Desorption Of Tetracycline Research Articles

Intraparticle sorption and desorption of antibiotics

Intraparticle domains are the critical locations for storing contaminants and retarding contaminant transport in subsurface environments. While the kinetics and extent of antibiotics sorption and desorption in subsurface materials have been extensively studied, their behaviors in intraparticle domains have not been well understood. This study investigated the sorption and desorption of antibiotics (ATs) in the intraparticle domains using quartz grains and clay, and antibiotic tetracycline (TC) and levofloxacin (LEV) as examples that are commonly present in groundwater systems. Batch experiments coupled with the analyses using various microscopic and spectroscopic techniques were performed to investigate the sorption and desorption kinetics, and to provide insights into the intraparticle sorption and desorption of TC and LEV. Results indicated that both TC and LEV with different physiochemical properties can migrate into intraparticle domains that were consistent with sorptive diffusion. The rate and extent of the sorption are a function of intraparticle surface area and properties, pore volume and connectivity, and ionic properties of the ATs. The sorptive diffusion led to the slow desorption of both TC and LEV after their sorption, apparently showing an irreversible desorption behavior (with desorption percentage about 1.86–20.51%). These results implied that intraparticle domains can be important locations for storing ATs, retarding ATs transport, and may serve as a long-term secondary source for groundwater contamination.

Insights into behavior and mechanism of tetracycline adsorption on virgin and soil-exposed microplastics

Microplastics (MPs), as vectors of pollutants, have attracted extensive attention because of their environmental effects. However, the adsorption behavior and antibiotic mechanism of environmentally exposed MPs is limited. Here, the adsorption of tetracycline (TC) onto virgin and soil-exposed polylactic acid (PLA), polyvinyl chloride (PVC) and polyethylene (PE) MPs showed that the adsorption capacity of MPs for TC increased after soil exposure, and PLA showed the strongest increase. Soil exposure increased the time to reach equilibrium, and the adsorption rate was controlled by both intraparticle diffusion and membrane diffusion. The isothermal adsorption results of soil-exposed PE and PLA indicated that TC adsorbed on heterogeneous surfaces was affected by the physicochemical adsorption process. The equilibrium absorption capacity of MPs for TC increased by 88% (PLA), 26% (PVC) and 15% (PE) after soil exposure. Soil dissolved organic matter promoted the desorption of TC from MPs, and TC speciation changed with pH. Soil-exposed MPs have the potential to promote TC degradation in solution without the addition of biological inhibitors. Moreover, density functional theory calculations verified that PE and PVC adsorbed TC through physical interactions, while hydrogen bonds were formed on PLA with TC. These results clarified the behavior and mechanisms of TC adsorption on virgin and soil-exposed MPs, which can help in the risk assessment of concomitant pollution of MPs and antibiotics.

Promotion of tetracycline degradation by electro-Fenton: Controlling the reaction zone by N-doped modified activated carbon cathode

The effective matching of ·OH produced by an electro-Fenton cathode with liquid-phase pollutants is the key to the efficient degradation of pollutants by using electro-Fenton systems. Therefore, tetracycline (TC) was enriched near a carbon cathode through N-doped modification, and the modified carbon cathode increased ·OH generation. The zone of TC degradation by ·OH and zone of ·OH generation were both controlled near the cathode. This phenomenon was called “controlling the reaction zone.” The adsorption capacities of NAC-1000/GF considerably increased by 9.16% and 31.09% for TC and H2O2, respectively. In addition, the modified cathodic electro-Fenton system (NAC-1000/GF) showed 17.15 mg L−1 improvement in the degradation effect of TC compared with the unmodified system. This improvement is substantially higher than that of the pure adsorption system (5.98 mg L−1). The degradation efficiency of TC reached 83.07% in 120 min. Structural characterization, molecular dynamics simulation, and electrochemical experiments revealed that pyrrolic-N enhanced the adsorption capacity of the activated carbon cathode, and pyridinic-N and graphitic-N further hindered TC desorption, which provided a favorable guarantee for controlling the reaction zone. Pyridinic-N and graphitic-N also enhanced the 2e-ORR selectivity of the cathode and promoted ·OH generation, which was conducive to the continuous and efficient degradation reaction in the zone. In addition, the theoretical calculation confirmed that an effective synergy existed between adsorption and electrolysis. This study provides a new direction and theoretical guidance for the development of electro-Fenton technology for water pollutant degradation.

Effect of Biochar Modification by Vitamin C, Hydrogen Peroxide or Silver Nanoparticles on Its Physicochemistry and Tetracycline Removal

Chemical modification of biochars can improve their adsorption capacity relative to antibiotics, posing a serious threat to the environment. Therefore, this research is aimed at the treatment of sunflower husk biochar (BC) by vitamin C, hydrogen peroxide or silver nanoparticles and the impact of this procedure on the biochar porosity, surface chemistry, and ability to remove tetracycline (TC). During the study, BC was produced by pyrolysis of sunflower husks at 650 °C. All solids were characterized using potentiometric titration, nitrogen adsorption/desorption, Fourier transform infrared spectroscopy, etc. The experimental adsorption data was described by kinetics equations: pseudo-first order, pseudo-second order, and particle internal diffusion (IPD) models as well as by isotherms of Langmuir, Langmuir-Freundlich, and Redlich-Peterson. The obtained results indicated that the biochar upgraded by vitamin C (BCV) had the highest ability to attract antibiotic molecules and, as a result, the TC adsorption on its surface was the largest. Furthermore, the TC desorption from this material was minimal. The measured TC adsorbed amounts for the modified BCs were as follows: 47.75% (7.47 mg/g) for BCV, 37.35% (8.41 mg/g)-for biochar treated by hydrogen peroxide (BCH), and 42.04% (9.55 mg/g) for biochar modified by silver nanoparticles (BCA). The lowest adsorption level was noted for non-modified biochar, i.e., 34.17% (6.83 mg/g). Based on the presented results it can be stated that the upgraded biochars had a good potential to improve the tetracycline removal from aqueous media, e.g., groundwater.

Competitive adsorption and desorption of tetracycline and sulfadiazine in crop soils

In view of the environmental issues caused by antibiotics, this research studies competitive adsorption/desorption for tetracycline (TC) and sulfadiazine (SDZ) in agricultural soils. Competitive adsorption was studied in binary systems (adding equal concentrations of both antibiotics). In addition, it was compared with results from simple systems. In all cases, batch-type adsorption/desorption experiments were carried out. In the binary systems, for the highest antibiotic concentration added, adsorption percentages were always higher for TC (close to 100%) than for SDZ (10–90%). In these systems, TC desorption was lower than 5% for all soils, and generally <10% for SDZ. Comparing TC and SDZ adsorption for the different systems, SDZ was clearly affected by the presence of TC, with SDZ adsorption percentages being was much higher (with differences generally above 65%) in the binary than in the simple systems. On the contrary, comparing the results of TC adsorption in simple and binary systems, TC was not affected by the presence of SDZ, obtaining similar adsorption percentages in both systems. Kd and KF values (in the Linear and Freundlich models), were higher in the simple systems in the case of TC, which could be due to competition with SDZ, while for SDZ Kd and KF were higher in the binary systems, with a synergistic effect of TC favoring SDZ adsorption. Regarding desorption, it reached 100% for SDZ in some soils in simple systems, dropping to 10% in the presence of TC. TC desorption was <4%, not affected by SDZ. The results indicate that environmental risks would be higher for SDZ, showing differences when both antibiotics are present. This can be considered relevant as regards public health and environmental preservation, in view of direct toxicities and the promotion of resistance to antibiotics associated with the presence of these contaminants in the environment.

Tetracycline removal enhancement with Fe-saturated nanoporous montmorillonite in a tripartite adsorption/desorption/photo-Fenton degradation process.

The adsorption and photo-Fenton degradation of tetracycline (TC) over Fe-saturated nanoporous montmorillonite was analyzed. The synthesized samples were characterized using XRD, FTIR, SEM, and XRF analysis, and the adsorption and desorption of TC onto these samples, as well as the antimicrobial activity of TC during these processes, were analyzed at different pH. Initially, a set of adsorption/desorption experiments was conducted, and surprisingly, up to 50% of TC adsorbed was released from Mt structure. Moreover, the desorbed TC had strong antibacterial activity. Then, an acid treatment (for the creation of nanoporous layers) and Fe saturation of the montmorillonite were applied to improve its adsorption and photocatalytic degradation properties over TC. Surprisingly, the desorption of TC from modified montmorillonite was still high up to 40% of adsorbed TC. However, simultaneous adsorption and photodegradation of TC were detected and almost no antimicrobial activity was detected after 180min of visible light irradiation, which could be due to the photo-Fenton degradation of TC on the modified montmorillonite surface. In the porous structures of modified montmorillonite high, ˙OH radicals were created in the photo-Fenton reaction and were measured using the Coumarin technique. The ˙OH radicals help the degradation of TC as proposed in an oxidation process. Surprisingly, more than 90% of antimicrobial activity of the TC decreased under visible light (after 180min) when desorbed from nanoporous Fe-saturated montmorillonite compared to natural montmorillonite. To the best of our knowledge, this is the first time that such a high TC desorption rate from an adsorbent with the least residual antimicrobial activity is reported which makes nanoporous Fe-saturated montmorillonite a perfect separation substance of TC from the environment.

Activated Carbon Fiber Cloth/Biomimetic Apatite: A Dual Drug Delivery System

A biomaterial that is both bioactive and capable of controlled drug release is highly attractive for bone regeneration. In previous works, we demonstrated the possibility of combining activated carbon fiber cloth (ACC) and biomimetic apatite (such as calcium-deficient hydroxyapatite (CDA)) to develop an efficient material for bone regeneration. The aim to use the adsorption properties of an activated carbon/biomimetic apatite composite to synthetize a biomaterial to be used as a controlled drug release system after implantation. The adsorption and desorption of tetracycline and aspirin were first investigated in the ACC and CDA components and then on ACC/CDA composite. The results showed that drug adsorption and release are dependent on the adsorbent material and the drug polarity/hydrophilicity, leading to two distinct modes of drug adsorption and release. Consequently, a double adsorption approach was successfully performed, leading to a multifunctional and innovative ACC-aspirin/CDA-tetracycline implantable biomaterial. In a second step, in vitro tests emphasized a better affinity of the drug (tetracycline or aspirin)-loaded ACC/CDA materials towards human primary osteoblast viability and proliferation. Then, in vivo experiments on a large cortical bone defect in rats was carried out to test biocompatibility and bone regeneration ability. Data clearly highlighted a significant acceleration of bone reconstruction in the presence of the ACC/CDA patch. The ability of the aspirin-loaded ACC/CDA material to release the drug in situ for improving bone healing was also underlined, as a proof of concept. This work highlights the possibility of bone patches with controlled (multi)drug release features being used for bone tissue repair.

Dually organic modified bentonite with enhanced adsorption and desorption of tetracycline and ciprofloxacine

Tetracycline (TC) and ciprofloxacin (CIP) cause serious environmental and health issues upon their uncontrolled release to the aquatic system and hence their control required serious attention. In this study, adsorption and desorption performances of TC and CIP by sodium carboxymethylcellulose (CMC) and polyethyleneimine (PEI) modified magnetic bentonite (MBCP) were explored. It was found that active functional groups such as –COOH, –OH and –NH2 loaded on the surface of MBCP increased the selective adsorption performance of MBCP for TC and CIP. Meanwhile, MBCP had superior adsorption performance in a wide pH range, magnetic separation capability and good regeneration. Based on the adsorption kinetics, isotherm, pHPZC, FE–SEM, TEM, FT–IR, XRD, BET, XPS and VSM results, the mechanisms of MBCP adsorption and desorption were investigated which mainly involved electrostatic interaction, pores deposition, complexation and ions exchange phenomena. MBCP was realized higher adsorption capacity for TC (476 mg/g), and CIP (457 mg/g) than MB (300 and 270 mg/g, respectively). This study provides important reference information for the fabrication of MBCP as a novel and promising adsorbent for the remediation of antibiotics from wastewater on the industrial level.

Effects of suspended particulate matter from natural lakes in conjunction with coagulation to tetracycline removal from water

Coagulation is a common method used to remove suspended particulate matter (SPM) from the water supply. SPM has preferable adsorption ability for antibiotics in water; therefore, SPM adsorption and coagulation may be a possible way to remove tetracycline (TC) from water. This study carried out coagulation experiments combining SPM collected from a natural lake at a location with three common coagulants—polyaluminum sulfate, polyaluminum chloride, and polyferric sulfate—under different pH values, exploring the adsorption of TC by SPM, coagulation of SPM with TC, and the primary influencing factors of this process. The maximum removal rate of TC can reach 97.87% with an SPM concentration of 1000 mg/L. Multi-factor analysis of variance showed the importance of various TC removal factors, which were ranked as follows: SPM concentration ≫ initial TC concentration > type of coagulant > pH values. The higher the SPM concentration, the better the TC removal (p < 0.001). Fourier infrared spectroscopy results demonstrated the strong adsorption effect of SPM on TC after being combined with a coagulant, and scanning electron microscopy also indicated that SPM becomes effective nuclei in the coagulation process, which is a possible reason for better TC removal. However, the effluent turbidities under 1000 mg/L SPM concentrations were high without coagulant aid. With the addition of coagulant aid anion polyacrylamide, the TC removal remained unchanged, effluent turbidity significantly reduced, and the TC desorption became low. These results indicate that applying SPM from natural lakes in the coagulation process could potentially remove TC in water.

Co-existing TiO2 nanoparticles influencing adsorption/ desorption of tetracycline on magnetically modified kaolin

Interaction of coexisting nanoparticles (NPs) and other pollutants may affect their behavior in the environment. In this study, we investigated the effects of TiO2 NPs on the adsorption and desorption of tetracycline (TC) by magnetized kaolin (MK). The interactions among TC, TiO2 NPs, and MK were then discussed through their morphology and characteristics by using scanning electron microscopy, X-ray energy dispersive spectrometry, Transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy analyses. Results showed that TiO2 NPs increased TC adsorption on MK by 2.02% and increased TC desorption by 45.26%, TC increased the maximum adsorption of TiO2 on MK from 31.32 to 49.42mgg-1 and decreased the amount of stable adsorption state TiO2 NPs on MK from 17.92 to 12.71mgg-1. The characterization results demonstrated that TC molecules combined on MK though hydrogen bonding, π-π bonding and hydrophobic interaction. The adsorption of TiO2 NPs on MK can provide additional hydrogen-bonding sites for TC adsorption by increasing the number of hydroxyl groups. However, TC can decrease the electrostatic attraction sites for TiO2 NPs adsorption on the MK surface. The complexation of TC and TiO2 NPs weakened the electrical attraction between MK and TiO2 NPs and decreased the amount of stable adsorption state TiO2 NPs.

Removal of tetracycline from polluted water by chitosan-olive pomace adsorbing films

This paper focuses on the removal of tetracycline from polluted water by chitosan-olive pomace adsorbing films. More specifically, both raw olive solid wastes (olive pomace) and the olive solid wastes/chitosan composite were compared and used for this purpose. Adsorption capacities values of 16 mg × g−1 and 1.6 mg × g−1 were obtained for the two adsorbents respectively. However, chitosan/olive pomace is proposed as suitable for environmental applications avoiding the dispersion of the pomace blocked inside the chitosan film. To detail the adsorption process, the effect of several experimental parameters such as the pH values, ionic strength, amount of adsorbent and pollutant and temperature values was investigated. The results showed that the adsorption process improved increasing the pH values, with a maximum at pH 8, and it was negatively affected by the presence of salts that retarded the adsorption. Indeed, the desorption of tetracycline was obtained in a MgCl2 2 M solution. So, a low-cost and cleaner approach, fundamental for the pollutant recovery and for an adsorbent safe reuse, for several cycles of adsorption/desorption, transforming a waste in resource is presented. The kinetics, isotherms models of adsorption and the thermodynamic parameters (ΔG°, ΔH° and ΔS°) were also evaluated observing that the physisorption of the pollutant occurred with and an endothermic character (ΔH° > 0) with ΔG° < 0 and ΔS° > 0. The use of Advanced Oxidation Processes was proposed as possible alternative to the tetracycline recovery, obtaining its degradation after the desorption. With the present paper, the alternative reuse of olive pomace is reported avoiding its disposal in the environment claiming its potential in the removal/recover of emerging contaminants from water.

Desorption of heavy metals and tetracycline from goethite-coated sands: The role of complexation

Tetracycline (TC) has been widely employed in livestock breeding and clinical treatment. The prolific use of TC has resulted in a high prevalence of the compound in the environment. The electron-donor groups of TC allow it to form complex compounds with heavy metals, resulting in changes to each molecule’s environmental behavior. This study aims to evaluate the effects of the complexation of heavy metals and TC on their desorption from goethite-coated sands (GCS), using batch experiments and model calculations. Our results show that heavy metals can inhibit the desorption of TC from the GCS surface, and that TC exerts a similar influence on the desorption of heavy metals. The inhibition of copper (Cu) by TC was stronger than that of cadmium (Cd), possibly resulting from TC’s stronger complexation with Cu. In addition, a correlation analysis between the complexation and amount of desorption showed that the inhibition of the desorption on GCS was significantly positively correlated with the complexation of heavy metals and TC. This indicated that the complex products of heavy metals and antibiotics have a stronger affinity with GCS than the individual components, or that the formation of ternary complex products promotes resorption of the remaining contaminants in the solution. This work revealed that the desorption inhibition resulting from complexation between antibiotics and heavy metals could improve contaminant retention, reducing contaminant transportation and minimizing the environmental risk.

Effects of wind-wave disturbances on adsorption and desorption of tetracycline and sulfadimidine in water-sediment systems.

Wind-wave disturbances frequently disperse sediment particles into overlying water, which facilitates the adsorption and desorption of contaminants in aquatic ecosystems. Tetracycline (TC) and sulfadimidine (SM2) are common antibiotics that are frequently found in aquatic environments. This study utilized microcosms, comprising sediment and water from Lake Taihu, China, to examine the adsorption and desorption of TC and SM2 under different wind-wave disturbances in a shallow lake environment. The adsorption experiments were conducted with three different concentrations (1, 5, 10mg/L) of TC and SM2 in the overlying water, and two different (background and strong) wind-wave conditions for 72h. Subsequently, four microcosms were employed in a 12-h desorption study. Analysis of adsorption progress showed that TC concentration in the overlying water decreased quickly, while SM2 remained almost constant. In the desorption experiments, SM2 released to the overlying water was an order of magnitude greater than TC. These results indicate that sediment particles strongly adsorb TC but weakly adsorb SM2. Compared to background conditions, the strong wind-wave conditions resulted in higher concentrations of TC and SM2 in sediment and facilitated their migration to deeper sediment during adsorption, correspondingly promoting greater release of TC and SM2 from sediment particles into the overlying water during desorption.

The adsorption of tetracycline and vancomycin onto nanodiamond with controlled release

The unique properties and tailorable surface of detonation nanodiamonds have given rise to an abundance of potential biomedical applications. Very little is known about the details of adsorption/desorption equilibria of drugs on/from nanodiamonds with different purity, surface chemistry, and agglomeration state. The studies presented here delve into the details of adsorption and desorption of tetracycline (TET) and vancomycin (VAN) on nanodiamond, which are critically important for the rational design of the nanodiamond drug delivery systems. The nanodiamonds studied in these experiments were as-received (ND), purified and carboxyl terminated (ND-COOH), and aminated (ND-NH2). The monolayer capacities of the drugs loaded onto the nanodiamonds are reported herein using Langmuir and Freundlich isotherm models. The results from the desorption studies demonstrate that, by changing the pH environment of drug loaded nanodiamond using buffers of pH 4.09, 7.45, 8.02, and a phosphate buffered saline (PBS) solution, the drug release can effectively be triggered.

Gastroretentive montmorillonite-tetracycline nanoclay for the treatment of Helicobacter pylori infection

The paper aims to explore the potential benefits provided by an organically modified montmorillonite (nanoclay) in the problematic management of the Helicobacter pylori gastric infection that is one of the most prevalent infectious diseases worldwide. Two nanoclay samples were produced by the intercalation of tetracycline (TC) into the interlayer of montmorillonite (MM) under two different pH reaction conditions (pH 3.0 and 8.7). MM/TC nanoclays were characterized by EDX, XRD, FTIR, DSC, drug adsorption extent, in vitro mucoadhesiveness and desorption in simulated gastric media. The reaction between MM and TC led to a complete MM cation (Na+ and Ca2+) exchange process, an increase of MM characteristic interlayer spacing as well as an involvement of NHR3+ group of TC, regardless of the reaction pH value. However, MM/TC nanoclay obtained under alkaline conditions provided a lower TC adsorption as well as a drug fraction weakly linked to MM in comparison with the nanoclay obtained in acidic conditions. Both the nanoclays exhibited good mucoadhesion properties to porcine mucin and TC desorption occurring mainly via a cation exchange process by H+ ions. Based on the results obtained, TC intercalation into MM nanoplatelets could represent a potential advantageous approach allowing the antibiotic to distribute homogeneously on the gastric mucosa, diffuse through the gastric mucus layer and achieve the microorganism localization.

Sorption and desorption of tetracycline on layered manganese dioxide birnessite

Birnessite is one of the most common manganese oxides in the clay-sized fraction (<2 μm) of soils and has high cation exchange capacity and larger surface area. Birnessite was previously studied for decomposition of selected antibiotics from water. In this study, the removal of tetracycline (TC) by birnessite from aqueous solution was investigated as a function of initial tetracycline concentration, solution pH, temperature, and equilibrium time. Changes in solid phase after TC adsorption and desorption were characterized by X-ray photoelectron spectroscopy, X-ray diffraction (XRD), and Fourier transform infrared analyses. Desorption of exchangeable cations accompanying TC removal and partial desorption of TC from birnessite by AlCl3 confirmed that cation exchange was responsible for TC removal at low initial concentrations. Both the external and internal surface areas were readily available for TC uptake by birnessite. The intercalated TC formed a horizontal monolayer configuration in the interlayer of birnessite as deduced from XRD analyses.

Effects of Temperature on the Adsorption and Desorption of Tetracycline in Soils

Batch experiments of OECD Guide were conducted to the adsorption and desorption of tetracycline in soils. The adsorption and desorption isotherms of tetracycline in cinnamon soil and red soil were expressed well by the Freundlich equation at 20, 25 and 35°C. According to lg Kf and 1/n values of fitting parameters, tetracycline was strongly adsorbed by two soils with adsorption capacity (lg Kf) values from 3.06 to 3.59. Temperature from 20 to 30°C had little effects on the tetracycline adsorption in two soils. Thermodynamic parameters depict the exothermic nature of adsorption, and the process was favorable and spontaneous. Hysteresis effect was observed. The maximum adsorption capacity and hysteresis index of tetracycline were found at 20°C for cinnamon soil and 30°C for red soil, so there was little risk of tetracycline remobilization with temperature lower than 25°C in cinnamon soil or higher than 25°C in red soil.

Desorption of tetracycline from montmorillonite by aluminum, calcium, and sodium: an indication of intercalation stability

As the uptake of cationic drugs, such as tetracycline (TC), was attributed to cation exchange, the stability of adsorbed TC on a Ca-montmorillonite SAz-2 was studied using cationic solutions of different valence charges under different pH conditions. At the initial loading of 356 mg g−1, the amounts of TC desorbed by 0.05 M AlCl3, CaCl2, and NaCl were 133 ± 4, 83 ± 6, and 50 ± 4 mg g−1, respectively, or 37, 23, and 14 %. However, when the amount or percentage of TC desorbed was normalized to the equivalence of each cation, the values were in the range of 44–50 mg g−1 or 11–14 % per 10 mmol of charge. The kinetics of TC desorption were moderately fast and almost reached equilibrium in 6 h. The results followed the pseudo-second-order kinetic model with reaction rate in the order of AlCl3 > CaCl2 > NaCl at a higher initial TC loading level. The total amount of TC desorbed after five desorption cycles followed the order of AlCl3 > CaCl2 > NaCl, too, suggesting that cations with higher positive charges, thus, less hydrated, are preferred to remove adsorbed cationic drugs. The FTIR analyses showed larger band shift when Al3+ was used as the desorbing reagent. The XRD patterns before and after TC desorption revealed no changes in basal spacing, even after five desorption cycles, suggesting that the removal of TC from SAz-2 was largely from the external surfaces.

Adsorption and Desorption of Tetracycline on Activated Carbons

The adsorption and desorption of tetracycline were investigated by static experiments, and two kinds of activated carbons were employed as adsorbents. And related properties of the adsorbate and adsorbents were studied to support the adsorption mechanism exploration. The results suggested that fairly strong H-bonding exists between the functional groups of activated carbons and tetracycline.

Effects of Soil/Solution Ratios and Cation Types on Adsorption and Desorption of Tetracycline in Soils

The adsorption and desorption behavior of tetracycline on an Alfisol and an Ultisol was investigated at varying soil/solution ratios (1:10, 1:50, and 1:100) and different cation types (CaCl2, KCl, and NaCl) and H2O using a batch equilibration experiment. Kinetic studies revealed that the adsorption of tetracycline on the two soils was rate limited, and the adsorption kinetics could be well described by the Elovich equation and exponent equation. Changes in the soil/solution ratio affected the relative equilibration time in the Ultisol, but there was no effect of the initial tetracycline concentration. The adsorption rate in the soils decreased as the soil/solution ratio increased from 1:50 to 1:10. The adsorption and desorption data on tetracycline in the two soils could be described by the Freundlich isotherm equation, with r values &gt;0.952 under all experimental treatments. The Ultisol always had stronger adsorption (higher distribution coefficient [Kd] value) than the Alfisol under all experimental conditions. The Kd values decreased with increasing soil/solution ratios in the two tested soils at 1 or 1.25 mg L−1 of tetracycline; however, this trend did not occur at 25 mg L−1 of tetracycline. The adsorption isotherm had an S‐type curve that changed into an L‐type curve with decreasing soil/solution ratios from 1:10 to 1:100. The presence of cations in the soil solution, especially CaCl2, can significantly reduce the adsorption of tetracycline in soils. The presence of cations also significantly reduced the nonlinearity of the adsorption isotherms.