Oxidation Of Tetracycline Research Articles

Hierarchical porous graphite-like carbon nanosheet cooperated with Fe/Fe3C@Fe-N-C nanocomposites toward catalytic oxidation process

In this work, Fe, N co-doped hierarchical porous graphite-like carbon with carbon-encapsulated Fe/Fe3C@ Fe-N-C was synthesized by a facile solid-phase synthesis strategy, and was employed as an efficient catalyst to activate peroxymonosulfate (PMS) for oxidation of tetracycline (TC). The optimal Fe-N/C 800 outlined a highly catalytic performance in activating peroxymonosulfate (PMS) with TC decomposition rate reaching 89.2 % in 20 min at ultra-low catalyst dosage. Meanwhile, the effect of operating parameters was also investigated in order to evaluate the potential of using Fe-N/C 800 in practical applications. In addition, the characterization analysis and experiments results elucidated that graphitic N, pyridinic N, CO, Fe3C, Fe0 and FeN4 were considered as the main reactive species promoting the PMS activation to generate reactive oxygen species (ROS) (including singlet oxygen (1O2), sulfate radical (SO4•-) and hydroxyl radical (•OH)). The electron paramagnetic resonance (EPR) experiments and radicals quenching analyses further demonstrated that the non-radical species singlet oxygen (1O2) was the dominant reactive oxygen species. Moreover, the TC degradation pathways were presented by LC-MS. Ultimately, the toxicity of the intermediate products were also investigated by ECOSAR system.

The elaborately-designed Z-scheme Fe-g-C3N4/α-Fe2O3 photocatalytic platform equipping with active N-Fe-O bridges for enhanced synergistic removal of tetracycline and Cr(VI) via photoinduced electron transfer process

Nowadays, simultaneous removal of organic pollutants and heavy metals from wastewater is still a complicated task with great challenge. Herein, a newly-designed Fe-g-C3N4/α-Fe2O3 composite with an active N-Fe-O bridge was prepared by coupling Fe-doped g-C3N4 (namely Fe-g-C3N4) and α-Fe2O3. Interestingly, the combination of Fe-g-C3N4 with α-Fe2O3 broadened the light absorption region and restrained the photoinduced electron-hole pair recombination. Meanwhile, elaborate construction of N-Fe-O bridges based on coordination interaction can reduce electrochemical impedance and facilitate electron transfer, thereby prolonging the charge lifetime. As expected, the Fe-g-C3N4/α-Fe2O3 composite displayed excellent photocatalytic performance in simultaneous removal of tetracycline (TC) and Cr(VI). More importantly, Fe-g-C3N4/α-Fe2O3-mediated electron transfer from TC to Cr(VI) also played an essential role on TC oxidation and Cr(VI) reduction under visible light. Both experimental analyses and theoretical calculations revealed that the migration route of photogenerated carriers followed a direct Z-scheme heterojunction mechanism under built-in electric field. The Fe-g-C3N4/α-Fe2O3 composite with great stability also displayed promising practical application potential. In short, the current work not only provided a highly-efficient photocatalyst with N-Fe-O bridges but also shared new insights into the simultaneous removal of organic pollutants and heavy metals.

The insight into the synergistic effect between goethite and birnessite on the degradation of tetracycline

The environmental fate of tetracycline (TC) has been documented closely related to goethite (α-FeOOH) or birnessite (δ-MnO2) in soil, while their synergistic effect on TC transformation remains unclear. Herein, a series of δ-MnO2@FeOOH were synthesized to investigate the interaction between α-FeOOH and δ-MnO2 for TC transformation. The results showed that the higher specific surface area and larger amount of surface hydroxyl content were found in δ-MnO2@FeOOH than those of the bulk α-FeOOH and δ-MnO2, enhancing the adsorption capacity for TC. The α-FeOOH introduction was conducive to the electron transfer efficiency and the increase of Mn(III) species, thus, forming more reactive oxygen species (ROSs) for the oxidation of TC. Moreover, the comparative study of the degradation of the common organic pollutants in soli over δ-MnO2@FeOOH indicated the synergistic effect of δ-MnO2 and α-FeOOH showed selectivity in the TC degradation. In addition, 20%δ-MnO2@FeOOH displayed highest removal percentage of 98% for TC (10.0 mg/L) and the removal performance first increased and then decreased as δ-MnO2 loading on the surface of α-FeOOH from 10% to 70%. This study provides a new insight into the transformation of organic pollutant under the interaction between α-FeOOH and δ-MnO2.

Dual MOFs composites: MIL-53 coated with amorphous UiO-66 for enhanced photocatalytic oxidation of tetracycline and methylene blue

Dual MOFs composites: MIL-53 coated with amorphous UiO-66 for enhanced photocatalytic oxidation of tetracycline and methylene blue

A dual defect co-modified S-scheme heterojunction for boosting photocatalytic CO2 reduction coupled with tetracycline oxidation

To synchronously relieve energy shortage and wastewater remediation, herein, a dual-defect S-scheme heterojunction of I doped BiOBr modified N vacancy g-C3N4 (labeled as IB/CNx) was designed for simultaneously photocatalytic CO2 reduction coupled with tetracycline oxidation. The 70IB/CNx presented higher photocatalytic property for CO2 reduction coupled with TC removal than those of IB/CN, BiOBr/CNx, and BiOBr/CN. The improved photocatalytic activity was mainly attributed to the synergistic effect of doped I ions and N defects. Besides, such designed coupled reaction system presented much superior catalytic performance than those of two half-reactions, which achieved the full utilization of carriers. All in all, a dual-defect heterojunction enhanced a dual-function reaction system, in which the dual-defect active spots accelerated the transfer and separation of carriers, meanwhile, the dual-function reaction system realized the full utilization of the charges. This work highlighted the pivotal role of defect engineering to design efficient photocatalysts for environment and energy applications.

Hierarchical S-Scheme Heterostructure of CdIn2S4@UiO-66-NH2 toward Synchronously Boosting Photocatalytic Removal of Cr(VI) and Tetracycline.

Developing highly efficient photocatalysts toward synchronously removing heavy metals and organic pollutants is still a serious challenge. Herein, we depict hierarchical S-scheme heterostructured photocatalysts prepared via in situ anchoring UiO-66-NH2 nanoparticles onto the CdIn2S4 porous microsphere structures assembled with numerous nanosheets. In the mixed system of Cr(VI) and tetracycline (TC), the optimal photocatalyst (CIS@U66N-30) shows remarkable photocatalytic activities toward the synchronous removal of Cr(VI) (97.26%) and TC (close to 100% of) under visible-light irradiation for 60 min, being the best removal rates among those of the reported photocatalysts, and sustains the outstanding stability and reusability. Its reaction rate constants of Cr(VI) reduction and TC degradation are about 2.06 and 1.58 folds that in the single Cr(VI) and TC systems, respectively. The enhanced photocatalytic activities of CIS@U66N-30 mainly result from the following synergism: (1) its hierarchical structure offers abundant active sites, and the S-scheme migration mechanism of charge carriers in the heterostructure accelerates the separation and migration of the useful photoinduced electrons and holes with the high redox capability; (2) Cr(VI) and TC can serve as the electron scavenger for TC oxidation degradation and the hole and •OH scavenger for Cr(VI) reduction, respectively, further enhancing the separation and utilization efficiency of photoinduced electrons and holes. Besides, the possible TC degradation pathway and plausible S-scheme photocatalytic mechanism over CIS@U66N-30 for the concurrent elimination of Cr(VI) and TC are proposed.

Simultaneous removal of tetracycline and sulfamethoxazole by laccase-mediated oxidation and ferrate(VI) oxidation: the impact of mediators and metal ions.

This study explores the impact of mediators and metal ions of laccase-mediated oxidation and ferrate(VI) oxidation for the simultaneous removal of tetracycline antibiotics (TCs) and sulfonamide antibiotics (SAs) and to effectively remove their antimicrobial activity. The results showed that the antimicrobial activity of tetracycline against Bacillus altitudinis and Escherichia coli was significantly reduced, and the antimicrobial activity of sulfamethoxazole against B. altitudinis disappeared completely after treatment with the laccase-ABTS system. The combination of 6.0 U/mL of laccase and 0.2mmol/L of ABTS removed 100% of 20.0mg/L of tetracycline after 1.0min at pH 6.0 and 25.0°C, whereas the removal ratio of 20.0mg/L of sulfamethoxazole was only 6.7%. The Al3+ and Cu2+ ions promoted the oxidation, and the Mn2+ ion decelerated the oxidation of tetracycline and sulfamethoxazole by the laccase-mediator systems. In contrast, the antimicrobial activity of tetracycline against B. altitudinis and E. coli was shown to be significantly reduced, and the sulfamethoxazole still retained high antimicrobial activity against B. altitudinis after treatment with Fe(VI) oxidation. The removal ratio of 20.0mg/L of tetracycline was 100% after 1.0min of treatment with 982.0mg/L of K2FeO4 at pH 6.0 and 25.0°C, whereas the removal ratio of 20.0mg/L of sulfamethoxazole was only 49.5%. The Al3+, Cu2+, and Mn2+ ions both decelerated the oxidation of tetracycline and sulfamethoxazole by Fe(VI) oxidation.In general, the combination of the laccase-ABTS system and Fe(VI) was proposed for the simultaneous treatment of TCs and SAs in wastewater and to effectively remove their antimicrobial activity.

Peroxymonosulfate-based photocatalytic oxidation of tetracycline by Fe2(MoO4)3/Cd0.5Ni0.5S heterostructure; DFT simulation

The current research is meant to develop novel semiconductor photocatalysts, for the decomposition of tetracycline (TC) as a model organic contaminant in the aquatic environment. The fabrication of Fe2(MoO4)3/Cd0.5Ni0.5S (FMO/CNS) composite has proven to be an effective method for improving the sustainability and photocatalytic activity of Cd0.5Ni0.5S (CNS). Under visible light irradiation, FMO/CNS nanocomposite demonstrated significant PMS activation which led to 1.36 and 1.81 times TC removal efficiency as compared to immaculate Fe2(MoO4)3(FMO) and CNS. FMO/CNS composite potentially promotes the segregation of electron-hole pairs (e−-h+) and exemplifies amazing photocatalytic performance for TC degradation. Its significant photocatalytic activity is due to its unique structure, which includes tiny pores on the surface that confine the PMS molecule to the interface. The FMO/CNS composite has significantly greater piezocatalytic activity than pure FMO and CNS, demonstrating the synergistic effect of FMO and CNS. In the degradation of TC, holes and key reactive radicals (•O2−/•OH/SO4−•) played a major role. Computational studies (DFT) estimates, including the determination of intermediates, confirmed that the hydroxyl addition and C–N cleavage pathways were responsible for TC degradation. As a result, this work delivers a new approach to developing novel photocatalysts with high photocatalytic activity for the abatement of organic contaminants in water.

Application of FeS-activated persulfate oxidation system for the degradation of tetracycline in aqueous solution.

Tetracycline (TC), an antibiotic used to treat bacterial infectious diseases, is easily transferred to environmental matrixes and then sparks environmental concerns. In this study, TC was selected as a target pollutant to investigate the degradation performance of persulfate (PS) based advanced oxidation processes (AOPs) using FeS as the activator (FeS/PS). The results showed that with optimal PS and FeS concentrations of 1mM and a pseudo-second-order rate constant (k2) of 3.45 L mmol-1min-1, 91.39% of TC, was effectively removed within 60min. From the perspective of degradation rate, apart from CO32-, TC decompositions by FeS/PS were hardly disturbed by the coexistence of different concentrations of Cl-, NO3-, SO42-, and humin acid. The degradation of TC under the O2 bubbling, N2 bubbling, and light-proof conditions also had limited effects on these AOPs. In addition, FeS exhibited excellent stability and recyclability when used as a PS activator for TC removal. The PS activated by old FeS and used FeS showed nearly identical performances on TC removal compared with the fresh FeS. It is suggested that homogeneous and heterogeneous reactions are jointly responsible for TC oxidation by FeS/PS. With the contributions of the generated, highly reactive SO4-•, and, in particular, •OH, TC enabled the mineralization of inorganic products eventually. Therefore, FeS/PS is highly recommended as an alternative AOPs in the future for TC-contaminated wastewater purification.

Water caltrop-based carbon catalysts for cooperative adsorption and heterogeneous activation of peroxymonosulfate for tetracycline oxidation via electron transfer and non-radical pathway

In this study, a water caltrop-based metal-free carbon catalyst for peroxymonosulfate activation was prepared and modified using KOH. The carbonization process improved the crystallinity and porosity of the material, which was beneficial for the efficient modification of KOH. The modification results in higher specific surface area, high porosity, more functional groups, and a highly graphitized structure. BC-OH-700 exhibited excellent adsorption and degradation performance through the synergistic action of surface electrostatic adsorption, non-free radical pathway catalysis, and electron transport. The complete removal of tetracycline could be achieved within 60 min in the BC-OH-700/peroxymonosulfate system. The active sites altered the electrostatic potential distribution and caused the electrostatic adsorption of the reactive components. The surface functional groups could activate peroxymonosulfate to generate reactive oxygen species. The electrical conductivity of the materials could accelerate electron transfer and increase the catalytic degradation rate. The catalytic system was dominated by the 1O2 non-free radical pathway. Rapid electron transport could promote the formation of 1O2 in the non-radical pathway, thus maintaining the continuity and efficiency of the degradation reaction. The collaborative catalytic system greatly enhanced its adaptability to reaction conditions and provided more possibilities for advanced oxidation via catalytic degradation mechanisms.

Evaluation of iron-loaded granular activated carbon used as heterogeneous fenton catalyst for degradation of tetracycline

To optimize the efficiency of general adsorption-Fenton oxidation treatment, iron-loaded granular activated carbon (Fe-GAC) was prepared, characterized, and used as a catalyst in the heterogeneous Fenton oxidation of tetracycline (TC). Characterization revealed that the Fe(II) was successfully introduced onto the original granular activated carbon (GAC) and diversified the materials’ surface morphology and elemental compounds. Under an initial pH of 3.0, the Fe-GAC/Fenton system obtained a maximum removal rate of 92.6%, with hydrogen peroxide (H2O2) dosages of 9 mmol g−1. And the GAC/Fenton without iron supplementation was 89.5%, with H2O2 dosages of 8 mmol g−1. Additionally, the Fe-GAC/Fenton system consumed a lower Fe(II) dosage than GAC/Fenton, with Fe(II)/H2O2 molar ratios of 0.007:1 and 0.04:1, respectively. Analysis of total organic carbon demonstrated higher mineralization efficiency in the Fe-GAC/Fenton system (67.2%), which was approximately 1.3 times of GAC/Fenton. Desorption experiments showed that the adsorption and degradation accounted for 19.22% and 80.78% of the total TC removal by GAC/Fenton, and 10.58% and 89.42% in the Fe-GAC/Fenton system, respectively. Electron paramagnetic resonance (EPR) technique and quenching experiments demonstrated that the dominant reactive oxygen species (ROS) in synergistic treatments were hydroxyl (•OH) and hydroxy peroxyl (HO2•) radicals. In addition, three potential degradation pathways for TC were proposed according to the detected fourteen intermediates. Catalyst regeneration treatments were evaluated over six cycles, and the regeneration was 6.5% higher with the iron-supplemented carbon granules. Overall, the Fe-GAC can be used as an efficient catalyst in practical water treatment, and this study demonstrated a promising method to develop adsorption-Fenton technology.

Preparation of Graphite-UiO-66(Zr)/Ti electrode for efficient electrochemical oxidation of tetracycline in water.

Tetracycline (TC) is widely-used antibiotic pollutant with high toxicity, refractory, persistence and bacteriostasis, and its removal from water needs to be enhanced. In this work, a novel Graphite-UiO-66(Zr)/Ti electrode was successfully prepared and evaluated for electrochemical oxidation degradation of TC. The electrochemical performance tests indicate the Graphite-UiO-66(Zr)/Ti electrode had higher electrochemical oxidation activity, which achieved higher TC removal efficiency (98.1% ± 1.5%) than Ti plate (65.2% ± 3.5%), Graphite-MIL-53(Al)/Ti electrode (79.5% ± 2.9%) and Graphite-MIL-100(Fe)/Ti electrode (89.0% ± 2.6%). The influence of operating condition was also systematically studied, and the optimized condition was pH 5.0, 20 mA/cm2 current density and 0.1 M electrolyte (Na2SO4). Through the liquid chromatography mass spectrometry (LC-MS), the TC degradation pathway by Graphite-UiO-66(Zr)/Ti electrode oxidation was proposed. Under the •OH free radical oxidative decomposition effect, the double bond, phenolic group and amine group of TC were attacked. TC was transformed into intermediate product ① (m/z = 447), then was further degraded to intermediates ② (m/z = 401) and ③ (m/z = 417). The latter was fragmented into small fractions ④ (m/z = 194), ⑤but-2-enedioic acid (m/z = 116) and ⑥oxalic acid (m/z = 90, the proposed intermediate). In addition, TC removal remained at 89.6% ± 2.7% in the sixth cycle of operation, which confirmed the efficient reusability and stability for antibiotics removal from water.

Boosted photocatalytic antibiotic degradation performance of Cd0.5Zn0.5S/carbon dots/Bi2WO6 S-scheme heterojunction with carbon dots as the electron bridge

Building high-performance and robust S-scheme heterojunction photocatalysts for sustainable pollutant abatement has been a prospective tactics to restore environment. Herein, Cd0.5Zn0.5S/carbon dots/Bi2WO6 (CZS/CDs/BWO) S-scheme heterojunctions have been designed and fabricated as an efficient and durable visible-light-responsive photocatalyst for tetracycline oxidation with 0.7-fold, 6.4-fold and 0.5-fold enhancement compared with neat CZS, BWO and CZS/BWO. The superb photo-activity is primarily derived from the synergy between carbon dots and S-scheme heterojunction, which not only effectively diminishes the interface resistance but also achieves the fostered disintegration and preservation of the photo-carriers with great redox ability. The impact of water conditions on the photo-activity is explored in view of the complexity of the authentic aquatic environment. The findings of the scavenging tests and ESR analysis evidence that h+, O2−, and OH may mainly drive the antibiotic decomposition, mineralization and detoxification reaction. The photoreaction mechanism and TC degradation pathway over CZS/CDs/BWO are unraveled according to LC–MS analysis. The intermediate toxicity assessment indicates that most of the degradation byproducts’ acute and developmental toxicities are abated to a markedly lower level than that of TC. Moreover, CZS/CDs/BWO also could effectively degrade other popular pharmaceutical antibiotics (e.g., levofloxacin, norfloxacin, oxytetracycline, and enrofloxacin), demonstrating its universal photocatalytic potency for the treatment of pharmaceutical antibiotics. This work illustrates the potential practicability on carbon dots modulated S-scheme heterojunction photocatalysts for efficient water remediation.

Oxygen vacancy concentration modulation of perovskite-based heterogeneous catalysts for Fenton-like oxidation of tetracycline

Oxygen vacancies (V O ) constructing in metallic compounds have been verified to enhance hydrogen peroxide (H 2 O 2 ) activation for pollutants treatment. However, the interactions between surface V O concentration and H 2 O 2 were still ambiguous. In this study, perovskites with different surface V O concentration were successfully prepared by a simple sol-gel process. Experimental results showed that A-site cation deficient was capable of distorting FeO 6 octahedra in Ca 1−x FeO 3-δ (x = 0, 0.1, 0.2) orthorhombic perovskites for the regulation of surface V O concentration. Afterwards, Ca 0.9 FeO 3-δ exhibited excellent catalytic activity and stability for tetracycline (TC) degradation, which was 4 times higher of catalytic enhancement than that of the raw Ca 1.0 FeO 3-δ . Moreover, up to 9, 17 and 27 times of catalytic enhancement as compared with commercial Fe 3 O 4 , ɑ-FeOOH and Fe 2 O 3 towards TC degradation. Based on electron spin resonance and free radical quenching experiments, the hydroxyl radical (∙OH) was the main active species for the catalytic degradation of TC. Meanwhile, higher or lower surface V O concentration was harmful to the production of ∙OH. Additionally, the toxicity of TC degradation by-products exhibited a decreasing trend according to the results of toxicological simulation. This work provides a new strategy for designing an efficient and promising heterogeneous Fenton-likes catalyst for environmental remediation. • Perovskite with abundant surface V O was synthesized by sol-gel method. • Surface V O concentration was regulated by regulated the A-site cation deficient. • Higher or lower surface V O concentration was hamful to the activation of H 2 O 2 . • Degradation intermediates were identified, and possible pathways were proposed.

Oxygen vacancies-enriched Cu/Co bimetallic oxides catalysts for high-efficiency peroxymonosulfate activation to degrade TC: Insight into the increase of Cu+ triggered by Co doping

Bimetallic CuCo-doped graphene-like carbon nanosheets (CuCo@GCNs) were synthesized via a facile and efficient process using agarose as carbon templates to activate peroxymonosulfate (PMS) for tetracycline (TC) degradation. In this study, CuCo@GCNs/PMS system exhibited excellent TC removal efficiency (0.182 min−1), which was unaffected by various water matrices and applicable to a wide pH range (3.44–8.44). Radicals (SO4•−, •OH, and O2•−) and non-radical (1O2) pathways collectively contributed to catalytic TC oxidation based on quenching experiments and electron paramagnetic resonance (EPR) analysis. Density functional theory (DFT) calculations revealed that the mechanism of PMS molecules activated on the surface of CuCo@GCNs, in which CoO provided more catalytic sites while Cu2O further enhanced electron transfer. Moreover, the synergistic effect of CuCo bimetal could accelerate redox cycles of Cu+/Cu2+ and Co2+/Co3+, inducing the generation of abundant oxygen vacancies (OVs), thus enhancing PMS activation performance. Three potential TC degradation pathways were proposed according to fifteen possible intermediates detected by liquid chromatography-mass spectrometry (LC-MS). In brief, this work provides an efficient CuCo@GCNs heterogeneous catalyst and a new insight into PMS activation, which extends the application of bimetallic materials for environmental remediation.

Enhanced electrochemical oxidation of tetracycline and atrazine on SnO2 reactive electrochemical membranes by low-toxic bismuth, cerium doping

SnO2-Sb electrodes are widely used in electrochemical advanced oxidation processes for water treatment; however, the release of highly toxic Sb3+/Sb5+ has aroused environmental concern. This study systematically investigated the potential of Bi and Ce elements as substitutes to fabricate doped-SnO2 reactive electrochemical membrane (REM) for water purification. Compared with the control (SnO2-Sb-REM), SnO2-Bi-REM showed a higher direct electron transfer (DET) rate and •OH yield due to its larger electroactive surface area. The higher oxygen evolution potential of SnO2-Ce-REM enhanced selectivity for •OH generation. Although both SnO2-Bi-REM and SnO2-Ce-REM exhibited higher electrooxidation of tetracycline hydrochloride (TCH) and atrazine (ATZ) than SnO2-Sb-REM, only the service lifespan of SnO2-Bi-REM can meet the requirements of practical applications. Mechanistic studies of the degradation pathways indicated that the rapid degradation of TCH on SnO2-Bi-REM was mainly contributed by the DET process, while the transformation of intermediates involved the reactions with •OH. In comparison, aqueous •OH played an important role in the degradation of refractory ATZ. Moreover, a SnO2-Bi-REM system demonstrated ∼99% removal of trace TCH and ATZ from wastewater effluent in single-pass operation at a low electrical efficiency per log order removal (EE/O, 0.71 kWh m−3). To this end, the SnO2-Bi-REM is demonstrated to be a promising electrode to replace SnO2-Sb-REM for efficient and sustainable water purification.

Photo-deposition of Ag/AuNPs on TiO2 accelerating the oxidation of tetracycline under visible light

Photo-deposition of Ag and AuNPs at different compositions on TiO2 was performed under UV-light to yield TiO2@Ag(100), TiO2@Au-Ag(25:75), TiO2@Au-Ag(50:50), TiO2@Au-Ag(75:25), TiO2@Au(100). Photo-deposition of Ag/Au NPs on TiO2, which is limited in literature, was performed to control the size of NPs on TiO2, agreeing with the surface area. The formation of small Ag or AuNPs on TiO2 was obtained through non-epitaxial growth on TiO2NPs. TiO2@Ag/AuNPs, absorbing the visible light and are employed to oxidize tetracycline and analyzed the intermediate formation. Cell images of the samples were explored.

Multiple roles of hydroxylamine for degradation of tetracycline in HA/Fe-Al2O3/O3 process

Hydroxylamine (HA) and a heterogeneous catalyst Fe-Al2O3 prepared by the soak-calcination method were induced in the oxidation of tetracycline (TC) by ozone. The maximum 75.2% removal efficiency of total organic carbon (TOC) was achieved after 30 min of reaction at O3 flow rate 0.2 L/min, HA concentration 0.9 mM, dosage of Fe-Al2O3 6.6 g/L, and initial pH 4.8. The results indicated that TC was mainly degraded by ozone oxidation catalyzed with HA and Fe-Al2O3, where HA played multiple vital roles. HA not only catalyzed the oxidation of ozone, but also reduced Fe(III) to enhance the removal of pollutant. However, HA could also exhibit an inhibiting effect by consuming OH when initial pH was above 4.5. The catalysis of Fe3+/Fe2+, Fe-Al2O3 adsorption, and ozone direct oxidation also contributed to the degradation of TC. The electron paramagnetic resonance (EPR) result showed that OH was the main active substance in the HA/Fe-Al2O3/O3 system. In addition, the possible degradation pathways were proposed. The acute toxicity of wastewater treated with the HA/Fe-Al2O3/O3 system was less than the untreated wastewater. Overall, this study illustrates combination of HA and Fe-Al2O3 to catalyze ozonation is an efficient method to treat antibiotic wastewater.

Photocatalytic oxidation of tetracycline, reduction of hexavalent chromium and hydrogen evolution by Cu2O/g-C3N4 S-scheme photocatalyst: Performance and mechanism insight

An efficient Step-scheme heterojunction of Cu2O/g-C3N4 catalyst was synthesized and used in the degradation of pollutants and energy generation. Among the as-synthesized catalysts, 1-Cu2O/g-C3N4 showed the highest catalytic activity, the photocatalytic reduction efficiency of Cr6+ and the photocatalytic oxidation efficiency of tetracycline (TC) were 77.7% and 95.1%, respectively. The highest H2 production rate for the 1-Cu2O/g-C3N4 sample was 480.6 μmol g−1.h−1, which is 12 times that of a pristine Cu2O sample. The Cu2O/g-C3N4 catalyst showed satisfactory stability and perfect photocatalytic performance, which was attributed to the efficient interfacial charge separation and the formation of Step-scheme heterojunction photocatalyst retaining strong photocatalytic oxidation and reduction capabilities. Importantly, the charge density difference of Cu2O/g-C3N4 composite sample was simulated, which suggestedthat a built-in electric field was formed, it was helpful for fabricating the Step-scheme heterojunction structure between g-C3N4 and Cu2O.

Oxidation of tetracycline antibiotics by peracetic acid: Reaction kinetics, mechanism, and antibacterial activity change

Peracetic acid (PAA) is an emerging oxidant and disinfectant increasingly used in wastewater treatment. Tetracyclines (TCs) are extensively consumed antibiotics, and frequently detected in the wastewater and surface water. Herein, PAA was found to show high reactivity towards TCs for the first time. This reaction follows the second-order kinetics with the rate constant (k2,app) rapidly raised from pH 5 to 7, and then slightly increased to pH 9. Degradation of TCs by PAA was slightly influenced by water components, thus maintaining high efficiency in the real waters. Theoretical calculations revealed the electrons mainly concentrated on the B-ring of TCs, implying the B-ring as the reactive moieties for PAA oxidation. Transformation product analysis confirmed that oxidation of TCs by PAA mainly proceeded via hydroxylation and N-demethylation. Finally, PAA-promoted oxidation could remarkably reduce the antibacterial activity of TCs.