Adsorption Of Oxytetracycline Research Articles

Ni-TiO2-g-C3N4 nanosorbent for oxytetracycline antibiotic decontamination

ABSTRACT The release of antibiotics in the water and wastewater has created harm due to impending effects on the environment and thus their elimination, is of vital importance. Therefore, this work endeavours to eradicate the oxytetracycline (OT) antibiotic utilising a facile ultrasonic assisted sol-gel synthesised Ni-TiO2-g-C3N4 (NiTCN) composite as an adsorbent. Using various techniques, the prepared samples revealed the development of the target nanostructure as indicated by the X-ray diffraction (XRD) patterns, where the crystallite size of ≈ 50 nm and the characteristic functional groups of the composite were confirmed by the Fourier-transform infrared spectroscopy (FTIR) analysis. On the other hand, the elemental composition was verified by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The g-C3N4, TiO2, and NiO estimated percentages from the EDS data were 32.7%, 66.4%, and 0.9%, respectively. The large surface area enabled to efficiently eliminate the OT antibiotic. The OT adsorption fitted the Langmuir adsorption model concentration of 5–100 mg/l, 25 ml volume of OT, and 10 mg NiTCN at room temperature with a q max value of 266 mg/g, pseudo-second-order kinetics, and intraparticle and film adsorption contributions. Electrostatic attractions, surface complexation, π-π interactions, and hydrogen bonding were postulated as the modes of the OT anchoring to the adsorbent’s surface. The effect of ions such as Cl−, CO3 2−, Na+, and Mg2+ ions, which are usually present in water systems, on the OT adsorption was studied. The study findings shed light on the possible usage of the prepared nanocomposite to remove antibiotic pollutants‎.

Competitive adsorption of oxytetracycline and sulfamethoxazole by nanosized activated carbon in aquatic environments: Experimental analysis and DFT calculations

Nanosized activated carbon (NAC) is an emerging carbonaceous nanomaterial for water treatment, while oxytetracycline (OTC) and sulfamethoxazole (SMX) coexisting in aquatic environments may undergo competitive adsorption to influence its removal efficiency. This study investigated the competitive adsorption of OTC and SMX onto NAC under different interaction sequence, pH, electrolyte, and water matrix conditions, using experimental analysis and density function theory (DFT) calculations. Adsorption kinetics show that increasing concentration of one antibiotic inhibited the adsorption of another. Faster equilibrium was attained in binary systems than single systems due to competitive adsorption, with pseudo-second-order model providing the best fit in both systems. Adsorption isotherms suggest that NAC exhibited stronger affinity towards OTC (395.26 mg/g) than SMX (232.02 mg/g), with Langmuir model showing satisfactory fitting in both single and binary systems. Sequential adsorption of [NAC + OTC] + SMX was more favored than binary adsorption, aligning with the optimum configuration of SMX--[NAC-OTC±] with binding energy of −57.25 kcal/mol from DFT calculations. Competitive adsorption was preferred within pH 3.2–5.6, where electrostatic attraction existed between NAC and cationic antibiotics. Salting-out, charge screening, and complexation effects from Na+ and Ca2+ influenced competitive adsorption. Optimal removal of OTC and SMX by NAC was achieved in wastewater effluent among four water matrices in both single and binary systems. Hydrogen bonding, π − π electron donor–acceptor interactions, electrostatic interactions, and hydrophobic interactions contributed to adsorption. Sequential change in functional groups of NAC followed − OH → C − H → C − O → C = C and C = C → C − O → C − H → − OH in single and binary systems, respectively. The findings provide valuable insights into the competitive adsorption mechanisms of antibiotics on NAC, highlighting its potential for remediating mixtures of antibiotics in complex aquatic environments.

Optimizing oxytetracycline removal from aqueous solutions using activated carbon from barley lignocellulosic wastes with isotherms and thermodynamic studies

The excessive presence of antibiotics such as Oxytetracycline (OTC) in the wastewater has increased health problems due to their toxic impact on the aquatic ecosystem. Therefore, their removal has become an important topic. This study aims to produce high surface area-activated carbon derived from low-cost and environmentally friendly barley lignocellulosic wastes to remove OTC from aqueous solutions. The synthesized barley wastes-activated carbon (BW-AC) was characterized using Fourier-Transform Infrared spectroscopy, Thermal Gravimetric Analysis, X-ray diffraction analysis, N2 adsorption/desorption isotherms, and Scanning Electron Microscopy. A Central Composite Design under the Response Surface Methodology (CCD-RSM) was applied to optimize the operational parameters (adsorbent dosage, pH, OTC initial concentration, and contact time) affecting the adsorption capacity as the response factor. The optimum condition of OTC adsorption by BW-AC was the adsorbent dosage of 16.25 mg, pH of 8.25, initial concentration of 62.50 mg/L, and contact time of 23.46 min. An analysis of variance (ANOVA) was performed to investigate the significance of the designed quadratic model and evaluate the parameters interactions. The linear regression coefficient (R2) of 0.975 shows a good correlation between predicted and actual results. The adsorption isotherms were used to determine the contaminant distribution over the adsorbent surface, and the equilibrium data was best described by the Freundlich isotherm due to the R2 value of 0.99 compared to other isotherms and β parameter of 0.23 in Redlich-Peterson equation. Moreover, the n value of 1.25 in Freundlich equation and E value of 0.31 in Dubinin–Radushkevich equation indicates a physical nature of adsorption process. According to the equations results, the maximum adsorption capacity of BW-AC for OTC removal was 500 mg/g, based on the Langmuir isotherm equation. In addition, the thermodynamic studies indicated an endothermic process based on the 0.31 value of ΔH° and spontaneous nature due to the negative amount of ΔG° within the temperature range of 288–318 K. Consequently, the prepared BW-AC can be deemed as a highly effective adsorbent with a large surface area, resulting in significant capacity for removing OTC. This synthesized BW-AC can serve as an environmentally friendly adsorbent for affordable wastewater treatment and is poised to make valuable contributions to future research in this field.

Mechanisms of manganese-tolerant Bacillus brevis MM2 mediated oxytetracycline biodegradation process

Addressing the environmental threat of oxytetracycline (OTC) contamination, this study harnesses the bioremediation capabilities of Bacillus brevis MM2, a manganese-oxidizing bacterium from acid mine drainage. We demonstrate the strain's exceptional efficiency in degrading OTC under high manganese conditions, with complete removal achieved within 24 h. The degradation is facilitated by the production of Bio-MnOx, utilizing their high redox potential and large specific surface area, which significantly enhance the adsorption and oxidation of OTC. Advanced characterization techniques, including X-ray diffraction, scanning electron microscopy, High Resolution-Transmission Electronic Microscope and X-ray photoelectron spectroscopy, provide a detailed analysis of the structural and functional properties of Bio-MnOx. The study also reveals the crucial role of Mn(III) intermediates and reactive oxygen species in the OTC degradation process, with quenching experiments validating their substantial impact on efficiency. Laccase activity, a key manganese-oxidizing enzyme, is assessed spectrophotometrically, further highlighting the enzymatic contribution to Mn(II) oxidation and OTC breakdown. This research contributes valuable insights and approaches for the targeted bioremediation of OTC-contaminated aquatic environments, offering a promising strategy for combating pollution from antibiotics and analogous compounds.

Co-doped NH2-UiO-66 for fast and effective adsorption of oxytetracycline: Kinetics, thermodynamics and mechanism

Novel type of micro mesoporous materials Co-doped NH2-UiO-66 had been successfully prepared. The properties of the material were understood through a series of characterization. When the dosage of Zr:Co is 2:1, the modified material showed specific surface area of 840.02 m2∙g−1, which is larger than the material without Co. Especially, the material was transformed from microporous NH2-UiO-66 to micro-mesoporous Co-doped NH2-UiO-66 through the adjustment of metal Co. The Co-doped nanocomposite was then applied to the adsorption of oxytetracycline. The effects of initial concentration, pH, humic acid and ionic strength on the adsorption were investigated. It was found that 50 mg∙L−1 oxytetracycline can be effectively adsorbed by Co-doped NH2-UiO-66 in pH 7. Further research showed that adsorption was pseudo-second-order kinetics and fitted Freundlich model with the maximum adsorption capacity 223.7 mg∙g−1. In addition, the adsorption equilibrium time was only 2 h, which is shorter than the adsorption time of most adsorbents. The mechanism of pore adsorption, π-π interaction, hydrogen bonds and electrostatic interactions was deeply discussed. In conclusion, Co-doped NH2-UiO-66 was a fast and effective absorbent for the removal of oxytetracycline in aqueous solution.

Highly efficient MIL-53(Al)@Biomass hybrid for oxytetracycline elimination: Adsorption, LED-induced photocatalysis and pyrolytic recycling

The presence of antibiotics in water discharges represents a hazard for the ecosystems, as it could affect the biota equilibrium at the micro and macroscales. Consequently, it is crucial to develop effective adsorption and oxidation technologies to remove antibiotics from water. Herein, we assessed the effectivity and stability of a metal organic framework-biomass hybrid (MIL-53(Al)@RH) for the removal of oxytetracycline (OTC) via adsorption and photocatalytic degradation. Under equilibrated conditions, the hybrid retained 165mgg−1 OTC. When adsorption and photocatalytic degradation were arranged in tandem, the system removed 99% of OTC with a dose of 2.83mg H2O2/mg OTC. The thermo-kinetic interpretation of the adsorption measurements was well described by Sip´s isotherm and pseudo-second kinetic models, which along with the heat of adsorption (−104.8kJmol−1) suggest a chemical interaction between the OTC and MIL-53(Al)@Rice Husk hybrid active centres. The MIL-53(Al)@RH hybrid demonstrated a remarkable stability with an OTC removal above 90% after 10 operational cycles. Moreover, pyrolysis of OTC-saturated hybrid led to a carbonaceous structure which demonstrated an outstanding OTC adsorption capacity (221mgg−1 OTC). The results demonstrate that the MIL-53(Al)@RH hybrid presents a significant prospect for combined adsorption-photocatalytic treatment of water bodies contaminated with antibiotics.

Removal of aqueous oxytetracycline using copper-loaded biochar-activated peroxodisulfate: Synergistic mechanism of adsorption and nonradical 1O2

Antibiotic contamination from livestock and poultry farming wastewater has caused substantial adverse effects on the environment and humans. Therefore, in this study, bifunctional adsorption and synergistic degradation of Cu and N codoped biochar (Cu-N/BC) were utilized to efficiently promote the activation of peroxodisulfate (PDS) for removing oxytetracycline (OTC). Cu-N/BC exhibited a high adsorption affinity toward OTC. The adsorption of OTC (50 mg/L) by 0.4 g/L catalyst could reach 36.2 mg/g in 30 min, and the removal of OTC reached 97.24 % in 90 min after adding 0.5 mM PDS. Preadsorption experiments demonstrated that the OTC enriched on the Cu-N/BC surface facilitated the subsequent degradation reaction，its reaction rate constant increases from 0.026 to 0.037. Low-valent copper (Cu0/Cu+), pyridine N, and oxygen-containing functional groups (CO) were the main active sites of Cu-N/BC, and the main contribution toward OTC degradation was from the nonradical pathway of singlet oxygen. Furthermore, potential degradation pathways were revealed, and the intermediates in the OTC degradation process were identified. Cu-N/BC exhibited stable performance, a wide pH application range, and great potential for practical application. This study offers a new concept for designing a bifunctional carbon-based material to remove antibiotics from wastewater.

Removal of oxytetracycline from pharmaceutical wastewater using kappa carrageenan hydrogel

This study investigated the adsorption of Oxytetracycline (OTC) from pharmaceutical wastewater using a kappa carrageenan based hydrogel (KPB). The aim of the present study was to explore the potential of KPB for long-term pharmaceutical wastewater treatment. A sustainable adsorbent was developed to address oxytetracycline (OTC) contamination. The hydrogel’s structural and adsorption characteristics were examined using various techniques like Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), X-ray powder diffraction (XRD), and kinetic models. The results revealed considerable changes in the vibrational modes and adsorption bands of the hydrogel, suggesting the effective functionalization of Bentonite nano-clay. Kappa carrageenan based hydrogel achieved the maximum removal (98.5%) of OTC at concerntration of 40 mg/L, pH 8, cotact time of 140 min and adsorbent dose of 0.1 g (KPB-3). Adsorption of OTC increased up to 99% with increasing initial concentrations. The study achieved 95% adsorption capacity for OTC using a KPB film at a concentration of 20 mg/L and a 0.1 g adsorbent dose within 60 min. It also revealed that chemisorptions processes outperform physical adsorption. The Pseudo-Second-Order model, which emphasized the importance of chemical adsorption in the removal process, is better suited to represent the adsorption behavior. Excellent matches were found that R2 = 0.99 for KPB-3, R2 = 0.984 for KPB-2 and R2 = 0.989 for KPB-1 indicated strong chemical bonding interactions. Statisctical analysis (ANOVA) was performed using SPSS (version 25) and it was found that pH and concentration had significant influence on OTC adsorption by the hydrogel, with p-values less than 0.05. The study identified that a Kappa carrageenan-based hydrogel with bentonite nano-clay and polyvinyl alcohol (PVA) can efficiently remove OTC from pharmaceutical effluent, with a p-value of 0.054, but weak positive linear associations with pH, temperature, and contact time. This research contributed to sustainable wastewater treatment and environmental engineering.

Green synthesis of diatom–allophane bio-nanocomposites for highly efficient oxytetracycline adsorption

The extensive use of the antibiotic oxytetracycline (OTC) has led to considerable environmental contamination and other negative impacts, prompting an urgent need for a green, effective, and innovative OTC adsorption material. In this study, diatom–allophane bio-nanocomposites were synthesized using a simple and eco-friendly method, yielding a homogeneous coating of allophane nanoparticles on diatom surfaces. The resultant bio-nanocomposites were found to have hierarchically porous structures and abundant active sites derived from successful allophane loading and dispersion on diatom surfaces. The OTC adsorption capacity of this novel adsorbent is remarkable (219.112 mg·g−1), surpassing the capacities of raw allophane and diatoms by >5 and 10 times, respectively. Mechanistically, OTC adsorption by the bio-nanocomposites was found to be driven primarily by chemisorption through a process involving complexation between the amide and amino groups on OTC and the aluminum hydroxyl and carboxyl groups on the adsorbent surface. Electrostatic interactions and hydrogen bonding also contribute significantly to OTC capture. Furthermore, the diatom–allophane bio-nanocomposites exhibit excellent performance over a wide pH range (4–7), in the presence of various cations (Na+, K+, Ca2+, Mg2+) and anions (Cl−, NO3−, SO42−), and in real water bodies. These findings demonstrate the potential of the diatom–allophane bio-nanocomposite as a green, efficient, and promising biological-mineral adsorbent for environmental remediation, leveraging the combined utilization of biological and mineral resources.

Carbon dots-doped melamine–formaldehyde microsphere as a dual functional material for sensing and adsorption of oxytetracycline

The abuse of oxytetracycline (OTC) leaves serious environmental residues and triggers accumulation in organisms, constituting a threat to human health. Constructing an effective platform based on dual-functional materials for monitoring and removing OTC residues is a preferable solution. Herein, we proposed a novel composite material by doping carbon dots (CDs) into melamine–formaldehyde microsphere (MFM) through a one-pot method and named CDs@MFM, which inherited the fluorescence property of CDs and porous structure of MFM simultaneously. CDs@MFM demonstrated dual functions for the detection and removal of OTC concurrently within a few minutes, with its performance compared in detail with bare CDs and MFM as controls. By virtue of the pre-enrichment effect attributed to its porous structure, CDs@MFM exhibited a lower detection limit for OTC than bare CDs (0.027 mg/L vs 0.067 mg/L) and a higher adsorption capacity than MFM (73.01 mg/g vs 68.76 mg/g) resulting from more affiliated functional groups available for OTC provided by the CDs. Overall, CDs@MFM has proven to be an efficient and convenient candidate capable of monitoring and removing OTC synchronously, and this work offers an avenue for the design of dual-functional materials in the field of environmental science.

A liter scale synthesis of hierarchically mesoporous UiO-66 for removal of large antibiotics from wastewater.

The presence of antibiotics in water sources is a significant concern due to their potential environmental impact and the risks to human health. In the present research, hierarchically mesoporous UiO-66 (HP-UiO-66) with a high surface area (1011 m2/g) and large pore volume was synthesized using the reflux method on the liter scale. The successful synthesis was confirmed by FT-IR, XRD, FESEM/EDS, N2-adsorption/desorption, and zeta potential techniques. The HP-UiO-66 was utilized to remove two large structure antibiotics, chlortetracycline hydrochloride (CTC), and oxytetracycline (OTC). Box Behnken design was used to investigate the factors affecting the removal process and the interactions between them. The maximum adsorption capacities for OTC and CTC antibiotics were 252.9mg/g and 234.2mg/g at 35°C, respectively. The sum of the normalized error method was applied to the analysis of various error functions in the nonlinear fitting of equilibrium and kinetic data. The CTC and OTC adsorption kinetic followed a fractal-like pseudo-second-order model. The Langmuir isotherm fitted well to adsorption data. The results demonstrate that HP-UiO-66 can be used as a recyclable and efficient adsorbent for large molecule antibiotics removal.

Efficient removal of emerging pollutant oxytetracycline by cost‐effective biochar–hydroxyapatite composite

AbstractBiochar (BC) and hydroxyapatite (HAp) are widely used in environmental remediation due to their high adsorption capacity, porous structure, large specific surface area, chemical stability, non‐toxicity, and low solubility. Combining BC and HAp is a green and effective strategy for creating new adsorbents (BCH) that have a synergistic impact on wastewater treatment. In this study, BCH composites derived from apatite ore and macadamia nut shells were synthesized by the wet impregnation method to remove oxytetracycline (OTC) from aqueous solutions. The BC‐HAp composite with a ratio of 10:1 (by weight) was the most effective material for removing OTC. The Redlich–Peterson model achieved the highest correlation coefficient among the four models tested (Freundlich, Langmuir, Temkin, and Redlich–Peterson). The maximum adsorption capacity calculated with the Langmuir isotherm was 49.59 mg g−1. It was found that the adsorption process was significantly affected by the solution pH. The bipolar form of the drug was found to be OTC±, and the adsorption was most effective in solutions with a pH of 6. The OTC adsorption dominant mechanisms on nanocomposites could be electrostatic attraction, hydrogen bonding formation, surface complexation, or ion exchange. Therefore, the BCH composite showed great potential for removing OTC pollutants in a cost‐effective, and environmentally friendly manner.

Biogas slurry-derived dissolved organic matter inhibited oxytetracycline adsorption by tropical agricultural soils

The increasing presence of oxytetracycline (OTC) in agricultural soils has raised global environmental concerns. We investigated the environmental behavior and fate of OTC in two types of tropical agricultural soils, focusing on the impact of dissolved organic matter (DOM) from biogas slurry. Techniques such as three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM), Fourier Transform Infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and Ultraviolet-visible spectrophotometer (UV–vis) were used to explore the adsorption mechanisms. Our findings revealed that biogas slurry-derived DOM decreased the OTC adsorption on soils and extended the time to reach adsorption equilibrium. Specifically, the equilibrium adsorption of OTC by the two soils decreased by 19.41 and 15.32 %, respectively. These adsorption processes were effectively modelled by Elovich, intraparticle diffusion, linear, and Freundlich thermodynamic models. Thermodynamic parameters suggested that OTC adsorption onto soils was spontaneous and endothermic, with competitive interactions between biogas slurry-derived DOM and OTC molecules intensifying at higher DOM concentrations. The adsorption mechanisms were governed by both physical and chemical processes. Furthermore, the presence of Ca2+ and Na+ ions significantly inhibited OTC adsorption. These insights advanced our understanding of the fate and risk of OTC in soil environments influenced by DOM, contributing to more informed agricultural and environmental management practices.

Enhanced removal of antibiotics and heavy metals in aquatic systems using spent mushroom substrate-derived biochar integrated with Herbaspirillum huttiense.

A novel integrated removal strategy was developed to enhance the concurrent elimination of copper (Cu), zinc (Zn), oxytetracycline (OTC), and enrofloxacin (ENR) from the aqueous environments. The underlying adsorption mechanisms of spent mushroom substrate (SMSB) and the Herbaspirillum huttiense strain (HHS1), and their efficacy in removing Cu, Zn, OTC, and ENR was also examined. Results showed that the SMSB-HHS1 composite stabilized 29.86% of Cu and 49.75% of Zn and achieved removal rates of 97.95% for OTC and 59.35% for ENR through a combination of chemisorption and biodegradation. Zinc did not affect Cu adsorption, and ENR did not impact the adsorption of OTC on SMSB. However, the co-presence of OTC and ENR modified the adsorption behaviors of both Cu and Zn. Copper and Zn enhanced the adsorption of OTC and ENR by serving as bridging agents, facilitating the interaction between the contaminants and SMSB. Conversely, OTC and ENR inhibited the adsorption process of Cu by obstructing its interaction with the SMSB and occupying the oxygen-containing functional groups. The ‒OH (3415 cm-1) and C-O-C (1059 cm-1) functional groups were identified as the principal active sites to form hydrogen bonds and interact with Cu and Zn, leading to the formation of CuP4O11 and Zn4CO3(OH)6H2O. HHS1 also enhanced antibiotic removal through biodegradation, as evidenced by the decrease of ‒C‒O and increase of ‒C = O groups. This study underscores the innovative potential of the SMSB-HHS1 composite, offering a sustainable approach to addressing multifaceted pollution challenges in the aquatic environments.

Adsorption Characteristics of Antibiotic Oxytetracycline on CoFe2O4@Au nanocomposite

Oxytetracycline (OTC) is a widely used broad-spectrum antibiotic for treating bacterial infections in humans and animals. Gold nanoparticles (AuNPs) and cobalt iron oxide (CFO) were combined to create composite magnetic materials designed for the selective adsorption of OTC. The strong affinity of AuNPs for the amine group in the OTC molecule allows for the preferential adsorption of OTC. Simultaneously, the high magnetism of CFO enables the efficient retrieval of materials from the sample solution. The CFO@Au nanomaterials showed an enhanced adsorption capacity of 23.75 mg/g at optimum conditions of pH 7.0; an adsorption time of 90 min, and an adsorbent mass of 0.05g. The adsorption isotherm was in accordance with a Langmuir monolayer model while the kinetic adsorption follows pseudo–second-order kinetic model.. This study provides a simple method for the effective adsorption of OTC as well as a suggestion for the adsorption of other amine-containing substances.

The photodegradation of oxytetracycline by Degussa P25-TiO2/Fe0/ZnO ternary chain heterojunction in the presence of persulfate under visible light irradiation: The optimization and kinetic study

Degussa P25-TiO2/ZnO was impregnated with (Fe (NO3)3·9H2O) solution to give a ternary chain heterojunction of P25-TiO2/1.5 wt% Fe0/ZnO (denoted as P25/Fe0/ZnO) (Gap Energy, Eg = 2.84 eV). The obtained nanocomposite was used in the presence of K2S2O8 for the degradation of oxytetracycline (OTC) in an aqueous solution under visible-light irradiation. The response surface methodology (RSM) was employed to understand the effects of catalyst dosage, pH, and K2S2O8 on OTC degradation. The RSM could correlate the experimental value of OTC degradation with the predicted values. The best OTC degradation efficiency (89.3 %) was obtained with 0.28 g/L of P25/Fe0/ZnO at 3.02 mg/L of [K2S2O8] and pH 7.5 for 120 min. The superior performance of the catalytic system was attributed to the attraction effects between the negative charge on the catalyst surface and the positive charge on the dimethylammonium functional group on OTC at pH = 7.5. The OTC adsorption rate on P25/Fe0/ZnO was investigated using the linear form of the pseudo-second-order kinetic model. The heterogeneous nature of the catalyst was studied by a hot filtration test. Finally, the generated products of photocatalytic degradation were determined using GC–MS analysis, and the oxidation route and an acceptable mechanism were suggested.

Ternary heterojunction of cross-linked benzene Polymer/Bi2MoO6-Graphene oxide catalysts promote efficient adsorption and photocatalytic removal of oxytetracycline

Antibiotics are refractory degradable organic pollutants that present a significant hazard to water environments. In this work, a ternary composite (KB/BMO-GO) comprising of graphene oxide (GO), Bi2MoO6 (BMO), and a cross-linked benzene polymer (KB) was synthesized and applied to promote the synergistic adsorption-photocatalytic degradation of the refractory pollutant, oxytetracycline (OTC). The inclusion of GO and KB in the composite enhanced the OTC adsorption performance of the catalysts, and the construction of Z-scheme heterojunction promoted the photogenerated charge separation efficiency and broadened the range of light absorption, thereby enhancing the photocatalytic performance. Moreover, we compared the performance of catalysts loaded with different mass ratios of KB (x% KB/BMO-GO). Among them, the 15 % KB/BMO-GO catalyst sample had the best OTC degradation performance. Specifically, 15 % KB/BMO-GO could adsorb 69.7 % of OTC in 30 min, reaching an OTC degradation rate of 93.3 % under visible light irradiation. h+ and 1O2 are the main active substances in the photocatalytic process. In addition, the catalysts are acid-alkali and salt-resistant, as well as good reusability. This study provides a valuable reference for the preparation of highly efficient photocatalysts for synergistic adsorption-photodegradation processes.

Adsorption of oxytetracycline in hyporheic zone sediments mediated by microplastics: Experimental revelations and mechanistic insights

Microplastics (MPs), serving as carriers, possess a mediating effect on altering antibiotics (ATs) migration, yet this novel effect has not received due attention in the vulnerable hyporheic zones where surface water and groundwater converge. This study collected sediment layers from the typical hyporheic zone of the Weihe River, focusing on oxytetracycline (OTC) detected therein, and employed three types of MPs (polyethylene (PE), polypropylene (PP), and polymethyl methacrylate (PMMA) to establish various mediated adsorption systems. Through batch equilibrium adsorption experiments, morphological and spectroscopic characterizations combined with the impact of external environmental factors, the changes in OTC adsorption characteristics and the interactions before and after MPs mediation were systematically examined. The results indicate that MPs-mediated adsorption led to the formation of a rough, porous amorphous structure on the sediment surface, with potential internal hydrogen bonds. This exhibited an additional micropore diffusion step that delayed the adsorption kinetics equilibrium time, increased the isothermal maximum adsorption capacity along with desorption hysteresis effects, shifted thermodynamic enthalpy from physically dominated to semi-chemical adsorption participation, and resulted in an increased tendency towards disorder in entropy. The pH, ionic strength, and aging of MPs all affect the charge balance within the adsorption system, while MPs, OTC, and sediments can interact through the negative-charge-assisted hydrogen bond ((−)CAHB). The mediating effect of MPs stems from their role as receptors, facilitating the formation of (−)CAHB and thus crosslinking an amorphous structure available for OTC micropore filling. Compared to PE and PP, PMMA provides receptors through an additional free radical pathway, hence possessing a stronger mediating effect. These findings contribute to reevaluating the environmental fate of ATs and MPs from a new perspective, offering theoretical references for risk assessment and management of emerging pollutants.

Biofilm enhances the interactive effects of microplastics and oxytetracycline on zebrafish intestine

The enhanced adsorption of pollutants on biofilm-developed microplastics has been proved in many studies, but the ecotoxicological effects of biofilm-developed microplastics on organisms are still unclear. In this study, adult zebrafish were exposed to original microplastics, biofilm-developed microplastics, original microplastics absorbed with oxytetracycline (OTC), and biofilm-developed microplastics absorbed with OTC for 30 days. The intestinal histological damage, intestinal biomarker response, gut microbiome and antibiotic resistance genes (ARGs) profile of zebrafish were measured to explore the roles of biofilm in the effects of microplastics. The results showed that biofilm-developed microplastics significantly increased the number of goblet cells in intestinal epithelium compared with the control group. The biofilm-developed microplastics also induced the oxidative response in the zebrafish intestines, and biofilm changed the response mode in the combined treatment with OTC. Additionally, the biofilm-developed microplastics caused intestinal microbiome dysbiosis, and induced the abundance of some pathogenic genera increasing by several times compared with the control group and the original microplastics treatments, regardless of OTC adsorption. Furthermore, the abundance of ARGs in biofilm-developed microplastics increased significantly compared with the control and the original microplastic treatments. This study emphasized the significant influence and unique role of biofilm in microplastic studies.

Fe Oxides–Eggshell Composites: Development, Characterization, and Oxytetracycline Adsorption Test

Fe Oxides–Eggshell Composites: Development, Characterization, and Oxytetracycline Adsorption Test