Adsorption Of Chlortetracycline Research Articles

Construction of ligand functionalized MIL-101(Fe)-R and mechanism of efficient removal of chlortetracycline hydrochloride: Experiment and DFT calculation

Functionalization of ligands is an effective strategy to enhance the adsorption performance of adsorbents. In this study, MIL-101(Fe)-R (R = -H, –OH, –NH2, and –NO2) was selected as a platform for systematically studying the impact of functionalization on the adsorption behavior of chlortetracycline (CTC). A series of characterizations were conducted on the prepared MIL-101(Fe)-R to clarify the influence of organic linkers on the microscopic morphology, pore structure, and surface functionality of the adsorbents. Additionally, the effects of different functional groups on the adsorption behavior of MIL-101(Fe)-R were compared to screen for MOFs with high efficiency in removing CTC. Experimental results showed that the maximum adsorption capacities (qm) of MIL-101(Fe), MIL-101(Fe)–NH2, MIL-101(Fe)–OH, and MIL-101(Fe)–NO2 were 418.980 mg/g, 559.854 mg/g, 187.387 mg/g, and 154.131 mg/g, respectively. Among them, MIL-101(Fe)–NH2 exhibited a higher mass transfer rate (reaching equilibrium in 15 min). Based on apparent adsorption behavior, adsorption kinetics, isotherm and thermodynamic studies, as well as FTIR and XPS characterizations before and after adsorption, the performance modulation mechanism of MIL-101(Fe)-R in CTC adsorption was discussed in detail. Combined with density functional theory (DFT) calculations, the host–guest interaction controlling the adsorption behavior was understood at the molecular level, demonstrating the optimal binding sites of the adsorbents. This study provides guidance for the design of efficient MOF adsorbents for antibiotic wastewater treatment.

Study on the adsorption of chlortetracycline in water on peanut shells decorated with magnetic particles by ultrasonic-assisted method

Study on the adsorption of chlortetracycline in water on peanut shells decorated with magnetic particles by ultrasonic-assisted method

Effect of Acid–Base Modified Biochar on Chlortetracycline Adsorption by Purple Soil

We used three purple soil (Hechuan, Jialing, and Cangxi) samples from the Jialing River basin as the research objects and added different proportions of an acid–base modified Alternanthera philoxeroides biochar (Cm) to the purple soil to study the effect of Cm on the adsorption of chlortetracycline (CTC) in the purple soil. The results indicated the following: (1) At 30 °C and pH = 6, the soil adsorption capacity increased with an increasing initial concentration of CTC. The maximum adsorption amount of CTC for each tested sample was in the range of 2054.63–3631.21 mg/kg, and the adsorption capacity in different Cm amended soils was ranked in the order of 10% Cm > 5% Cm > 2% Cm > CK. The adsorption capacity of CTC increased with an increase in the proportion of Cm. Furthermore, under the same addition ratio of Cm, Hechuan soil was found to have a better adsorption effect for CTC than Jialing and Cangxi soil. (2) The Langmuir model was the most suitable for fitting the adsorption behavior of CTC on different purple soils, and the fitting coefficients were all greater than 0.9, indicating that the adsorption of CTC on each soil sample occurred via monolayer adsorption. The thermodynamic experiment results showed that an increase in temperature was beneficial to the process of CTC adsorption, which was a spontaneous, endothermic, and entropy-adding process. (3) At pH = 6, the ionic strength ranged from 0.01 to 0.5 mol/L and the adsorption capacity of CTC of the soil samples decreased with an increase in ionic strength. In the range of pH 2–10, the adsorption capacity of CTC in all the soil samples decreased with an increase in pH. The inhibition capacity of CTC in the soil samples under acidic conditions was notably higher than that under alkaline conditions.

Enhanced chlortetracycline removal by iron oxide modified spent coffee grounds biochar and persulfate system

Chlortetracycline (CTC) is a tetracycline derivative antibiotic that has been widely used in the livestock industry for prophylactic and therapeutic purposes. Effective measures should be taken to decrease the environmental risks associated with CTC-rich waste. Biochar produced by biomass waste showed great potential for organic contaminants removal by adsorption and catalytic degradation. This study prepared iron oxide-modified coffee grounds biochar (CGF) at different temperatures for enhanced CTC removal by adsorption and degradation. The main mechanism for CTC removal was found to be electrostatic interaction. In addition, pore diffusion, hydrogen bonds, and π-π bonds also contributed to CTC adsorption. Maximum CTC adsorption capacity was 223.63 mg/g for CGF800 (CGF prepared at 800 °C pyrolysis). The free radical content of CGF600 (CFG prepared at 600 °C pyrolysis) was higher than CGF800, and there were no significant advantages in using biochar prepared at a higher temperature for persulfate activation. The ion mass-to-charge ratio (M/z) is used to describe the ratio of mass to charge of an ion or peak, which can infer compound structure. The structure of CTC degradation products was analyzed by UPLC-MS, and the M/z values were determined as 444, 273, and 154. Thus, pyrolysis of coffee grounds at higher temperatures increased CTC adsorption capacity, and CGF can indirectly assist in CTC degradation by persulfate activation.

Adsorption of chlortetracycline in aquaculture wastewater by lanthanum modified multi-walled carbon nanotubes

The lanthanum modified multi-walled carbon nanotubes (La-CNTs) prepared by an impregnation method were investigated for the adsorption of chlortetracycline (CTC) in aquaculture wastewater. The adsorbents were characterized by SEM, EDS, XRD and BET. The effects of some factors including La-containing impregnant concentration, adsorbent dosage, CTC adsorbate concentration, adsorption time, pH of the adsorbate solution and additional ions on the CTC adsorption by La-CNTs were investigated in detail, and the optimal adsorption conditions were determined. The adsorption kinetics obeyed the quasi-second-order kinetic model. The adsorption isotherms obeyed the Langmuir model and the fitted maximum capacity of La-CNTs for CTC adsorption was 55.3 mg/g.

Nano-iron wrapped by graphitic carbon in the carbonaceous matrix for efficient removal of chlortetracycline

A magnetic composite of nano-iron wrapped by graphitic carbon in the carbonaceous matrix with hierarchical pores is an efficient, regenerative, and versatile adsorbent to remove antibiotics from water. • The magnetic composite of nano-iron wrapped by graphitic carbon in the carbonaceous matrix with hierarchical pores (Fe in /C-700) was synthesized through one-step thermolysis of Fe in /Zn-MOF. • Excellent chlortetracycline adsorption performances maintained with respect to various coexisting ions and actual water. • Fe in /C-700 exhibited highly effective adsorption capacities for chlortetracycline, ciprofloxacin, and sulfamethoxazole in the mixed antibiotic system. • Fe in /C-700 showed perfect reusability via magnetic recovery. The stability, versatility, and reusability of an adsorbent are of great significance to its practicability to remove antibiotics from water due to their universal residual. Herein, a magnetic composite of nano-iron wrapped by graphitic carbon in the carbonaceous matrix with hierarchical pores (Fe in /C-700) was constructed by one-step pyrolysis using Fe in /Zn-MOF as a precursor. Fe in /C-700 exhibited a core–shell structure and superparamagnetism behavior, which showed excellent chlortetracycline (CTC) adsorption with the maximum adsorption capacity of 546.5 mg/g. The adsorption process matched well with the pseudo-second-order kinetics model and Langmuir model, indicating chemisorption was likely contributed to the CTC adsorption. Electrostatic interaction, surface complexation, hydrogen bond, and π-π EDA interaction were the dominant driving forces. Cl - and SO 4 2- significantly enhanced the CTC adsorption due to the electrostatic attraction or hydrogen bond formed among Fe in /C-700, anions, and CTC. Fe in /C-700 maintained high adsorption capacities in the mixed antibiotic system (255.1, 143.3, and 169.6 mg/g for CTC, ciprofloxacin, and sulfamethoxazole), in actual water (372.9, 383.3, 390.6, and 366.7 mg/g for CTC in Pearl River water, lake water, tap water, and ultrapure water), and regeneration (366.7, 354.2, 360.4, 314.6, and 301.0 mg/g for CTC in five runs), indicating a promising reusable adsorbent for the remediation of antibiotics in water. These findings provide a feasible and straightforward strategy to synthesize high stable magnetic nanoparticles derived from MOFs.

Sorption studies and removal of chlortetracycline and oxytetracycline using theta phosphorene nanoribbon – A DFT outlook

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.

Adsorption and desorption behaviors of antibiotics by tire wear particles and polyethylene microplastics with or without aging processes

Tire wear particles (TWP), as the significant proportion of microplastics (MPs), has adsorbed much attention due to its widespread presence in aquatic ecosystem. However, compared with traditional MPs, few studies have investigated the interaction between TWP and coexisting contaminants. The adsorption-desorption behavior of chlortetracycline (CTC) and amoxicillin (AMX) by original and aged TWP was studied, and polyethylene (PE) was studied for comparison. After aging, small holes and cracks were produced on the surfaces of the TWP and PE. Meanwhile, the specific surface areas (SBET) of TWP and PE increased, but the aged TWP had a larger SBET than the aged PE, which indicated that TWP was more likely to degrade than PE. The adsorption kinetics results showed that the adsorption of CTC and AMX by TWP and PE conformed to the pseudo-second-order model. The adsorption isotherm results showed that the Freundlich model could describe the adsorption isotherm data of TWP and PE. The adsorption capacity of antibiotics by TWP increased by 1.13–23.40 times, and by 1.08–14.24 times on PE, after aging. Desorption experiments showed that the desorption amount of antibiotics on TWP and PE in simulated gastric fluid was greater than that in ultrapure water. The desorption amount and rate of CTC and AMX from TWP were higher than those of PE, indicating that TWP might be more harmful to the aquatic environment and organisms. These findings indicated that, compared with PE, TWP might have stronger carrier effects on antibiotics, which might pose more serious potential risks to the aquatic environment and organisms, especially considering the effects of the aging process. This study would expand the research on environmental risk of MPs and contribute to providing new insights into the evaluation of tire material particles.

MOF-derived cluster-shaped magnetic nanocomposite with hierarchical pores as an efficient and regenerative adsorbent for chlortetracycline removal

The presence of large amounts of antibiotic residues can potentially threaten environmental sustainability and human health. Thus, it is imperative to develop convenient and effective technologies for eliminating antibiotics from aquatic environments, which are major contaminant reservoirs. Herein, based on Zn/Fe-MIL-88B, we designed and synthesized a magnetic nanocomposite (MC) that contains hierarchical pores and as an effective and regenerative adsorbent for the removal of chlortetracycline (CTC) from water. The characteristics of the MC and its CTC adsorption performance were investigated systematically. The synthesized MC sample pyrolyzed at 800 °C (MC-800) consisted of metallic iron and N/O-doped graphitic carbon along with cluster-like particles with a mesoporous structure. Further, the adsorption of CTC on MC-800 (maximum adsorption amount of 1158.0 mg/g) could be described using the Freundlich isotherm model and a pseudo-second-order model, indicating that the surface of MC-800 was heterogeneous. The adsorption is likely driven by weak chemical forces, including hydrogen bond formation, cation-π electron donor–acceptor (EDA), and π-π EDA interactions. Finally, MC-800 could be recovered readily through facile magnetic separation and regenerated such that its adsorption rate remained higher than 85% even after five cycles.

Low-temperature constructing N-doped graphite-like mesoporous structure biochar from furfural residue with urea for removal of chlortetracycline from wastewater and hydrothermal catalytic degradation mechanism

A novel N-doped graphite-like mesoporous structure biochar (NBC) was prepared from furfural residue with urea under mild low temperature, its performance in the removal of chlortetracycline (CTC) from aqueous solution and the hydrothermal catalytic degradation mechanism were investigated. This preparation strategy of the adsorbent demonstrated the properties of urea as a crosslinking agent and reactive reagent in the heat treatment process from room temperature to 300 °C. In addition, the pore structure, species and number of surface active adsorption sites of NBC were verified through SEM/EDS, FTIR, BET, XRD, TG and XPS analyses. The results showed that N atoms could be uniformly distributed on the surface of NBC, up to 17.7%, which was about ten times higher than that of direct pyrolysis of biomass (pristine BC) and NBC with graphite-like mesoporous structure had the abundant surface nitrogenous functional groups, such as pyrrolic-N and graphitic-N species besides the oxygen-containing functional groups. Batch adsorption studies indicated that NBC achieved equilibrium faster for CTC adsorption (200 min) than other reported adsorbents. The maximum adsorption capacity of CTC onto NBC was 44.3 mg/g, and the adsorption efficiency was still 26.7 mg/g after four recycling. The adsorption experimental data fitted well with the pseudo-second-order kinetic model and the Freundlich isotherm model. Besides, its catalytic degradation of CTC with hydrothermal treatment also exhibited a potential catalytic activity, and catalytic degradation pathway was proposed through the identification of intermediates using LC-MS. The furfural residue is industrially relevant to the furfural production process and hence NBC may be a promising new environment-friendly material.

Adsorption of chlortetracycline from aquaculture wastewater using modified zeolites

In this study, lanthanum modified zeolite (La-Z) was used to adsorb chlortetracycline (CTC) from aquaculture wastewater. La-Z was characterized by SEM, TEM, EDS, XRD, FTIR and BET. The effects various factors on the adsorption of CTC by La-Z were investigated, including the lanthanum modification concentration on zeolites, the dosage of La-Z, solution pH and reaction time. Orthogonal experiments were performed to determine the optimal adsorption conditions. Adsorption kinetics were studied by quasi-first-order model, quasi-second-order model, Weber-Morris, Boyd and Bangham models, while isotherms were analyzed by the Langmuir and Freundlich models. The removal rate reached 98.4%, when the modified concentration was 0.02 mol/L, the adsorbent dosage was 0.04 g, the initial concentration of CTC was 5 mg/L, the adsorption time was 20 min, and the pH was 7. The initial CTC concentration had the greatest influence on the adsorption process. The kinetic results showed a significant linear correlation between the experimental results and the quasi-second-order kinetic model. From the results of the internal diffusion model, it was found that the La-Z adsorption rate was controlled by both internal diffusion and external diffusion, in a multi-step process. The adsorption isotherm conforms to the Langmuir model, with the maximum adsorption quantity reaching 127.55 mg/g. Thermodynamic analysis showed that the adsorption process was an endothermic process of entropy increase, which occurs spontaneously.

Adsorption of chlortetracycline from aqueous solution by chitin

In this study, the performance of chitin for removing chlortetracycline (CTC) from aqueous solutions was assessed. The effects of pH, chitin dose, CTC concentration and contact time on CTC adsorption by chitin were investigated. The maximum CTC removal efficiency of 82.9% was determined at pH 7, chitin dose of 5 g/L, CTC concentration of 8.8 mg/L and contact time of 120 min. The highest CTC adsorption capacity was found as 12.01 mg/g for CTC of 82.2 mg/L concentration at pH 7. The results demonstrated that CTC removal efficiency decreased from 82.9% to 73.0% with increasing CTC concentration from 8.8 to 82.2 mg/L. The equilibrium data for CTC adsorption indicated a good fit to the Freundlich isotherm model. Pseudo-second-order kinetic model was the best model for describing the adsorption reactions.

Adsorption of CTC in mariculture wastewater on modified ACF

Activated carbon fibre (ACF) was modified through the sulfuric acid impregnation method and used as an adsorbent for chlortetracycline (CTC) in mariculture wastewater. The modified ACF was characterised by scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller area analysis. Six factors (namely, modification time, dosage of ACF, initial concentration of CTC, adsorption time, pH value and interfering ion) were screened to study their effects on the adsorption of CTC. A full 16-factorial design was employed for optimising the adsorption process. The removal rate of CTC reached 96% under optimal conditions: modification time of ACF of 60 min, pH value of 6, dosage of modified ACF of 0·04 g, reaction time of 4 h and initial concentration of CTC of 20 mg/l. The dosage of modified ACF had the most positive effect on CTC. The adsorption kinetics favoured the pseudo-second-order model. The isotherm favoured the Langmuir model with the maximum adsorption capacity of 87 mg/g. The present work showed that the modified ACF is an effective adsorbent for the removal of CTC from mariculture wastewater.

Engineered biochar composites with zeolite, silica, and nano-zerovalent iron for the efficient scavenging of chlortetracycline from aqueous solutions.

Date palm waste-derived biochar (DBC) was produced through pyrolysis (600°C) and modified with zeolite (Z-DBC), silica (S-DBC), or nano-zerovalent iron (nZVI-DBC) to design efficient sorbents. The pristine and engineered biochars were characterized by SEM, XRD, BET, TGA, CHNS-O, and FTIR to investigate the surface, structural, and mineralogical composition. The nZVI-DBC exhibited lowest pH (6.15) and highest surface area (220.92m2g-1), carbon (80.55%), nitrogen (3.78%), and hydrogen (11.09%) contents compared with other biochars. Isotherm sorption data for chlortetracycline (CTC) removal from aqueous solutions was described well by Langmuir and Redlich-Peterson isotherms showing the highest fitness (R2 values in the range of 0.88-0.98 and 0.88-0.99, respectively). Langmuir predicted maximum CTC adsorption capacity was in order of nZVI-DBC (89.05mgg-1) > S-DBC (45.57mgg-1) > Z-DBC (30.42mgg-1) > DBC (28.19mgg-1). Kinetics adsorption data was best described by power function model (R2 = 0.93-0.99), followed by interaparticle diffusion (R2 = 0.85-0.96) model. The nZVI-DBC performed outclass by removing 98% of CTC, followed by S-DBC (68%), Z-DBC (35%), and DBC (36%). Chemisorption, H-bonding, and interaparticle diffusion were the operating mechanisms for CTC adsorption onto DBC, S-DBC, and Z-DBC, while π-π electron donor-accepter interactions and redox reactions augmented these mechanisms for highest CTC adsorption onto nZVI-DBC. Therefore, nZVI-DBC may serve as an efficient green technology for the removal of CTC from aqueous solutions and to reduce surface date palm waste pollution. Graphical abstract .

Prediction of chlortetracycline adsorption on the Fe3O4 nanoparticle using molecular dynamics simulation

Molecular dynamics (MD) simulation was applied to investigate the adsorption mechanism of chlortetracycline (CTC) antibiotic molecule as the aqueous pollutant on the Fe3O4 nanoparticle (NP). Two different NP sizes with a diameter of about 1.4 nm and 3.5 nm were selected. Initially, the stability of both NPs in water was investigated by calculating radial distribution function curves of NP atoms. Simulation results confirmed the stable crystallographic structures of both NPs. However, small NP induce greater structural stabilization. Then, CTC molecules were adsorbed on NPs surface in various pollutant concentrations. Electrostatic and hydrogen bond were the major types of interactions between CTC molecules and the adsorbent surface. CTC molecules formed a complex with NP surface from their amine side chains; while they were parallel to each other in their aromatic rings and π-π bond between two CTC molecules was formed. Diffusion rate of CTC molecules could predict the adsorption mechanism. At lower concentration of CTC, CTC molecules tend to adsorb on the NP surface. At these concentrations, the diffusion rate of CTC was high. By increasing the CTC concentration, the pollutant agglomeration was enhanced which decreased the diffusion rate. At this time, the surface of NP was saturated. In addition, the results of isotherm curves showed that CTC adsorption on small NPs could be defined with both Langmuir and Freundlich isotherm models, while Freundlich isotherm model was more appropriate for larger NPs. In conclusion, observations confirmed that MD simulation could successfully predict the behavior of CTC adsorption on the Fe3O4 NP surface.Communicated by Ramaswamy H. Sarma

Adsorption properties, kinetics & thermodynamics of tetracycline on carboxymethyl-chitosan reformed montmorillonite

This paper describes a modification method of Na-montmorillonite (Na-Mt) with carboxymethyl-chitosan (CMC). The as-prepared samples were analyzed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface analyzer and thermogravimetric analysis (TGA). Two common tetracycline antibiotics, tetracycline (TET) and chlortetracycline (CTC), were selected as the represented pollutants and adsorbed by CMC-Mt under different experimental conditions. The intercalation of CMC obviously amplified the basal spacing of the interlayers confirmed by XRD measurements and improved the adsorption capacities of montmorillonite to some degree. The results showed that the tetracycline antibiotic sorption onto CMC-Mt was mainly dependent on pH and was not affected by temperature. Besides, the removal of TET and CTC rapidly attained an equilibrium within 2 h of contact time. The kinetic data of adsorption was determined by first-order, second-order kinetics and intraparticle diffusion models. The kinetic study indicates that the TET and CTC adsorption processes obeyed the second-order kinetics. The Freundlich isotherm study was in agreement with the practical data, suggesting a heterogeneous sorption process. Furthermore, the thermodynamic studies revealed that the removal process was more spontaneous at a lower temperature, implying it an exothermic reaction. The synthesized adsorbent CMC-Mt can be widely used in the treatment of wastewater.

Adsorption of chlortetracycline onto biochar derived from corn cob and sugarcane bagasse.

Biochar was prepared from two different types of biological waste materials, corn cob (CC) and sugarcane bagasse (SB). The adsorption capacity of each class of adsorbent was determined by chlortetracycline (CTC) adsorption tests. The adsorption kinetics and isotherms of chlortetracycline onto sugarcane bagasse biochar (SBB) and corn cob biochar (CCB) were studied. Experimental results indicated that pseudo-second-order adsorption kinetics of CTC onto SBB and CCB were more reasonable than pseudo-first-order kinetics, and the adsorption kinetic model of CTC onto SBB was slightly better than that onto CCB. The maximum adsorption capacity of CTC onto SBB was 16.96 mg/g at pH 4, while the highest adsorption efficiency of CTC onto CCB was achieved at pH 5 with a maximum adsorption of 12.39 mg/g. The Freundlich isotherm model was better than the Langmuir model at illustrating the adsorption process of CTC onto SBB and CCB. These results provide a way to understand the value of specific biochars, which can be used as efficient and effective adsorbents for CTC removal from waste-water. Compared with raw pinewood, SBB and CBB were considered as alternative materials to remove antibiotics from aqueous environments.

Comparing adsorption properties of NH 4 Cl-modified activated carbon towards chlortetracycline antibiotic with those of commercial activated carbon

Abstract In this work, kinetics, equilibrium, thermodynamic and other adsorption properties of a novel activated carbon with regular-shaped pores (NH4Cl-modified activated carbon, NAC) for removal of chlortetracycline antibiotic from aqueous solutions was compared with those of a commercial standard activated carbon (SAC). Effects of temperature, on chlortetracycline adsorption by both adsorbents were carefully investigated and compared. Then optimum conditions were used for comparing the adsorption properties of adsorbents. Among the isotherm models studied, the equilibrium experimental data of both activated carbons were followed by Redlich-Peterson model, and the parameters calculated from the studied models showed more favourability of chlortetracycline adsorption onto NAC via the physical π-π electron-donor-acceptor interaction. The experimental data were fitted to several kinetic models and, based on calculated respective parameters such as rate constants, equilibrium adsorption capacities, correlation coefficients and statistical indices, both the Ritchie second order and pseudo second-order model showed the best in describing the adsorption process for both activated carbons, and the kinetic performance of NAC was significantly higher than that of SAC. The calculated thermodynamic parameters of the adsorption process revealed that, under the conditions used in this study, the adsorption of chlortetracycline onto NAC is more feasible, spontaneous and endothermic than its adsorption onto SAC. Overall, the results indicated that, compared to SAC, NAC is a more suitable choice for removal of chlortetracycline antibiotic from aqueous solutions.

Sorption and Transport of Veterinary Pharmaceuticals in Soil—A Laboratory Study

Land application of manure can change soil chemical properties, thus affecting fate and mobility of agricultural antibiotics in soil. The main objective of this study was to examine the effects of dissolved organic C (DOC) and background electrolyte cation type on the sorption and transport of chlortetracycline (CTC), tylosin (TYL), and sulfamethazine (SMT) in two different soils. A series of batch isotherm and column miscible displacement experiments were conducted using surface and subsurface soils of Etowah clay loam (fine‐loamy, siliceous, semiactive, thermic Typic Paleudults) and Captina sandy loam (fine‐silty, siliceous, active, mesic Typic Fragiudults). Decreased retention of CTC and TYL to soils was observed in the presence of Ca2+ ion compared with Na+. For example, the Freundlich coefficient (KF) for TYL ranged from 67 to 341 under a Na+ system while it ranged from 17 to 173 under a Ca2+ system. Sorption of CTC and TYL decreased on the addition of DOC extracted from dairy manure, while SMT sorption increased by DOC addition. For example, in the Ca2+ system, CTC KF values without DOC ranged from 2.40 × 103 to 4.84 × 103 while they ranged from 1.52 × 103 to 2.86 × 103 with the addition of DOC. Column transport experiments generally agreed with the batch study results, showing increased CTC mass recovery in effluents (i.e., increased from 2.1–4.3% for both surface and subsurface soils) and decreased retardation factors (R) in the presence of dairy manure DOC (i.e., from 890–371). The reduced CTC adsorption may be explained by competition between the DOC and CTC for sorption sites or by the aqueous association of CTC with DOC. Elevated levels of DOC also resulted in increased mobility of TYL and SMT for surface soil column. In summary, changes in background electrolyte cation type and DOC level in soil solution caused by addition of animal manure can influence fate and transport of agricultural antibiotics in soils.

Kinetics of tetracycline, oxytetracycline, and chlortetracycline adsorption and desorption on two acid soils.

The purpose of this work was to quantify retention/release of tetracycline, oxytetracycline, and chlortetracycline on two soils, paying attention to sorption kinetics and to implications of the adsorption/desorption processes on transfer of these pollutants to the various environmental compartments. We used the stirred flow chamber (SFC) procedure to achieve this goal. All three antibiotics showed high affinity for both soils, with greater adsorption intensity for soil 1, the one with the highest organic matter and Al and Fe oxides contents. Desorption was always <15%, exhibiting strong hysteresis in the adsorption/desorption processes. Adsorption was adequately modeled using a pseudo first-order equation with just one type of adsorption sites, whereas desorption was better adjusted considering both fast and slow sorption sites. The adsorption maximum (qmax) followed the sequence tetracycline > oxytetracycline > chlortetracycline in soil 1, with similar values for the three antibiotics and the sequence tetracycline > chlortetracycline > oxytetracycline in soil 2. The desorption sequences were oxytetracycline > tetracycline > chlortetracycline in soil 1 and oxytetracycline > chlortetracycline > tetracycline in soil 2. In conclusion, the SFC technique has yielded new kinetic data regarding tetracycline, oxytetracycline, and chlortetracycline adsorption/desorption on soils, indicating that it can be used to shed further light on the retention and transport processes affecting antibiotics on soils and other media, thus increasing knowledge on the behavior and evolution of these pharmaceutical residues in the environment.