Production of activated carbon from agave residues and its synergistic application in a hybrid adsorption-AOPs system for effective removal of sulfamethazine from aqueous solutions.

Tequila production in Mexico generates large quantities of agave bagasse (AB), a waste that could be used more efficiently. AB has a high cellulose, hemicellulose, and lignin content, which allows its use as a precursor for synthesizing carbonaceous materials. In the present work, the synthesis of activated carbon impregnated with Fe2+ (AG-Fe-II) and Fe3+ (AG-Fe-III) was carried out and evaluated in a hybrid adsorption-AOP (advanced oxidation process) methodology for sulfamethazine removal (SMT). The materials were characterized before and after the process to determine their morphological, textural, and physicochemical properties. Subsequently, the effect of the main operational variables (pH, initial SMT concentration, mass, and activator dosage) on the hybrid adsorption-degradation process was studied. The Fenton-like reaction was selected as the AOP for the degradation step, and potassium persulfate (K2S2O8) was used as an activating agent. The main iron crystallographic phases in AG-Fe-II were FeS, with a uniform distribution of iron particles over the material's surface. The main crystallographic phase for AG-Fe-III was Fe3O4. The hybrid process achieved 61% and 78% removal efficiency using AG-Fe-II and AG-Fe-III samples, respectively. The pH and initial SMT concentration were the most critical factors for removing SMT from an aqueous phase. Finally, the material was successfully tested in repeated adsorption-degradation cycles.

Degradation of sulfonamide antibiotic via UV/MgO2 system: kinetic, application, and mechanism.

In response to antibiotic residues in the water, a novel advanced oxidation technology based on MgO2 was used to remediate sulfamethazine (SMTZ) pollution in aquatic environments. Upon appropriate regulation, the remarkable removal efficiency of SMTZ was observed in a UV/MgO2 system, and the pseudo-first-order reaction constant reached 0.4074 min-1. In addition, the better performance of the UV/MgO2 system in a weak acid environment was discovered. During the removal of SMTZ, the pathways of SMTZ degradation were deduced, including nitration, ring opening, and group loss. In the mineralization exploration, the further removal of residual products of SMTZ by the UV/MgO2 system was visually demonstrated. The qualitative and quantitative researches as well as the roles of reactive species were valuated, which revealed the important role of ·O2-. Common co-existing substances in actual wastewater such as NO3- HA, Cl-, Fe2+, Co2+, and Mn2+ can slightly inhibit the degradation of SMTZ in the UV/MgO2 system. Finally, the capacity of efficient degradation of SMTZ in actual wastewater by the UV/MgO2 system was proved. The results indicated that the innovative UV/MgO2 system was of great practical application prospect in antibiotic residue wastewater remediation.

[Effect of Manure Application on the Adsorption of Antibiotics to Soil].

Sulfonamide antibiotics and florfenicol(FFC) are commonly used antibiotics in Zhejiang Province. They have weak adsorption on soil and are easy to migrate, with high environmental risks. In recent years, most of the studies on the potential risk of fecal-derived antibiotics to farmland soil were conducted by adding manure under laboratory conditions; therefore, it is impossible to assess the risk of antibiotic pollution under natural fertilization. Therefore, batch balance experiments were conducted to explore the effects of different soil types and manure types on the adsorption of antibiotics in the soil, in which five types of dryland farmland soils[Lin'an(LA), Jiashan(JS), Longyou(LY), Kaihua(KH), and Jinhua(JH)]in Zhejiang Province that have been used with different fertilizers(chicken manure, pig manure, and chemical fertilizer) for a long time were chosen, and four types of commonly used antibiotics[sulfadiazine(SD), sulfamethazine(SMT), sulfamethoxazole(SMZ), and FFC]were selected. The results showed that the adsorption of the four antibiotics in the experimental soil was weak, and the adsorption capacity decreased in the order of:SMT(1.44-13.23 mg1-(1/n)·L1/n·kg-1)>SMZ(0.73-6.05 mg1-(1/n)·L1/n·kg-1)>SD(0.16-5.57 mg1-(1/n)·L1/n·kg-1)>FFC(0.27-3.81 mg1-(1/n)·L1/n·kg-1). The Freundlich model was superior to the linear model in fitting the isotherm adsorption of SD, SMT, and FFC, in which SD and FFC belonged to "S" type adsorption, and SMT belonged to "L" type adsorption. For SMZ, the fitting effect of the linear model was better than that of the Freundlich model. The contents of total organic carbon(TOC) and dissolved organic carbon(DOC) could better predict the adsorption capacity of the four antibiotics(r=0.548-0.808), and the values of cation exchange capacity(CEC) and electrical conductivity(EC) could better predict the adsorption capacity of SMT and FFC(r=0.758-0.841). Compared with the application of chemical fertilizer, manure application increased the values of TOC, DOC, CEC, and EC in acidic and neutral soils, which was conducive to the adsorption of antibiotics on the soil. Meanwhile, manure application also increased pH in acidic and neutral soils, which was not conducive to the adsorption of antibiotics on the soil. In addition, manure application reduced the values of TOC, DOC, CEC, EC, and pH in alkaline soils. The lower pH was conducive to antibiotic adsorption on the soil, whereas the lower content of the other four was not conducive to antibiotic adsorption on the soil. For the acidic soil with low fertility, the application of manure increased soil fertility and thus increased the adsorption of antibiotics on the soil, such as the LA soil with chicken manure, the LY(1) soil with pig manure, and the JH soil with chicken manure and pig manure. However, for the acidic and neutral soils with high fertility, the application of manure had significantly increased soil pH and thus reduced the adsorption of antibiotics on the soil, such as the JS soil with chicken manure and pig manure and the LY(2) soil with chicken manure. For calcareous soil with high fertility and pH(such as KH soil), the adsorption profiles of the four types of antibiotics on the soil showed diversity after the application of manure:the adsorption capacity of SD increased significantly after the application of chicken manure and pig manure, whereas the adsorption capacity of SMT and SMZ decreased significantly, and the adsorption capacity of FFC declined significantly after the application of chicken manure. Therefore, manure application according to soil fertility could effectively control the environmental risk of fecal antibiotics.

2D MOF-enhanced SPR sensing platform: Facile and ultrasensitive detection of Sulfamethazine via supramolecular probe.

Sulfamethazine (SMZ) is widely present in the environment and can cause severe allergic reactions and cancer in humans. Accurate and facile monitoring of SMZ is crucial for maintaining environmental safety, ecological balance, and human health. In this work, a real-time and label-free surface plasmon resonance (SPR) sensor was devised using a two-dimensional metal-organic framework with superior photoelectric performance as an SPR sensitizer. The supramolecular probe was incorporated at the sensing interface, allowing for the specific capture of SMZ from other analogous antibiotics through host-guest recognition. The intrinsic mechanism of the specific interaction of the supramolecular probe-SMZ was elucidated through the SPR selectivity test in combination with analysis by density functional theory, including p-π conjugation, size effect, electrostatic interaction, π-π stacking, and hydrophobic interaction. This method facilitates a facile and ultrasensitive detection of SMZ with a limit of detection of 75.54 pM. The accurate detection of SMZ in six environmental samples demonstrates the potential practical application of the sensor. Leveraging the specific recognition of supramolecular probes, this direct and simple approach offers a novel pathway for the development of novel SPR biosensors with outstanding sensitivity.

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.

Sulfonamide drugs: Low-cost spectrofluorometric determination using a computer monitor calibrator for detection.

A possibility of the use of a common monitor calibrator as a portable and inexpensive tool for the fluorometric determination of sulfonamide drugs after their reaction with fluorescamine was examined. The luminescence measurements with a calibrator are based on irradiation of a test sample by the device lamp with a broadband spectrum in the visible and near UV regions and simultaneous registration of the secondary radiation by the device detector. Two types of cuvettes with black light absorbing sides eliminating the reflected self-radiation were tested. The commercially available Eppendorf-type black plastic microtubes ("LightSafe") were suggested as a good option for such measurements. It was shown that a monitor calibrator can be applied for optimization of the determination conditions. By the example of sulfanilamide and sulfamethazine, it was shown that the procedure should be carried out at pH 4-6 and fluorescamine concentration of 200 µmol L-1, and 40 min of the interaction. The limit of detection of sulfanilamide and sulfamethazine using a monitor calibrator is 0.9 µmol L-1 and 0.8 µmol L-1, respectively, which is comparable with their spectrophotometric determination.

[Effects of Sulfamethazine in Soil on Rice Growth].

For the sake of investigating the effects of residual antibiotics in soil on plant growth, sulfamethazine, which is commonly detected in soil, was selected in this project. In general, the growth index of rice at the seedling and mature stages, physiological/biochemical characteristics of roots and leaves, antibiotic residues, enrichment factors, and transport coefficients in various rice organs were respectively tested and analyzed to evaluate the ecological effects of sulfamethazine residues on rice. The results revealed that the inhibitory effect of sulfamethazine on plant height and biomass was maintained during the whole growth cycle. Moreover, the effect at the seedling stage was greater than that at the growth maturity stage, and the root part was more easily influenced than the seedling section. The root activity, nitrate reductase activity, and leaf chlorophyll content at the seedling stage were hindered by the increase in antibiotic content. By contrast, the antioxidant enzyme change showed a different tendency, in which the superoxide was activated, and the catalase and peroxidase were firstly activated and then inhibited. The sulfamethazine accumulation in various rice organs was in the order of root>leaf>sti>grain. The results of antibiotic risk assessment of rice grains exhibited that EDI/ADI was less than 0.1, indicating no health risk. The effect of sulfamethazine on enrichment factors and transport coefficients at the growth maturity stage was more obvious than that at the seedling stage. Considering the adverse effects of sulfamethazine on rice, we need to take the ecological effects of sulfamethazine on plants into consideration when applying livestock manure as organic fertilizer or using aquaculture water for irrigation, to ensure crop production safety.

Oxidation of sulfamethazine by peracetic acid activated with biochar: Reactive oxygen species contribution and toxicity change.

Peracetic acid (PAA) as an emerging oxidative has been concerned increasingly due to its high oxidation capacity and low byproducts formation potential. This study was to investigate the oxidation of sulfamethazine (SMZ) by PAA activated with activated biochar (ABC) after thermal modification. The results demonstrated that PAA could be effectively activated by ABC to degrade SMZ in a wide pH range (3-9), which followed the pseudo-second-order kinetics (R2 > 0.99). Both non-radicals (singlet oxygen) and free radicals (alkoxy radicals, hydroxyl radicals) existed in the ABC/PAA system, and the degradation of SMZ was dominated by singlet oxygen. Humic acid (HA), SO42- and HCO3- slightly inhibited the degradation of SMZ in the ABC/PAA process, while Cl- and Br- promoted the degradation of SMZ. The cleavage of S-N, S-C bond, and SO2 extraction reaction rearrangement was the main oxidation process of SMZ. Meanwhile, the results of the ECOSAR program showed that the acute toxicity of most by-products was significantly reduced compared to SMZ, which revealed the potential applicability of the ABC/PAA process in the treatment of antibiotics pollution and their detoxification.

Amorphous Co@TiO2 heterojunctions: A high-performance and stable catalyst for the efficient degradation of sulfamethazine via peroxymonosulfate activation.

Persulfate-based advanced oxidation processes (AOPs) cannot easily achieve the efficient degradation of persistent organic pollutants (POPs) with high stability. In this study, a simple in situ precipitation method was used to prepare an amorphous Co@TiO2 heterojunction catalyst. The deposition of Co oxide on TiO2, which is relatively nontoxic, efficiently activated peroxymonosulfate (PMS) to degrade sulfamethazine (SMT) and reduce the leaching of Co ions (0.915%). A catalytic system prepared using 0.3 g L-1 Co@TiO2 and 0.5 g L-1 PMS could degrade SMT within 30 min with a degradation rate of 95.8%. Co@TiO2 could activate PMS over a wide pH range (5.00-9.00) to efficiently degrade other antibiotics and dyes. Radical-capture experiments and electron paramagnetic resonance analysis suggested that SMT degradation occurs through a combination of the free radical and non-radical pathways, in which singlet 1O2 played a major role. Owing to the novelty of the proposed composite materials, the degradation path of SMT, which was determined through liquid chromatography-mass spectrometry, differed from that reported previously. This study provides not only an advanced and renewable catalyst for SMT degradation but also a feasible strategy for designing materials for AOPs.

Long-term sulfamethazine leaching simulation in two different soils using the MACRO model.

Physically based models have been part of many risk assessment studies concerning pesticide or nutrient transport within (sub)catchments or at plot scale, but they are only poorly validated for simulating the transport of veterinary medicinal products. Veterinary medicinal products not only pose a risk to the quality of our waters but also tend to accumulate in soils, where they are associated with the appearance of resistant bacteria and long-term leaching. In this study, the physically based leaching model MACRO 5.2 was applied for simulating sulfamethazine (SMZ) transport over a period of more than 10 yr. The model was set up using reversible kinetic adsorption and equilibrium adsorption forming non-extractable residues. Two different calibration periods were used to estimate uncertainties in predicted SMZ leaching associated with calibration based on short-term data. Using the whole period for model calibration, SMZ leaching could be simulated adequately, but parameter ranges were wide due to correlation between the parameters. When using only the first period for calibration, the quality of the prediction strongly depended on the information content of the data set. The calculation of temporal sensitivity indices revealed that the effect of complex sorption parameters on the model output increased with time. Thus, parameters that appeared insensitive in a short-term calibration were required for reliable long-term simulations. In conclusion, a temporal sensitivity analysis beyond the calibration period might identify parameters that were not constrained enough by the calibration procedure. This could help to confirm leaching predictions even for periods without sampling data.

High yield M-BTC type MOFs as precursors to prepare N-doped carbon as peroxymonosulfate activator for removing sulfamethazine: The formation mechanism of surface-bound SO4•- on Co-Nx site.

M-BTCs (M = Fe, Co and Mn)/melamine were used to prepare N-doped carbon materials, and their performances as activator of peroxymonosulfate (PMS) for sulfamethazine (SMZ) removal were compared. M-BTC type metal-organic frameworks (MOFs) were synthesized under room temperature, with their yield about 7.5 times of ZIF-67 which is the most used MOFs to prepare N-doped carbon materials as the catalyst of persulfate-based advanced oxidation processes. Co-BTC/melamine derived N-doped carbon materials (Co-BTC/5MNC) performed the best, even better than that of ZIF-67 derived N-doped carbon materials. Initial pH (3-9), 0-10 mM inorganic anions (Cl-, NO3-, HCO3- and H2PO42-) and humic acid (5 and 10 mg/L) had no obvious inhibition on SMZ removal with Co-BTC/5MNC as catalyst. The results of both X-ray photoelectron spectroscopy and density functional theory (DFT) calculations indicated that N-coordinated cobalt single atom site (Co-Nx) was the possible active site of Co-BTC/5MNC. Importantly, surface-bound SO4•- was identified as the dominant reactive oxygen species for SMZ removal. The SO4•- generated through the charge transfer between PMS and catalyst, and was tightly adsorbed on Co-Nx site.

Colorimetric detection of sulfamethazine based on target resolved calixarene derivative stabilized gold nanoparticles aggregation.

Sulfamethazine (SMZ) is one of the most used broad-spectrum antibiotics owing to its low cost and high efficacy towards bacterial diseases. This workreports a novel label-free SMZ sensor based on para-sulfonatocalix[4]arene (pSC4) capped gold nanoparticles (pSC4-AuNPs) for colorimetric detection through the host-guest interaction. The existence of SMZ resulted in the aggregation of pSC4-AuNPs and can be observed through colorimetric assay. A good linear relationship in the range 2.5 ~ 20 nM was obtained with a correlation coefficient of 0.9908. The limit of detection for SMZ was 1.39 nM. High recoveries (90.18-107.06%) were obtained, and RSD ranged from 1.21 to 2.05%. The color changes can be observed from red to gray within 10 min. Combining the supermolecule's recognition and AuNP's optical performance, the method paves a new, easy, and rapid way for small target sensing.

Temperature and pH-responsive in situ hydrogels of gelatin derivatives to prevent the reoccurrence of brain tumor.

Glioblastoma multiforme (GBM) is a grade IV malignant brain tumor with a median survival time of approximately 12-16 months. Because of its highly aggressive and heterogeneous nature it is very difficult to remove by surgical resection. Herein we have reported dual stimuli-responsive and biodegradable in situ hydrogels of oligosulfamethazine-grafted gelatin and loaded with anticancer drug paclitaxel (PTX) for preventing the progress of Glioblastoma. The oligosulfamethazine (OSM) introduced to the gelatin backbone for the formation of definite and stable in situ hydrogel. The hydrogels transformed from a sol to a gel state upon changes in stimuli. pH and temperature and retained a distinct shape after subcutaneous administration in BALB/c mice. The viscosity of the sol state hydrogels was tuned by varying the feed molar ratio between gelatin and OSM. The porosity of the hydrogels was confirmed to be lower in higher degree OSM by SEM. Sustained release of PTX from hydrogels in physiological environments (pH 7.4) was further retarded up to 63% in 9th days in tumor environments (pH 6.5). While the empty hydrogels were non-toxic in cultured cells, the hydrogels loaded with PTX showed antitumor efficacy in orthotopic-GBM xenograft mice. Collectively, the gelatin-OSM formed porous hydrogels and released the cargo in a sustained manner in tumor environments efficiently suppressing the progress of GBM. Thus, gelatin-OSM hydrogels are a potential candidate for the direct delivery of therapeutics to the local areas in brain diseases.

A novel photocatalytic reactor for the extended reuse of W-TiO2 in the degradation of sulfamethazine.

In this study, a photocatalytic reactor with a novel engineering design has been used for the extended degradation of sulfamethazine (SMZ). The reactor employed four consecutive stainless-steel plates immobilized by tungsten-dope TiO2 (W-TiO2) using polysiloxane. The characterization of W-TiO2 by X-ray diffraction (XRD), Raman spectroscopy, and energy-dispersive X-ray (EDX) denoted successful doping of tungsten in the lattice of anatase crystals of TiO2 suggesting a high photocatalytic activity under UV and visible light. A Box-Behnken experimental design was employed for the optimization of the operating parameters such as solution pH, flow rate, and the initial SMZ concentration. The residual SMZ concentration was below the detection limit after 30 min of the photocatalytic reaction under the optimum operating conditions. A highly remarkable degradation of SMZ was observed in five consecutive cycles, which reveals an extended stable photocatalytic activity offered by the reactor design. The transformation products were identified by tandem mass spectrometry, and they were employed to propose the degradation pathway. These results highlight the importance of using the photocatalysts in retained forms and open additional avenues for the practical application of photocatalysis in wastewater treatment.

Cu2+ activated persulfate for sulfamethazine degradation.

Sulfonamide antibiotics (SAs) are widely used in veterinary medicine but are poorly metabolized in biological systems; thus, they can cause a selective pressure to promote the proliferation of antibiotic resistant pathogens and threaten human health. Persulfate (PS)-based advanced oxidation processes (AOPs) have been applied for SA degradation, but using transition metal ions as PS activators is relatively limited. In this study, sulfamethazine (SMZ) was used as a model SA to evaluate the performance of a Cu2+ -activated PS system. Cu2+-PS exhibited better SMZ removal than other metal ions, and 25 mg/L SMZ can be degraded in the presence of 0.2 mM Cu2+ and 2.5 g L-1 PS within 120 min. Various anions inhibited SMZ degradation to different degrees except HCO3-. Among the cations, Fe3+ significantly inhibited SMZ removal, while Ni2+ increased the removal rate. High concentrations of humic acid and protein also increased the degradation rate of SMZ. Radical and singlet oxygen quenching experiments, together with the results of electron spin-resonance spectroscopy (ESR), showed that the main active species generated from Cu2+-PS are SO4·- and ·OH. The degradation pathway of SMZ was identified through HPLC-HRMS. Direct SO4·- and ·OH oxidation products of SMZ were not found, suggesting that the complex formed between Cu2+ and SMZ may affect the fate of SMZ. On the other hand, the efficiency and selectivity of Cu2+-PS against different SAs were confirmed. Overall, this study provides a facile and effective method for SMZ and other SA removal.

Adsorption of Sulfamethazine Drug onto the Modified Derivatives of Carbon Nanotubes at Different pH.

The sulfamethazine drug interaction with carbon nanotubes was investigated with the aim of improving the adsorption capacity of the adsorptive materials. Experiments were performed to clarify how the molecular environment affects the adsorption process. Single-walled carbon nanotubes have a higher removal efficiency of sulfamethazine than pristine or functionalized multi-walled carbon nanotubes. Although the presence of cyclodextrin molecules improves the solubility of sulfamethazine, it reduces the adsorption capacity of the carbon nanotube towards the sulfamethazine drug and, therefore, inhibits the removal of these antibiotic pollutants from waters by carbon nanotubes.

Biochar-mediated Fenton-like reaction for the degradation of sulfamethazine: Role of environmentally persistent free radicals.

Swine manure biochar (SBC) pyrolyzed at 300 °C, 600 °C and 900 °C were utilized to degrade sulfamethazine (SMT) in heterogeneous Fenton-like systems which achieved excellent degradation efficiency (over 85% in 30 min). Experiments results demonstrated that SBC possessed the poor SMT adsorption capacity but high catalytic performance. Electron Paramagnetic Resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that there were oxygen-centered environmentally persistent free radicals (EPFRs) and carbon-centered EPFRs with an adjacent oxygen atom in SBC. The oxygen-centered EPFRs played a major role in the catalytic process which tended to convert to carbon-centered EPFRs after the reaction. Besides, the electron transfer pathways were the most likely catalytic mechanism of SBC and the contribution of OH was dominant through Electron capture experiments and Linear sweep voltammetry (LSV) measurements. The acidic or alkaline condition can promote the catalytic ability of SBC. The presence of dissolved salts (NaCl) inhibited the catalytic process but the inhibition was slightly weakened at high concentration of NaCl, which showed the high tolerance of Cl- in Fenton/Fenton-like systems. Moreover, real wastewater application suggested that SBC600/H2O2 system possessed excellent catalytic efficiency and good adaptability. This research provides a novel swine manure reuse process with high practicability and presents a more explicit perspective about the reaction mechanisms of EPFRs in biochar.

Enhancement of ionizing radiation-induced catalytic degradation of antibiotics using Fe/C nanomaterials derived from Fe-based MOFs.

In present work, we studied a novel Fe/C nanomaterial fabricated using Fe-based metal organic frameworks (MOFs) as precursors through thermal pyrolysis to catalyze gamma irradiation-induced degradation of antibiotics, cephalosporin C (CEP-C) and sulfamethazine (SMT) in aqueous solution. The MOFs-derived Fe/C nanomaterials (DMOFs) had the regular octahedrons structure of MOFs and contained element C, Fe and O, while Fe° with a fraction of Fe3O4 and Fe2O3 were identified. Results showed that DMOFs addition could accelerate the generation of OH during gamma irradiation, while the intermediates of bonds cleavages of antibiotic molecules and OH addition were identified. DMOFs were more effective to improve the decomposition of antibiotic having the higher adsorption capacity like SMT. The degradation rate of CEP-C and SMT increased by 1.3 times and 1.8 times, and TOC reduction at 1.0 kGy reached 42 % and 51 %, respectively by gamma/DMOFs treatment, while only 20.2 % (CEP-C) and 4.5 % (SMT) of TOC reduction were obtained by γ-irradiation alone. The crystal structure, functional groups and magnetism of DMOFs changed slightly after gamma irradiation, which made it possible to be reused. DMOFs were promising to enhance the degradation of antibiotics during gamma irradiation.

Effects of pine bark amendment on the transport of sulfonamide antibiotics in soils.

In the present work, laboratory column experiments were carried out to study the effect of pine bark amendment (at doses of 0, 12, 48 and 96 Mg ha-1) on the transport of three sulfonamide antibiotics (sulfadiazine -SDZ-, sulfamethazine -SMT-, and sulfachloropyridazine -SCP-) through two crop soils. All three sulfonamides showed high mobility in the unamend soils, with absence of retention in most cases. However, some differences were detected regarding the degree of interactions between sulfonamides and soils, being higher for soil 1, which was attributed to its higher organic carbon content. For both soils, interactions with the antibiotics studied followed the sequence SDZ < SMT < SCP, indicating an increase as a function of the hydrophobicity of sulfonamides. Pine bark amendment significantly increased the retention of the three sulfonamides in both soils. Specifically, in the case of soil 1, the incorporation of the highest dose of pine bark (96 Mg ha-1) caused that retention increased from 0% to 70.3% for SDZ, from 2.7% to 71.3% for SMT, and from 0% to 85.4% for SCP. This effect of pine bark is mainly attributed to its high organic carbon content (48.6%), including substances with potential to interact and retain antibiotics, as well as to its acidic pH (4.5). Therefore, pine bark amendment would be an effective alternative to reduce the transport of sulfonamides in soils and, thus, decrease risks of passing to other environmental compartments, as well as harmful effects on the environment and public health.

Effect of molecular structure on the adsorption affinity of sulfonamides onto CNTs: Batch experiments and DFT calculations.

In order to investigate the adsorption behaviors of sulfonamides onto hydroxylated multi - walled carbon nanotubes (CNTs) with a porous structure and large specific surface area, six typical sulfonamides including sulfanilamide (SAM), sulfamerazine (SMR), sulfadimethoxine (SMX), sulfadiazine (SDZ), sulfamethazine (SMT) and sulfametoxydiazine (SMD) were selected to be adsorbed respectively on CNTs, and in the same time the structural parameters of the six sulfonamides molecules were calculated according to the density functional theory (DFT). Based upon above mentioned experiments and the structural parameters, the quantitative correlation between the structural parameters of sulfonamides molecules and their adsorption affinity (e.g. adsorption capacity and adsorption rate constant) onto CNTs was established, respectively. The adsorption data of sulfonamides fitted well with the pseudo - second - order kinetic model and the Langmuir isotherm model. The order of both pseudo - second - order kinetic constant and maximum adsorption capacity of the six sulfonamides were SAM < SMR < SMX < SDZ < SMT < SMD. The frontier molecular orbital energy (EHOMO) and dipole moment (µ) could be used as indicators for the adsorption affinity of sulfonamides onto CNTs. Accordingly, the possible adsorption mechanism was proposed.