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Facile fabrication of Fe3O4-Biochar hybrid nanomaterials as catalysts for Photo-Fenton degradation of tetracycline
Abstract
In this work, a simple hydrothermal method was designed to prepare Fe3O4/Biochar (Fe3O4/BC) for removing tetracycline (TC) with high efficiency. The material composition and optical properties of the catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the degradation rate of tetracycline was the highest when the material was synthesized at the ratio of 1:1 under the action of UV lamp and C2H2O4 , which could reach 99%. The degradation efficiency of pure BC was only 29%, and the maximum kinetic rate constant was 0.051min−1 , which was 9.27 times than that of pure BC (0.0055min−1). Performance optimization experiments were carried out with initial concentration, pH and other factors, and it can be concluded that the photocatalyst prepared by us greatly improves the degradation efficiency of TC. The current work provides a promising strategy for designing cheap and efficient iron-based photocatalysts that can remove antibiotics from sewage for Fenton catalysis and other environmental applications.
... It is a new and environmentally friendly method of adding Fe 3 O 4 magnetic particles to the reactor for the enhancement of wastewater treatment which has attracted the attention of scholars at home and abroad. Fe 3 O 4 /Biochar (Fe 3 O 4 /BC) prepared by hydrothermal method was found to efficiently remove tetracycline (TC) up to 99%, while the degradation efficiency of pure BC was only 29% [7]. Removal of copper ions from wastewater using Fe 3 O 4 and Fe 3 O 4 -PVP hybrid nanomaterials with a maximum wastewater treatment capacity of 97% for Fe 3 O 4 and 70% for Fe 3 O 4 -PVP [8]. ...
In this paper, a magnetic sequencing batch reactor (SBR) was constructed, and the influence rule of magnetic particle dosing performance of denitrification was investigated. The diversity, structure, and potential functions of the microbial community were comprehensively explored. The results showed that the particle size and the dosage of Fe3O4 magnetic particles were the main parameters affecting the sedimentation performance of activated sludge. The start-up phase of the SBR reactor with Fe3O4 magnetic particles was 5 days less than the control. Moreover, total nitrogen removal efficiency during the start-up phase was improved, with the maximum value reaching 91.93%, surpassing the control by 9.7% with the Fe3O4 dosage of 1.2 g L⁻¹. In addition, the activated sludge concentration and dehydrogenase activity were improved, compared to the control. High-throughput sequencing showed that the denitrifying bacterium Saccharimonadales dominated the reactor and was enriched by magnetic particles. According to predicted functions, the abundance of genes for denitrification increased with the addition of magnetic particles, suggesting the capacity of nitrogen removal was enhanced in the microbial community. Overall, the Fe3O4 magnetic particles provide great potential for enhanced wastewater nitrogen removal.
Graphical Abstract
... Then the reactive OH . converts the organic dye molecule into less harmful by-products like CO 2 and H 2 O [72][73][74][75][76][77][78]. ...
This research presents a comprehensive investigation into the synthesis and application of novel composite photocatalysts, namely Mg0.75Ce0.25Fe12O19@ZIF-67 for the degradation of Rhodamine B (RhB) dye under sunlight irradiation. The synthesis involved the preparation of Mg0.75Ce0.25Fe12O19 and ZIF-67 frameworks, followed by the fabrication of the composite catalyst. Various characterization techniques, such as XRD, SEM, EDX, and FTIR, were employed to assess the structural, morphological, and compositional properties of the synthesized materials. Photocatalytic experiments were conducted to evaluate the efficiency of the catalysts in degrading RhB, revealing remarkable enhancement in degradation efficiency (90%) using the composite photocatalyst compared to individual components. The effects of catalyst type, dosage, and pH on the degradation process were systematically investigated. Furthermore, a proposed mechanism elucidated the role of the Mg0.75Ce0.25Fe12O19@ZIF-67 cocatalyst for RhB degradation under solar light, highlighting the generation of radicals as key contributors for degradation process.
Advanced oxidation processes based on sulfate radical are considered one of the most promising wastewater treatment technologies currently. Among heterogeneous catalysts, cobalt metal–organic framework (MOF) has been widely reported. However, the inherent powder form of MOF hinders its practical application and reusability. Therefore, innovative methods to increase the loading capacity and the accessibility of MOF active sites in monolithic materials are required. Therefore, a simple and scalable method of fabricating a stable, hierarchical porous zeolitic imidazolate framework (ZIF‐67) 3D sponge by growing MOF on a short electrospun fiber network is shown. The sponge can efficiently activate peroxymonosulfate and rapidly degrade an exemplary organic dye (Rhodamine B) with a degradation efficiency of 100%. The resulting multilevel, hierarchical porous structure is beneficial to the mass transfer of reagents making the catalytic process efficient. This also enables the use of the ZIF‐67 as an efficient catalytic filter for continuous removal of dye. The sponge can be recycled and reused for several cycles due to its robustness without loss in efficiency. The proposed research strategy provides a new way to design MOF 3D monolithic materials.
The aim of this study was to determine the toxicity of cefixime in the inlet solution and effluent treated with the sono-electro-Fenton process using standard strains of microorganisms. This research was performed as an experimental study, which was conducted on a laboratory scale. The standard strains of Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) were used for bioassay. First, the stock solution of 1000 mg/L containing Cefixime was prepared, and for each bacterium (gram-positive and gram-negative), 5 samples from the inlet solution of the reactor and 5 samples from effluent treated with the sono-electro-Fenton process were collected under optimal conditions. Finally, each sample was transferred to 10 mL of sterile lactose broth, and a loop of E. coli or S. aureus was dissolved in each sample. Toxicity changes were investigated by calculating the percentage of growth inhibition. The results showed that after 10 hours, the growth rate of both bacteria in the control and the effluent samples was higher, while the growth of bacteria in the inlet solution was lower and had higher toxicity. Based on the results of the study, the toxicity rate for E. coli was reduced from 70% in the inlet solution to 9.3% in the effluent (86.7% reduction in toxicity), and in the case of S. aureus, it was diminished from 25.3% in the inlet solution to 7% in the effluent (72.3% reduction in toxicity) after 10 hours. Based on the results of the present study, bioassay using microorganisms is an effective and useful method to study changes in the toxicity of cefixime.
The aim of the present study was to evaluate the efficiency of advanced oxidation processes (electrochemical, Fenton, and electro-Fenton) in the removal of oxytetracycline antibiotic from aquatic environments using SS316 and SS316/β-PbO2 anodes. This study was performed experimentally on a laboratory scale in a 250-mL reactor. First, experiments were designed for the electrochemical process using a central composite design (CCD), and the optimal conditions for the variables pH (3.53), current density (3.85 mA/cm²), initial concentration of oxytetracycline (20 mg/L), and electrolysis time (42.35 min) were obtained; then, under these conditions, the efficiency of Fenton process with FeSO4 variable without the presence of electrodes was evaluated, and its optimal value was 0.3 g/L, and then in the presence of optimal values of the above four variables, the efficiency of the electro-Fenton process with H2O2 changes was investigated and the optimal value of 0.12 mg/L was obtained for H2O2. The removal efficiencies of oxytetracycline in electrochemical, Fenton, and electro-Fenton processes were 84.7%, 73.4%, and 98.2%, respectively. Under optimal conditions, the SS316/β-PbO2 anode electrode enhanced the oxytetracycline efficiency by electro-Fenton process to 100%. The results of bioassay with microorganisms showed that the reduction of toxicity of the effluent treated by the electro-Fenton process for Pseudomonas aeruginosa and Staphylococcus aureus was 84.5% and 69%, respectively.
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Iron oxychloride (FeOCl) has been reported to be a highly efficient heterogeneous Fenton catalyst over a wide pH range. In order to determine the true catalytic performance of FeOCl, we simultaneously quantified the adsorptive and oxidative removal of formate, oxalate, and rhodamine-B (RhB) and the formation of RhB oxidation products at both pH 4.0 and 7.0. FeOCl was found to be a poor Fenton catalyst at either pH, as gauged by the oxidation of formate, oxalate, and rhodamine B and the decomposition of H2O2, in comparison with ferrihydrite (Fhy), one of the most common Fe-containing Fenton catalysts. The adsorption of target contaminants to FeOCl and homogeneous Fenton processes, induced by dissolved iron, resulted in overevaluation of the catalytic performance of FeOCl, especially for (i) the use of strongly adsorbing target compounds, without consideration of the role of adsorption in their removal and (ii) exceedingly high concentrations of H2O2 to remove trace quantities of target contaminants. Overall, this study highlights that the systematic quantification of H2O2 decomposition, target compound adsorption, and oxidation as well as the concentrations of oxidized products formed are prerequisites for unequivocal elucidation of the catalytic nature and reaction mechanism of solid Fenton catalysts.
We have explored the impact of elevated growth and annealing temperatures on the local interfacial structure of thin Fe(12 nm)/Pt(10 nm) spintronic bilayers, epitaxially grown on MgO (100), and their correlation to magnetization reversal and dynamics. Electron-beam evaporation growth and subsequent annealing at 450 °C causes significant roughening of the MgO/Fe interface with irregular steps and multilevel (100) MgO surface terraces. Consequently, threading dislocations emerging at the step edges propagated in the Fe layer and terminated at the Fe/Pt interface, which appears pitted with pits 1.5–3 nm deep on the Fe side. Most of the pits are filled with the overlying Pt, whereby others by ferrimagnetic Fe3O4, forming nanoparticles that occupy nearly 9% of the Fe/Pt interfacial area. Fe3O4 nanoparticles occur at the termination sites of threading dislocations at the Fe/Pt interface, and their population density is equivalent to the density of threading dislocations in the Fe layer. The morphology of the Fe/Fe3O4/Pt system has a strong impact on the magnetization reversal, enhancing the coercive field and inducing an exchange bias below 200 K. Furthermore, low-temperature spin pumping and inverse spin Hall effect voltage measurements reveal that below their blocking temperature the nanoparticles can influence the spin current transmission and the spin rectification effects.
The global energy demand is projected to rise by almost 28% by 2040 compared to current levels. Biomass is a promising energy source for producing either solid or liquid fuels. Biofuels are alternatives to fossil fuels to reduce anthropogenic greenhouse gas emissions. Nonetheless, policy decisions for biofuels should be based on evidence that biofuels are produced in a sustainable manner. To this end, life cycle assessment (LCA) provides information on environmental impacts associated with biofuel production chains. Here, we review advances in biomass conversion to biofuels and their environmental impact by life cycle assessment. Processes are gasification, combustion, pyrolysis, enzymatic hydrolysis routes and fermentation. Thermochemical processes are classified into low temperature, below 300 °C, and high temperature, higher than 300 °C, i.e. gasification, combustion and pyrolysis. Pyrolysis is promising because it operates at a relatively lower temperature of up to 500 °C, compared to gasification, which operates at 800–1300 °C. We focus on 1) the drawbacks and advantages of the thermochemical and biochemical conversion routes of biomass into various fuels and the possibility of integrating these routes for better process efficiency; 2) methodological approaches and key findings from 40 LCA studies on biomass to biofuel conversion pathways published from 2019 to 2021; and 3) bibliometric trends and knowledge gaps in biomass conversion into biofuels using thermochemical and biochemical routes. The integration of hydrothermal and biochemical routes is promising for the circular economy.
A UV-assisted heterogeneous photo-Fenton process based on powder activated carbon (PAC)/Fe3O4 catalyst was investigated to degrade metronidazole (MTZ). Successful uniform synthesis of PAC/Fe3O4 has confirmed by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive X-Ray spectroscopy mapping (EDX-mapping), vibrating sample magnetometer (VSM), and Fourier transform infrared spectroscopy (FTIR) techniques. The interaction of five independent variables in the MTZ degradation in the UV + PAC/Fe3O4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${P}{A}{C}/{{F}{e}}_{3}{{O}}_{4}$$\end{document}+H2O2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{H}}_{2}{{O}}_{2}$$\end{document} photo-Fenton system was optimized by a three-level full-face-centered central composite design (CCD). Proposed model proved to have adequacy and validity in prediction of MTZ degradation (P value < 0.0001 and R² = 0.9512). Although the desirable pH for MTZ degradation was 3, Fenton-like reaction was ongoing over a wide range of pH. However, at alkaline pH, the process efficiency was more affected by MTZ concentration than acidic pH. MTZ degradation by UV+PAC/Fe3O4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${P}{A}{C}/{{F}{e}}_{3}{{O}}_{4}$$\end{document} + H2O2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{H}}_{2}{{O}}_{2}$$\end{document} heterogeneous Fenton system followed the pseudo-first-order model (R² > 0.95). High stability, reusability, and separation capability of PAC/Fe3O4 were confirmed by EDX and VSM analyses and iron leach investigation. This process could represent the MTZ degradation, DOC, and COD removal efficiencies of 96.12%, 93.67, and 94.87%, respectively. Also, increasing of the AOS value from -0.422 to 0.437 and increasing of the COS value from -0.422 to 3.773 indicate that the MTZ has been highly mineralized and the solution biodegradability has been improved. MTZ degradation intermediates, mechanism, and pathways were proposed. The abundancy of intermediates with m/z < 70 confirmed the strong degradation of MTZ in the photo-Fenton system.
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Correction for ‘Facile preparation of novel quaternary g-C 3 N 4 /Fe 3 O 4 /AgI/Bi 2 S 3 nanocomposites: magnetically separable visible-light-driven photocatalysts with significantly enhanced activity’ by Anise Akhundi et al. , RSC Adv. , 2016, 6 , 106572–106583. DOI: 10.1039/C6RA12414C.
A series of g-C3N4/SrTiO3 (CN/SrTiO3) composites with the different mass ratio of g-C3N4 were prepared by facile in situ hydrothermal growth method, which was utilized to degrade tetracycline antibiotics (TC) under the visible light. The obtained samples were characterized by XRD, SEM, XPS, FT-IR, and UV-vis DRS. The photocatalytic performance was also investigated in detail. The obtained 20% CN/SrTiO3 composite is sixfold of the pure SrTiO3 and twofold of the pristine g-C3N4 under the visible light irradiation. This impressive performance of the heterojunction is ascribed to the effective restraint of the charge carrier recombination and expanded light absorption region. Moreover, the stability of the composite is also researched in detail. At last, a possible photocatalytic mechanism and charge carrier transfer pathway were further discussed.
A novel photo-Fenton catalytic system for the removal of organic pollutants was presented, including the use of photo-Fenton process and a submerged magnetic separation membrane photocatalytic reactor (SMSMPR). We synthesized TiO 2 -Fe 3 O 4 composites as the photocatalyst and made full use of the magnetism of the photocatalyst to realize the recollection of the catalyst from the medium, which is critical to the commercialization of photocatalytic technology for wastewater treatment. The photo-Fenton performance of TiO 2 -Fe 3 O 4 is evaluated with amoxicillin trihydrate (AMX) as a target pollutant. The results indicate that the TiO 2 -Fe 3 O 4 /H 2 O 2 oxidation system shows efficient degradation of AMX. Fe 3 O 4 could not only enhance the heterogeneous Fenton degradation of organic compounds but also allow the photocatalyst to be magnetically separated from treated water. After four reaction cycles, the TiO 2 -Fe 3 O 4 composites still exhibit 85.2% removal efficiency of AMX and show excellent recovery properties. Accordingly, the SMSMPR with the TiO 2 -Fe 3 O 4 composite is a promising way for removing organic pollutants.
The intrinsic peroxidase-like activity of magnetite magnetic nanoparticles (Fe3O4 MNPs) has to be improved to activate H2O2 under mild conditions for practical applications. Herein copper-doped Fe3O4 (Fe3-xCuxO4, x: 0.06-0.23) MNPs were successfully prepared by oxidative precipitation-combined ionothermal synthesis and characterized by XRD, VSM, XPS, BET, etc. The Cu²⁺ dopants are mainly substituted for Fe²⁺ ions at octahedral sites and significantly surface-enriched, which expedite the Fe³⁺/Fe²⁺ redox cycling and enhance the H2O2-activation ability of Fe3-xCuxO4 MNPs. Kinetic study showed that the decomposition of H2O2 on Fe2.88Cu0.12O4 was much faster than that on the undoped Fe3O4 (0.584 vs. 0.153 h⁻¹ at 25 °C) due to the lower activation energy of the former (55.3 vs. 62.1 kJ/mol). The enhanced H2O2-activation ability upon copper doping was exploited to efficiently degrade recalcitrant organic pollutants (e.g., rhodamine B) with H2O2 at pH 7 and 25 °C on Fe2.88Cu0.12O4 with good stability and reusability (16 h tested in eight cycles).
This article aims to analysis high photocatalytic/PMS activation synergy ability of graphitic carbon nitride (g-C3N4) by improving the carriers transfer efficiency and reducing energy band based on controlling the morphology of materials. In this study, tubular g-C3N4 (TCN) with porous structure was prepared by an acid-induced-assembly step and the photocatalysis/PMS activation effects were discussed. Compared with bulk g-C3N4 (BCN), TCN could exhibit enhanced visible light absorption, effectively inhibit electrons and holes recombination in the system, which significantly improved PMS-assisted visible light catalytic efficiency. 97.15% Rhodamine B (RhB) and 62.3% Tetracycline (TC) degradation were achieved within 60 min. In addition, the synergistic effect of PMS activation and TCN photocatalysis has a broad pH application range, which is very beneficial for application in practical aqueous systems. Quenching experiments showed that the synergistic effect of photocatalysis/PMS activation on TCN principally the cause of formating 1O2. Based on the intermediate products detected by liquid chromatography-mass spectrometry (LC-MS) technology, a possible photodegradation pathway of TC was proposed. This paper provides an original perspective to improve carriers transfer and reduce energy band due to conduct the morphology g-C3N4, which could further broaden the applications in the field of environmental governance.
Fabricating highly efficient catalysts for the degradation of persistent antibiotics is challenging. Herein, a series of CuInS2/WO3 hybrid heterostructures with different WO3:CuInS2 weight ratios were fabricated via the in situ growth of CuInS2 nanosheets onto WO3 nanoplates surfaces using a solvothermal reaction. The as-fabricated CuInS2/WO3 hybrid heterostructures were used as S-scheme photocatalysts to remove tetracycline hydrochloride (TCH) from water sources via an efficient photo-Fenton reaction. The phase structures and morphology of the as-fabricated CuInS2/WO3 hybrid heterostructures were systematically characterised using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The experiments performed to evaluate the structure–activity relationship for the CuInS2/WO3 hybrid heterostructures demonstrated that an S-scheme mechanism was critical for the highly efficient photo-Fenton degradation of TCH. Moreover, the S-scheme mechanism of the CuInS2/WO3 hybrid heterostructures was confirmed using active species trapping and electron paramagnetic resonance measurements. We believe that our study provides useful insights for the fabrication of highly efficient photo-Fenton catalysts.
Biogenic manganese oxides (BMO) are widely distributed in groundwater and provides promise for adsorbing and oxidizing a wide range of micropollutants, however, the continuous biodegradation and bioavailability of micropollutants via cycle biogenic Mn(II) oxidation remains to be elucidated. In this study, glyphosate was degraded and to serve as the nutrient source by a Pseudomonas sp. QJX-1. The addition of glyphosate will not affect the Mn(II) oxidation function of the strain but will affect its Mn(II) oxidation process and effect. The glyphosate degradation products could further be used as the C, N and P sources for bacterium growth. Analysis of the RNA-seq data suggested that Mn(II) oxidation driven by oxidoreductases for glyphosate degradation. The long-term column experiments using biological Mn(II) cycling to realize continuous detoxification and metabolism of glyphosate, and thus revealed the synergism effects of biological and chemical conversion on toxic micropollutants and continuous metabolism in an aquatic ecosystem.
Various detection, analysis and remediation methods have been reported for pharmaceuticals and personal care products (PPCPs) in wastewater. In this review, the biotoxicity of PPCPs were briefly introduced. Because of PPCPs’ hazardous to the environment, the enrichment and extraction methods (e.g., solid phase extraction, soxhlet extraction, supercrtical fluid extraction, and microwave assisted extraction) for PPCPs were systematically described. PPCPs analysis technologies (e.g., liquid chromatography-mass spectrometry, gas chromatograph-mass spectrometer, capillary electrophoresis, and sensors) were summarized. The removal performances and mechanisms of PPCPs through different electrochemical treatment approaches (e.g., electro-Fenton, photoelectrocatalytic degradation, and electrochemical membrane bioreactor) were critically analyzed and discussed. Finally, the concluding remarks and suggestions for future researches concerning the topic of PPCPs detection, analysis, and electrochemical treatments were proposed. This work could provide an overview for the detection/analysis techniques and electrochemical treatments of PPCPs from wastewater.
In the present study, Ni-doped BiFeO3 (BiFe1-xNixO3, marked as BFNO, x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) visible light photocatalytic materials were prepared by sol-gel method. It is found that Ni doping could make the BiFeO3 absorption band red-shifted, enhance the absorption of visible light and reduce the bandgap. The photogenerated electron-hole complex of the material was effectively suppressed after Ni doping. Meanwhile, the magnetic measurements indicated that Ni doping could significantly enhance the saturation magnetization of BiFeO3, and the saturation magnetization of the materials increased exponentially with the increase of Ni doping. The photo-Fenton degradation performance of BFNO on tetracycline (TC) was investigated under visible light exposure. It was found that BFNO-8 (BiFe1-xNixO3, x = 0.08) was an effective catalyst for the degradation of TC, and the addition of 4 mmol/L H2O2 and 0.7 g/L of BFNO-8 could improve the degradation rate of TC to 96% within 120 min. The photocatalytic performance of BFNO-8 was so stable that it maintained a high degradation rate of TC even after 4 reuse times. Based on the radical capture experiments and electron paramagnetic resonance (EPR) results, the possible reaction mechanism of TC degradation by BFNO-8 was speculated to be that photocatalysis accelerated the Fe²⁺/Fe³⁺ recycling, formed the electron capture center, and accelerated the effective decomposition of H2O2.
This paper aims to investigate hydroxylamine activated by discharge plasma for tetracycline degradation in water. Results indicated that hydroxylamine can be activated by discharge plasma successfully, and promoted tetracycline degradation. The degradation efficiency of tetracycline by discharge plasma could improve from 70.7% to 90.0% with 0.25 mmol/L hydroxylamine. The energy efficiency (G50) could enhance from 2.28 g/kWh to 3.18 g/kWh, respectively. Synergetic effect could be generated between discharge plasma and hydroxylamine. Ozone and electrons produced by plasma can interact with hydroxylamine to produce more •OH. Capture agent experiment and ESR technique verified that •OH, O2•⁻, ¹O2 and electrons all participated in tetracycline degradation in plasma/hydroxylamine system. The degradation process was investigated thoroughly based on three dimensional fluorescence, LC-MS and DFT analysis, and two main pathways were proposed. Enhancing applied voltage was beneficial to the degradation of tetracycline. Higher degradation efficiency of tetracycline was obtained at lower initial concentration. Compared with acidic condition, alkaline condition was conducive to the decomposition of tetracycline. The addition of hydroxylamine in plasma system promoted the mineralization of tetracycline. Overall, the plasma/hydroxylamine method can be considered as a preferable potential option for the reduction of tetracycline in water.
In this study, a matrix composite material of CdZnS and α-FeOOH on carbon cloth ([email protected]@CC) was prepared by a hydrothermal method, and was used for the degradation of As(III). The composite material has good photocatalytic activity of removing As(III) in the presence of oxalate. [email protected]@CC can completely degrade 10 mg/L As(III) within 10 min under visible light irradiation. The influence factors of [email protected]@CC composite material on catalytic oxidation of As(III) were also studied in the oxalate system. The photocatalytic oxidation efficiency of As(III) is affected by the oxalate concentration in the reaction system, and the atmosphere plays a major role in the degradation of As(III). Under visible light, oxalate first combines with Fe(III) on the surface of iron oxide to form Fe(III)-oxalate complex, and then the Fe(III)-oxalate composite is activated to produce ·C2O4⁻. In the presence of oxygen, Fe(II) readily reacts with O2 and oxidizes to Fe(III). The introduction of CdZnS promoted the separation of interfacial electron holes, and accelerated the REDOX cycle of Fe(II)/Fe(III). This study provides a feasible and simple method for accelerating the catalytic removal of heavy metals from wastewater by iron-based materials.
Upcycling waste plastics into advanced semiconductor photocatalysts provides a new strategy to reasonably and economically solve the huge amount of waste plastics, which however remains challenging. Herein, we synthesize carbon nitride‐based donor‐acceptor (D‐A) conjugated copolymer by copolymerization of dicyandiamide and terephthalic acid from discarded polyethylene terephthalate (PET) using Zn(OH)2 as catalyst and template at 360–440°C. The morphology and structure of the conjugated copolymer are well regulated by the calcination temperature. The resultant conjugated copolymer exhibits merits of high light absorption and low electron‐hole recombination probability. Consequently, it works excellently in the persulfate‐based advanced oxidation process for visible light‐driven photocatalytic degradation of tetracycline. The kinetic constant (3.4 × 10−2 min−1) is 40.5 and 2.3 times that of the conjugated copolymer system and persulfate system, respectively. Furthermore, the reactive species (including •OH, SO4•−, •O2−, 1O2 and h+) and degradation intermediates of tetracycline are analyzed to expound its degradation process. This work not only pioneers design guidelines on upcycling of waste plastics in a sustainable manner, but also provides a facile strategy to synthesize carbon nitride‐based D‐A conjugated copolymers for the efficient activation of persulfate‐based advanced oxidation process in wastewater treatment. This article is protected by copyright. All rights reserved
Upsurge in the usage of antibiotics in medical treatment has led to their spikes in water bodies, including drinking water causing health concerns. Here, we report a very efficient method of photocatalytic degradation of tetracycline antibiotic in an aqueous medium using 0.10ZnWO4/Bi2MoO6 nanocomposites as Z-scheme heterojunction based solar photocatalyst. The structure, composition, and morphology of the photocatalyst have been thoroughly characterized. The photocatalytic degradation of tetracycline is initiated by spiking a trace quantity of hydrogen peroxide (H2O2) in the reaction medium. Compared to pristine Bi2MoO6 photocatalyst, the photocatalytic degradation of tetracycline by 0.10ZnWO4/Bi2MoO6 nanocomposites is 5.3 times enhanced. This is attributed to improved inhibition of charge carrier recombination owing to the Z-scheme heterojunction formed in 0.10 ZnWO4/Bi2MoO6 and due to better charge carrier mobility. More than 95% of tetracycline is degraded in 90 min, corresponding to a photocatalytic degradation rate of 0.123 L mg−1 min−1. The total organic carbon analysis suggested 66.4% mineralization of TC. The generation of reactive oxygen species (ROS), e.g., hydroxyl radicals, superoxide radicals, and their role towards photocatalytic degradation of tetracycline is confirmed by showing negative results in the presence of ROS scavengers. The sustained generation of H2O2 in the reaction medium is discussed. The degradation mechanism has been discussed by analyzing the degradation products via coupled ultra-performance liquid chromatography to quadrupole time-of-flight mass spectrometry technique (UPLC–Q-Tof–MS).
The development of metal–organic frameworks (MOFs) as a nanoplatform for emerging antibacterial agents has gained great attention. In this work, TiO2 nanoparticles in-situ incorporated in zeolitic imidazolate framework-L (ZIF-L) successfully grow on the non-textile fabric substrate as a novel antibacterial composite [email protected]2/fabric with improved visible-light driven antibacterial activity. The morphology and composition of the as-prepared antibacterial composite are characterized via SEM, TEM, XRD, and XPS analysis. The material with high light use efficiency can generate more reactive oxygen species (ROS) under light irradiation than that in dark, which suggests the synergistic effect between TiO2 nanoparticles and ZIF-L in the visible region. Correspondingly, [email protected]2/fabric exhibits outstanding antibacterial effect against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which can also be verified by the Leica SP5 laser scanning confocal microscope (LSCM) results. Furthermore, the possible antibacterial mechanism is proposed. Under visible light irradiation, the synergy of TiO2 nanoparticles and ZIF-L is in favor of producing hydroxyl radical (·OH) and superoxide radicals (·O2⁻) that directly leads to the death of bacteria. The sufficient antibacterial activity of [email protected]2/fabric (over 95% after six antibacterial assay cycles) ensures the long-term use of the material. At this point, the newly synthesized material gives new sight on preparing other MOFs based composites with photocatalytic antibacterial effect for bacterial issues.
Zero waste multistage utilization of biomass from Ginkgo biloba branches (GBBs) was achieved through extraction of bioactive components, analysis of antioxidant and antibacterial activities, preparation and composition of pyrolyzate, adsorption and reuse of modified biochar. The results showed that GBBs had abundant bioactive components for potential application in the industry of food, chemical raw materials and biomedicine. Especially, the bioactive compounds in acetone extract (10 mg/mL) of GBBs identified by DPPH and ABTS had free radical scavenging abilities of 92.28% and 98.18%, respectively, which are equivalent to vitamin C used as an antioxidant in food additives. Fourier Transform Infrared and X-Ray Diffraction analysis showed that carboxymethyl cellulose (CMC) and magnetic Fe3O4 were successfully incorporated into raw biochar (RB) to form CMC-Fe3O4-RB nanomaterial. Scanning electron microscopy and X-Ray Diffraction spectroscopy displayed Fe, C, and O existed on the surface of CMC-Fe3O4-RB. Compared with RB, CMC-Fe3O4-RB had a larger specific surface area, pore volume and pore size. Meanwhile, nanomagnetic CMC-Fe3O4-RB solved the problem of agglomeration in traditional magnetized biochar production, and improved the adsorption capacity of Pb²⁺, which was 29.90% higher than that of RB by ICP-OES. Further, the Pb²⁺ (10 mg/L) adsorption capacity of CMC-Fe3O4-RB reached the highest level in 2 h at the dosage of 0.01 g/L, and remained stable at 52.987 mg/g after five cycles of adsorption and desorption. This research aided in the creation of a strategy for GBBs zero waste multistage usage and a circular economic model for GBBs industry development, which can be promoted and applied to the fields of food industry and environment improvement.
The aim of this study was to synthesize activated carbon from low-cost material and then magnetize it with CoFe2O4 nanoparticles for evaluating its efficiency in the removal of cephalexin from aqueous media. The physical and structural properties of the synthesized adsorbent were analyzed by SEM, BET, XRD, and VSM techniques. In addition, the effect of parameters, including pH, the concentration of cephalexin, adsorbent dose, and contact time, were studied to determine the equilibrium adsorption process isotherms and kinetics. The results of this study showed that the removal efficiency of cephalexin increases with increasing contact time and adsorbent dose and decreases with increasing pH and the initial concentration of cephalexin. As the concentration of antibiotics increased from 50 to 250 mg/L, the removal efficiency of cephalexin decreased from 96.8% to 36.1%. Optimal conditions for cephalexin removal were obtained at pH = 3, time = 30 min, antibiotics concentration = 50 mg/L, and adsorbent dose = 2 g/L. Cephalexin antibiotic adsorption process follows the Freundlich isotherm (R² = 0.9817) and pseudo second-order kinetics (R² = 0.939). Although the removal of cephalexin increases with increasing adsorbent dose, the amount of cephalexin adsorbed per unit mass of adsorbent (qe) decreases from 27.5 to 18.3 mg/g from 0.25 to 2.5 g/L of activated carbon. The present study showed that magnetized low-cost material activated carbon, in addition to having properties such as rapid and easy separation, has a high potential for cephalexin adsorption.
Despite advancements in biomedical sciences and medicine, bacterial infection remains a leading cause of death globally. The conventional treatment of bacterial infections through general administration of antibiotics has been challenged by the emergence of antibiotics resistance. An exciting direction to solve current challenges that attracted enormous interest in the last decade is focused on designing stimuli-responsive systems incorporating a wide range of antimicrobial nanomaterials. The aim of this review is to highlight fundamental principles involved in the design of bacteria-responsive nanosystems that release their antibacterial load in response only to the specific environment and factors produced endogenously by bacteria. Such specific changes to the micro-environment include changes in pH, reactive oxygen species, and production of enzymes specific to bacteria. We provide examples and a critical review of such systems and finish with the authors’ perspective for the future of the field.
The reduced S-modified MIL-53(Fe) was prepared by sulfurizing MIL-53(Fe) at low temperature, which was an efficient electro-Fenton catalyst at wide pH range (3-9) for sulfamethazine (SMT) degradation. The best temperature and MIL-53(Fe)/S ratio were 350 °C and 1:2, at which the BET surface area was much enlarged. The MIL-53(Fe) surface was etched by S to many 2D nanosheets with the thickness of ~50 nm, while S2-2 replaced OH⁻ to coordinate with Fe²⁺ and increased the Fe²⁺ content, which improved the catalytic performance. Even at initial pH of 7.0, the SMT removal was 95.8%, and the rate constant (k) in the Hetero-EF process was 16-folds of that in the Homo-EF process. The turnover frequency (TOFd) value of MIL-53(Fe)/S(1:2)-350 was 0.48 L g⁻¹ min⁻¹, which was 6.8 times that of commercial FeS2. The S2-2in catalyst adjusted the pH superfast, and promoted the generation of Fe²⁺ and thus efficiently activating H2O2 to form surface ·OH, which was verified to be the main radical by EPR and radical scavenger experiments. This catalyst showed promising prospect for environmental application and could be regenerated by sulfidation method. S-doped MIL-53(Fe) was an excellent pH regulator, thus promoting promising application in Hetero-EF processes.
Naphthenic acids (NAs) are a mixture of aliphatic and alicyclic carboxylic acids which are persistent in the environment. In this study, a sludge-based biochar/iron oxide (B-FeOx) catalyst with 3D flower-like shaped structure was prepared through a facile hydrothermal method. For the first time, the B-FeOx catalyst was employed to activate peroxymonosulfate (PMS) for the removal of two model NA compounds (1-adamantanecarboxylic acid (ACA) and 4-methylheptanoic acid) at pH 8.50. Compared to biochar or FeOx alone, a higher degradation efficiency (96.1%) and faster degradation rate (k = 0.100 min⁻¹) of ACA were obtained by the B-FeOx composite at a catalyst dose of 2.0 g/L and PMS dose of 2.5 mM. The higher degradation efficiency of B-FeOx was attributed to the improved surface area and pore volume as well as the abundant reactive sites induced by the flower-like structure. Furthermore, the hydroxyl radical (•OH) generated in the B-FeOx/PMS system was the dominant radical for both ACA and 4-methylheptanoic acid degradation as demonstrated through radical quenching experiments. The presence of chloride ions in the B-FeOx/PMS system showed a suppression effect on the degradation of ACA and 4-methylheptanoic acid at Cl⁻ concentrations between 5 and 20 mM. No significant difference in the degradation rates of ACA and 4-methylheptanoic acid was observed at different Cl⁻ concentrations. Overall, the results of this study showed that the sludge (waste material)-based B-FeOx composite may have the potential to be utilized as PMS catalyst for the removal of NAs that are especially abundant in oil sands process water.
Antibiotics resistance genes (ARGs) in concurrence with antibiotic resistant bacteria (ARB) have been identified globally as contaminants that threatens public health. These contaminants enter into wastewater treatment plants through different channels such as hospital, domestic, pharmaceutical, and agricultural activities. These channels are responsible for disseminating antibiotic resistance genes among the non-resistant bacteria by horizontal gene transfer, making wastewater a hotspot for ARB/ARGs. Conventional and advanced treatment processes have been widely used to mitigate or minimize conjugative gene transfer risk. Application of these processes alone can successfully inactivate ARB during the treatment process, but there is a possibility that the existing ARGs present in the cell debris could still confer resistance through transformation and transduction without live donor cells. Also, most of the disinfection/treatment processes may enrich ARB and ARGs' concentration in the long run. As a result of these drawbacks, systematic mechanisms that would effectively remove bacteria DNA and inactivate ARB may provide a solution that would enable the public to access effluents free from ARGs. This review provides concise information on the commonly used antibiotics, their abundance in wastewater and natural waters, coupled with available technologies for their removal from water and wastewater, which may minimize the risk of accessing ARGs contaminated water. Therefore, the adoption of these well-detailed technologies may be a promising way that would stop ARG proliferation.
The potential of green nanomaterials for environmental and agricultural fields is emerging due to their biocompatible, eco-friendly, and cost-effective performance. We report the use of Canna indica flowers extract as new capping and stabilizing source to bio-fabricate ZnO nanoparticles (ZnO NPs for dyes removal, seed germination. ZnO NPs was biosynthesized by ultrasound-assisted alkaline-free route to reach the critical green strategy. The physicochemical findings of ZnO revealed small crystallite size (27.82 nm), sufficient band-gap energy (3.08 eV), and diverse functional groups. Minimum‑run resolution IV approach found the most pivotal factors influencing on removal of Coomassie Brilliant Blue G-250. Uptake studies pointed out that pseudo second-order, and Langmuir were the best fitted models. Dye molecules behaved monolayer adsorption on ZnO surface layers, and controlled by chemisorption. Natural solar light was used as effective source for photocatalytic degradation of methylene blue (94.23% of removal and 31.09 mg/g of uptake capacity). Compared with H2O and ZnSO4, ZnO NPs positively affected the growth of shoot and root lengths (10.2–27.8%) of bean seedlings in most cases. ZnO acts an agrochemical for boosting weight gain, and germination ratio. This study may be promising for developing the recyclable, multifunctional ZnO nanoparticles for environmental and agricultural applications.
A highly active mediator (magnetic [email protected], MFB) for peroxymonosulfate (PMS) activation was prepared by employing FeSO4·7H2O and poplar sawdust as the precursor, for pesticides remediation in soil and groundwater. The magnetic [email protected] prepared at 500°C (MFB-500) did not only showed good performance in activating PMS to degrade 2,4-dichlorophenoxyacetic acid (2,4-D), but also longer lifetime. Due to the introduction of FeS, the defect degree of MFB-500 was higher according to Raman spectra result and favored in PMS activation. The X-ray photoelectron spectroscopy (XPS) and Mössbauer spectra confirmed that sulfur species promoted the regeneration of Fe(II). Moreover, EPFRs also showed an electron shuttle to enhance the recycle of Fe(II)/Fe(III) and increased the PMS activation performance. Electron paramagnetic resonance (EPR) spectroscopy identified SO4•-, •OH and ¹O2 as the reactive oxygen species (ROS) in 2,4-D degradation. The optimized reaction parameters of MFB-500/PMS were determined as [MFB-500] = 700 mg/L, [PMS] = 2.6 mM, [2,4-D] = 0.045 mM. Meanwhile, the interfacial adsorption and catalytic reaction of 2,4-D degradation by MFB-500/PMS is accurately described by a newly mixed order kinetics model with adsorption and decay dominant rate constants kα and kγ, respectively. The effect of pH0 and coexisting anions was also studied, and it was found that acidic conditions are conducive to the degradation of 2,4-D, while alkaline conditions inhibited. Cl⁻, NO3⁻ and SO4²⁻ play a slight inhibitory effect, and HCO3⁻ and H2PO4⁻ will play a significant inhibitory effect. This work provides a promising approach to the rational design of high-performance active mediators for environmental remediation.
Diverse antibiotic drugs have been used for the treatment of bacterial infections; however, their overuse, improper handling, and limitations in treatment facilities can result in their accumulation and biotransformation in the water systems. These bio-accumulated antibiotics can lead to more detrimental effects due to the emergence of multi-resistant bacterial genes at the micro-level, which in turn enhance the chances of bacterial survival.
The current review discusses the prevalence of this contaminant in India and different countries around the globe. Since prevention of antibiotic release is the most effective strategy for controlling water pollution, the importance of several governing bodies and their guidelines for antibiotic use and release have been discussed. As a solution to the increasing threat of antibiotics in treated wastewater and natural waters, various treatment strategies have been explored, of which photocatalytic degradation is one of the significant treatment options. In particular, the review focuses on the multiple approaches of photocatalytic degradation in a stand-alone system and in combination with other techniques and nanomaterials. Different photo-active materials, reactor systems, oxide molecular release, kinetic mechanisms, influence of different parameters and characterizations involved have been discussed in detail in order to understand the optimum conditions for photocatalytic degradation of antibiotics.
Climate change, global warming, and population growth have led researchers to use eco-sociable procedures for the N2 reduction reaction. It has discovered that N2 molecule can be transformed into NH3 in ambient circumstances with nanocomposites upon visible irradiation. In this research paper, a new visible-light-driven photocatalyst was constructed, with various weight percents of FeOCl particles (10, 20, 30, and 40%) that have adhered on NS-CN. Subsequently, multiple features of the nanocomposites were assayed in detail. The results illustrated that the NS-CN/FeOCl (20%) system has remarkable photoactivity in the NH4+ production reaction in comparison with the NS-CN and CN, which showed 2.5 and 8.6 higher activity, respectively. The durability of NS-CN/FeOCl (20%) system, as a substantial factor, was assayed for 5 recycles. Moreover, the effect of electron quenchers, pH of media, and solvent was studied. At last, a feasible Z-scheme mechanism for the remarkable improvement of N2 fixation efficiency was offered.
As an emerging semiconductor different from regular white TiO2, black TiO2 has attracted intensive attention on visible light driven photocatalysis for degrading dyes, but rarely for degradation of antibiotics. In this study, black anatase-TiO2 was demonstrated to be an effective catalyst for tetracycline (TC) visible light photodegradation. 66.2% removal efficiency of TC was achieved over black TiO2 under visible light illumination, while white TiO2 and N-doped TiO2 exhibited 43.4% and 59.6% removal efficiencies, respectively. Furthermore, only ∙O- 2 radicals played an important role in TC photodegradation over white TiO2, whereas both ∙O- 2 and h⁺ were responsible for the degradation over black TiO2 and N-doped TiO2. Different from white TiO2 for visible light photocatalytic TC degradation that follows photosensitization, the visible light photodegrataion over black TiO2 is due to photoexcitation.
The present work reported the utilization of Fe3O4@C nanocomposite for removing a series of six organic dyes from aqueous solutions and dealing with simulated hospital effluents. Single-step fabrication of magnetic Fe3O4@C nanocomposite was facilely performed at 500°C. This material was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Core–shell Fe3O4 NPs (∼ 40 nm in average size) were dispersed well and encapsulated by ultrathin carbon coatings with the thickness of 4-5 nm. Fe3O4@C nanocomposite owned surface functional groups important for dyes adsorption. The adsorption results showed that maximum adsorption capacity values of organic dyes on Fe3O4@C obeyed an order as follows: methyl orange (38.03 mg/g) < rhodamine B (87.32 mg/g) < methylene blue (95.61 mg/g) < methyl red (153.1 mg/g) < congo red (165.3 mg/g) < crystal violet (181.6 mg/g). Two simulated hospital effluents could also be treated from 63.6–84.5% using this nanocomposite. In addition, Fe3O4@C could be reused up to 5 cycles without considerable decrease in uptake capacity.
The occurrence of antibiotics in the ambient environment has raised serious concerns. In this work, the kinetics and mechanism of photocatalytic degradation tetracycline (TC) was investigated using three-dimensional network structure perylene diimide supramolecular organic photocatalyst (3D-PDI). Under visible-light irradiation, 3D-PDI exhibited excellent degradation performance and stability for several tetracycline-based antibiotics (e.g., tetracycline; chlortetracycline; oxytetracycline.). The adsorption and degradation rate of TC by 3D-PDI were 8.21 and 12.7 times higher than that of bulk-PDI. The enhanced adsorption and degradation performance of TC by 3D-PDI were mainly due to the larger specific surface area and π-electron conjugation of 3D network supramolecular system. Superoxide radical (O2⁻), hydrogen peroxide (H2O2) and hole (h⁺) the main reactive species (RSs) for TC degradation. Under the attack of photocatalytic RSs, TC undergoes hydroxylation, demethylation, aromatization, and ring-opening processes, and finally complete mineralization into CO2 and H2O. These results revealed that perylene diimide supramolecular photocatalyst may be efficiently applied for the remediation of tetracycline contaminated natural waters.
To develop a photocatalyst with novel structure and high performance, a Z-scheme AgSCN/AgCl/FeOCl heterojunction has been successfully prepared by the in-situ synthesis and anion exchange method for the first time. The photocatalytic activity and photo-Fenton catalytic activity of the AgSCN/AgCl/FeOCl nanosheets for the degradation of ibuprofen are 40.7 times and 4.1 times higher than that of FeOCl, respectively. The interfacial structure of the AgSCN/AgCl/FeOCl heterojunction photocatalyst accelerated the separation of the photogenerated electron-hole pairs. The core-shell structure of AgSCN/AgCl effectively suppressed the photocorrosion. This study provides a new approach to the rational design of photocatalysts for emerging environmental applications.
Ag/g-C3N4 plasmonic photocatalysts with porous structure (Ag/PCN) were successfully synthesized via a thermal exfoliation strategy and photo-reduction method. Owing to the combined merits of porous structure and surface plasmon resonance effect of silver nanoparticles, the Ag/PCN catalysts exhibited excellent photocatalytic performance for the degradation of antibiotic agents. With the optimal Ag loading, the Ag/PCN-2 catalyst exhibited the optimal catalytic activity for TC degradation under visible light, which shows about 11.8 times enhancement in the photocatalytic removal efficiency as compared to pure g-C3N4, respectively. This phenomenon can be attributed to the increased specific surface area, broadened visible light absorption and improved charge separation. The radical quenching results confirmed that h⁺ and ·O2⁻ radicals were the major active species during removal of TC. The degradation of TC is increased with the increment of Ag/PCN-2 catalysts, and the optimum catalyst was found to be 1.67 g/L. The hindering effect of selected of anions (Cl⁻, CO3⁻, H2PO4⁻) was found to follow the order H2PO4⁻ > CO3⁻ > Cl⁻. Ag/PCN-2 sample also possessed high stability after six cycles of reuses. Furthermore, the possible degradation pathways of TC and photocatalytic mechanism over Ag/PCN-2 were proposed in detail.
In recent years, the application of algae and metal oxides to treat heavy metal wastewaters has attracted considerable attention. However, algae are difficult to recover due to their low density, which will cause secondary pollution and limit its development in the treatment process. In this paper, metal oxide (Fe2O3) as an adsorptive material is used to form a composite material with algae, which not only can achieve the purpose of immobilizing microalgae but can also improve the adsorption effect. We controlled the synthesis temperature of the Fe2O3 to reach a good immobilization effect for microalgae, and the adsorption capacity of the composite material (Fe2O3@Microalgae) was tested. The results showed that the adsorption of Fe2O3@Microalgae for Cr(VI), Cu(II), Pb(II) and Cd(II) followed the pseudo second-order model (R ² > 0.99). The equilibrium data of Fe2O3@Microalgae agreed well with the Langmuir adsorption isotherm model and the maximum adsorption capacity of Fe2O3@Microalgae was higher than that of microalgae or commercial Fe2O3 alone. The adsorption capacity for metal ions can be ranked in the following order: Cr(VI) (69.77 mg/g) > Pb(II) (62.63 mg/g) > Cd(II) (42.12 mg/g) > Cu(II) (38.68 mg/g). Functional groups, such as OH and COOH on the adsorbent surface, were involved in the adsorption process. Therefore, Fe2O3@Microalgae not only achieved the purpose of immobilizing microalgae, but also combined the material with the biosorbent, thereby enhancing the adsorption effect. The biocomposite is thus has potential as an adsorbent for sewage treatment.
Nowadays, the presence of antibiotics in the environment has been identified as an important concern for the various life cycle. Thus, this study was conducted to evaluate ciprofloxacin (CIP) adsorption efficiency onto the multi-walled carbon nanotube (MWCNTs) and magnetic multi-walled carbon nanotube (MMWCNTs). In this experimental study, the characteristics of the studied adsorbents were determined using SEM, FTIR and XRD methods. The effects of operational parameters including contact time (10–120 min), initial concentration of CIP (10–100 mg/L), adsorbent dosage (0.1–1 g/L) and pH (3–9) were evaluated. The isotherm and kinetics studies of the CIP adsorption onto the studied adsorbents were also carried out. The adsorption efficiency increases by increasing the contact time and adsorbent dosage, while it increased by increasing the CIP initial concentration. The results showed that higher CIP adsorption efficiency was observed at pH = 7, adsorbent dosage of 0.5 g/L, CIP concentration of 30 mg/L and contact time of 120 min. The isotherm and kinetics studies revealed that the CIP adsorption data were better described by the Langmuir isotherm model and pseudo-second-order kinetics equation model. It can be concluded that both of these adsorbents have suitable potential to remove the CIP from aqueous solution but this ability is greater in MMWCNTs.
In this work, corn straw (CS) based porous carbon was prepared by one-step phosphoric acid (H3PO4) low temperature activation. The impregnation ratios (H3PO4/CS, g/g) played an important role in the pore development. ACS300-1 engineered at 300 °C and the impregnation ratio of 1.0 showed the maximal specific surface area of 463.89 m2/g with total pore volume of 0.387 cm3/g, attaining a high tetracycline (TC) uptake of 227.3 mg/g. The adsorption of TC onto ACS300-1 was found tolerant with wide pH (2.0-10.0) and high ionic strength (0 - 0.5 M). The adsorption data can be fitted well by the pseudo-second order kinetic model and Langmuir isotherm model. The endothermic and spontaneous properties of the adsorption system was implied by Thermodynamic study. The findings of the current work conclude that one-step H3PO4 activation is a green and promising method for corn straw based porous carbon that may be found with great potentials in antibiotic containing wastewater treatment.
A high-efficiency hollow BiOCl@CeO2 heterostructured microspheres with type-II staggered-gap type was successfully synthesized by precipitation-hydrothermal process loaded with BiOCl nanoparticles on CeO2 microspheres. XRD, FT-IR, EDS, SEM, HRTEM and XPS results show that the prepared materials have good crystallization, morphology and retain hollow spherical structure of CeO2. Batch experiments indicate that the photocatalytic performance of BiOCl@CeO2 towards Tetracycline (TC) is superior to pure BiOCl or CeO2 owing to the distinctive hollow structures and the formed heterostructure between BiOCl and CeO2. Cyclic experiment exhibits that the optimal BiOCl@CeO2 photocatalyst can still photodegrade more than 80% of TC in 120 min after 4 cycles. Additionally, the reactive oxidation species (ROS) trapping experiments reveal that the critical ROS include photogenerated holes (h+) and superoxide radical anions (O2-). Finally, the possible degradation pathways of TC and enhanced photodegradation mechanism was systematically discussed. On this basis, the hollow BiOCl@CeO2 heterostructured microspheres provide a new alternative with great potential in efficient visible-light-driven photodegradation of persistent organic pollutants.
Constructing homojunction is more favorable to transfer and separation of charge carriers at the interface between structural units owing to the matching chemical and electronic structures, nevertheless it still is difficult to fabricate the morphology-controlled nonmetal homojunction. Herein, a nonmetal 2D/3D homojunction is constructed via the facile surface in-situ polymerization process, where 3D g-C3N4 (3D CC) microspheres tightly anchor on the surface of 2D g-C3N4 (2D CN) nanosheets. The obtained nonmetal 2D/3D CN/CC homojunction displays the dramatically enhanced photocatalytic performance for degrading tetracycline hydrochloride (TC-HCl) compared with single 2D CN nanosheets and 3D CC microspheres, mainly attributing to the improved transfer and separation efficiency of charge carriers resulted from synergetic effect of 2D-3D structural coupling and energy band controlling. Moreover, the important degradation pathway, intermediate products and photocatalytic mechanism are investigated in detail. This work develops a feasible exemplificative strategy for fabricating new morphology-controlled nonmetal homojunction to improve photocatalytic activity.
Antibiotics wastewater poses a major threat to the global environment and human health. In this work, red mud (RM) and modified RM (after calcination treatment), as industrial solid wastes discharged from the aluminum industry, were used as effective photocatalysts for removal of tetracycline (TC) from water under visible light irradiation. The results showed that the photocatalytic degradation activity of modified RM on TC was obviously better than that of original RM (RM-raw). Furthermore, RM-350 (calcination temperature is 350 °C) exhibits the best photocatalytic performance (100 mL, 10 mg/L; 88.4% degradation of TC within 80 min) under visible light as well as outstanding stability after three reaction cycles. The improvement in photocatalytic performance by modified RM is mainly due to an increase in specific surface area and crystallinity, which is benefit for promoting adsorption of organic pollutants and accelerating photo-induced charges. The effects of catalyst dosage and initial concentration on the catalytic degradation of TC were studied. Our work has proved that RM is a novel low-cost photocatalyst, which not only provides a useful solution for the reuse of RM, but also plays an important role in environmental protection.
Antibiotic residues are widespread in the environment and their presence is known to contribute to the propagation of antibiotic resistance. Nevertheless, knowledge on processes involved in their degradation is scattered. This second part of a two part review aims at compiling knowledge on the (bio-) degradation of antibiotics, focusing on β-lactams, macrolides, quinolones and ionophores, as well as some less common classes. Detailed metabolic and molecular aspects are discussed, as well as the role of antibiotic degraders in natural microbial communities. This exercise led to the conclusion that among the classes analyzed, the majority of antibiotics are prone to microbial cleavage or transformation.
Antibiotics are non-biodegradable and can remain for a long time at aquatic environments and they have a big potential bio-accumulation in the environment. The antibiotics are broadly metabolized by humans, animals and plants and they or their metabolites, after metabolization, are entered into the aquatic environment. This study aimed to optimize the operational parameters by Taguchi design and to carry out the kinetic studies for removal of cephalexin antibiotic from aqueous solutions by US/H2O2/NiO hybrid process. This experimental study was performed on a laboratory scale in a 500 mL pyrex-made reactor. The main operational parameters to influence the US/H2O2/NiO process were identified as the initial concentration of CEX (20–80 mg/L), hydrogen peroxide (H2O2) (10–40 mL/L), NiO nanoparticle (2.5–10 mg/L) and reaction time (15–90 min) and therefore, the influence of these factors were studied. Under optimum conditions (pH = 3, reaction time = 90 min, CEX = 40 mg/L, NiO = 7.5 mg/L and H2O2 = 30 mL/L) and using the US/H2O2/NiO process, the removal efficiencies of CEX, COD and TOC were 93.86%, 72.46% and 54.55%, respectively. The percentage contribution of each factor was also determined. Results introduced the solution pH as the most powerful factor, and its percentage contribution value was up to 94% in the studied process. It was also identified that the removal of CEX antibiotic using the hybrid process obeys the pseudo-first-order kinetics.
Deep eutectic solvents (DES), prepared from choline chloride (ChCl) compound as hydrogen bond acceptor and lactic acid (LA), oxalic acid (OA), potassium hydroxide or urea (UA) as the electrostatic attracting donors in different amount ratios, were synthetized, applied and studied for lignocellulosic biomass fractionation. The mixtures of ChCl with OA or KOH were found to dissolve beech wood polymers more effectively compared to ChCl with LA or UA. In addition to DES screening test experiments, the influences of the process performance parameters, like measurement reaction time (2–24 h), temperature (60–100 °C) and the chip to solution mass relationship (1:100–1:10), on particle size distribution, solid residue's properties, functional cellulose, hemicellulose and lignin contents, the concentration of sugars, polyphenolics and volatile chemical products in raw liquid extract, as well as kinetics were experimentally determined. The further spectroscopic, microscopic and chromatographic analysis of solubilisation demonstrated that ChCl with OA selectively isolated phenols, could potentially be scalable and could be utilized in lignin-first bio-refinery plant. Purified cellulose-rich material was obtained, according to attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), while polyphenols were above 15 g L−1 (gallic acid equivalent, examined by Folin–Ciocalteu method), revealing predominant dissolution. Conversely, for ChCl with KOH, aromatics were below detection limit value, while polysaccharides dropped for a factor of 10, paralleled to sawdust's fresh sample. The DES recovery by centrifugation, anti-solvent-assisted phase separation and vacuum distillation operation was also performed. While promising, NADES must be additionally developed, especially considering recycling, stability and economics.
Nanoscale zero-valent iron (nZVI) has been recognized as one of the most promising materials for the removal of a wide range of pharmaceuticals in water; however, aggregation and instability of nZVI in aqueous media reduces its efficacy. In this study, graphene oxide (GO) supported nZVI/copper bimetallic-nanoparticles (BNPs) were fabricated for high-efficiency removal of tetracyclines (TCs). In comparison to pure nZVI, the addition of Cu to the nano-adsorbents enhanced the efficacy of TC removal by 13%. The GO supporter mitigated the aggregation of BNPs and reduced the dissolution of metal nanoparticles, thereby demonstrating a higher working efficacy than Fe/Cu BNPs, even over five consecutive runs. At the optimal condition (pH 5–7, [TCs]: [Fe/Cu-GO] = 1:2.5 w/w), the Fe/Cu-GO nanocomposite showed near-complete (∼100%) TCs-removal within 15 min. The adsorption of TCs by Fe/Cu-GO fits the Freundlich model, with an adsorption capacity of 201.9 mg g−1. The Fe/Cu-GO nanocomposite showed pH-dependent assembly behavior to potentially recycle GO at a pH > 9 condition to generate new nanoparticles. The high removal efficiency of TCs, combining with high stability and easy separation performance in the aqueous environment, makes Fe/Cu-GO nanocomposites a promising material for treating latent antibiotics in water.
Sulfamethazine (SMT) is widely used in human and veterinary medicine as growth promoters and antibacterial drugs and it can pose potential threats to human and ecosystem health. In this study, removal of SMT by ultrasound pre-magnetized Fe⁰/PS process was investigated for the first time. Degradation rate for removing SMT increased 3.3 folds and the synergy factor increased from 1.2 to 2.7 compared with US/Fe⁰/PS process. Affecting factors such as pH (3–10), Fe⁰ dosage (0–0.8 mM) and initial SMT concentration (0–10 mg L⁻¹) were studied. Stronger signals of DMPO–OH and DMPO–SO4 adduct also illustrated more and faster SO4[rad]− and [rad]OH radicals produced in the system. FeOOH was detected through the mossbauer spectrum which could both enhance the catalysis of H2O2 and activation of PS. The intermediates of the SMT degradation were investigated, and a degradation pathway was proposed. Higher correlation factor (△k and △S) in US/pre-magn-Fe⁰/PS system illustrated the good synergistic effect between US input power and magnetic field. Moreover, the process could efficiently remove SMT in municipal wastewater and keep pH neutral. So, US/pre-magn-Fe⁰/PS process is a energy saving and promising approach to remove antibiotics in real wastewater.
Persulfate is the latest oxidant which is being used increasingly for the remediation of groundwater and soil contaminated with organic compounds. It is of great significant to offer readers a general summary about different methods of activating persulfate, mainly including heat-activated, metal ions-activated, UV-activated, and alkaline-activated. Meanwhile, in addition to persulfate concentration as an influencing factor for persulfate oxidation process, selected information like temperature, anions, cations, pH, and humic acid are presented and discussed. The last section focuses on the advantages of different activated persulfate processes, and the suggestions and research needs for persulfate-based advanced oxidation in the remediation of polluted groundwater and soil.
In this study, mesoporous carbon (MC) supported nano Fe⁰ was prepared from polyvinyl alcohol (PVA) using MnCO3 as template, which was used as the catalyst to activate persulfate (PS) for the removal of tetracycline hydrochloride (TC) from aqueous solution. The nano Fe⁰ was immobilized on MC by liquid phase reduction to overcome the drawbacks of nano Fe⁰ for persulfate (PS) activation, including being easily aggregated and oxidized. The experimental results showed that the nano Fe⁰/MC+PS system achieved 92.1% of TC removal, while the MC+PS system and nano Fe⁰+PS systems showed 78.5% and 33.7% of TC removal, respectively. High removal efficiency in the nano Fe⁰/MC+PS system could be attributed to the superior PS activation capability due to the synergistic effects of nano Fe⁰ and MC. In order to better understand the removal mechanism, the effects of nano Fe⁰ loading amount (c), dosage (m), PS/TC mole ratio (Rm) and initial pH on TC removal were evaluated in the nano Fe⁰/MC+PS system. The results showed that the removal efficiency of TC was enhanced with the increase of nano Fe⁰ loading amount and dosage, while slightly decrease with the increase of PS/TC mole ratio. The maximum removal of TC was 97.7% under the optimal conditions: c=20%, m=0.8 g/L, Rm=50/1 and pH=5. According to the results of radical scavengers’ studies and intermediates analysis, SO4•-, which was produced from catalytic activation of PS by nano Fe⁰ and Fe²⁺ on the surface of Fe⁰/MC, plays a significant role for TC degradation in the nano Fe⁰/MC+PS system. The Fe⁰/MC + PS system exhibited a superior oxidation process for the removal of TC from aqueous solution with excellent stability and reusability of Fe⁰/MC.
A magnetic quasi-circular nano-Fe3O4 was synthesized by coprecipitation and used for the decolorization of rhodamine B (RhB) in contact glow discharge electrolysis (CGDE). The results indicated that nano-Fe3O4 significantly enhanced the decolorization of RhB. The decolorization efficiency reached 94.0% and 33.6% of RhB was mineralized in only 20 min when the dosage of nano-Fe3O4 was 1 g L− 1. The effects of initial pH, temperature, RhB concentration and nano-Fe3O4 dosage on the decolorization efficiency and the catalytic mechanism were also studied. It has been demonstrated that H2O2 produced in CGDE underwent decomposition in the presence of nano-Fe3O4. Nano-Fe3O4 appears to be an excellent catalyst in the degradation of RhB solution by the CGDE process.