtained will further advance the application of PAA-based AOPs.

New insights into the binding mechanism of lysozyme by 2-sulfanilamido-4-methylpyrimidine and 3-sulfanilamido-5-methylisoxazole: Density function theory, multispectral techniques and molecular docking

Over-accumulation of 3-Sulfanilamido-5-methylisoxazole (SMZ) and 2-sulfanilamido-4-methylpyrimidine (SMD) by organisms could lead to irreversible potential toxicity. Herein, the interaction mechanism of SMZ/SMD was demonstrated in combination with multispectral techniques, density functional theory (DFT) and molecular docking with the use of lysozyme (Lys) as a model protein. The quenching of Lys intrinsic fluorescence by SMD is greater than that by SMZ because the affinity of SMD for Lys is stronger than that of SMZ. The binding of SMD/SMZ to Lys is an exothermal process that is carried out automatically (ΔG<0), which is proved by thermodynamic parameters. The concept that the interaction between SMD/SMZ and Lys was mainly achieved through hydrogen bonding and hydrophobic interactions was also validated for molecular docking. These results reveal potential toxicological mechanisms about the interaction of SMD/SMZ with Lys and provide theoretical support for reducing the harm of sulfonamide antibiotics.

TikTok: An Opportunity for Antibiotic Education?

Health information and misinformation on social media have become a growing concern for the medical community. Antimicrobial resistance continues to advance, threatening public health and safety. TikTok, a popular social media platform, provides an avenue for providers to educate patients on clinical topics and medication use. As leaders in patient education and counseling, pharmacists are equipped to provide trustworthy information on TikTok and other platforms. Pharmacists can thus advance the practice of pharmacy and build rapport with patients through a new medium. Current health-related videos on TikTok have not been robustly evaluated for quality and reliability. This study evaluates antibiotic-related content from healthcare providers and non-healthcare providers on TikTok for balance, reliability, and quality using the DISCERN score. Introduction: Antimicrobial resistance is increasing at an alarming rate. Patient education is a critical component of both stewardship and combating health misinformation. TikTok is a video-sharing social media platform with 1 billion monthly users and contains videos that discuss health information. The objective of this study was to evaluate antibiotic-themed TikTok videos for their validity and reliability. Methods: In March 2021, a search on TikTok using the term "antibiotics" was performed and the top 300 consecutive videos were identified. The following data was collected for each video: number of likes, associated disease state, medications, educational aim, mention of COVID-19, and if performed by a healthcare professional (HCP). Non-English language videos were excluded. The DISCERN score was used to evaluate all videos for reliability. Chi-square and Mann-Whitney U were used for statistical analysis. A p-value less than .05 was considered statistically significant. Results: The first 300 consecutive videos were assessed using the DISCERN score for validity. Of the 300 videos, the majority (n=224) were created by non-health care professionals (non-HCPs). The number of "likes" per video ranged from 1 like to 2 million likes with a mean of 34,949 ± 143,482. Videos produced by HCPs were significantly more valid and reliable (mean DISCERN score of 1.65 vs 1.17, p <0.00001) than non-HCPs. They were found to be more relevant (p<0.00001), have clearer aims (p<0.00001), and were more balanced/unbiased (p=0.00188). Videos created by HCPs were more likely to have an educational focus (p<0.0001). There was no difference between groups in clarity of sources utilized or risk/benefits discussed of each treatment. Across all videos, the most common disease states mentioned were urinary tract infection, skin and soft tissue infection, upper respiratory tract infection, and dental infection. Herbal or supplement products, penicillins, and sulfa antibiotics were the most commonly discussed medications. Conclusions: Videos created by HCPs were significantly more valid and reliable than those created by non-HCPs. The videos created by HCPs were also more likely to have clear aims and be more relevant. However, the majority of the videos evaluated were created by non-HCPs. It may be beneficial for HCPs to provide informative TikTok videos that are valid and reliable for patient education.

Oxidation of sulfonamide micropollutants by versatile peroxidase from Bjerkandera adusta

The oxidation of five sulfonamide antibiotics by the versatile peroxidase (VP, EC. 1.11.1.16) from Bjerkandera adusta was quantitatively assessed. The biocatalytic activity of the enzyme was studied by assaying different reaction conditions. Conversion levels were higher than 90 % for all five sulfonamide antibiotics in the model reaction system. In addition, the enzyme performance was also studied in treated wastewater effluents, where three sulfonamide antibiotics were oxidized at a higher level (greater than 85 % oxidation) and two were oxidized at a lower level (up to 50 %). The identified reaction products for two antibiotics, sulfasalazine, and sulfamethoxazole, showed higher antimicrobial activity than the parental compounds. Docking analyses exhibited that the reaction products interacted with the catalytic pocket of the dihydropteroate synthase from Escherichia coli, similar to the parental antibiotics. Though the oxidation is carried out at high velocity and conversion rates, the application of VP in the enzymatic oxidation technology of sulfonamide antibiotics must overcome the production of more toxic products.

Rapid adsorption of sulfamethazine on mesoporous graphene produced from plastic waste: optimization, mechanism, isotherms, kinetics, and thermodynamics

Sulfonamide antibiotics like sulfamethazine (SMZ) can threaten aquatic and terrestrial life even in small concentrations (≤ 1 mg/L); hence, their removal from wastewater is indispensable. However, the need to explore new promising adsorbents that are cheap, effective, and reusable also remains crucial to developing adsorption technology. This work presents a one-pot solvent-free conversion of the current most ubiquitous anthropogenic bio-resistant solid waste (plastics) into valuable carbon materials to remove SMZ from aqueous solution. High-density polyethylene waste was pyrolyzed at 500–1000 °C in an enclosed stainless-steel reactor to produce mesoporous graphene. The graphene products were characterized via microscopic and spectroscopic analyses. The effect of temperature on the graphene yield and properties was investigated. The optimum sulfamethazine (SMZ) adsorption was achieved with 600 °C carbon product (CP-600) due to its high porosity and aromatic structure. The adsorption parameters (pH, catalyst dose, and SMZ concentration) were optimized by response surface methodology (RSM) with a central composite design. 99.99% SMZ removal was achieved at 0.9 g/L adsorbent dose, 12.4 mg/L SMZ concentration, and pH 3 at 25 °C. FTIR analysis revealed that the SMZ adsorption occurred mainly via π–π/π+–π electron interactions between the aromatic and pyrimidine rings of SMZ and the benzene ring of graphitic CP-600. The SMZ adsorption followed the pseudo-second-order kinetics, Langmuir, and Freundlich isotherm models. The adsorption was controlled by film and intraparticle diffusion and was spontaneous and endothermic. The carbon synthesized in this work is reusable and can rapidly remove more SMZ than other SMZ adsorbents.

Utility of a non-target screening method to explore the chlorination of similar sulfonamide antibiotics: Pathways and N[sbnd]Cl intermediates

Sulfonamides (SAs) are ubiquitous antibiotics that are increasingly detected in aquatic environments and can react with free available chlorine to produce transformation products (TPs) during disinfection. However, the TPs generated during chlorination remains poorly understood. Here, a non-target screening method based on the PyHRMS program was used to assess the transformation pathways of five SAs, particularly the transient NCl intermediates, during a simulated chlorination process. We observed 210 TPs during SA chlorination using a non-target screening method based on high-resolution mass spectrometry, and the reaction mechanisms mainly included chlorine substitution, desulfonation, and hydroxylation. Among the TPs, 87 were tentatively proposed to be NCl intermediates as they instantly disappeared after quenching with Na2S2O3. The MS2 spectra of 13 of these potential NCl intermediates were obtained, and all displayed an [M-Cl]+ fragment. A diagnostic fragment ion (DFI) strategy was applied to explore the structural relationship between parent compounds and TPs. Based on the result, five SAs and 101 TPs (if their MS2 spectra were available) could be connected through the same fragments, and this method was also proved effective in a real wastewater treatment plant effluent sample. We believe this novel method can help explore the TPs of organic compounds during chlorination in drinking water plants.

Magnetic nitrogen-doped carbon nanotubes as activators of peroxymonosulfate and their application in non-radical degradation of sulfonamide antibiotics

Advanced oxidation processes based on peroxymonosulfate (PMS) are an efficient strategy to eliminate environmental micropollutants. Carbon nanotubes (CNTs) have been used as activators for PMS, but they still suffer from complex preparation processes and suboptimal catalytic performance. In this study, nitrogen-doped CNTs encapsulating cobalt nanoparticles (CoNCT) were prepared by a facile and economical calcination method using graphitic carbon nitride as a precursor. As expected, this novel CoNCT catalyst could rapidly activate PMS, and the CoNCT/PMS system could efficiently degrade eight types of sulfonamide antibiotics. It should be noted that singlet oxygen rather than the conventional sulfate and hydroxyl radicals were the predominant reactive species in the CoNCT/PMS system, which revealed a non-radical mechanism for the activation of PMS by CNTs. With the benefit of this mechanism, the CoNCT/PMS system maintained good oxidation performance over a wide pH range and exhibited strong resistance to anions, dissolved organic matter, and real water matrixes. This work not only contributes to the development of efficient carbon nanotubes as PMS activators, but also provides comprehensive insights into the non-radical mechanism involved in advanced oxidation processes for environmental decontamination.

The interaction between cucurbit[7]uril and trimethoprim and its effect on the properties of trimethoprim

Trimethoprim (TMP) is a broad-spectrum antibacterial agent that exhibits an obvious synergistic effect when used in combination with sulfa antibiotics, but its poor solubility and other drawbacks limit its applications. Herein, the interaction between TMP and cucurbit[7]uril (Q[7]), and the effect of Q[7] on the properties of TMP were investigated using UV-vis and fluorescence spectroscopy, isothermal titration calorimetry (ITC), 1H NMR spectroscopy and mass spectrometry. The results showed that TMP and Q[7] interacted to form a 1:1 inclusion complex (TMP@Q[7]). After interacting with TMP, Q[7] increased the solubility of TMP in an aqueous solution by 7.75-fold, effectively prolonging the release time of TMP in artificial gastroenteric juice, and plays a role in its sustained release. However, the stability and antibacterial activity of TMP in artificial gastroenteric juice were not affected.

Para-Aminobenzoic Acid Biosynthesis Is Required for Listeria monocytogenes Growth and Pathogenesis.

Biosyntheses of para-aminobenzoic acid (PABA) and its downstream folic acid metabolites are essential for one-carbon metabolism in all life forms and the targets of sulfonamide and trimethoprim antibiotics. In this study, we identified and characterized two genes (pabA and pabBC) required for PABA biosynthesis in Listeria monocytogenes. Mutants in PABA biosynthesis were able to grow normally in rich media but not in defined media lacking PABA, but growth was restored by the addition of PABA or its downstream metabolites. PABA biosynthesis mutants were attenuated for intracellular growth in bone marrow-derived macrophages, produced extremely small plaques in fibroblast monolayers, and were highly attenuated for virulence in mice. PABA biosynthesis genes were upregulated upon infection and induced during growth in broth in a strain in which the master virulence regulator, PrfA, was genetically locked in its active state (PrfA*). To gain further insight into why PABA mutants were so attenuated, we screened for transposon-induced suppressor mutations that formed larger plaques. Suppressor mutants in relA, which are predicted to have higher levels of (p)ppGpp, and mutants in codY, which is a GTP-binding repressor of many biosynthetic genes, partially rescued the plaque defect but, notably, restored the capacity of the mutants to escape from phagosomes and induce the polymerization of host cell actin. However, these suppressor mutant strains remained attenuated for virulence in mice. These data suggest that even though folic acid metabolites exist in host cells and might be available during infection, de novo synthesis of PABA is required for L. monocytogenes pathogenesis.

Comparison of sulfamethoxazole (SMX) degradation effect under different experimental conditions

Sulfonamides are an important class of synthetic antibacterial medications that is widely utilized and pollute many water bodies. In this study, sulfamethoxazole was selected as the representative of sulfa antibiotics. A molybdenum disulfide-based catalyst was synthesized by hydrothermal method and used to activate peroxymonosulfate (PMS) for the degradation of sulfamethoxazole in water. Co@MoS2 was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The experimental conditions, Cobalt ion concentration, and light effect have been investigated. High-Performance Liquid Chromatography (HPLC) was used to measure the concentration of sulfamethoxazole. The results showed that the Co@MoS2 /PMS experimental conditions could effectively degrade sulfamethoxazole wastewater.

Highly Efficient Degradation of Sulfisoxazole by Natural Chalcopyrite-Activated Peroxymonosulfate: Reactive Species and Effects of Water Matrices

In this study, chalcopyrite (CuFeS2), a natural mineral with a bimetallic structure, was used as the activator to generate radicals for removing organic pollutants from aqueous solutions via the activation of peroxymonosulfate (PMS). Sulfisoxazole (SIX), a sulfonamide antibiotic, was selected as the model pollutant. The results showed that chalcopyrite was highly reactive toward the activation of PMS; under the conditions of 50 µM PMS and 1 g/L chalcopyrite, approximately 95.7% of the SIX was degraded after reaction for only 5 min. An increase in the loading of chalcopyrite (0.25–2 g/L) promoted the degradation of SIX, while elevated levels of PMS (0.05–0.5 mM) slightly retarded the degradation kinetics. Although the best performance was observed under acidic conditions (pHs 3 and 4), near complete degradation of SIX was also achieved at pH 5.5. Identification of reactive species revealed that both a hydroxyl radical and a sulfate radical were formed in chalcopyrite–PMS oxidation, and they were responsible for the degradation of SIX. Trace amounts of copper and iron were leached out from chalcopyrite during the activation, and both the heterogeneous and homogeneous activation of PMS contributed to the generation of oxidizing radicals. Common water constituents including Cl−, HCO3−, and natural organic matter at their environmentally relevant levels showed a limited effect on the degradation of SIX, which suggests that chalcopyrite–PMS oxidation has high reactivity and stability in the degradation of organic pollutants and shows great practical application potential.

Carbon Quantum Dot-Decorated BiOBr/Bi2WO6 Photocatalytic Micromotor for Environmental Remediation and DFT Calculation

Efficient photocatalysts are crucial for degrading antibiotic pollutants in water and vital for environmental remediation. In this study, an efficient carbon quantum dot (CQD)-modified BiOBr/Bi2WO6 hybrid material was prepared by a mild hydrothermal method. Meanwhile, a visible-light-driven micromotor based on the photocatalyst was developed. The micromotor can achieve self-propelled motion powered by the photocatalytic degradation reaction. It exhibited remarkable photocatalytic activity toward common pollutants in water, such as sulfonamide, quinolone, and tetracycline antibiotics. Among them, 10CQD/BiOBr/Bi2WO6-4 (10CBBr-4) exhibited the highest photocatalytic activity, which was 2.8 and 5 times higher than those of BiOBr and Bi2WO6, respectively. The high activity is attributed to the decoration of CQDs, which promoted visible-light absorption. Additional contributions may be due to the specific Z-type electron transport mode and flower-like BiOBr inserted by two-dimensional (2D) Bi2WO6 nanosheets, which enriched the active reaction sites, facilitated the adsorption of antibiotic molecules, and promoted the final radical attack. Based on the theoretical calculation of molecular orbitals and the Fukui index, the possible intermediate products, degradation pathways, and photocatalytic mechanism were elucidated. This study suggests that structural engineering based on CQD modification effectively allows the design of self-propelled microrobots for antibiotic degradation.

Enhanced removal of sulfonamide antibiotics from water by phosphogypsum modified biochar composite

Antibiotic pollution has become a global eco-environmental issue. To reduce sulfonamide antibiotics in water and improve resource utilization of solid wastes, phosphogypsum modified biochar composite (PMBC) was prepared via facile one-step from distillers grains, wood chips, and phosphogypsum. The physicochemical properties of PMBC were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Zeta potential, X-ray diffraction (XRD), etc. The influencing factors, adsorption behaviors, and mechanisms of sulfadiazine (SD) and sulfamethazine (SMT) onto PMBC were studied by batch and fixed bed column adsorption experiments. The results showed that the removal rates of SD and SMT increased with the increase of phosphogypsum proportion, while decreased with the increase of solution pH. The maximum adsorption capacities of modified distillers grain and wood chips biochars for SD were 2.98 and 4.18 mg/g, and for SMT were 4.40 and 8.91 mg/g, respectively, which was 9.0–22.3 times that of pristine biochar. Fixed bed column results demonstrated that PMBC had good adsorption capacities for SD and SMT. When the solution flow rate was 2.0 mL/min and the dosage of PMBC was 5.0 g, the removal rates of SD and SMT by modified wood chips biochar were both higher than 50% in 4 hr. The main mechanisms of SD and SMT removal by PMBC are hydrogen bonding, π-π donor-acceptor, electrostatic interaction, and hydrophobic interaction. This study provides an effective method for the removal of antibiotics in water and the resource utilization of phosphogypsum.

Quantification of adsorption mechanisms distribution of sulfamethoxazole onto biochar by competition relationship in a wide pH range

This study aimed to investigate the degree of contribution of adsorption mechanisms of sulfamethoxazole (SMX) on corncob-derived biochar CC800 through competition experiments. The SMX adsorption was governed by diverse mechanisms under different pH, resulting in high pH dependent adsorption of SMX on biochar. The adsorption of SMX on CC800 in the presence of ions was evaluated, demonstrating that the ion exchange mechanism had a weak effect on the adsorption. The intense competitiveness of SMX structural analogs verified π+–π electron donor-acceptor (EDA) effect was the dominant adsorption mechanism of SMX on CC800 at low pH, and the negative charge-assisted hydrogen bond (CAHB) was critical to the adsorption at high pH. The adsorption mechanisms contribution of SMX on CC800 were further quantified. The SMX adsorption on CC800 was mainly controlled by 51% pore filling and 43% π+–π EDA effect in the acid region, 62% pore filling mechanism and 25% (−)CAHB mechanism in the alkalic region, and less than 5% of hydrophobic interaction and ion exchange. Consequently, the above mechanisms provided a theoretical basis for biochar application to remove sulfonamide antibiotics and other similar organic contaminants and targeted design of biochar products. Also, this quantification method can be extended to quantify the adsorption mechanisms between other antibiotics or organics and biochar adsorbent materials by selecting suitable adsorption competitors.