Adsorption Of Oxytetracycline Research Articles

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

Water-based Synthesis of MIL-53(Al) at Room Temperature: An Eff ective Adsorbent for Oxytetracycline (OTC) Antibiotic Removal from Water

MIL-53(Al), a fl exible metal-organic framework, was synthesized by a facile method through a water-based method at room temperature, aligning with the principles of green chemistry. The objective was to investigate its effectiveness in removing pharmaceuticals and personal care products (PPCPs), specifi cally focusing on oxytetracycline (OTC). Our fi ndings revealed that MIL-53(Al) possesses a structure with both micropores and mesopores, with a specifi c surface area of 916 m2/g. MIL-53(Al) notably exhibited a higher OTC adsorption capacity than commercially available powder activated carbon (PAC). The adsorption kinetics followed a pseudo-second-order model, while the Langmuir model accurately described the experimental isotherms for OTC adsorption. MIL-53(Al) outperformed previously reported MOF-based adsorbents with a maximum of 1005 mg/g capacity at pH 7. The fl exible structure induces a breathing effect that signifi cantly improves intraparticle diffusion for OTC, contributing to its adsorption effi ciency. The adsorption of OTC was infl uenced by the solution pH, the acid dissociation constants of OTC, and the charged surface of the adsorbent. Pore fi lling, hydrogen bonding, π-π interaction, electrostatic interaction, and hydrophobic interaction were all associated with the adsorptive interaction between OTC and MIL-53(Al). The MIL-53(Al) also demonstrated good regeneration and reuse, with just a little decreased adsorption capacity after three reuse cycles. These fi ndings indicate that green material MIL-53(Al) has the potential to be an effective adsorbent for removing OTC from water matrices

Self-Assembled Aminated and TEMPO Cellulose Nanofibers (Am/TEMPO-CNF) Aerogel for Adsorptive Removal of Oxytetracycline and Chloramphenicol Antibiotics from Water.

Antibiotics are used for the well-being of human beings and other animals. Detectable levels of antibiotics can be found in pharmaceutical, municipal, and animal effluents. Therefore, the treatment of antibiotic contaminated water is of great concern. In this study, we fabricated a sustainable aminated/TEMPO cellulose nanofiber (Am/TEMPO-CNF) aerogel to remove oxytetracycline (OTC) and chloramphenicol (CAP) from synthetic wastewater. The prepared aerogel was characterized using different analytical techniques such as elemental analysis, FTIR, TGA, SEM-EDS, and N2 adsorption-desorption isotherms. The characterization techniques confirmed the presence and interaction of quaternary amine -[NR3]+ and -COOH groups on Am/TEMPO-CNF with OTC and CAP, which validates the successful modification of Am/TEMPO-CNF. The adsorption process of the pollutants was examined as a function of solution pH, concentrations, reaction time, and temperatures. The maximum adsorption capacity was 153.13 and 150.15 mg/g for OTC and CAP, respectively. The pseudo-second order (PSO-2) was well fitted to both OTC and CAP, confirming the removal is via chemisorption. Hydrogen bonding and electrostatic attraction have been postulated as key factors in facilitating OTC and CAP adsorption according to spectroscopic studies. Energetically, the adsorption was spontaneous and endothermic for both pollutants. In conclusion, the efficient removal rate and excellent reusability of Am/TEMPO-CNF indicate the strong potential of the adsorbent for antibiotics' removal.

Alkaline-modified biochar and nitrifying microbiome synergistically mitigate the toxicity of oxytetracycline and its toxic by-products

The widely used antibiotic oxytetracycline (OTC) is found in various natural and engineered water environments, where it can potentially disrupt important ecosystem functions such as nitrification. This work proposed the use of alkaline-pretreated biochar (BC) with a nitrifying microbiome to mitigate OTC disturbance and enhance the removal and detoxification of both OTC and its by-products (BPs). The OTC adsorption capacity of BC was pre-optimized using a 1 M NaOH solution. While exposure to OTC led to the replacement of the dominant sub-species populations within Nitrosomonas, the addition of BC preserved the original diversity and structure of the nitrifying microbiome. The evaluation of long-term reactor operation and batch tests using advanced analytical methods revealed that the addition of BC significantly increased the removal of OTC with a novel biotransformation pathway. Structure-based toxicity modeling and antimicrobial susceptibility experiments were performed to assess the toxicity of OTC, its BPs, and bulk effluent containing both OTC and its known/unknown BPs. Three OTC BPs were found to have 6–90 times higher toxicity than OTC itself. In comparison to the microbiome alone, the addition of BC had the potential to enhance the detoxification of both OTC and its BPs. Collectively, the results of the present study indicate that the addition of BC to nitrifying systems may be a promising retrofitting option that proactively maintains the biological function and stability of the system in the presence of toxic waste streams via the synergistic control of both the original contaminants and their BPs in conjunction with nitrifying microbiomes.

Hierarchical porous UiO-66 composites modified by dual competitive strategy for adsorption of oxytetracycline

Adsorption is a popular technology for solving water-pollution problems because it is highly efficient, affordable and environmentally friendly. In this study, a dual competition strategy was developed to improve oxytetracycline adsorption by modulating the UiO-66 defects. A series of defect-rich hierarchical porous UiO-66 was prepared using the competitive strategy of bi-metal (Zn2+/Zr4+) and bi-ligand (terephthalic acid/monocarboxylic acid). Compared with the pristine UiO-66, the defect-rich hierarchical porous UiO-66 has a higher adsorption efficiency and faster adsorption rate. Among them, the greatest adsorption ability of But-HP-UiO-66 was 209.97 mg∙g−1 at pH= 6.0, which was 9.89 times greater than UiO-66. The kinetic and isotherm fitting results showed that the adsorption was consistent with the Elovich and Freundlich models. According to the response surface model design based on four factors (OTC concentration, pH, humic acid and SO42- intensity), But-HP-UiO-66 exhibited an excellent adsorption effect and strong anti-jamming ability. The prominent advantages of this composite are its rich pore structure and abundant defects. The adsorption mechanism showed that the electrostatic interactions, metal-organic complexation, pore adsorption, hydrogen bonding and π-π interactions performed vital functions. This study provides a promising method for manufacturing strongly hierarchical porous MOFs and strengthens their potential applications in antibiotic elimination.

Adsorption of oxytetracycline and ciprofloxacin on carbon-based nanomaterials as affected by pH

Adsorption of oxytetracycline and ciprofloxacin on carbon-based nanomaterials as affected by pH

Adsorptive removal of oxytetracycline using MnO2-engineered pine-cone biochar: thermodynamic and kinetic investigation and process optimization.

Indiscriminate use of oxytetracycline is linked to the development of antibiotic-resistant genes, posing a serious threat to human health and ecosystem balance. This article reports the adsorptive elimination of oxytetracycline (OTC) from aqueous solution using a newly developed MnO2-modified pine-cone biochar (MnO2/PCBC). The MnO2/PCBC was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, CHNS analyzer, inductively coupled plasma-optical emission spectroscopy, and Brunauer-Emmett-Teller N2 adsorption analyzer. Batch adsorption experiments, designed using the central composite design framework of response surface methodology, were conducted to investigate the influence of process variables on the adsorption of OTC onto MnO2/PCBC. The optimized conditions for achieving maximum removal (88.1%) were found to be at pH 8, MnO2/PCBC dose 0.44 g/L, initial OTC concentration 200 mg/L, and temperature 303 K. The adsorption process follows Langmuir (R2=0.95) and Freundlich (R2=0.95) isotherms and pseudo-second-order (R2=0.99) adsorption kinetics. The adsorption process was found to be endothermic (ΔH0 = 33.04 kJ/mol) and spontaneous in nature (ΔG0 from -1.33 kJ/mol at 283 K to -5.65 kJ/mol at 313 K). The synthesized MnO2/PCBC could be recycled and reused for OTC removal with a percentage removal of around 80% after fifth cycle. The results indicate an effective removal of oxytetracycline with only 0.44 g/L MnO2/PCBC with maximum adsorption capacity of 357.14 mg/g which demonstrates improved performance in comparison to many adsorbents reported in literature. This implies that MnO2/PCBC offers potential to be developed into a cost-effective technique for antibiotic removal from water.

Study on removal of oxytetracycline by KOH-modified chestnut shell biochar: Based on two-dimensional spectroscopy and molecular density functional theory

The adsorption type and mode of biochar have been extensive research. However, as an indispensable link to reveal the adsorption mechanism, the study of the adsorption sequence is greatly lacking, especially for different pollutants, the way of adsorption is different. In this study, the observation of the adsorption sequence was amplified by KOH modification and optimization of experimental conditions. Persistent radicals (PFRs) combined with liquid mass spectrometry (LC-MS) eliminated interference from oxidation-reduction. Notability, two-dimensional correlation spectroscopy (2D-COS), Raman and Fourier-transform infrared (FTIR) spectroscopy reveals that the vibration amplitude and velocity of the hydroxyl group are better than those of the carboxyl group, methyl group, and methylene group under time interference. Electrostatic adsorption (EA), H-bood (HB), and π-π* contribute 63.5 %, 35.3 %, and 1.2 %, respectively, to the adsorption of oxytetracycline (OTC). The density functional calculation shows that the nucleophilic and electrophilic reactions of OTC are easy to occur near oxygen atoms and nitrogen atoms. The Fukui function proves that the free radical weight of the N atom is 0.096, which is further confirmed the theoretical predictions by liquid chromatography and four-stage electrostatic field orbital trap mass spectrometry. Finally, this study provides a deeper insight into the biochar adsorption OTC.

Multifunctional carboxymethyl cellulose/graphene oxide/polyaniline hybrid thin film for adsorptive removal of Cu(II) and oxytetracycline antibiotic from wastewater

The antibiotics and metal ions in the contaminated water bodies must be removed using appropriate methods for sustainable development. In this study, the multifunctional carboxymethyl cellulose/graphene oxide/polyaniline (CMC/GO/PANI) hybrid thin film was synthesized and utilized for adsorptive scavenging of (Cu(II) and oxytetracycline (OTC) from wastewater. The prepared thin films' morphology, chemical compositions, functionality, and surface charge were analyzed by well-known physicochemical techniques. The adsorption process of the selected model pollutants was examined as a function of reaction time, Cu(II), and OTC solution pH, concentrations, and temperatures. Results showed that CMC/GO/PANI hybrid thin film had higher Cu(II) and OTC adsorption than CMC, GO/CMC, and PANI/CMP thin films due to the multifunctional synergetic effect. The adsorption kinetic data were fitted to the pseudo-second-order model. Redlich-Peterson isotherm model well interpreted Cu(II) and OTC scavenging equilibrium data. Energetically, the adsorption was spontaneous and endothermic for both pollutants. The multifunctional CMC/GO/PANI thin film was recycled and reused seven times during adsorption-desorption cycles. The study outcomes demonstrated that CMC/GO/PANI thin film could be reused multiple times for large-scale wastewater purification.

Activated sludge microbiome with H2O2-modified biochar enhances the treatment resilience and detoxification of oxytetracycline and its toxic byproducts

The widespread presence of oxytetracycline (OTC) in aquatic ecosystems poses both health risks and ecological concerns. The present study revealed the beneficial role of hydrogen peroxide (H2O2)-pretreated biochar (BC) derived from agricultural hardwood waste in an activated sludge (AS) bioprocess. The BC addition significantly enhanced the removal and detoxification of OTC and its byproducts. BC was initially modified using H2O2 to improve its OTC adsorption. Two AS reactors were then established, one with H2O2-modified BC and one without, and both were exposed to OTC. The BC-added reactor exhibited significantly higher OTC removal rates during both the start-up (0.97 d−1) and steady-state (0.98 d−1) phases than the reactor without BC (0.54 d−1 and 0.83 d−1, respectively). Two novel transformation pathways for OTC were proposed, with four byproducts originating from OTC identified, some of which were found to be more toxic than OTC itself. The BC-added reactor had significantly higher system functioning in terms of its heterotrophic activity and the reduction of the toxicity of OTC and its byproducts, as illustrated by structure-based toxicity simulations, antimicrobial susceptibility experiments, analytical chemistry, and bioinformatics analysis. Bioinformatics revealed two novel bacterial populations closely related to the known OTC-degrader Pandoraea. The ecophysiology and selective enrichment of these populations suggested their role in the enzymatic breakdown and detoxification of OTC (e.g., via demethylation and hydrogenation). Overall, the present study highlighted the beneficial role of H2O2-modified BC in combination with the AS microbiome in terms of enhancing treatment performance and resilience, reducing the toxicological disruption to biodiversity, and detoxifying micropollutants.

Adsorptive-Photocatalytic Performance for Antibiotic and Personal Care Product Using Cu0.5Mn0.5Fe2O4.

The amount of antibiotics and personal care products entering local sewage systems and ultimately natural waters is increasing and raising concerns about long-term human health effects. We developed an adsorptive photocatalyst, Cu0.5Mn0.5Fe2O4 nanoparticles, utilizing co-precipitation and calcination with melamine, and quantified its efficacy in removing paraben and oxytetracycline (OTC). During melamine calcination, Cu0.5Mn0.5Fe2O4 recrystallized, improving material crystallinity and purity for the adsorptive-photocatalytic reaction. Kinetic experiments showed that all four parabens and OTC were removed within 120 and 45 min. We found that contaminant adsorption and reaction with active radicals occurred almost simultaneously with the photocatalyst. OTC adsorption could be adequately described by the Brouers-Sotolongo kinetic and Freundlich isotherm models. OTC photocatalytic degradation started with a series of reactions at different carbon locations (i.e., decarboxamidation, deamination, dehydroxylation, demethylation, and tautomerization). Further toxicity testing showed that Zea mays L. and Vigna radiata L. shoot indexes were less affected by treated water than root indexes. The Zea mays L. endodermis thickness and area decreased considerably after exposure to the 25% (v/v)-treated water. Overall, Cu0.5Mn0.5Fe2O4 nanoparticles exhibit a remarkable adsorptive-photocatalytic performance for the degradation of tested antibiotics and personal care products.

Highly adsorptive removal of oxytetracycline in water environment using polyanion modified alumina nanoparticles

In this study, adsorptive removal of an antibiotic oxytetracycline (OTC) using polyanion poly(2-acrylamide-2-methylpropane sulfonic acid), PAMPs modified α-Al2O3 nanoparticles (PAMNA) was investigated. Surface modification of α-Al2O3 nanoparticles by PAMPs enhanced the removal efficiency of OTC significantly from 35.5 to 90.7 %. The optimum conditions for adsorptive removal of OTC using PAMNA were found to be pH 4, contact time 120 min and adsorbent dosage 20 mg/mL. Under selected conditions, the removal efficiency of OTC using PAMNA was greater than 90 % while the maximum adsorption capacity reached 140.2 mg/g. After three regenerations, the removal efficiencies of OTC were still higher than 75 %. The results of adsorption isotherms of OTC on PAMNA and the surface charge change of PAMNA indicate that both electrostatic and non-electrostatic interactions control OTC adsorption on PAMNA.

Highly efficient nanocomposite of Y2O3@biochar for oxytetracycline removal from solution: Adsorption characteristics and mechanisms

Nano Y2O3-modified biochar composites (Y2O3@BC600) were fabricated successfully and exhibited great adsorption toward oxytetracycline (OTC). The Langmuir adsorption capacity of Y2O3@BC600-1:4 for OTC reached 223.46 mg/g, 10.52 times greater than that of BC600. The higher dispersion of Y2O3 nanoparticles, increased surface area of 175.65 m2/g and expanded porosity of 0.27 cm3/g accounted for higher OTC adsorption by Y2O3@BC600-1:4. Y2O3@BC600-1:4 could resist the interference of co-existing cations (Na+, K+, Mg2+, Ca2+) and anions (Cl−, NO3−, SO42−) on OTC removal. Y2O3 coating changed surface charge property of BC600, favoring the contribution of electrostatic interaction. Synchrotron radiation-based Fourier transform infrared spectroscopy detected obvious peak shift and intensity change of surface –OH when OTC adsorption occurred. Accordingly, stronger H-bonding (charge-assisted hydrogen bond, OTC–H2N+···HO–Y2O3@BC600-1:4) was proposed for OTC adsorption. Y2O3@BC600 exhibited renewability and stability in the adsorptive removal of OTC. Therefore, Y2O3@BC600 may be a novel and suitable adsorbent for antibiotic removal.

Adsorption of oxytetracycline on subalpine meadow soil from Zoige Plateau, China: Effects of the coexisting Cu2+

Subalpine meadow soil with high moisture and humus content is a unique soil type in the Zoige Plateau. Oxytetracycline and copper are common soil contaminants which interact to form compound pollution. Oxytetracycline's adsorption on natural subalpine meadow soil and its components (humin and the soil without iron and manganese oxides) was studied in the laboratory with and without the presence of Cu2+. The effects of temperature, pH and Cu2+ concentration were documented in batch experiments, allowing deduction of the main sorption mechanisms. The adsorption process had two phases: one rapid, taking place in the first 6 h, and another slower, reaching equilibrium at around 36 h. The adsorption kinetics were pseudo-second-order, and the adsorption isotherm conformed to the Langmuir model at 25 °C. Higher concentrations oxytetracycline increased the adsorption, but higher temperature did not. The presence of Cu2+ had no effect on the equilibrium time, but the amount and rate adsorbed were much greater with Cu2+ concentration increased (except for the soil without iron and manganese oxides). The amounts adsorbed with/without Cu2+ were in the order the humin from subalpine meadow soil (7621 and 7186 μg/g) > the subalpine meadow soil (7298 and 6925 μg/g) > the soil without iron and manganese oxides (7092 and 6862 μg/g), but the difference among those adsorbents was slight. It indicates that humin is a particularly important adsorbent in the subalpine meadow soil. The amount of oxytetracycline adsorbed was greatest at pH 5–9. In addition, Surface complexation through metal bridging was the most important sorption mechanism. Cu2+ and oxytetracycline formed positively-charged complex that was adsorbed and then formed a ternary complex “adsorbent-Cu(II)-oxytetracycline”, in which Cu2+ acted as a bridge. These findings provide a good scientific basis for soil remediation, and for assessing environmental health risks.

Evidence for the feasibility of transmembrane proton gradient regulating oxytetracycline extracellular biodegradation mediated by biosynthesized palladium nanoparticles

Extracellular biodegradation is a promising technology for removing antibiotics and repressing the spread of resistance genes, but the strategy is limited by the low extracellular electron transfer (EET) efficiency of microorganisms. In this work, biogenic Pd0 nanoparticles (bio-Pd0) were introduced in cells in situ to enhance oxytetracycline (OTC) extracellular degradation and the effects of transmembrane proton gradient (TPG) on EET and energy metabolism mediated by bio-Pd0 were investigated. The results indicated that the intracellular OTC concentration gradually decreased with increase in pH due to the simultaneous decreases of OTC adsorption and TPG-dependent OTC uptake. On the contrary, the efficiency of OTC biodegradation mediated by bio-Pd0@B. megaterium showed a pH-dependent increase. The negligible intracellular OTC degradation, the high dependence of OTC biodegradation on respiration chain and the results on enzyme activity and respiratory chain inhibition experiments showed that NADH-dependent (rather than FADH2-dependent) EET process mediated by substrate-level phosphorylation modulated OTC biodegradation due to high energy storage and proton translocation capacity. Moreover, the results showed that altering TPG is an efficient approach to improve EET efficiency, which can be attributed to the increased NADH generation by the TCA cycle, enhanced transmembrane electron output efficiency (as evidenced by increased intracellular electron transfer system (IETS) activity, the negative shift of onset potential, and enhanced one-electron transfer through bound flavin) and stimulation of substrate-level phosphorylation energy metabolism catalyzed by succinic thiokinase (STH) under low TPG conditions. The results of structural equation model that OTC biodegradation was directly and positively modulated by the net outward proton flux as well as STH activity, and indirectly regulated by TPG through NADH level and IETS activity confirmed the previous findings. This study provides a new perspective for engineering microbial EET and application of bioelectrochemistry processes in bioremediation.

Adsorption of antibiotic, heavy metal and antibiotic plasmid by a wet-state silicon-rich biochar/ferrihydrite composite to inhibit antibiotic resistance gene proliferation/transformation

Decreasing bioaccessible antibiotics, heavy metals, and antibiotic resistance genes (ARGs) in soil by adsorption is an attractive, but unrealized, approach for ARG risk reduction. This approach has the potential to reduce the (co)selection pressure from antibiotics and heavy metals on bacteria and ARG horizontal gene transformation to pathogens. Here, a wet-state silicon-rich biochar/ferrihydrite composite (SiC–Fe(W)) synthesized by loading ferrihydrite onto rice straw-derived biochar was examined for i) adsorption of oxytetracycline and Cu2+ to reduce (co)selection pressure and ii) adsorption of extracellular antibiotic resistance plasmid pBR322 (containing tetA and blaTEM-1) to inhibit ARG transformation. SiC–Fe(W) gained the adsorption priority of biochar (for Cu2+) and wet-state ferrihydrite (for oxytetracycline and pBR322) and showed adsorptive enhancement (for Cu2+ and oxytetracycline) from a more wrinkled and exposed surface from biochar silica-dispersed ferrihydrite and a more negatively charged biochar, and the adsorption capacity for SiC–Fe(W) was 17–135 times that of soil. Correspondingly, 10 g/kg SiC–Fe(W) amendment increased the soil adsorption coefficient Kd by 31%–1417% and reduced the selection pressure from dissolved oxytetracycline, co-selection pressure from dissolved Cu2+, and transformation frequency of pBR322 (assessed with Escherichia coli). The development of Fe–O–Si bonds on silicon-rich biochar in alkaline enhanced ferrihydrite stability and adsorption capacity (for oxytetracycline), presenting a new potential strategy of biochar/ferrihydrite composite synthesis for adsorptive inhibition of ARG proliferation and transformation in ARG pollution control.