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High Capacity of Oxytetracycline Hydrochloride Removal in Wastewater Via Mikania Micrantha Kunth-Derived Biochar Modified by Zn/Fe-Ldh
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In this paper, coconut shell biochar (BC), pickling biochar (HBC), and nano-zero-valent iron-loaded biochar (nZVI-HBC) were prepared; these were used to remove oxytetracycline (OTC), and the removal mechanism and degradation product were analyzed. These biochars were characterized using SEM, XRD, FTIR, and XPS. The effects of biochar addition amount, pH, ion type, and ion concentration on OTC adsorption were studied by a batch adsorption experiment. Under the optimal conditions, the equilibrium adsorption capacity of nZVI-HBC to OTC was 196.70 mg·g−1. The adsorption process can be described by Langmuir isothermal adsorption equations, conforming to the pseudo-second-order dynamics model, indicating that adsorption is dominated by single-molecule chemical adsorption, and a spontaneous process of increasing heat absorption entropy. Mass spectrometry showed that the OTC removal process of nZVI-HBC included not only adsorption but also degradation. These results provide a practical and potentially valuable material for the removal of OTC.
Biochar (BC) has exhibited a great potential to remove water contaminants due to its wide availability of raw materials, high surface area, developed pore structure, and low cost. However, the application of BC for water remediation has many limitations. Driven by the intense desire of overcoming unfavorable factors, a growing number of researchers have carried out to produce BC-based composite materials, which not only improved the physicochemical properties of BC, but also obtained a new composite material which combined the advantages of BC and other materials. This article reviewed previous researches on BC and BC-based composite materials, and discussed in terms of the preparation methods, the physicochemical properties, the performance of contaminant removal, and underlying adsorption mechanisms. Then the recent research progress in the removal of inorganic and organic contaminants by BC and BC-based materials was also systematically reviewed. Although BC-based composite materials have shown high performance in inorganic or organic pollutants removal, the potential risks (such as stability and biological toxicity) still need to be noticed and further study. At the end of this review, future prospects for the synthesis and application of BC and BC-based materials were proposed. This review will help the new researchers systematically understand the research progress of BC and BC-based composite materials in environmental remediation.
Biological invasions are responsible for substantial biodiversity declines as well as high economic losses to society and monetary expenditures associated with the management of these invasions1,2. The InvaCost database has enabled the generation of a reliable, comprehensive, standardized and easily updatable synthesis of the monetary costs of biological invasions worldwide3. Here we found that the total reported costs of invasions reached a minimum of US26.8 billion. Moreover, we estimate that the annual mean cost could reach US$162.7 billion in 2017. These costs remain strongly underestimated and do not show any sign of slowing down, exhibiting a consistent threefold increase per decade. We show that the documented costs are widely distributed and have strong gaps at regional and taxonomic scales, with damage costs being an order of magnitude higher than management expenditures. Research approaches that document the costs of biological invasions need to be further improved. Nonetheless, our findings call for the implementation of consistent management actions and international policy agreements that aim to reduce the burden of invasive alien species. Analysis of the InvaCost database shows that the costs of biological invasions have markedly increased between 1970 and 2017 and show no sign of slowing down, highlighting the importance of evidence-based and cost-effective management actions.
The method of preparing Zn0.75Mn0.75Fe1.5O4/ZnFe2O4/ZnO photocatalyst was the precipitation grinding. This photocatalyst was characterized by UV-Vis, PL, EDS, SEM, and XRD. The results indicated the Zn0.75Mn0.75Fe1.5O4/ZnFe2O4/ZnO photocatalyst was highly active under the visible light. The photocatalytic degradation efficiency of chlortetracycline hydrochloride was analyzed in mariculture wastewater by various experimental parameters, namely calcination temperature, dosage of Zn0.75Mn0.75Fe1.5O4/ZnFe2O4/ZnO, Zn2+/Fe3+/Mn2+ molar ratio, H2O2 mass concentration, chlortetracycline hydrochloride initial concentration, and illumination time. The degradation of chlortetracycline hydrochloride in mariculture wastewater was optimized by orthogonal experiments. When the H2O2 mass concentration was 0.3 g/L, calcination temperature was 500 °C, Zn2+/Fe3+/Mn2+ molar ratio was 10:1:4, dosage of Zn0.75Mn0.75Fe1.5O4/ZnFe2O4/ZnO was 0.7 g/L, illumination time was 4.0 h, chlortetracycline hydrochloride initial concentration was 0.01 g/L, and the degradation rate of chlortetracycline hydrochloride reached 73.04% by Zn0.75Mn0.75Fe1.5O4/ZnFe2O4/ZnO photocatalyst. The degradation rate of chlortetracycline hydrochloride was 52.86% by ZnFe2O4/ZnO photocatalyst. The results indicated that the Zn0.75Mn0.75Fe1.5O4/ZnFe2O4/ZnO photocatalyst obviously enhanced the degradation rate of chlortetracycline hydrochloride, compared with pure ZnO and ZnFe2O4/ZnO photocatalyst.
Biochar/layered double hydroxide (LDH) composites have gained considerable attention in recent times as low-cost sustainable materials for applications in water treatment. This paper critically evaluates the latest development in applications of biochar/LDH composites in water treatment with an emphasis on adsorption and catalytic degradation of various pollutants. The adsorption of various noxious contaminants, i.e., heavy metals, dyes, anions, and pharmaceuticals onto biochar/LDH composites are described in detail by elaborating the adsorption mechanism and regeneration ability. The synergistic effect of LDH with biochar exhibited significant improvement in specific surface area, surface functional groups, structure heterogeneity, stability, and adsorption characteristics of the resulting biochar/LDH composites. The major hurdles and challenges associated with the synthesis and applications of biochar/LDH composites in water remediation are emphasized. Finally, a roadmap is suggested for future research to assure the effective applications of biochar/LDH composites in water purification.
In this study, date-palm biochar MgAl-augmented double-layered hydroxide (biochar-MgAl-LDH) nanocomposite was synthesized, characterized, and used for enhancing the removal of phosphate and nitrate pollutants from wastewater. The biochar-MgAl-LDH had higher selectivity and adsorption affinity towards phosphate compared to nitrate. The adsorption kinetics of both anions were better explained by the pseudo-first-order model with a faster removal rate to attain equilibrium in a shorter time, especially at lower initial phosphate-nitrate concentration. The maximum monolayer adsorption capacities of phosphate and nitrate by the non-linear Langmuir model were 177.97 mg/g and 28.06 mg/g, respectively. The coexistence of anions (Cl − , SO 4 2− , NO 3 − , CO 3 2− and HCO 3 −) negligibly affected the removal of phosphate due to its stronger bond on the nano-composites, while the presence of Cl − and PO 4 3− reduced the nitrate removal attributed to the ions' participation in the active adsorption sites on the surface of biochar-MgAl-LDH. The excellent adsorptive performance is the main synergetic influence of the MgAl-LDH incorporation into the biochar. The regeneration tests confirmed that the biochar-MgAl composite can be restored effortlessly and has the prospective to be reused after several subsequent adsorption-desorption cycles. The biochar-LDH further demonstrated capabilities for higher removal of phosphate and nitrate from real wastewater.
The need to design low-cost adsorbents for the detoxification of industrial effluents has been a growing concern for most
environmental researchers. So modelling of experimental data from adsorption processes is a very important means of predicting
the mechanisms of various adsorption systems. Therefore, this paper presents an overall review of the applications of adsorption
isotherms, the use of linear regression analysis, nonlinear regression analysis, and error functions for optimum adsorption data
analysis.
Biochars showed a potential as adsorbents for organic contaminants, however, have not been tested for carbofuran, which has been detected frequently in water. This study provides evidences for the use of infused tea residue derived biochar for carbofuran removal. Biochars were produced at 300, 500 and 700 °C by slow pyrolysis and were characterized by proximate and ultimate analysis, FT-IR, SEM, BET and pore size distribution. Pyrolysis temperature showed a pronounced effect on biochar properties. The maximum carbofuran removal was achieved at pH 5. Freundlich and Temkin models best fit the equilibrium data. Biochars produced at 700 °C showed the highest sorption intensity. The adsorption process was likely to be a favorable chemisorption process with electrostatic interactions between carbofuran molecules and biochar surface. Acid-base interactions, electrophilic addition reactions and amide bond formations are the possible mechanisms of carbofuran adsorption. Overall, biochars prepared from tea waste can be utilized as effective adsorbents for removal of aqueous carbofuran.
In this study, sycamore flocs (SF), which caused environmental and health problems, were utilized to prepare biochar. SFB2-900 obtained under the conditions of activation agent K2CO3, pyrolysis temperature 900℃ and m(K2CO3): m(BC) 2 had the strongest adsorption capacity (730 mg/g) for oxytetracycline hydrochloride (OTC-HCl). The pseudo-second-order kinetic model and Langmuir model described the adsorption kinetics and isotherms best. SFB2-900 exhibited high OTC-HCl adsorption capacity in both higher ionic strength and wide pH range. The theoretical simulation indicated that the closest interaction distance between OTC-HCl and SFB2-900 was 2.44 Å via π-π stacking configuration. Pore filling, π-π electron donor acceptor (EDA) interaction, H-bonding and electrostatic interactions were also involved in the process of OTC-HCl removal. SFB2-900 showed great removal efficiency for OTC-HCl in different water matrices and good regeneration ability. This study solved the problems caused by SF, realized waste biomass recycling, and achieved preparing high-efficient adsorbent for antibiotic.
Efficient removal of oxytetracycline hydrochloride (OTC) from wastewater is of great significance but extremely challenging. Herein, a novel adsorbent lignin-based multi-metal ferrite biochar (FeNiZn-LBC) was synthesized through pyrolysis with controllable temperature and hydrothermal reaction using lignin of sinocalamus oldhami as raw material. The adsorption property of FeNiZn-LBC for OTC was systematically researched, and the results displayed that adsorption of FeNiZn-LBC to OTC accorded with the Langmuir model and the equilibrium adsorption capacity was 476 mg g⁻¹. Notably, FeNiZn-LBC can be regenerated with 0.100 mol L⁻¹ NaOH. Additionally, we raised rational explanations for the mechanisms of adsorption behavior based on the zeta potential and XPS spectra. The adsorption of FeNiZn-LBC for OTC was mainly controlled by the electrostatic interactions, hydrogen bonds and complexation involving FeNiZn-LBC and OTC, especially the metal-oxide bond (M-O) generated after loaded with multi-metal ferrite played a positive role in the removal of OTC from water. Our work highlighted the potential of FeNiZn-LBC for excellent adsorption of OTC in next generation.
The presence of residual antibiotics will lead to potential environmental risks. Here cyclodextrins (CDs) were successfully used to modify graphene-based iron nanoparticles ([email protected] NPs) to enhance the absorption of oxytetracycline hydrochloride (OTC). The removal of OTC decreased in the order: γ[email protected] NPs > β[email protected] NPs > α[email protected] NPs > [email protected] NPs, with better performance than that of bare GO and Fe NPs. Characterization techniques were applied to better understand how CDs impact the structure of [email protected] NPs and improve removal performance. Raman and X-ray diffraction analysis showed that GO acted as a carrier to support Fe NPs within the grafted cyclodextrin, where GO also participated in the removal process. Cyclodextrin modified [email protected] NPs had relatively small particle sizes (15 nm), with a high surface area (61.7 m²·g⁻¹). X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy suggested that cyclodextrin acted as both a stabilizing and capping agent during green synthesis, which could protect the reactivity of Fe NPs and simultaneously reduce aggregation. A potential synthesis mechanism of cyclodextrins modified composites was also proposed, and subsequent wastewater testing indicated that γ[email protected] NPs had high potential for practical applications.
Metal-free carbonaceous catalysts are receiving increasing attention in wastewater treatment. Here, nitrogen and sulfur co-doped carbon sphere catalysts (N,S-CSs900-OH) were synthesized using glucose and L-cysteine via a hydrothermal method and high temperature alkali activation. The N,S-CSs900-10%-OH exhibited excellent catalytic performance for the degradation of oxytetracycline (OTC). The degradation rate was 95.9% in 60 min, and the reaction equilibrium rate constant was 0.0735 min⁻¹ (k0–15 min). The synergistic effect of adsorption-promoting degradation was demonstrated in the removal process of OTC. The excellent adsorption capacity of N,S-CSs900-10%-OH ensured the efficient oxidation of OTC. N,S-CSs900-10%-OH reduced the activation energy of the OTC degradation reaction (Ea=18.23 kJ/mol). Moreover, the pyrrolic N, thiophene S and carbon skeleton played an important role in the degradation of OTC based on density function theory, and the catalytic mechanism was expounded through radical and nonradical pathways. The active species involved in the reaction were O2•−, ¹O2, SO4•− and •OH, of which O2•− was the primary reactive species. This study provides a new insight into the reaction mechanism for efficient treatment of organic pollutants using metal-free doped porous carbon materials.
The regulation of surface electrons by non-metal doping of biochar (BC) is environmentally and ecologically significant. However, systematic studies on the regulation of surface electrons by transition metal doping are lacking. The present study is based on the observation that the removal efficiency of oxytetracycline (OTC) by Mn-doped BC is eight times higher than that of undoped BC in 20 min. The effects of Mn doping on the crystal phase formation, persistent free radicals (PFRs), electron density, molecular orbitals, and nucleophilic active sites of BC are investigated, and the intermediate products of OTC are evaluated. Mn doping enhances the signal for sp²-hybridised carbon–carbon double bond, forms more delocalised π-bonds, and promotes the formation of free radicals centred on the carbon atoms. The specific surface area of BC increases, and manganese oxide is formed on the its surface. Density functional theory calculations show that Mn doping accelerates the electron transfer of BC, provides additional electrons for the BC system, and makes this system more ionised. OTC molecules preferentially attack the nucleophilic reaction sites near Mn atoms based on molecular electrostatic potential measurements. Therefore, this study provides new insights into the surface electronic structures regulated by transition metal elements.
We present the chemisorption of chlortetracycline (CTC) and oxytetracycline (OTC) on theta phosphorene nanoribbon (theta-PNRibbon) based on the first-principles framework. The formation energy of theta-PNRibbon is noticed to be -3.759 eV per atom, which ensures structural stability. The theta-PNRibbon exhibits a band gap of 1.376 eV that belongs to the semiconductor. The presence of CTC and OTC molecules on a water medium requires a removal substrate. The adsorption energy for the complex structure is found to be in the range of -2.778 eV to -9.268 eV. Based on the adsorption energy and charge transfer between CTC and OTC molecules and theta-PNRibbon, the chemisorption of target molecules is observed. Also, the electronic properties of theta-PNRibbon owing to adsorption of CTC and OTC molecules are investigated with band structure and density of states studies. The findings reveal that theta-PNRibbon is one of the base substrates for the removal of CTC and OTC in the water bodies.
Non-thermal plasma coupled with graphene-TiO2-Fe3O4 nanocomposites was applied to promote oxytetracycline (OTC) degradation in water. Graphene-TiO2-Fe3O4 nanocomposites were systematically characterized and calculated based on the density functional theory (DFT). Graphene-TiO2-Fe3O4 nanocomposites exhibited higher specific surface area, carrier separation rate and magnetic intensity. More importantly, graphene-TiO2-Fe3O4 nanocomposites were very prone to separation from solution. Compared to Fe3O4 and graphene-TiO2, graphene-TiO2-Fe3O4 nanocomposites further enhanced the removal efficiency of OTC. The highest removal efficiency could reach 98.1% when the doping amount of Fe3O4 was 20 wt%. The optimal parameters of catalyst dosage, peak voltage, air flow rate and pH value were 0.24 g/L, 18 kV, 4 L/min and 3.2, respectively. Compared with graphene-TiO2, the addition of graphene-TiO2-Fe3O4 nanocomposites decreased the concentration of O3 and H2O2, but increased the production of ·OH. ·OH, O3 and H2O2 played certain role for OTC elimination. The degradation process was explored by UV-Vis spectrum, three dimensional fluorescence, liquid chromatography-mass spectrometry (LC-MS), ion chromatography (IC) and discrete Fourier transform (DFT) analysis. Reactive molecular dynamical (MD) simulation was also performed to further investigate the reaction mechanisms, and the simulation show a good agreement with the experimental observation by analyzing the bond breaking and formation. The actual toxicity of OTC was alleviated after plasma-catalytic treatment.
The present work provides the first attempt of using manganese dioxide loaded poly(sodium acrylate) hydrogel (MnO2@PSA) to address potential threats posed by oxytetracycline (OTC) antibiotics in aqueous environment. The MnO2@PSA was prepared via a facile approach and demonstrated enhanced removal performance even under extremely high concentrations of OTC. The outstanding performance exhibited by MnO2@PSA was attributed to synergetic effects of adsorption oxidative degradation. The synthesized composite was characterized evaluated under varying conditions. The adsorption pH was optimized at pH 5, at which the removal efficiency OTC was reached 91.46%. According to the kinetics study, the pseudo-second-order kinetic model was the best to explain the adsorption data, implying the interaction mechanisms were dominated by chemisorption. The Langmuir isotherm model was the best to explain the isotherm data, and the corresponding maximum adsorbed amount of OTC was 1,150.4 mg g-1. The MnO2@PSA was highly selective for OTC adsorption and degradation under the presence of natural organic matter and common environmental metal ions. The oxidative degradation study indicated that OTC molecules were structurally degraded into 15 intermediate products via six reaction pathways. Both the theoretical models and spectroscopic methods demonstrated the removal mechanism of OTC onto MnO2@PSA was governed by ion exchange, cation-π bonding, hydrogen-bonding, and π-π electron donor-acceptor. Overall, MnO2@PSA is an excellent and environmentally sustainable material to remove OTC from water and wastewater via the combined effects of adsorption and oxidative degradation.
Kaolinite and methoxy-modified kaolinite were used as novel adsorbents for oxytetracycline (OTC) removal and recovery from aqueous media. Batch adsorption experiments were performed to study the effect of pH, ionic strengths, initial concentration, and contact time on OTC adsorption. The adsorbents were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after adsorption. Adsorption of OTC reached its maximum when solution pH increased up to 6 for 0.001 M ionic strength, above which adsorption decreased further when solution pH increased. Freundlich and Langmuir’s models best fit the equilibrium data with a strong dependency on OTC adsorption capacity giving its maximum at 36 mg g⁻¹. Binding is postulated for OTC adsorption on pristine kaolinite as a special case of Hill model with independent binding interaction of OTC adsorption onto the clay that affects the adjacent sites on the pristine kaolinite, in contrast with the adsorption of OTC on methoxy-modified kaolinite. Nitrogen peaks of the XPS spectra indicated changes in the oxidation states of C-N bonds in the N1s peaks by forming tertiary amide C-N and methoxy O-CH3 bonds which corroborated with the results from FTIR spectra. Removal efficiencies and spectroscopic results indicate that performance on methoxy-modified kaolinite is a promising modification on the clay for recovering antibiotics from wastewater.
Laboratory investigations show that rates of adsorption of persistent organic compounds on granular carbon are quite low. Intraparticle diffusion of solute appears to control the rate of uptake, thus the rate is partially a function of the pore size distribution of the adsorbent, of the molecular size and configuration of the solute, and of the relative electrokinetic properties of adsorbate and adsorbent. Systemic factors such as temperature and pH will influence the rates of adsorption; rates increase with increasing temperature and decrease with increasing pH. The effect of initial concentration of solute is of considerable significance, the rate of uptake being a linear function of the square-root of concentration within the range of experimentation. Relative reaction rates also vary reciprocally with the square of the diameter of individual carbon particle for a given weight of carbon. Based on the findings of the research, fluidized-bed operation is suggested as an efficient means of using adsorption for treatment of waters and waste waters.
In this study, the reduced graphene oxide-supported bimetallic palladium-zero-valent-iron (Pd/nZVI/rGO) composites were synthesized using a facile one-step liquid-phase reduction method. Physicochemical and textural properties as well as chemical composition of the as-prepared composites were firstly characterized. Transmission electron microscopy (TEM) and X-ray diffractometry (XRD) analysis revealed that the presence of rGO sheets prevented the aggregation of Pd/nZVI nanoparticles and retarded the transformation of iron corrosion products from magnetite/maghemite to lepidocrocite, inducing such nanoparticles to be dispersed more homogeneously. In addition, the loading of Pd/nZVI nanoparticles could avoid the stacking of rGO sheets effectively. The synthesized Pd/nZVI/rGO composites were then used to remove antibiotic oxytetracycline (OTC) from aqueous solutions. It was found that the introduction of an optimal amount of rGO into Pd/nZVI nanoparticles enhanced significantly OTC removal. In particular, the presence of 5 wt.% of rGO in Pd/nZVI/rGO composite (dose, 0.1 g/L) exhibited the highest OTC removal of 96.5% (initially, 100 mg/L) after 60-min reaction at pH 5.0 and 25°C. The removal of OTC by Pd/nZVI/rGO composite was contributed by adsorption process, Fenton-like reactions, and reduction reactions. The Pd/nZVI/rGO composites exhibited better reusability than pristine nZVI particles. The pathways of OTC degradation over Pd/nZVI/rGO nanocomposite were also proposed.
Oxytetracycline (OTC), as one of widely applied veterinary antibiotic, has become a new environmental pollutant. To explore the feasibility of the nanocomposites of reduced graphene oxide (rGO) with the ZrO2 nanoparticles for OTC removal, two nanocomposites of monoclinic-ZrO2@rGO and tetragonal-ZrO2@rGO through controlling the dosage of triethanolamine are prepared successfully and characterized. Detail investigation of the adsorption for the family of tetracycline antibiotics on the two nanocomposites has been assessed. For comparison, the tetragonal-ZrO2@rGO (198.4 mg g–1) exhibits a higher adsorptive amount than the monoclinic-ZrO2@rGO (177.9 mg g–1), whereas two nanocomposites demonstrate a remarkably selective uptake of OTC among the family of tetracycline antibiotics due to their higher affinity towards OTC. Adsorption of OTC by in 15 minutes can reach the equilibrium and is independent on pH in the range of 4-8. The adsorption of OTC by the two nanocomposites is well matched by both pseudo-second order and Langmuir models and exhibits a favorable, endothermic and spontaneous nature. Fourier transform infrared and XRD analysis reveal the interactions between OTC and the nanocomposites such as surface complexation, π-π and cation-π bonding interactions with a crucial role.
Metal-organic framework and nano carbon materials were widely used in separation field in recent years. In this study, nanocomposite of MIL-100(Fe) and multi-walled carbon nanotubes (MIL-100(Fe)-CNTs) was prepared and characterized and its adsorption property towards Oxytetracycline (OTC) was presented. MIL-100(Fe)-CNTs exhibits higher adsorption capacity compared to MIL-100(Fe), making this composite as one of the favorable adsorbents. The adsorption capacity of MIL-100(Fe)-CNTs reached 429 mg·g⁻¹ at 313 K. The langmuir model and Koble-Corrigan model were better to predict the equilibrium data while the pseudo-second-order kinetic model could well describe the kinetic process. The process was endothermic and spontaneous while the ion exchange was the main adsorption mechanism of OTC on MIL-100(Fe)-CNTs. The nanocomposite is promising to effectively remove OTC from solution.
In this study, biochar derived from municipal sludge was activated by zinc chloride, which was first time used as the precursor for hydrothermal synthesis of magnetic sludge biochar (Fe/Zn-SBC) for tetracycline (TC) and ciprofloxacin (CIP) removal. The maximum adsorption capacity of Fe/Zn-SBC for TC and CIP were 145 mg g-1 and 74.2 mg g-1 at 25 °C, respectively. Kinetics, isotherms, thermodynamics and characterization analysis suggested that the adsorption process was dominated by pore filling, oxygen-containing groups complexation, π-π conjugation and hydrogen bonding. Fe/Zn-SBC had the high selective adsorption capacity for TC and CIP in a wide pH range and even at the high ionic strength. The magnetic sensitivity ensured its easy separation performance. The co-processing of ultrasound and ethanol could effectively regenerate the used Fe/Zn-SBC. Also, it exhibited great environmental safety in the pH range of 3 to 12. These superiority suggested that it is a promising adsorbent for antibiotics removal.
In this study, Fe3O4-HA-La composite was prepared by chemical coprecipitaion method, and the oxytetracycline (OTC) adsorption efficiency of the obtained adsorbent was investigated with batch experiment. Characterization methods, including BET, SEM, XRD, FTIR, XPS and VSM, were employed to study its physiochemical properties. The batch experiment results indicated that > 90% of OTC was removed using the adsorbent Fe3O4-HA-La under wide pH range from 5 to 9. The regeneration experiment showed that after three cycles of adsorption/regeneration, Fe3O4-HA-La kept the OTC removal efficiency > 80% and saturation magnetization (Ms) value > 55 emg g⁻¹. The OTC adsorption process was better fitted with pseudo-second-order kinetic model. The OTC adsorption process was better fitted with Redlich-Peterson model (R² > 0.99). High correlation coefficient (R² > 0.97) was also observed for Langmuir model, which showed the Qmax of 23.43 mg g⁻¹. The complexation reaction between OTC and HA, La and Fe on Fe3O4-HA-La were contributed to the efficient removal of OTC by Fe3O4-HA-La.
As an "up-and-coming" two-dimensional (2D) material, black phosphorus (BP) has attracted much attention due to its abundant metal-free properties and broad application prospects in photocatalysis. This study introduces a promising sunlight-driven metal-free photocatalyst for oxytetracycline hydrochloride degradation and hexavalent chromium reduction in water and wastewater. The roles of BP quantum dots (BPQDs) in the distribution of electrons and photocatalytic performances were well identified by experimental and density functional theory (DFT) calculations. As expected, the specially designed 0D/1D structure shows unusual photocatalytic efficiency toward the degradation of oxytetracycline hydrochloride (0.0276 min⁻¹) and reduction of hexavalent chromium (0.0404 min⁻¹). Reactive species, namely, O2⁻ and h⁺ comprised the primary photocatalytic mechanisms for oxytetracycline hydrochloride degradation. This work highlights that the combination of tubular g-C3N4 (TCN) with BPQDs facilitates the charge spatial separation in the photocatalytic process, and provides alternative strategy for design of highly active and metal-free nanomaterials toward environmental remediation and sustainable solar-to-chemical energy conversion.
In this study, oxytetracycline (OTC) as a target pollutant in swine wastewater was removed by aerobic granular sludge (AGS). The removal rate of 300 μg/L OTC in aerobic granular sludge sequencing batch reactor (AGSBR) increased to 88.00% in 33 days and maintained stable. The chemical oxygen demand (COD), ammonium nitrogen (NH4+-N) and total phosphorus (TP) in wastewater were also efficiently removed. The removal of OTC mainly depended on the adsorption and biodegradation of AGS, and the biodegradation was increased obviously after AGS adaptation to OTC. The degradation products of OTC were analyzed by mass spectrometry. The analysis of metagenome sequencing revealed that the enzymes, such as glycosyl transferases (GTs), polysaccharide lyases (PLs) and auxiliary activities (AAs), may play an important role in the removal of OTC. The Lefse analysis showed that the Flavobacteriia, Flavobacteriales, Cryomorphaceae and Fluviicola were four kinds of microbes with significant difference in OTC feed reactor, which are considered to be drug-resistant bacteria in AGSBR. Furthermore, the dynamics of microbial community changed significantly at three levels, including the enrichment of drug-resistant microorganisms and the microorganisms that gradually reduced or even disappeared under the pressure of OTC.
Pharmaceuticals are emerging pollutants present mainly in industrial and municipal wastewater. Herein, structurally variable binary and ternary metal hydroxides based on copper, manganese, and aluminum were used for the adsorptive scavenging of the oxytetracycline (OTC) antibiotic. A facile hydrothermal method was used for the synthesis of binary CuAl-hydroxide, MnAl-hydroxide, and ternary CuMnAl-hydroxide. Structural and morphological characteristics of the metal hydroxides (MHs) were studied by X-ray diffraction (XRD), Fourier transformed infrared spectrum (FTIR), X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM) analysis. The adsorptive removal for OTC was found in the order CuMnAl-hydroxide > CuAl-hydroxide > MnAl-hydroxide. The highest removal of OTC by CuMnAl-hydroxide and CuAl-hydroxide was observed at pH 7 while MnAl-hydroxide showed the optimum adsorption at pH 9. All three materials showed different saturation time and equilibrium concentration for OTC adsorption. The mechanism investigation found that strong electrostatic attraction, hydrogen bonding, and anion exchange were mainly responsible for the removal of the OTC and adsorption process followed the pseudo-second-order kinetic model and equilibrium data was best fitted to the Langmuir isotherm model. The adsorption of OTC was influenced by the presence of Cu (II) and Cr (VI) ions in the aqueous solution due to the competitive adsorption of co-ions. Moreover, the adsorption of OTC was endothermic in nature, and maximum adsorption capacity was found to be 250.07 mg/g at 50 °C.
In this study, cetyl trimethylammonium bromide (CTAB) (cationic) and sodium dodecyl benzene sulfonate (SDBS) (anionic) were used to modify natural sepiolite (SEP) to obtain a type of organic sepiolite (C-S-SEP). It was further applied for adsorption of oxytetracycline (OTC), a common antibiotic in water. The changes of SEP crystal structure and physicochemical properties before and after modification were analyzed by the means of XRD, FTIR, TG, SEM/EDS, BET, XPS and zeta potential. The adsorption performance and mechanism of OTC on C-S-SEP were studied by static adsorption method. The results showed that the adsorption capacity of C-S-SEP increased significantly, and the removal rate of OTC increased from 50.26% to 99.42%. The partition coefficient of SEP and C-S-SEP was 0.356 and 2.172 mg g-1 μM-1, respectively. CTAB and SDBS were successfully loaded onto the surface of SEP without entering its interlaminar domain, and the original crystal structure of SEP was well maintained. In the range of the studied ratio, anionic and cationic surfactants had the synergistic solubilization effect. The adsorption process conformed to the pseudo-second-order kinetic model and Langmuir isothermal adsorption model. The adsorption reaction was exothermic and a process of entropy reduction. The increase of temperature was not conducive to adsorption, and the adsorption reaction was basically unaffected by the pH value. The adsorption of C-S-SEP on OTC was the result of the combination of distribution and surface adsorption. The organic modified SEP was expected to become a low-cost environmentally friendly adsorption material that can effectively remove OTC from water.
A novel strategy to remove oxytetracycline (OTC) from aqueous solution was proposed by two-step process of adsorption followed by oxidation degradation: OTC was firstly concentrated on the surface of the Zn⁰-CNTs-Fe3O4 composite by adsorption process under neutral condition. Then, the concentrated OTC on the surface of Zn⁰-CNTs-Fe3O4 was oxidized by Zn⁰-CNTs-Fe3O4/O2 Fenton-like process at pH of 3 with high solid-water ratio, which can reduce the amount of acid used for adjusting pH for Fenton reaction. Approximately 98.6% of OTC was oxidized at initial OTC concentration of 100 mg/L by the two-step process, which was higher than that by the one-step process of adsorption-oxidation at pH 3 or pH 6. The used Zn⁰-CNTs-Fe3O4 in two-step process could be reused after Zn⁰ was reloaded. The removal efficiency of OTC decreased only 6.7% after four-recycle use of the Zn⁰-CNTs-Fe3O4. The possible adsorption mechanism of OTC onto the Zn⁰-CNTs-Fe3O4 surface and the oxidation mechanism of the concentrated OTC by the Zn⁰-CNTs-Fe3O4/O2 process were proposed.
The growing occurrence of As(III) pollutant in surface and ground water has serious implications to human and plant life. Developing and understanding the interaction between priority pollutants and low-cost adsorbent materials is of importance in finding solution to the ever-growing threat of water pollution. In this study, pine cone biomass, an agricultural waste was chemically activated and applied as potential adsorbent for As(III) in water. Effect of sorption parameters such as pH and dose were investigated. Temperature effect on adsorption kinetics and equilibrium studies indicates ligand exchange as the main sorption mechanism with an activation energy of 26.24 kJ/mol. Ligand exchange mechanism was confirmed by FTIR, XPS and pHPZC analysis before and after adsorption and As(III)/NO3 exchange reaction. Effect of ionic strength and anion competition of several environmentally occurring anions on the uptake of As(III) by the adsorbent were also tested. The results showed that As(III) inhibition increased with pH and among the anions, anions inhibited As(III) ion adsorption strongly while As(III) uptake was slightly increased in the presence of , and Cl⁻ anions.
In this paper, a Zeolite Imidazole Framework-8 (ZIF-8), was investigated for the removal of a mixture of two common antibiotics, tetracycline (TC) and oxytetracycline hydrochloride (OTC). Batch experiments showed that 90.7% of TC and 82.5% of OTC were simultaneously removed using ZIF-8. The maximum adsorption capacities for TC and OTC were 303.0 and 312.5 mg g⁻¹, respectively. For both antibiotics’ adsorption followed pseudo-second-order kinetics and best fit the Langmuir adsorption model with R² of 0.963 and 0.981, for TC and OTC at 303 K, respectively. The relatively large specific surface area of ZIF-8 (1158.2 m² g⁻¹) combined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that both antibiotics were adsorbed on to the surface of ZIF-8. X-ray powder diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy both indicated the presence of benzene ring structures, associated with both pollutants, on ZIF-8 after reaction; which confirmed adsorption was occurring. XPS also showed the presence of C[dbnd]O double bonds on the surface of ZIF-8 indicating the presence of antibiotics. The adsorption mechanism most likely involved π-π interactions between the conjugated groups in TC/OTC and the imidazole rings of ZIF-8.
In the adsorption literature, the Van't Hoff equation is used in different manners without any criteria about the concepts of physical-chemistry of equilibrium for calculation of thermodynamic parameters of adsorption. Indeed, the equilibrium constant (K) should be dimensionless for being used in the Van't Hoff equation. However, this is not a simple adjustment of units, as being spread in the literature, to become K dimensionless. In this paper, it will be calculated the equilibrium constants using numeric examples and show the flaws of the thermodynamics calculations, when the value of K is wrongly calculated, and what are the expected results of the changes in enthalpy (ΔH°) and changes in the entropy (ΔS°) that are spread in the literature.
Enhancement of As(III) adsorption by magnetite immobilized on pine cone (MNP-PCP) as compared with pine cone (PCP) was studied. The adsorbents were characterized using FTIR, VSM, XRD and XPS. The PCP, MNP, MNP-PCP and physical mixtures of PCP and MNP (1:1, 2:1 and 1:2) were evaluated for As(III) adsorption. The results show that the composite had better As(III) uptake, FTIR peaks at 812 to 813 cm⁻¹ show As-O bonding. Pseudo second-order model and Langmuir isotherm gave good fit with the experimental data and monolayer capacities of PCP and MNP-PCP were 14.83 and 18.02 mg/g at 299 K. The adsorption type was found to be ion exchange as obtained from Dubinin–Radushkevich parameter E with values of 11.7 and 12.13 kJ/mol for PCP and MNP-PCP, respectively at 299 K. A slight increase in As(III) uptake with increasing ionic strength and shift in pHPZC to lower values after As(III) uptake which was higher for MNP-PCP confirmed the participation of ion exchange reaction.PO4³⁻ anions only caused a reduction in As(III) uptake which was stronger in MNP-PCP. HCl and NaOH desorbed a higher percentage of As(III) from MNP-PCP (82 and 66%) and MNP-PCP gave a more stable As(III) capacity after three cycle desorption/reuse.
Chromium metal-organic framework (MIL-101(Cr)) has been widely studied for removing organic contaminants from aqueous solutions due to its excellent water stability and giant pore size, but its low adsorption capacity limits the application. In this study, a new adsorbent MIL-101 loaded with CuCo bimetallic nanoparticles (CuCo/MIL-101) was successfully fabricated and applied in removal of tetracycline (TC) from aqueous solutions. The adsorption capacity of CuCo/MIL-101 for TC increased by 140% compared with that of pure MIL-101, which may be attributed to the chemical bonding between Cu and Co BNPs in MIL-101 and TC molecules. The effects of pH, ionic strength, humic acid and contact time on the adsorption were also discussed in detail. The results showed that the removal efficiency of TC solution with high concentration (100 mg L-1) by CuCo/MIL-101 was still as high as 82.9%. The data of adsorption kinetics and isotherms could be well fitted by Elovich model and Freundlich model, respectively. According to the fitting parameters, the maximum adsorption capacity of CuCo/MIL-101 reached up to 225.179 mg g-1. Additionally, the adsorption process of TC onto CuCo/MIL-101 was spontaneous and endothermic. Electrostatic interactions could play an important role in the adsorption process. The enhanced adsorption capacity, excellent reusability and water stability demonstrated the potential of CuCo/MIL-101 composite as a novel adsorbent for the removal of TC from aqueous solutions.
In this work, new Cu-coated biochar composites for the adsorption of Re(VII) through complexation mechanism was synthesized successfully. The sensitivity of Cu-coated biochars to solution pH decreased greatly and the adsorption capacity was increased by 3–12 times compared with pristine biochar at pH 3–6. The environmental effect factors and mechanisms of Re(VII) adsorption onto Cu-coated biochar composites (Cu-BC) were investigated. The Re(VII) adsorption nicely fits the Redlich-Peterson isotherm model, and the recovery of Re(VII) from acidic solution by Cu-coated biochar composites follows pseudo-second-order kinetics. Besides, the thermodynamic parameters depicted the spontaneous endothermic nature for the adsorption of low concentration Re(VII). These results demonstrate that easily synthetic Cu-coated biochar composites have promising potential for the recovery of low concentration Re(VII) in acidic solution.
Pollution of water by single antibiotics has been investigated in depth. However, in reality, a wide range of different contaminants is often mixed in the aquatic environment (contaminant cocktail). Here, single and competitive sorption dynamics of ionizable norfloxacin (NOR), sulfamerazine (SMR) and oxytetracycline (OTC) by both pristine and modified biochars were investigated. Sorption kinetics of the three antibiotics was faster in ternary-solute than single-solute system. Sorption efficiency was enhanced in the competitive system for NOR by the pristine biochar, and for OTC by both the pristine biochar and the modified biochar, while SMR sorption by the pristine biochar and the KOH-modified biochar was inhibited. Sorption was governed by electrostatic interactions, π-π EDA and H-bonds for antibiotics sorption by biochar. SMR and OTC sorption by biochar was influenced by cation bridging and surface complexation, respectively. This research finding will guide the development of treatment procedures for water polluted by multiple antibiotics.
The presence of antibiotics in the water and wastewater has raised problems due to potential impacts on the environment and consequently their removal is of great importance. For this reason, this article aims to perform a study on the possibility of oxytetracycline (OTC) adsorption from aqueous medium by using the hydroxyapatite (HA) nanopowders as adsorbent materials. The hydroxyapatite nanopowders were synthesized by wet precipitation method by using orthophosphoric acid and calcium hydroxide as raw materials and investigated by XRD, SEM-EDX, FTIR and BET methods. The uncalcined and calcined hydroxyapatite samples have hexagonal crystal structure with crystal sizes smaller than 100nm and a specific surface area of 316m2/g and 139m2/g, respectively. The adsorption behavior of oxytetracycline, a zwitterionic antibiotic, on nanohydroxyapatite was investigated as a function of pH, contact time, adsorbent dosage and drug concentration by means of batch adsorption experiments. High oxytetracycline removal rates of about 97.58% and 89.95% for the uncalcined and calcined nanohydroxyapatites, respectively, were obtained at pH8 and ambient temperature. The adsorption process of oxytetracycline onto nanohydroxyapatite samples was found to follow a pseudo-second order and intraparticle diffusion kinetic models. The maximum adsorption capacities of 291.32mg/g and 278.27mg/g for uncalcined and calcined nanohydroxyapatite samples, respectively, have been found. The adsorption mechanism of OTC on the hydroxyapatite surface at pH8 can be established via surface complexation. The obtained results are indicative of good hydroxyapatite adsorption ability towards oxytetracycline drug.
In the present investigation, the adsorptive removal of the antibiotic drug oxytetracycline (OTC) and toxic heavy metal cadmium (Cd) from aqueous solution was carried out using forest and wood-processing residues. Numerous biochars were prepared using different chemical agents (H3PO4, H2SO4, NaoH and KOH) and pyrolysis times and temperatures. Several elemental, chemical and structural characterizations were performed. The optimum conditions for pyrolysis to enable the production of biochars with well-developed porosity was 600 °C for 1 h, for both residues. The adsorption process using selected activated biochars was optimized with respect to reaction time, pH, temperature and initial load of pollutants. Under optimized operating conditions, and based on equilibrium modeling data, the biochars which showed the highest removal efficiencies of OTC and cadmium were “5M H3PO4 forest” (263.8 mg/g) and “1M NaoH forest” (79.30 mg/g), respectively. Compared to adsorbents reported in the literature, the efficiencies of those biochars are highly competitive.
In order to study the optimum atmosphere condition for preparing waste tea-based activated carbon by H3PO4 activation, activated carbons were prepared under nitrogen (NAC), air (AAC) and steam (SAC) atmospheres, respectively. The physicochemical properties of the three activated carbons were characterized by N2 adsorption/desorption and Fourier transform infrared spectroscopy (FTIR). AAC exhibited highest values of the Brunauer–Emmett–Teller (BET) surface area (880 m²/g) and total pore volume (0.680 cm³/g) than that of NAC (824 cm²/g and 0.666 cm³/g) and SAC (785 cm²/g and 0.629 cm³/g). Nevertheless, the adsorption results for oxytetracycline (OTC) showed that SAC had the strongest adsorption capacity than NAC and AAC. The adsorption equilibrium data for OTC adsorption onto the three activated carbons agreed well with the Freundlich model, and the adsorption kinetics were well fitted in pseudo-second-order model. Results revealed that activated carbon prepared under air atmosphere showed the largest BET surface area and activated carbon prepared under steam atmosphere showed the best adsorption capacity.
Hydrothermal carbonization (HTC) of carbohydrates is an economic and sustainable technique for the synthesis of carbon materials. However, the assembly of carbohydrates with soft templates is susceptible to hydrolysis, degradation, and relatively high HTC temperature. Thus, it is still challenging to control the HTC/soft templating of carbohydrates and prepare mesoporous carbon with specific properties. Herein, a simple and effective self-transformation strategy is proposed to improve the HTC/soft templating, which introduces an insoluble melamine sulfate into the formation processes. Mechanism studies indicate that the assembly of d-fructose with soft templates is greatly promoted by coassembling with the gradually released melamine sulfate. As a result, carbonaceous composites with a flower-like structure and N-doping were synthesized. Further, ordered mesoporous carbons with N-doping are obtained after calcination. The obtained carbons exhibit outstanding ability for heavy metal adsorption and supercapacitors. Significantly, this self-transformation strategy will open up new avenues for synthesizing carbohydrate-based functional carbons.