Antibiotics In Water Environment Research Articles

Characteristics of chemical aged biochars and their adsorption behaviors for norfloxacin

The biochar after long-term application will inevitably undergo ageing, thus promoting or inhibiting its remediation efficiency for antibiotics due to the differences in feedstocks and ageing process. To elucidate the adsorption performance and mechanisms of norfloxacin (NOR) by the different aged biochars, a batch of fresh biochars (BCs) prepared from Platanus orientalis Linn. leaf at 400 and 700 ℃ were aged by H2O2 (HBCs) and KMnO4 (MBCs) to simulate the natural ageing process. Compared with BCs, HBCs and MBCs showed larger specific surface area, richer micropores and O-containing functional groups. The maximum adsorption capacities of MBCs (43.96–49.32 mg g−1) and HBCs (18.38–19.79 mg g−1) were generally greater than those of BCs (16.44–20.01 mg g−1), which was resulted from the enhanced pore filling and hydrogen bonds. Furthermore, MBCs introduced with MnOx showed higher adsorption performances than those of HBCs, mainly due to the surface complexation. Na+ and Ca2+ inhibited the NOR adsorption by all the aged biochars. Humic acid and citric acid enhanced NOR adsorption at pH 3.0 but weakened the adsorption at pH 7.0. Furthermore, the NOR removal efficiency of BCs and aged biochars in the natural waters were reduced by 20–25 % and 6–17 %, respectively, showing the excellent sorption performance of the aged biochars. Our findings clarified the enhanced adsorption capacities of NOR by the aged biochar and the potential adsorption mechanism, providing the evidence for predicting the environmental fate of antibiotics in water environment and designing the functional biochars for controlling antibiotic pollution.

Nanoscale zero-valent iron alleviate antibiotic resistance risk during managed aquifer recharge (MAR) by regulating denitrifying bacterial network

The frequent occurrence of antibiotics in reclaimed water is concerning, in the case of managed aquifer recharge (MAR), it inevitably hinders further water purification and accelerates the evolutionary resistance in indigenous bacteria. In this study, we constructed two column reactors and nanoscale zero-valent iron (nZVI) amendment was applied for its effects on water quality variation, microbial community succession, and antibiotic resistance genes (ARGs) dissemination, deciphered the underlying mechanism of resistance risk reduction. Results showed that nZVI was oxidized to iron oxides in the sediment column, and total effluent iron concentration was within permissible limits. nZVI enhanced NO3--N removal by 15.5% through enriching denitrifying bacteria and genes, whereas made no effects on oxacillin (OXA) removal. In addition, nZVI exhibited a pivotal impact on ARGs and plasmids decreasing. Network analysis elucidated that the diversity and richness of ARG host declined with nZVI amendment. Denitrifying bacteria play a key role in suppressing horizontal gene transfer (HGT). The underlying mechanisms of inhibited HGT included the downregulated SOS response, the inhibited Type-Ⅳ secretion system and the weakened driving force. This study afforded vital insights into ARG spread control, providing a reference for future applications of nZVI in MAR.

Removal of ciprofloxacin and cephalexin antibiotics in water environment by magnetic graphene oxide nanocomposites; optimization using response surface methodology

This study investigates the efficient removal of ciprofloxacin (Cip) and cephalexin (Cep) using magnetic graphene oxide (Fe3O4/GO) as an adsorbent. To this end, the magnetic nanocomposite was synthesized via a co-precipitation method. The surface and properties of the adsorbent were characterized using pHpzc, XRD, FE-SEM, FT-IR, VSM, and TEM techniques. The XRD and FT-IR results were consistent with those of previous results. The FE-SEM and TEM results of the synthesized nanoparticles were less than 30 nm in size and showed a spherical shape. The maximum saturation magnetization of the Fe3O4/GO nanocomposite was 45.97 emu g−1. Also, the pHpzc of the nanocomposite was 6.2. The optimal conditions for independent variables were found to be an antibiotic concentration of 15 mg L−1, pH of 7, a contact time of 33 min, and a nanocomposite amount of 0.55 g. Furthermore, under these optimal conditions, Fe3O4/GO magnetic nanocomposite removed 96.39 % of Cip and 97.69 % of Cep from the water samples. Among different eluents (i.e., acetonitrile, chloroform, methanol, and ammonia), significant desorption of Cip and Cep antibiotics was achieved using methanol. Furthermore, applying the Fe3O4/GO magnetic nanocomposite on real water samples revealed that nanocomposite could remove Cip and Cep antibiotics in the range of 89.96–95.83 %. Considering the high potential of Fe3O4/GO magnetic nanocomposite in removing Cip and Cep antibiotics, it can be considered a suitable candidate for removing antibiotics from contaminated water sources.

Magnetized algae catalyst by endogenous N to effectively trigger peroxodisulfate activation for ultrafast degraded sulfathiazole: Radical evolution and electron transfer

An innovative Fe–N co-coupled catalyst MN-2 was prepared from waste spirulina by co-pyrolysis as a highly active carbon-based catalyst for the activation of peroxydisulfate (PDS) for the degradation of sulfathiazole (ST). The protein-rich raw material Spirulina provided sufficient N during the pyrolysis process, thus achieving N doping without an additional nitrogen source, optimizing the interlayer structure of the biochar material and effectively inhibiting the leaching of the ligand metal Fe. MN-2 showed highly efficient catalytic activity for peroxydisulfate (PDS), with a degradation efficiency of 100% for ST within 30 min and a kinetic constant (kobs) reached 0.306 min−1, benefiting from the excellent adsorption ability of MN-2 forming MN-2-PDS* complexes and the electron transfer process generated by Fe3+ and Fe2+ cycling, oxygen-containing functional groups. The effects of PDS dosage, initial pH and coexisting anions on the oxidation process were also investigated. Free radical quenching, electron paramagnetic resonance and electrochemical measurements were employed to explain the hydroxyl (·OH) and sulfate (SO4·−) as the dominant active species and the electron transfer effect on the removal of ST. MN-2 maintained a ST removal rate of 84% after four recycling experiments, showing a high reusability performance. This work provides a simple way to prepare magnetized N-doped biochar, a novel catalyst (MN-2) for efficient activation of PDS for ST degradation, and a feasible method for removing sulfanilamide antibiotics in water environment.

3D/2D CuBi2O4@Bi2O2CO3 Z-scheme heterojunction: The construction of adsorption-photocatalytic synergistic effect for tetracycline hydrochloride removal

To solve the contamination of organic antibiotics in water environment, the 3D/2D CuBi2O4@Bi2O2CO3 (CBO@BOC) hierarchical structure was constructed through the in situ growth of Bi2O2CO3 nanosheets on the surface of CuBi2O4 microspheres. The performance of the as-prepared CBO@BOC composites for the removal of tetracycline hydrochloride (TCH) was investigated by varying the composition ratio, pH of the reaction system, initial pollutant concentration and anion interference. With the synergistic effects of adsorption and photocatalysis, the removal efficiency of CBO@BOC hierarchical composites was significantly improved, which achieved 90% for 20 mg/L TCH. In addition, the CBO@BOC composite also maintained excellent removal ability for TCH in different actual environments and exhibited good cycling stability. In the photocatalytic process,·O2- and h+ acted as the main active components to fully oxidize TCH, which constructed Z-scheme heterojunction photocatalysis mechanism. This work pointed out a new perspective on hierarchical heterostructure for the effective removal of organic antibiotic contaminants via synergistic adsorption and photocatalysis effect.

Enhanced peroxymonosulfate activation by Co-bHAP catalyst for efficient degradation of sulfamethoxazole

The abuse of antibiotics has drawn wide attention owing to their potential risk in human health and ecosystem. As one of the most commonly used sulfonamide antibiotics, sulfamethoxazole (SMX) can hardly be removed by conventional wastewater treatment methods, and thus it has become one of the most frequently detected antibiotics in water environment. In this study, a new cobalt-based heterogeneous catalyst (Co-bHAP) was successfully prepared using the simple impregnation method with animal bone-derived hydroxyapatite (bHAP) as the support, and applied to activate peroxymonosulfate (PMS) for the degradation of SMX in water. The physicochemical properties of Co-bHAP catalyst were investigated by series of characterization methods, and the results showed that this catalyst has a rough and porous morphological structure, as well as homogeneously distributed active component, which is mainly in the form of Co3O4. The developed Co-bHAP can provide abundant reaction active sites and exhibit excellent catalytic activity and stability in PMS activation. The kinetic constant of Co-bHAP activating PMS to degrade SMX is up to 0.1524 min−1, which is 4.5 times larger than that of bare Co3O4. The SMX (20 mg/L) degradation efficiency within 30 min in Co-bHAP/PMS system reached as high as 98.7% and still maintained at 86% after 5 times consecutive operation, with slight cobalt ions leaching less than 0.1 mg/L. Based on radical quenching experiment, electron paramagnetic resonance (EPR) test and XPS analysis, the reaction mechanism was proposed. The balance among Co3+/Co2+, O2−/O2 and PMS decomposition in Co-bHAP/PMS system ensured the continuous generation of sulfate radical (SO4•–) and hydroxyl radical (HO•), both of which are responsible for SMX degradation, while SO4•– plays a leading role. In addition, four possible pathways of SMX degradation were proposed according to the eight detected intermediate products. All the results suggested that this catalyst could have a promising potential in activating PMS to degrade sulfonamide antibiotic pollutants in water.

Photodegradation of Sulfamethoxazole and Enrofloxacin under UV and Simulated Solar Light Irradiation

Antibiotics, as typical emerging contaminants, are frequently detected in the aquatic environment due to their widespread and massive use, posing potential risks to aquatic ecology and human health. To characterize the photodegradation behavior of typical antibiotics in water environment, sulfamethoxazole (SMX) and enrofloxacin (ENR) were selected in this study, and the photodegradation behaviors of these two antibiotics under UV and simulated solar light irradiation were investigated. The degradation rates of SMX under the two light sources were 0.235 min−1 and 0.024 min−1, respectively, and ENR were 0.124 min−1 and 0.043 min−1, respectively. Furthermore, the effects of typical influencing factors including different light intensities, initial concentrations, inorganic anions, and natural organic matter on the photodegradation behaviors of these two antibiotics were studied. The effect of several active substances was explored by adding several quenching agents, and the photodegradation pathway was proposed. The study of the photodegradation characteristics and mechanisms of these two antibiotics may help to provide a reference for the subsequent development of innovative and efficient photocatalytic materials and techniques to remove antibiotics from water.

Contamination by antibiotics and their degradation and removal methods

Context Antibiotics are a new pollutant with biological activity. In recent decades, the presence and fate of antibiotics in water environment have received special attention because of their persistence and resistance to biodegradation and potential risks to ecological and human health. Aims This review addresses the current state of antibiotics, concerning the input sources and the distribution characteristics in China, and mainly summarised the degradation and removal methods applied to the antibiotics. Methods The relevant literature from the past 20 years was reviewed, the distribution of antibiotics in China was summarised, and the method of removing antibiotics was proposed. Key results Further optimisation and combination of the above methods was an important development direction in the future. Conclusions The results showed that, at present, antibiotic pollution in the middle and lower reaches of the Yangtze River and the lakes in China is serious, posing a potential threat to human health and the entire ecosystem. Conventional treatment, oxidative degradation and physical removal could remove degradable antibiotics to a certain extent. Further optimisation and combination of the above methods will be an important development direction in the future. Implications The research results provided data support for exploring effective antibiotic removal methods.

Distribution Coefficient of QNs in Urban Typical Water and Its Main Environmental Influencing Factors

Sediment is the main storage medium of antibiotics in a water environment, and a growing body of research has focused on the distribution behavior of antibiotics in water-sediment. However, most of the previous studies were based on laboratory simulation, and less attention was paid to the distribution behavior of antibiotics in a natural water environment and its correlation with environmental factors. Thus, the surface water and sediment in Shijiazhuang were taken as the research object for this study. The temporal and spatial distribution characteristics of quinolone (QNs) antibiotics in Shijiazhuang water were analyzed by using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS), calculating the distribution coefficients of quinolone (QNs) antibiotics in water and sediment, and confirming the main environmental factors influencing the distribution coefficient in natural water. The results showed that:① the content of ΣQNs in water and sediment ranged from 8.0 to 4.4×103 ng·L-1 and 16 to 2.2×103 ng·g-1 in Shijiazhuang water, whereas the primary QNs in water and sediment were enrofloxacin (ENR) and ofloxacin (OFL), respectively. ② The total concentrations of ΣQNs in Shijiazhuang water showed a tendency of being higher in December (1.0×104 ng·L-1) than in April (5.5×103 ng·L-1), and QNs in sediment were also higher in December (7.8×103 ng·g-1) than in April (6.2×103 ng·g-1). ③ The distribution coefficient of QNs in Shijiazhuang water varied from 34 to 2.9×105 L·kg-1 and showed a trend of being greater in December than in April. ④ The results of correlation analysis showed that total nitrogen (TN), nitrate nitrogen (NO3--N), nitrite nitrogen (NO2--N), and ammonia nitrogen (NH4+-N) were significantly correlated with most distribution coefficients of QNs[OFL, norfloxacin (NOR), ENR, difloxacin (DIF), and oxolinic acid (OXO)], whereas temperature (T), total organic carbon (TOC), and total dissolved solids (TDS) were significantly correlated with individual distribution coefficients of QNs[marbofloxacin (MAR) and DIF]. Therefore, the eutrophication level of water affects the distribution behavior of antibiotics in water-sediment.

A novel amorphous porous biochar for adsorption of antibiotics: Adsorption mechanism analysis via experiment coupled with theoretical calculations

High-performance activated carbons are crucial for adsorbing antibiotics in water environment. In this work, amorphous porous biochars (APBCs) with high specific surface area (935 m2·g-1) were achieved by using sesame straw. Compared with the conventional biochars precursor, sesame straw with the advantages of rich resources and low price is more economical and environmentally friendly. Moreover, KOH and Ca(OH)2 were selected as co-activators, which characterization results revealed that co-activators significantly increased the coarseness of activated carbon surface and enlarged pore structure. In addition, the adsorption mechanism of norfloxacin (NOR), ciprofloxacin (CIP) and enrofloxacin (ENR) on APBCs were further investigated by experiments and density functional theory (DFT) calculations. The results discovered that pseudo second-order kinetics and Sips model followed the adsorption experiment data, implying that the adsorption process was heterogeneous and multilayer. And the interactions between APBCs and antibiotics were electrostatic interaction, hydrogen bond and π-π interaction, which were conducive to chemical adsorption.

A novel slag-based Ce/TiO2@LDH catalyst for visible light driven degradation of tetracycline: performance and mechanism

As a kind of bulk solid waste in iron and steel industry, titanium-bearing blast furnace slag (Ti-BFS) poses a serious threat to the environment, its disposal and reuse has been a hot and difficult spot. In this study, a new and high efficient hydrotalcite-like photocatalytic material (denoted CeTL) was prepared from Ti-BFS, and applied to the visible light catalytic degradation of antibiotics in water environment. The results showed that the degradation rate of tetracycline (TC) by the optimized CeTL reached 92.8% after 90 min of illumination. Dissolved organic matter with molecular weight 1–3 kDa was the most inhibiting to degradation rate. The introduction of Ce contributed to the nanopore structure and increased the specific surface area (302.58 m²/g), and effectively promoted the development of active surface oxygen and oxygen vacancies in the lattice, thus reducing the excited energy of photoelectron and expanding the spectral response range. Moreover, Ce acted as a medium to transfer photoelectrons, which successfully separates the reducing photoelectron in conduction band (CB) and the oxidized hole in valence band (VB), and generated·O2− and·OH with O2 and OH−, respectively. These active species attacked TC molecules adsorbed on CeTL surface, degraded them into small molecules, and improved the antibacterial activity of CeTL. The good adsorption capacity and the enhanced visible light catalysis of CeTL synergistic realized the efficient removal of TC. This work enriched the research system of comprehensive utilization of Ti-BFS, and provided a new strategy for the preparation of efficient applied photocatalysts and the recycling of resources.

Amino-functionalized NH2-MIL-125(Ti)-decorated hierarchical flowerlike Znln2S4 for boosted visible-light photocatalytic degradation

Developing novel heterojunction photocatalysts with visible-light response and remarkable photocatalytic activity have been verified to applying for the photodegradation of antibiotics in water environment. Herein, NH2-MIL-125(Ti) was integrated with flowerlike ZnIn2S4 to construct NH2-MIL-125(Ti)@ZnIn2S4 heterostructure using a one-pot solvothermal method. The photocatalytic performance was evaluated by the degradation of tetracycline (TC) under visible light illumination. The optimized NM(2%)@ZIS possesses a photodegradation rate (92.8%) and TOC removal efficiency (58.5%) superior to pristine components, which can be principally attributed to the positive cooperative effects of well-matched energy level positions, strong visible-light-harvesting capacity, and abundant coupling interfaces between the two. Moreover, the probable TC degradation mechanism was also clarified using the active species trapping experiments. This study inspires further design and construction of NH2-MIL-125(Ti) and ZnIn2S4 based photocatalysts for effective removal of antibiotics in water environment.

Facile synthesis of cobalt-iron layered double hydroxides nanosheets for direct activation of peroxymonosulfate (PMS) during degradation of fluoroquinolones antibiotics

How to efficiently and fast remove the serious perniciousness of the residual antibiotics in water environment is crucial for protecting ecosystem. Herein, we reported the Fenton-like system based on layered double hydroxides (LDHs) nanosheets for direct peroxymonosulfate (PMS) activation efficient for fast removing the typical five fluoroquinolones antibiotics ciprofloxacin (CIP), norfloxacin (NOR), levofloxacin (LEV), enrofloxacin (ENR) and ofloxacin (OFL). A series of CoFe-LDHs nanosheets was one-step fabricated by integrating coprecipitation and in-situ exfoliation method. The as-obtained CoFe-LDHs nanosheets catalysts exhibit thin nanosheets (~3 nm) with high redox properties, abundant oxygen vacancies, appreciable adsorption capacity, remarkable catalytic performance and favorable stability. The variable valent state, cheap, easy-to-obtain and low-toxic Co and Fe elements were used to construct stable LDHs for efficient activation of PMS to degrade quinolone antibiotics. Among them, Co1Fe1-LDHs nanosheets exhibited the best CIP degradation efficiency of 86.9% within 12 min, which is superior to most of previous candidates. The impacts of different reaction parameters, catalyst stability, main reactive oxygen species, the main CIP degradation mechanism and rational degradation pathways were systematically studied. This work offers a feasible strategy to tune the performance of LDHs-based materials in Fenton-like system degradation of antibiotics.

Enhanced peroxymonosulfate activation over heterogeneous catalyst Cu0.76Co2.24O4/SBA-15 for efficient degradation of sulfapyridine antibiotic

The largest source of resistant bacteria or viruses is the overuse and misuse of antibiotics in humans and animals. These resistant bacteria or viruses may evolve into superbacteria or superviruses, which causes global plague. Therefore, it is significant to find a highly efficiency and low-cost method to eliminate antibiotics in water environment from inappropriate discharge. Here, a highly active and highly stable heterogeneous catalyst, Cu0.76Co2.24O4/SBA-15 (CCS) was prepared for peroxymonosulfate (PMS) activation in aim of decomposing persistent sulfapyridine (SPD). The reaction mechanism was thoroughly investigated via in situ quenching test and in situ electron paramagnetic resonance. Four reactive species, SO4·−, O2·−, 1O2 and ·OH were generated in Cu0.76Co2.24O4/SBA-15/PMS (CCSP) system. The SO4·− and O2·− were dominant active species responsible for SPD degradation. Co(Ⅱ)↔Co(Ⅲ)↔Co(Ⅱ) redox reaction cycle was constructed due to the different redox potential of Co(Ⅱ)/Co(Ⅲ), HSO5-/SO4∙-, and HSO5-/SO5∙-. Interestingly, Cu(Ⅰ) could urge the redox reaction cycle for PMS activation to be more thermodynamically feasible. Therefore, CCS possessed a highly catalytic activity and excellent stability. Meanwhile, the anions interference test indicated Cl-, NO3-, HCO3-, and H2PO4- had almost no inhibitory effect on SPD degradation over this catalytic system. We sincerely expected that this catalyst system would be applied extensively into antibiotics degradation in real water bodies.

Synthesis of CQDs@FeOOH nanoneedles with abundant active edges for efficient electro-catalytic degradation of levofloxacin: Degradation mechanism and toxicity assessment

The occurrence of antibiotics in water environment has drawn great concerns in recent years. In this work, CQDs@FeOOH electro-catalyst with abundant active edges was synthesized and applied to the degradation of antibiotics. About 99.6 % levofloxacin (LEVO) and 53.7 % TOC could be efficiently removed by CQDs@FeOOH after 60 min degradation. The high LEVO degradation performance of CQDs@FeOOH was demonstrated to be attributed to the high mass transfer ability and the high OH generation ability of the special needles structure. The OH was found to be the main radical for LEVO degradation, and the highest OH generation ability of CQDs@FeOOH was found to be resulted from the moderate adsorption energy of the exposed (1 1 0) facets (needles) toward OH. A possible LEVO degradation pathway has been proposed and toxicity changes during LEVO degradation were detailed investigated. This study offers an efficient method to reduce the amount and toxicity of antibiotics in water.

Combined toxicity characteristics and regulation of residual quinolone antibiotics in water environment

In this study, the mixture toxicity index method was used to evaluate the combined toxicity of residual Quinolones (QNs) on algae in twelve groups of water environment reported in the literature. The selected three sets of data (II, Ⅺ, and Ⅻ) combined with full factorial design method were used to analyze the significance of the combined toxicity. Subsequently, molecular docking was used to reveal the significant mechanism of the primary effect of the combined toxicity. Finally, based on the sensitivity analysis method, the acid-base conditions affecting the combined toxicity were screened, and molecular dynamics simulation was used to control the combined toxicity in the water environment. The results of the mixture toxicity index method showed that the combined toxicity in all the twelve groups of water environments was synergistic. The full factorial design method revealed that ciprofloxacin, norfloxacin, enrofloxacin, lomefloxacin, and their binary combinations from the combined toxicity system of QNs, were the significant factors that caused the synergistic toxicity of QNS on algae. Molecular docking confirmed that the total number of amino acids, the number of significant amino acids, and hydrogen bonds of QNs toxic targets were significantly related to the synergistic effect of the combined toxicity. In addition, the molecular dynamics simulation showed that the binding energy of residual QNs and toxic targets changes with the acid-base conditions of the water environment. Thus, the combined toxicity can be slowed down or reduced by adequately adjusting the acid-base condition of the water.

Catalytic degradation of sulfamethoxazole by persulfate activated with magnetic graphitized biochar: Multiple mechanisms and variables effects

The widespread occurrence of antibiotics in water environment, especially the recalcitrant sulfamethoxazole (SMZ), has sparked increasing concern due to their potential to threat non-target organisms, contaminate food and induce bacterial resistance. In this study, magnetic graphitized biochar (GMBC) was synthesized via a facile one-step strategy employing pine wood-derived biochar as precursor and with potassium ferrate (K2FeO4) modification, and introduced as heterogeneous catalyst for persulfate (PS) activation and SMZ degradation. Utilizing K2FeO4 as both activator (KOH) and catalyst (Fe), porous structure, high graphitization degree, abundant electron-rich functional groups and iron loading of GMBC were simultaneously achieved, which afforded the high catalytic efficiency (almost 100 % degradation of SMZ within 60min) through accelerating electron transfer. Pyrolysis temperatures affected the structure and catalytic performance of GMBCs. A systematic mechanistic study, including quenching experiment, electron spin resonance analysis and electrochemical measurements, unveiled that both radical pathways (HO, SO4− and O2−-mediated oxidation) and non-radical pathways (electron shuttle and 1O2-mediated oxidation) were responsible for the SMZ degradation. Vacancies/defective edges formed on graphitized carbon framework, iron loading sites and the electron-rich ketonic group might be the active sites. In this process, GMBC played versatile roles in accumulating reactants, activating PS as well as mediating the electron transfer from SMZ to PS. Benefited from the multiple mechanisms, the GMBC/PS system can maintain superior oxidation efficiency under various environment conditions, with high anti-interference ability to surrounding compounds and solution pH. This study proposes an economic and green template-free strategy to prepare graphitized biochar catalyst for PS activation and gives underlying insight into the multiple roles of biochar in the eco-friendly remediation of contaminated water.

Degradation of sulfamethazine by biochar-supported bimetallic oxide/persulfate system in natural water: Performance and reaction mechanism

The rapid development of aquaculture results in the increased concentrations and kinds of antibiotics in water environment, and the sharply growing antibiotic contamination has caused increasing concerns. Herein, an innovative sulfamethazine (SMT) removal approach was developed by activation of persulfate (PS) using biochar-based materials prepared by co-precipitation and pyrolysis: Fe-Mg oxide/biochar (FeMgO/BC). Experiments on the activation of PS by FeMgO/BC under different factors were carried out. The involved mechanism and degradation pathway were also studied. Notably, the SMT removal rate reached 99 % under the optimum reaction condition, while the TOC removal efficiency reached 77.9 %. PS was activated by FeMgO/BC and the dominated active radical was SO4•−. Fe2+ from FeMgO and the hydroxyl and carboxyl groups on the surface of biochar contributed to the production of SO4•−. The dehydrogenation, bond cracking and unsaturated bond addition process occurred in the degradation of SMT. Furthermore, FeMgO/BC exhibits excellent reusability and stability. Considering the outstanding actual water application performances and the weak biotoxicity, FeMgO/BC shows a promising potential in the removal of antibiotics under actual water conditions.

Formation, characteristics and microbial community of aerobic granular sludge in the presence of sulfadiazine at environmentally relevant concentrations

The growing occurrence of antibiotics in water environment is causing increasing concern. To investigate the impact of frequently detected sulfadiazine on the formation of aerobic granular sludge, four sequencing batch reactors (SBRs) were set up with different environmentally relevant concentrations of sulfadiazine. Results showed that sulfadiazine pressure could lead to larger and more compact sludge particles and cause slight effect on reactor performance. Presence of sulfadiazine apparently increased the extracellular polymeric substances (EPS) secretion of microorganisms. Quantitative polymerase chain reaction (qPCR) showed that the abundances of sulfanilamide resistance genes in sludge increased with addition of sulfadiazine significantly. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was used to predict functional genes, results showed that sulfadiazine led to an increase of specific functional genes. Thereby, it concluded that microorganisms could change the community structure by acclimating of functional bacteria and antibiotic resistance species to adapt to the antibiotic stress.