Enhanced Tetracycline Adsorption Research Articles

Enhanced Tetracycline Adsorption Using KOH-Modified Biochar Derived from Waste Activated Sludge in Aqueous Solutions.

Antibiotic pollution poses a serious environmental concern worldwide, posing risks to ecosystems and human well-being. Transforming waste activated sludge into adsorbents for antibiotic removal aligns with the concept of utilizing waste to treat waste. However, the adsorption efficiency of these adsorbents is currently limited. This study identified KOH modification as the most effective method for enhancing tetracycline (TC) adsorption by sludge biochar through a comparative analysis of acid, alkali, and oxidant modifications. The adsorption characteristics of TC upon unmodified sludge biochar (BC) as well as KOH-modified sludge biochar (BC-KOH) were investigated in terms of equilibrium, kinetics, and thermodynamics. BC-KOH exhibited higher porosity, greater specific surface area, and increased abundance of oxygen-based functional groups compared to BC. The TC adsorption on BC-KOH conformed the Elovich and Langmuir models, with a maximum adsorption capacity of 243.3 mg/g at 298 K. The adsorption mechanisms included ion exchange, hydrogen bonding, pore filling, and electrostatic adsorption, as well as π-π interactions. Interference with TC adsorption on BC-KOH was observed with HCO3-, PO43-, Ca2+, and Mg2+, whereas Cl-, NO3-, and SO42- ions exhibited minimal impact on the adsorption process. Following three cycles of utilization, there was a slight 5.94% reduction in the equilibrium adsorption capacity, yet the adsorption capacity remained 4.5 times greater than that of unmodified sludge BC, underscoring its significant potential for practical applications. This research provided new insights to the production and application of sludge biochar for treating antibiotic-contaminated wastewater.

Gas-phase self-assembly: Converting 2D graphitic carbon nitride into 1D nanotubes for improved photocatalytic tetracycline degradation

Achieving precise control and optimization of structure and composition is paramount for advancing photocatalyst performance. In this study, we successfully synthesized nitrogen-defect and boron-doped one-dimensional g-C3N4 nanotubes (BCNNT) with a tube diameter of approximately 100 nm using a one-step gas-phase self-assembly strategy. Intriguingly, the introduction of boric acid induced a transformation from a two-dimensional g-C3N4 structure to a one-dimensional tubular form. The physicochemical properties and photocatalytic performance of BCNNT were found to be influenced by the quantity of boric acid employed. The as-synthesized BCNNT exhibited notable advantages, including enhanced visible light absorption, a 0.1 eV reduction in the band gap, 5.1 times increase in photocurrent density, effective suppression of electron-hole recombination, and significant improvement in mass transfer compared to pure g-C3N4. Consequently, the first-order kinetic constant of BCNNT increased by 73.7 %, resulting in nearly 80 % degradation of tetracycline (TC) within half an hour. The boron doping played a crucial role in reducing the surface energy required for nanotube formation during synthesis, a key factor in their structural development. Both density functional theory (DFT) calculations and experimental studies confirmed that the Lewis acid site B enhanced tetracycline adsorption, while nitrogen-deficient sites suppressed electron-hole recombination, thus accelerating photocatalytic degradation rate. This research provides a novel perspective on fabricating tubular g-C3N4 structures and compositions, offering insights for improving the kinetics of photocatalytic reactions.

Change of tetracycline speciation and its impacts on tetracycline removal efficiency in vermicomposting with epigeic and endogeic earthworms

Tetracycline pollution is common in Chinese arable soils, and vermicomposting is an effective approach to accelerate tetracycline bioremediation. However, current studies mainly focus on the impacts of soil physicochemical properties, microbial degraders and responsive degradation/resistance genes on tetracycline degradation efficiencies, and limited information is known about tetracycline speciation in vermicomposting. This study explored the roles of epigeic E. fetida and endogeic A. robustus in altering tetracycline speciation and accelerating tetracycline degradation in a laterite soil. Both earthworms significantly affected tetracycline profiles in soils by decreasing exchangeable and bound tetracycline but increasing water soluble tetracycline, thereby facilitating tetracycline degradation efficiencies. Although earthworms increased soil cation exchange capacity and enhanced tetracycline adsorption on soil particles, the significantly elevated soil pH and dissolved organic carbon benefited faster tetracycline degradation, attributing to the consumption of soil organic matter and humus by earthworms. Different from endogeic A. robustus which promoted both abiotic and biotic degradation of tetracycline, epigeic E. foetida preferently accelerated abiotic tetracyline degradation. Our findings described the change of tetracycline speciation during vermicompsiting process, unraveled the mechanisms of different earthworm types in tetracycline speciation and metabolisms, and offered clues for effective vermiremediation application at tetracycline contaminated sites.

Heavy metal-mediated adsorption of antibiotic tetracycline and ciprofloxacin on two microplastics: Insights into the role of complexation

Microplastics (MPs) have recently become an emerging environmental concern. Nevertheless, limited information is known about the adsorption of MPs for organic contaminants under combined heavy metals pollution, with an emphasis on the role of complexation. Thus, this study aims to comprehensively compare and investigate the adsorption performance of antibiotic tetracycline (TC) and ciprofloxacin (CIP) on two polar MPs (polyamide (PA) and polyvinyl chloride (PVC)) affected by Cu(II) and Cd(II) with contrasting complexation abilities. Batch adsorption experiments were used in combination with speciation calculation, zeta potential determination, FTIR spectroscopy characterization and investigation of the affinity of MPs for heavy metals. Results showed that the sorption kinetics and isotherms of TC and CIP on PA and PVC could be well fitted to pseudo-second-order and Langmuir models, respectively, both in the absence and presence of Cu and Cd, suggesting that multiple interactions and monolayer adsorption played an important role in the adsorption process. The presence of Cu substantially improved TC and CIP adsorption and obviously changed the pH dependence of their adsorption onto both MPs, which may result from the Cu-induced strong complexation with TC and CIP. The presence of Cd slightly enhanced TC adsorption on both MPs while reduced CIP adsorption especially on PVC, which may be ascribed to the Cd-induced cationic bridging effects in TC adsorption and the competitive adsorption of Cd in CIP adsorption. Therefore, the heavy metal-mediated complexation effects may play a dominant role in antibiotic adsorption by MPs only in the presence of heavy metals with strong complexation ability while the adsorption performance in the presence of heavy metals with negligible complexation capacity may be influenced by effects other than complexation. This study helps further understand the heavy metal-mediated adsorption behavior of organic contaminants on polar MPs and the role of complexation reactions therein.

Preparation of magnetic porous biochar through hydrothermal pretreatment combined with K2FeO4 activation to improve tetracycline removal

Modification is a key way to enhance the adsorption of tetracycline (TC) by biochar (BC), while how to optimize and identify the most suitable modification methods still need further exploration. In this study, hydrothermal pretreatment combined with K2FeO4 activation were applied to prepare the magnetic porous biochar (H-Fe-BC) derived from a typical biomass (tea waste), with the physicochemical properties of the obtained samples as well as the behaviors and mechanisms toward TC adsorption were systematically investigated. Results showed that, compared with K2FeO4 activated biochar (Fe-BC) and pristine BC, the H-Fe-BC was characterized with enhanced surface area, pore volume, and carbon structure defects, as well as different element compositions, magnetic components and surface functional groups. Elovich, Two-compartment first-order, and Langmuir models can describe well the adsorption process for TC. The maximum adsorption capacity for TC on H-Fe-BC was 229.3 mg g−1, which was 1.7 times and 4.7 times than those of Fe-BC and BC, respectively. The environmental factors such as pHs and co-existing ions exhibited no obvious influence on TC adsorption. The adsorption mechanisms including the pore-filling, π-π interactions, surface complexation, electrostatic interactions and hydrogen bonding were responsible for the enhanced TC adsorption. The results indicate that combined hydrothermal pretreatment and K2FeO4 activation of BC can be used as a feasible modification technology for aquatic contaminant removal.

Adsorption of tetracycline and Cd(II) on polystyrene and polyethylene terephthalate microplastics with ultraviolet and hydrogen peroxide aging treatment

Microplastics (MPs) could serve as vectors of antibiotics and heavy metals through sorption and desorption. However, the combined adsorption process of antibiotics and heavy metals on aged MPs has rarely been studied. In this study, combined adsorption/desorption of tetracycline (TC) and Cd(II) on/from polystyrene (PS) and polyethylene terephthalate (PET) MPs, as well as ultraviolet (UV) and H2O2 aged MPs, was investigated. The specific surface areas of the MPs increased after UV and H2O2 aging. Adsorption experiments showed that the pseudo-second-order kinetic model and Freundlich model fitted adsorption of TC and Cd(II) on all of the MPs. The adsorption capacities of TC and Cd(II) were higher on aged MPs than on the pristine MPs, especially on H2O2 treated MPs. TC adsorption on the MPs was hardly affected by Cd(II), and Cd(II) adsorption was not significantly affected by TC when the solution pH value was below 8.0. Cd(II) slightly enhanced TC adsorption on the MPs at pH 8.0, especially on the aged MPs. The TC adsorption capacities increased with increasing pH, reaching a maximum at pH 5.0 or 6.0, and they then decreased, while the largest level of Cd(II) adsorption was at approximately pH 6.0. Adsorption of TC and Cd(II) on the pristine and aged MPs was thermodynamically favorable and spontaneous. The trend of the desorption rates of TC and Cd(II) from the MPs in different background solutions was ultrapure water < surface water < simulated gastric fluid. The desorption rates of TC and Cd(II) from the aged MPs were lower than those from the pristine MPs. The results revealed the mechanism of the TC and Cd(II) combined adsorption process on aged MPs, which will provide insight for understanding the aging process and its potential effects on sorption and desorption of antibiotics and heavy metals in the real environment.

Effects of modification and magnetization of rice straw derived biochar on adsorption of tetracycline from water

Rice straw derived biochar shows low-cost superiority as a potential adsorbent in tetracycline (TC) removal, but limited by its poor adsorption capacity and N, P leaking risk. Herein, an alkali-acid combined and magnetization method was proposed for its modification. The sorption kinetic and isotherm data showed modification enhanced the performance for tetracycline removal with adsorption capacity up to 98.33 mg·g−1. The strong adsorption mechanisms were dominated by hydrogen bonding and pore-filling effect due to the increase of specific surface area and pore volume. Furthermore, the effect of pH was insignificant over a pH range from 3 to 10. The strong competition between ionic and TC was identified, where Ca2+ and PO43− markedly inhibited the sorption. The enhanced TC adsorption, strong N and P removal, easy magnetic recovery, and good reusability in water samples entrusted it with good potential for wastewater treatment and rice straw resource disposal.

Enhanced adsorption and photocatalytic activities of ultrathin graphitic carbon nitride nanosheets: Kinetics and mechanism

Different from most composite structures with a common configuration of adsorbent-catalyst, g-C3N4 thin nanosheets (CNNS) with the thickness of 8–11 nm had more efficient and stable adsorption and photocatalytic activities in the removal of tetracycline (TC) from aqueous solution. In comparison with common g-C3N4 counterparts, the adsorption performance of CNNS increased by at least 10.3 times and that for photocatalytic efficiency increased for more than 4.8 times. The large contact area and delocalized π bonds provided by CNNS resulted in the enhanced TC adsorption capacity. The efficient separation and prolonged-lifetimes of photogenerated charge carriers, and the strong adsorption brought about a reinforced photocatalytic activity for TC degradation. The adsorption of TC onto CNNS was well followed the pseudo-second-order adsorption kinetics, and the obtained adsorption isotherm was well fitted to the Langmuir isotherm model. Due to the efficient adsorption and photocatalysis of CNNS, the zero-order and first-order kinetics models were presented during the different reaction time for TC photodegradation, the h+, O2− and OH radicals were confirmed as the major reactive oxidative species, and the degradation products were determined. This study provided a new route for the development of catalysts with efficient adsorption and photocatalytic activity in the purification of organic wastewaters.

Encapsulation of Fe0-dominated Fe3O4/Fe0/Fe3C nanoparticles into carbonized polydopamine nanospheres for catalytic degradation of tetracycline via persulfate activation

Porous carbonized polydopamine nanospheres encapsulated with Fe0-dominated Fe3O4/Fe0/Fe3C nanoparticles (Fe@C-PDA) were feasibly fabricated by a one-step pyrolysis of the Fe-PDA polymer, which was employed to activate persulfate (PS) toward degrading tetracycline (TC). The morphology, structure, chemical compositions and textural properties of the resulting catalyst were characterized systematically, and effects of catalyst dosages, PS concentration, inorganic anions (HCO3− and Cl−), natural organic matter and practical water body were studied in detail. The N-doping derived from C-PDA not only enhanced TC adsorption capacity, but also worked as active sites for PS excitation. Moreover, Fe@C-PDA displayed an excellent efficiency and stability in the 5th cycle tests. Electron paramagnetic resonance, classical radical scavenging experiments and X-ray photoelectron spectroscopy analysis disclosed that the active species in the system were identified as sulfate radicals (SO4−) and hydroxyl radicals (OH), and the variable chemical valences of Fe3O4/Fe0/Fe3C nanoparticles as well as N-doping in the C-PDA nanospheres contributed to the outstanding catalytic activity. This work can provide new insight of making this kind of Fe-based materials as the promising catalysts for application in eliminating organic pollutants.

Adsorption of tetracycline on Fe (hydr)oxides: effects of pH and metal cation (Cu2+, Zn2+ and Al3+) addition in various molar ratios.

Iron (Fe) (hydr)oxides control the mobility and bioavailability of tetracycline (TC) in waters and soils. Adsorption of TC on Fe (hydr)oxides is greatly affected by polyvalent metals; however, impacts of molar metal/TC ratios on TC adsorptive behaviours on Fe (hydr)oxides remain unclear. Results showed that maximum TC adsorption on ferrihydrite and goethite occurred at pH 5–6. Such TC adsorption was generally promoted by the addition of Cu2+, Zn2+ and Al3+. The greatest increase in TC adsorption was found in the system with molar Cu/TC ratio of 3 due to the formation of Fe hydr(oxide)–Cu–TC ternary complexes. Functional groups on TC that were responsible for the complexation with Cu2+shifted from phenolic diketone groups at Cu/TC molar ratio < 1 to amide groups at Cu/TC molar ratio ≥ 1. For the addition of Al3+, the complexation only took place with phenolic diketone groups, resulting in the enhanced TC adsorption at a molar Al/TC ratio of 1. However, TC adsorption decreased for Al/TC molar ratio > 1 as excess Al3+ led to the competitive adsorption with Al/TC complexes. For the Zn2+ addition, no significant correlation was found between TC adsorption capacity and molar Zn/TC ratios.

Uncovering potentials of integrated TiO2(B) nanosheets and H2O2 for removal of tetracycline from aqueous solution

This study investigates the impacts of hydrogen peroxide (H2O2) addition on the removal of tetracycline (TC) from aqueous solution by TiO2(B) nanosheets (NSs) and compares the changes of its characteristics due to adsorption treatment. The morphology and textural properties of the TiO2(B) NSs structure before and after the treatment were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Effects of pertinent parameters such as dose of TiO2(B) and/or H2O2 concentration, initial adsorbate concentration, pH, and temperature on the TC adsorption by TiO2(B) NSs were examined. The adsorption mechanisms of TC by the integrated treatment of TiO2(B) NSs and H2O2 are also presented. The results demonstrated that the integrated treatment of TiO2(B)-H2O2 system had significantly improved the TC removal by 250% (with its adsorption capacity (qmax) of 212.77mgg−1), as compared to that of the TiO2-H2O2 system (paired t-test; p≤0.05) under the same optimum conditions (2gL−1 of TiO2(B) NSs; 20mM of H2O2; 0.1gL−1 of initial TC concentration). The enhanced TC adsorption by the integrated TiO2(B)-H2O2 system not only is due to the H-bonding between the TC molecules and the –OOH groups formed on TiO2(B) surface, but it is also because of electrostatic interactions. Their adsorption isotherms followed the Elovich model and were also applicable to both the Langmuir and the Freundlich models. In spite of the adsorbent's promising performance, its treated effluents still could not meet the required TC effluent limit of <62.5μgL−1. This suggests that further subsequent treatment like biological processes is still necessary to completely remove the target pollutant from the wastewater samples.

Enhanced tetracycline adsorption onto hydroxyapatite by Fe(III) incorporation

Contamination of tetracycline (TC) in surface and ground water has proven to be a serious environmental concern, due to the extensive usage and the relatively high solubility of TC in water. Iron-incorporated hydroxyapatite (Fe-HAP) with different iron contents was prepared to improve the dispersibility and TC removal from water. Results indicated that Fe-HAP had higher dispersion stability and greater adsorption ability for TC compared with virgin HAP. TC adsorption was found to increase with increasing temperature but decrease with increasing pH values. Addition of exogenous ions (Na+ and Ca2+) resulted in a decrease of TC adsorption due to electrostatic screening and the competitive effect. However, Cu2+ and humic acid could promote TC adsorption by acting as a bridge to form Fe-HAP-Cu2+-TC surface complex. Meanwhile humic acid can also improve adsorption through hydrogen-bonding between carboxylic, phenolic hydroxyl groups of humic acid and the electron-donors (OH/O, NH2) of TC. The peak variations of CO and NH2 in tricarbonyl amide group and CO in phenolic deketone group in the FTIR spectra of TC equilibrated with Fe-HAP revealed that TC adsorption was attributed to surface complexation. This study, therefore, showed that Fe-HAP could be a promising adsorbent for the removal of TC from aqueous solution.

A novel solid digestate-derived biochar-Cu NP composite activating H2O2 system for simultaneous adsorption and degradation of tetracycline

Solid digestate, a by-product of anaerobic digestion systems, has led to a range of environmental issues. In the present study, a novel composite based on a solid digestate-biochar-Cu NP composite was synthesized for tetracycline removal from an aqueous medium. The removal efficiency values for tetracycline (200 mg L−1) were 31.5% and 97.8%, respectively, by the biochar-Cu NP composite (0.5 g L−1) in the absence and presence of hydrogen peroxide (H2O2, 20 mM) within 6 h of reaction time. The possible degradation pathway of tetracycline was investigated using liquid chromatography-mass spectrometry. The desorption experiment results suggested that no significant concentration of tetracycline was detected on the composite after the reaction, but a small amount of intermediates in terms of total organic carbon (TOC) accounting for 3.1%, and 23.3% of the end-product NH4+ was adsorbed onto the biochar sheets. The dispersive Cu NPs on the biochar resulted in an increase in the surface area and pore volume of the biochar-Cu NP composite, which enhanced tetracycline adsorption as well as the degradation efficiency. Relative tetracycline removal mechanisms were dominantly ascribed to ·OH generation from the Cu(II)/Cu(I) redox reaction with H2O2 and the electron-transfer process of free radicals (FRs) in biochar. The proposed approach serves dual purposes of waste digestate reuse and treatment of antibiotic pollutants.This study highlights the activation of H2O2 by the dispersive Cu NPs coupling with biochar derived from a waste solid digestate for tetracycline treatment.

Adsorption of tetracycline from aqueous solutions onto multi-walled carbon nanotubes with different oxygen contents.

Oxidized multi-walled carbon nanotubes (MWCNTs) with different oxygen contents were investigated for the adsorption of tetracycline (TC) from aqueous solutions. As the surface oxygen content of the MWCNTs increased, the maximum adsorption capacity and adsorption coefficient of TC increased to the largest values and then decreased. The relation can be attributed to the interplay between the nanotubes' dispersibility and the water cluster formation upon TC adsorption. The overall adsorption kinetics of TC onto CNTs-3.2%O might be dependent on both intra-particle diffusion and boundary layer diffusion. The maximum adsorption capacity of TC on CNTs-3.2%O was achieved in the pH range of 3.3–8.0 due to formation of water clusters or H-bonds. Furthermore, the presence of Cu2+ could significantly enhanced TC adsorption at pH of 5.0. However, the solution ionic strength did not exhibit remarkable effect on TC adsorption. In addition, when pH is beyond the range (3.3–8.0), the electrostatic interactions caused the decrease of TC adsorption capacity. Our results indicate that surface properties and aqueous solution chemistry play important roles in TC adsorption on MWCNTs.

Adsorption of tetracycline (TC) onto montmorillonite: Cations and humic acid effects

The adsorption of tetracycline (TC) on a Na-montmorillonite was studied as a function of five background electrolyte cations (Li+, Na+, K+, Mg2+ and Ca2+), one transitional metal cation (Cu2+) and humic acid (HA) over a pH range from 3 to 9 using batch experiments combined with XRD and FTIR measurement. Results showed that pH had great effect on the TC adsorption and acidic condition is more favored. Monovalent (Li+, Na+ and K+) and divalent (Mg2+, Ca2+ and Cu2+) cations showed very different effects on the TC adsorption onto montmorillonite. In the presence of monovalent cations, the adsorption edge curves were little affected by the types of cations. They presented a great decrease at pH<6, then an increase to a local maximum at about pH 8, followed by a gradual decrease (8<pH<9), which might resulted from cation exchange at the interlayer surface sites and surface complexation at the basal or edge sites. In the presence of divalent cations, the adsorption of TC was enhanced compared to the ones in the presence of monovalent cations, indicating other mechanism might involve. The enhanced TC adsorption has an order: Cu2+≫Ca2+>Mg2+, which might be due to the capability of “bridge” effect of divalent cations. The difference of enhancing TC adsorption in the presence of Ca2+ and Mg2+ might be a result of different ionic radii and different interacting groups in TC molecular. XRD results showed that TC was intercalated into interlayers of montmorillonite since the interlayer expansion was observed. The band changes of amide carbonyl and amino groups in tricarbonyl methane group and the carbonyl group in phenolic deketone group in the FTIR spectra of TC equilibrated with montmorillonite confirmed that TC was adsorbed to the clay via cation exchange and surface complexation. It was also found that the effect of HA on the TC adsorption was pH-dependent and the presence of HA significantly reduced the mobility of TC in solution especially under acidic condition due to the complexation between cationic or zwitterionic TC species and the deprotonated sites on HA (mainly carboxylic groups) via electrostatic attraction. These results suggested that coexistence of divalent cations and HA would reduce TC's mobility in soil environment, especially at acidic condition.