Adsorption behavior and quantum chemical analysis of surface functionalized polystyrene nano-plastics on gatifloxacin.

Adsorption behavior and quantum chemical analysis of surface functionalized polystyrene nano-plastics on gatifloxacin. | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Adsorption behavior and quantum chemical analysis of surface functionalized polystyrene nano-plastics on gatifloxacin. Jie Yang, Wei Ji, yanan Li, Yaning Wu, Meijing Yao, Weiqin Wu, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4370552/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 31 Oct, 2024 Read the published version in Environmental Science and Pollution Research → Version 1 posted 6 You are reading this latest preprint version Abstract Micro / nano plastics will age and produce a variety of functional groups, but there are few studies on the interaction behavior of surface-functionalized nano-plastics with antibiotics. In this paper, 400 nm polystyrene microspheres (PS), amino modified PS-NH 2 , carboxyl modified PS-COOH (PSNPs) and gatifloxacin (GAT) were selected as research objects. The adsorption of GAT by PSNPs was comparatively studied by both experimental and theoretical calculations, and the adsorption mechanism of nano-plastics to antibiotics were revealed. The equilibrium adsorption capacity of PSNPs to GAT was PS-NH 2 > PS-COOOH > PS, and adsorption capacity of PS-NH 2 was the largest, which was 236 mg/g. The adsorption kinetics of GAT showed that adsorption was controlled by both physical and chemical mechanisms, and the intra-particle diffusion and external diffusion jointly controlled the adsorption rate. All of Na + , alginic acid, Cu 2+ and Zn 2+ inhibited the adsorption, and the inhibition effect of Cu 2+ and Zn 2+ on PS-NH 2 adsorption of GAT was the most significant., which may be related to the inhibition of hydrogen bond formation by chelates formed by amino functional groups and heavy metals. The theoretical calculation results showed that π-π interaction and electrostatic interaction were the main interactions between PS and GAT, and electrostatic interactions, hydrogen bonds and van der Waals forces (vdW) were the main interactions between PS-COOH, PS-NH 2 and GAT. The surface electrostatic potential of PS-COOH and PS-NH 2 was significantly larger than PS, and the maximum penetration distance of van der Waals was GAT-PS-NH 2 (1.20 Å) > GAT-PS-COOH (1.06 Å) > GAT-PS (0.63 Å). The results provided a theoretical basis for the migration and synergistic removal of antibiotics and micro-nano-plastics. nano-polystyrene functionalization gatifloxacin adsorption quantum chemical calculations Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction The production of plastic has grown exponentially since the 1950 s all over the word (Ostle et al., 2019 ), about 8 million tons of plastic eventually flows into the sea every year, most of which come from land, and plastic has become a global pollutant (Baeta et al., 2021). Plastics have been reported to be found in many sampling sites from high mountains to the seafloor, and bulk plastics in the environment can be decomposed into microplastics (MPs, 1 µm < MPs particle size < 5 mm), including PP, PA, PS, PVC, et al., by physical, chemical and biological actions. For example, the concentration of microplastics in rivers is about 1.6–41 mg/L (Moore et al., 2011 ). Part of microplastics can be further degraded into nano-plastics (1 nm < NPs particle size < 1 µm) (Vandermeersch et al., 2015 ; Andrady et al., 2011; Lambert et al., 2016) with smaller particle size under the action of photodegradation, mechanical wear and biodegradation. micro / nano plastics will age and produce functional groups, such as amino group and carboxyl group, on their surface. Moreover, the micro / nano plastics can adsorb various heavy metal ions and organic pollutants, like lead ions, cadmium ions, antibiotics, pesticides and so on (Yu et al., 2020 ; Xu et al., 2021 ; Bao et al., 2021 ; Wang et al., 2020 ; Wang et al., 2019 ; Dong et al., 2020 ). However, due to the difficulties of current sampling and analysis strategies of granular plastics, it is difficult to evaluate their real exposure to humans or biota at a given location and their harm to human and biological health (Vandermeersch et al., 2015 ; Bergmann et al., 2019 ; Bergmann et al., 2017 ). With the development of pharmaceutical industry, more and more antibiotics are used to treat microbial infections in people (Lage et al., 2018 ). Fluoroquinolones have ranked first in the use of all kinds of antibiotics since 2002, and the consumption of fluoroquinolones in 2013 was estimated to be as high as 27300 tons (Zhang et al., 2015 ). Especially, the output and dosage of fluoroquinolone antibiotics such as pefloxacin, ciprofloxacin and norfloxacin reached the maximum (Yu et al., 2020 ). However, the treatment efficiency of fluoroquinolone antibiotics was only 56–75% (Carvalho et al., 2016), with the concentration of antibiotics in the wastewater at the effluent of pharmaceutical factories even reached 30 mg/L (Aus et al., 2016), and antibiotics were also detected in many water bodies, such as East Dongting Lake, Pearl River Estuary, etc. (Yu et al., 2019 ; Ma et al., 2016 ). Various behaviors of micro / nano plastics and antibiotics, such as aggregation and dispersion, adsorption, migration and deposition, may affect their compound pollution toxicity and ecological effect. The previous studies on the adsorption behavior of micro or nano plastics to antibiotics mainly included the adsorption of amoxicillin, tetracycline, ciprofloxacin, sulfadiazine, pefloxacin and levofloxacin by polystyrene (PS), polyethylene (PP), polyvinyl chloride (PVC) and polyamide (PA), mostly focusing on the kinetics, isotherm and pH, temperature, salt ions, etc., on the adsorption (Yu et al., 2020 ; Li et al., 2018 ; Atugoda et al., 2020 ). The adsorption of antibiotics by microplastics was mainly physical or chemical adsorption, which was jointly controlled by external and intra-particle diffusion, and the main mechanisms included hydrogen bonding, electrostatic interaction, van der Waals forces (vdW), hydrophobic interaction and so on (Li et al., 2018 ; Atugoda et al., 2020 ; Chen et al., 2021 ; Zhang et al., 2020 ). For example, electrostatic interaction was the main mechanism of pH affecting the adsorption of polyethylene to antibiotics (Chen et al., 2021 ), and due to the competitive adsorption and ion exchange among pollutants, the increase of dissolved organic matter concentration and ion strength will reduce the adsorption amount (Yu et al., 2020 ). Compared with micron plastics, nano-plastics had larger specific surface area, higher surface hydrophobicity and better adsorption effect for heavy metals, polychlorinated biphenyls, antibiotics and other pollutants (Li et al., 2018 ; Zhang et al., 2020 ; Da Costa et al., 2016 ). In particular, the saturated adsorption capacity of nano-plastics for antibiotics is higher than that of microplastics for antibiotics, the former 20-50mg/g, the latter concentrated within 10 mg/g or less. Interestingly, PS-COOH adsorbed antibiotics better than PS because of the polarity between them, and for norfloxacin and levofloxacin, the adsorption capacity of PS-COOH was 54.9% and 69.6% higher than PS, respectively (Zhang et al., 2020 ; Yilimulati et al., 2021 ). However, there is still a lack of data on the interaction between functionalized nano-plastics and antibiotics. Therefore, in this paper, 400 nm polystyrene microspheres (PS), carboxyl modified PS (PS-COOH) and amino modified PS (PS-NH 2 ) were selected as the research objects to explore their adsorption mechanism for gatifloxacin (GAT), a typical fluoroquinolone antibiotic. The effects of physical and chemical conditions, including pH, temperature, ionic strength, heavy metal ions and dissolved organic matter, on the interaction were investigated, and the interaction mechanism and theory between nano-plastics and antibiotics were clarified, which will provide theoretical guidance for the transformation and removal of micro-nano plastics in practical environment. 2. Materials and methods 2.1 Materials, reagents and instruments Nano-polystyrene microspheres (PS, 400 nm, 2.5% (w/v)), carboxyl nano-polystyrene microspheres (PS-COOH, 400 nm, 2.5% (w/v)), amino nano-polystyrene microspheres (PS-NH 2 , 400 nm, 2.5% (w/v)) were purchased from Jiangsu Zhijie Technology Co., Ltd, and Gatifloxacin (GAT, powder, 98%) were purchased from Shanghai McLean biochemical Technology Co., Ltd. The resistivity of Milli-Q water in the experiment was 18.2 MΩ·cm, obtained by Milli-Q water purification system, and the polystyrene colorimetric cell (FIS14-955125) used in the measurement of potential and particle size was purchased from Fisherbrand Company of USA. The 0.22µm cellulose acetate membrane used in filtration was purchased from Corning Company of New York, USA. The instruments used in the adsorption experiment included constant temperature oscillator (THZ-C, Taicang Haocheng Experimental instrument Manufacturing Co., Ltd.), pH meter (PHS-3C, Shanghai instrument Co., Ltd.), Ultrasonic Cleaner (KQ5200E, Kunshan Ultrasonic instrument Co., Ltd.), dynamic light scattering (DLS, Zetasizer Nano ZS90, Malvern instrument Co., Ltd.), high performance liquid chromatograph (HPLC, G711A, Agilent Technology Co., Ltd.), microelectrophoresis instrument (JS94H2, Shanghai Zhongchen Digital Technology equipment Co., Ltd.), scanning electronic micromirror (SEM, Czech Tescan MIRA LMS), fourier transform infrared spectrometer (FTIR, American Thermo Scientific Nicolet iS20). 2.2 Experimental methods 2.2.1 Solution preparation and adsorption experiment Accurately weighed 100 mg of Gatifloxacin (GAT) and make up a 100 mg ·L − 1 stock solution. The solution was stored in a 500 mL brown volumetric bottle and kept in dark in 4℃ refrigerator. The experimental steps of adsorption kinetics, adsorption isotherm and adsorption thermodynamics were shown in Text S1, S2, S3. 2.2.2 Experiment on the effect of solution pH The 10 mg·L − 1 PSNPs were added to 50mL GAT solution of 10 mg·L − 1 , respectively, in 100mL conical bottles, adjusting pH to 3–9. The conical bottles were then placed in an oscillator and oscillate in dark. The oscillator temperature was set at 298K and the rev was 150 r·min − 1 . The samples were taken 24 hours later, and filtered quickly with 0.22µm acetate fiber filter membrane. The concentration of GAT in the samples was measured. 2.2.3 Effects of NaCl, alginic acid and Cu 2+ , Zn 2+ To assess the impact of environmental factors, a series concentration of NaCl (0.1–0.5 mol·L − 1 ), dissolved organic alginic acid (1–20 mg·L − 1 ), Cu 2+ (1–20 mg·L − 1 ) and Zn 2+ (1–20 mg·L − 1 ) were selected to prepare antibiotic solution (mass concentration 10 mg·L − 1 ) and mixed with nano plastic solution. The conical bottles were oscillated in a constant temperature oscillator. The temperature of the oscillator was 298K and the rotational speed was 150 r·min − 1 . After 24 hours, the samples were quickly filtered with 0.22µm cellulose acetate membrane, and then the concentration of antibiotics was determined. 2.3 Analysis and detection methods (1) Particle morphology analysis. Scanning electronic micromirror (SEM) was used to analyze the particle morphology. A few nanoparticles were added to 50% anhydrous ethanol solution of 20 mL to form a dilute solution, which was then observed under scanning electron microscope after ultrasound. (2) Functional group and mechanism analysis. The nanoparticles before and after adsorption were freeze-dried, and then placed in a Fourier transform infrared spectrometer (FTIR) instrument for infrared spectrum analysis after treating by KBr tablet method. The test range was 400–4000 cm − 1 with 32 times scanning. (3) Particle size and electric potential analysis Dynamic light scattering (DLS) was used for particle size potential analysis. The samples were prepared by using ultra-pure water with different pH values, and placed in a special dish equipped with the nanoparticle size potentiometer. The particle size and its distribution and potential of the nanoparticles were measured separately. (4) Analysis of GAT concentration By high performance liquid chromatograph (HPLC) to determine the concentration of GAT. The chromatographic column was InfinityLab Poroshell 120, the mobile phase was 80% acetonitrile and 20% formic acid water ( w = 0.1%), the injection volume was 50 µL, the flow rate was 0.8 mL·min − 1 , and the GAT detection wavelength was 291 nm. (5) Quantum chemistry calculation The surface electrostatic potential distribution of nano-plastics was calculated by Gaussian 09 and GaussView 6.0 software (Gaussian Inc., USA). B3LYP/6-31G(d) was used for structural optimization, and M062X/6-31G(d) was used for energy calculation. Multiwfn 3.8 and Visual Molecular Dynamics (VMD 1.9.3) software (University of Illinois) (Humphrey et al., 1997 ; Lu et al., 2012) were used to further process the above calculation results, including reduced density gradient (RDG) analysis, etc. The surface electrostatic potential distribution and van der Waals force penetration of the complex were calculated by using the compound formed by the connection of two nano-plastic monomers, and the strength of the interaction force between GAT and nano-plastics was quantitatively analyzed. 3. Results and discussion 3.1 Characterization of nano-plastics Figure 1 a, b and c are the SEM morphologies of PSNPs. They were all spherical particles with smooth and uniform surface. The particle size distribution of the three kinds of nanoparticles was shown in Fig. 1 d, e and f. The average particle size of PS particles, PS-COOH particles and PS-NH 2 measured by DLS were 395.33 ± 27.59 nm, 458.73 ± 62.63 nm and 480.6 ± 26.4 nm, respectively, and the dispersion index was 0.036, 0.064 and 0.055, respectively. Figure 1 g shows the variation of Zeta potential of PSNPs with pH, the surfaces of PSNPs are all negatively charged. the surface negative charge gradually increased when the pH increased, and the electronegativity also increased. The negative charge of PS-NH 2 was the highest, with its electronegativity the strongest, followed by that of PS-COOH, and the negative charge of PS was the lowest. 3.2 Adsorption kinetics The change of adsorption amount of GAT by PSNPs with adsorption time was studied at 298K, shown in Fig. 2 . PSNPs all showed rapid adsorption to GAT at the initial stage, and then the adsorption slowed down and finally reached the adsorption equilibrium at 12 h. Adsorption sites on the particle surface affected the adsorption capacity, and the initial number was large, when the adsorption amount increased, the adsorption sites gradually decreased, and the adsorption amount also decreased. The equilibrium trend and equilibrium time point of PS and PS-COOH were almost the same, while the equilibrium time of PS-NH 2 was relatively short. The modified PS exhibited significantly stronger adsorption capacity for GAT than PS. The existence of carboxyl and amino groups increased the polarity of the modified nano-plastic surface and made it more hydrophilic, easier to adsorb GAT (Zhang et al., 2020 ). The adsorption of PS-NH 2 to GAT was better than that of PS-COOH, which may be due to the fact that the amino group was more likely to form hydrogen bonds with water molecules than the carboxyl group, which made PS-NH 2 more hydrophilic. The adsorption processes of GAT on PSNPs conformed to the pseudo-first-order and pseudo-second-order kinetic models in Table 1 and Fig. 2 , the results showed that the adsorption of GAT on the surface of nano-plastics was influenced by both physical and chemical mechanisms.. The fitting results of Fig. 2 c showed that none of the lines pass through the origin, indicating that the main control mode of adsorption was not intra-particle diffusion, and the external diffusion may happen (Sun et al., 2022 ). To sum up, the adsorption of GAT by PSNPs was controlled by both external and intra-particle diffusion. Table 1 Fitting results of kinetic equation Nano-plastic type pseudo-first-order kinetic pseudo-second-order kinetic Qe K 1 R 2 Qe K 2 R 2 (mg/g) (h − 1 ) (mg/g) (g/mg·h) PS 77.6 0.134 0.937 86.0 0.013 0.957 PS-COOH 96.7 0.096 0.954 103.2 0.006 0.994 PS-NH 2 248.2 0.168 0.910 283.7 0.003 0.963 3.3 Adsorption isotherm Figure 3 showed the adsorption amount of PSNPs for GAT. the adsorption amount of GAT by PSNPs increased when the concentration of GAT increased, and finally became saturated. In Fig. 3 and Table 2 , Langmuir and Freundlich models were fitted to the experimental data of adsorption isotherm. The correlation coefficient R 2 fitted by Langmuir model was 0.935–0.996 and by Freundlich model was 0.92–0.986, which indicated that Langmuir model fitted better, suggesting that the adsorption of GAT on nano-plastics tended to be monolayer adsorption. K f and 1/n values indicated that PS-NH 2 had a stronger affinity for GAT than PS-COOH and PS in the Freundlich model. The 1/n were all 0–1, indicating that the three nano-plastics had good adsorption effect on GAT at different temperatures. Compared with PS, the adsorption amount of PS-NH 2 and PS-COOH was obviously larger and the adsorption effect was better. On the one hand, in Table S1 , the modification of carboxyl and amino groups increased the molecular polarity index (MPI), and thus increased the polarity of the particle surface (Zhang et al., 2020 ). In addition, PS-COOH and PS-NH 2 formed hydrogen bonds with GAT, which promoted adsorption. Previous studies showed that hydrogen bonding was an important mechanism by which aging microplastics adsorb antibiotics (Zhang et al., 2020 ), and the N-H functional group contained in PS-NH 2 may further promote adsorption, resulting in the adsorption better effect of PS-NH 2 . Table 2 Langmuir and Freundlich isotherm fitting results of GAT adsorption by PS and PS-COOH Nano-plastic type Temperature Langmuir isotherm Freundlich isotherm Q max K L R 2 K f n R 2 PS 283K 92.4 0.418 0.952 26.21 2.002 0.967 298K 119.8 0.144 0.954 28.33 1.182 0.942 313K 148.1 0.874 0.996 66.73 2.617 0.961 PS-COOH 283K 90.1 0.150 0.988 10.18 0.917 0.986 298K 95.8 0.268 0.935 43.11 1.767 0.926 313K 148.6 0.750 0.996 65.67 2.183 0.948 PS-NH 2 283K 205.0 0.351 0.981 53.77 1.745 0.980 298K 268.5 0.127 0.964 77.24 1.295 0.969 313K 287.8 0.452 0.989 92.29 1.348 0.920 3.4 Adsorption thermodynamics According to the formula (6)–(8) in Text S3, the ΔH 0 , ΔS 0 and ΔG 0 were calculated, and the results were shown in Table 3 . All the free energy changes were less than 0, suggesting that the adsorption of GAT on PSNPs was spontaneous. The free energy changes decreased as the temperature increases, indicating that the lower the ΔG 0 , the stronger the adsorption driving force (Chen et al., 2021 ). The enthalpy change ΔH 0 of the adsorption of GAT on PSNPs was greater than 0, showing that PSNPs adsorbed GAT was an endothermic process. It was reported that physical adsorption dominated when the adsorption enthalpy change was less than 40 kJ·mol − 1 (Wang et al., 2018), and it mainly included electrostatic interaction and valence bond force action (Chen et al., 2021 ; Zhou et al., 2019 ). Therefore, the adsorption process of PSNPs to GAT was a spontaneous physical adsorption process. Moreover, all the adsorption entropy changes were positive, implicating that the degree of confusion of the adsorption system increased, which was a typical entropy increase reaction (Ahmed et al., 2014; Zhang et al., 2019 ). Table 3 Adsorption thermodynamic parameters of GAT adsorbed by PS, PS-COOH and PS-NH 2 Nano-plastic type ΔH 0 (kJ/mol) ΔS 0 (J/mol·K) ΔG 0 (kJ/mol) 283K 298K 313K PS 16.45 32.18 -5.738 -6.912 -8.095 PS-COOH 18.31 33.92 -5.851 -7.240 -8.413 PS-NH 2 18.66 93.27 -7.741 -9.850 -10.56 3.5 Environmental factors 3.5.1 pH In Fig. 4 a, When the pH increased, the adsorption amount of PSNPs to GAT showed the same trend, that was, it increased at first and then decreased. The adsorption effect of PS and PS-NH 2 in neutral and weak acid conditions was better than that in strong acid and strong alkaline conditions, while the adsorption effect of PS-COOH in neutral and alkaline conditions was significantly better than that in acid conditions, showing that pH was one of the key factors affecting adsorption amount. It can be seen from Fig. 1 that PSNPs all had negative charges on their surfaces, and their absolute zeta potential values were positively correlated with pH. The ionic forms of nanoparticles PSNPs and GAT all changed with the change of pH. As shown in Fig. 4 b, under acidic conditions, when the pH of the solution was less than 6, GAT molecules mainly existed in a positively charged form. When the pH increased, the negative charges on the surface of PSNPs gradually increased, therefore, the electrostatic interaction between particles gradually increased as well, resulting in the increase of the adsorption amount of nanoparticles, with the maximum value at pH 6. When the pH was greater than 6, GAT mainly neutral molecules. Subsequently, the alkalinity gradually increased, and the proportion of negatively charged form of GAT gradually increased, and GAT and PSNPs surface electrostatic repulsion also increased, leading to the decrease of adsorption amount. In conclusion, electrostatic interaction was one of the main mechanisms of the adsorption process. 3.5.2 NaCl In Fig. 5 a, when NaCl concentration increased, the adsorption capacity of PSNPs to GAT decreased, indicating that NaCl inhibited the adsorption (Ge et al., 2018 ; Yu et al., 2020 ). The reasons were as follows: (1) the existence of ionic strength reduced the negative charge of PS and PS-COOH, thus weakening the electrostatic interaction. The increase of NaCl concentration compressed the double electric layer, resulting in weaker and weaker electrostatic attraction, thus reducing the adsorption amount (Wu et al., 2020 ). (2) NaCl competes with GAT for action sites on PSNPs, thereby inhibiting adsorption amount (Yu et al., 2020 ). (3) When NaCl increased to a certain concentration, PSNPs will agglomerate, and the aggregation products will reduce the action sites, thus inhibiting the adsorption (Li et al., 2018 ; Yu et al., 2016 ). The critical aggregation concentration of micron grade polystyrene plastics in NaCl solution was 14.9mM (Li et al., 2018 ). (4) When NaCl concentration increased, the viscosity and density of the solution increased accordingly, so that the transfer of mass from water to solid phase (PS, PS-NH 2 , PS-COOH) was restrained, and the adsorption amount decreased (Wu et al., 2018 ). 3.5.3 Dissolved organic matter Alginic acid is a kind of dissolved organic matter, and it could combine with various cations in seawater to form various kinds of alginate, which widely existed in seawater, and are found in lakes and rivers, therefore the effect of alginic acid concentration on the adsorption capacity of PSNPs on GAT adsorption was studied, shown in Fig. 5 b. The adsorption amount of PSNPs on GAT was negatively correlated with alginate concentration. It has been reported that as the concentration of fulvic acid increases, the adsorption amount of PS and PS-COOH for norfloxacin and levofloxacin decreased (Zhang et al., 2020 ), and the adsorption capacity of PS, PE and PBS for norfloxacin was negatively correlated with the concentration of fulvic acid (Sun et al., 2022 ). This showed that the existence of dissolved organic matter might inhibit the adsorption. The first, alginic acid produced competitive adsorption with GAT, thus making the adsorption amount decrease (Wan et al., 2019 ). The second, dissolved organic matter can also adsorb antibiotics through ion exchange, hydrogen bonding and so on, resulting in the reduced GAT adsorption amount on PSNPs (Feng et al., 2018 ). 3.5.4 Cu 2+ , Zn 2+ Cu 2+ , Zn 2+ are common heavy metal ion in water environment. In Fig. 5 c, d, as the concentration of Cu 2+ increases, the adsorption amount of PSNPs to GAT decreased, indicating that Cu 2+ could inhibit the adsorption. It may be because Cu 2+ was adsorbed by PSNPs through electrostatic interaction and ion exchange, occupying the adsorption sites of PSNPs, which reduced the adsorption amount (Yu et al., 2020 ). The possible reason for the significant inhibition of PS-NH 2 adsorption by Cu 2+ was that the amino groups in PS-NH 2 were heavy metal coordination groups, which can form chelates with heavy metals, preventing hydrogen bonds from forming, and further inhibiting the adsorption of GAT on PS-NH 2 . Notely, at low concentration, Cu 2+ slightly promoted the adsorption of GAT by PS and PS-COOH, which may be due to the formation of metal bridging effect between GAT and PS and PS-COOH surface caused by Cu 2+ to promote adsorption (Zhou et al., 2019 ). As the concentration of Zn 2+ increases, the adsorption amount of PS and PS-NH 2 to GAT decreased at first and then increased. The reasons for the inhibition may be that Zn 2+ was adsorbed by PS and PS-NH 2 through electrostatic interaction and ion exchange (Sun et al., 2022 ), occupying the adsorption sites of PS-NH 2 and PS, or that a complex reaction happened between -NH 2 in PS-NH 2 and Zn 2+ (Song et al., 2016 ). When the Zn 2+ concentration was further increased, Zn 2+ helped to form a metal bridge on the surface of PS, PS-NH 2 and GAT (Zhou et al., 2019 ), which weakened the inhibition effect and increased the adsorption amount. Whereas the adsorption amount of PS-COOH for GAT decreased gradually, might resulting from the complex reaction between the carboxyl group contained in PS-COOH and Zn 2+ . 3.6 Adsorption mechanisms In Fig. 6 , the adsorption mechanism of PSNPs on GAT was clarified by FTIR analysis. The characteristic peak benzene ring of PS was found to be transferred from 1703 to 1601 cm − 1 , show that PS adsorbed GAT mainly through π-π interaction (Sun et al., 2022 ; Xiong et al., 2020 ). There were no other functional groups before and after adsorption, indicating that the adsorption of GAT by PS was physical adsorption (Zhang et al., 2020 ). The characteristic peak C-O group of PS-COOH was transferred from 1227 cm − 1 to 1247 cm − 1 , and the intensity of the stretching vibration peak of O-H decreased at 3445 cm − 1 after adsorption, indicating that the mechanism of PS-COOH adsorption to GAT included π-π interaction and hydrogen bond (Sun et al., 2022 ). No other functional groups appeared before and after adsorption, indicated that the adsorption of GAT by PS-COOH was physical adsorption as well. The O-H peak of PS-NH 2 at 3443 cm − 1 becomes stronger after adsorption, indicating that the main adsorption mechanism of PS-NH 2 to GAT is hydrogen bond (Mamtimin et al., 2023 ). GAT, PS, PS-COOH and PS-NH 2 all contained benzene ring structure, and there was π-π interaction mechanism between benzene rings. The addition of carboxyl functional groups was reported to weaken the electron supply capacity of PS-COOH, thus weakening the π-π interaction (Lavrinenko-Ometsinskaya et al., 1989 ). Therefore, the π-π interaction of PS-COOH was weaker. However, it was found in this study that the ability of PS-COOH to adsorb GAT was stronger than that of PS, which showed that π-π interaction was not the main adsorption mechanism of PS-COOH. In conclusion, the main mechanism of adsorption of GAT by PS was π-π interaction, and the main mechanism of adsorption of GAT by PS-NH 2 and PS-COOH may be vdW and hydrogen bond (Mamtimin et al., 2023 ). To further clarify the adsorption mechanism of PSNPs to GAT, the electrostatic potentials, one of the main driving forces of GAT adsorption (Wang et al., 2022 ), on the surfaces of PSNPs were calculated by Gaussian 09 (B3LYP/6-31g (d)) density functional theory and analyzed by Multiwfn 3.8 and VMD software. As shown in Fig. 7 a-f and Fig. S1 , the highest electrostatic potential (41.49 kcal·mol − 1 ) on the surface of GAT corresponded to -H on the carboxyl group, which was conducive to the formation of electrostatic guided hydrogen bonds between GAT and nano-plastics, while the lowest potential (-68.84 kcal·mol − 1 ) corresponded to = O on quinoline and = O on the carboxyl group. The electrostatic potential of PS ranged from − 19.81 kcal/mol to 12.87 kcal/mol, which made PS have stable chemical properties (Wang et al., 2022 ). In Fig. S2, through the analysis of van der Waals force penetration position and interaction region indicator (IRI), it can be seen that the interaction between PS and GAT was mainly carried out through π-π interaction (green part). The surface electrostatic potential of PS-COOH ranged from − 35.28 to 46.57 kcal·mol − 1 , with the highest and lowest potential appearing at -H and = O of -COOH, respectively, and the surface electrostatic potential of PS-NH 2 ranged from − 32.22 to 33.74 kcal·mol − 1 , with the lowest potential appearing at N of -NH 2 . It can be seen that the range of surface electrostatic potential of PS-NH 2 and PS-COOH was obviously larger than that of PS. Moreover, according to the analysis by the reduced density gradient method (RDG), shown in Fig. 8 , hydrogen bonds were formed between -H on the carboxyl group of GAT and N on the -NH 2 of PS-NH 2 , =O on GAT quinoline and -H on the carboxyl group of PS-COOH, and the vdW existed between them were significant. The theoretical calculation results showed that the surface functionalized PS was easier to adsorb GAT than the PS, which was echoed with the experimental results. Interestingly, the maximum penetration distance of van der Waals (Fig. 7 g,h, Fig.S2,S3, Table S2) was calculated as GAT-PS-NH 2 (1.20 Å) > GAT-PS-COOH (1.06 Å) > GAT-PS (0.63 Å), showing that the interaction force between GAT and PS-NH 2 was greater than that between GAT and PS-COOH. It's theoretically proved that the adsorption amount of PS-NH 2 to GAT was particularly higher than that of PS-COOH. In addition, -NH 2 (weakly acidic) and-COOH (weakly basic) on GAT may also react slowly to form amide groups to bind them together. 4. Conclusions The experimental results of the adsorption kinetics of PSNPs to GAT showed that the adsorption was influenced by both physical and chemical mechanisms, and the adsorption rates were controlled by both intraparticle diffusion and external diffusion, physical adsorption was dominant. Isothermal adsorption, the adsorption thermodynamics experiment results showed that the adsorption process of GAT was spontaneous, entropy increase reaction. Density functional theory showed that the interaction between PS and GAT was mainly through π-π interaction and electrostatic interaction, and the interaction between PS-COOH, PS-NH 2 and GAT was mainly through electrostatic interaction, hydrogen bond and vdW, the maximum penetration distance of van der Waals was GAT-PS-NH 2 (1.20 Å) > GAT-PS-COOH (1.06 Å) > GAT-PS (0.63 Å). The equilibrium adsorption capacity of functionalized PS to GAT was greater than that of PS, and the adsorption amount of PS-NH 2 to GAT was particularly higher than that of PS-COOH. pH affected the adsorption of PSNPs to GAT by changing the surface charge of nano-plastics. NaCl inhibited adsorption through electrostatic interaction and aggregation of nanoparticles. Alginate and heavy metal ions inhibited adsorption by competitive adsorption and metal bridging. Since the amino functional group was a heavy metal coordination group, it could form chelates with heavy metals to prevent the formation of hydrogen bonds, so the inhibition of metal ions on PS-NH 2 was particularly obvious. The experiment is of great significance for understanding the interaction between nano-plastics and GAT in water environment. Declarations Ethical approval Not applicable. Consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests Funding This work was supported by the Research Project Supported by Shanxi Scholarship Council of China (No. 2023-054), the Applied Basic Research Project of Shanxi Province, China (No. 20210302123121), and the National Natural Science Foundation of China (No. 52170045). Author contribution Jie Yang : Conceptualization, Formal analysis, Investigation, Methodology, Data curation, Writing - original draft. Wei Ji : Validation, Writing – review & editing. Yanan Li : Conceptualization,Funding acquisition, Supervision. Yaning Wu : Investigation. Meijing Yao : Investigation. Weiqin Wu : Investigation. Kangjian Jing : Investigation. Guokai Zhnag : Investigation. Data availability The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. References Ahmed MJ, Theydan SK (2014) Fluoroquinolones antibiotics adsorption onto microporous activated carbon from lignocellulosic biomass by microwave pyrolysis. J Taiwan Inst Chem Eng 45:219–226 Andrady AL (2011) Microplastics in the marine environment. Mar Pollut Bull 62:1596–1605 Atugoda T, Wijesekara H, Werellagama DRIB, **adasa KBSN, Bolan NS, Vithanage M (2020) Adsorptive interaction of antibiotic ciprofloxacin on polyethylene microplastics: Implications for vector transport in water. 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Sci Total Environ 750:142370 Yu F, Ma J, Wang J, Zhang M, Zheng J (2016) Magnetic iron oxide nanoparticles functionalized multi-walled carbon nanotubes for toluene, ethylbenzene and xylene removal from aqueous solution. Chemosphere 146:162–172 Yu F, Yang C, Zhu Z, Bai X, Ma J (2019) Adsorption behavior of organic pollutants and metals on micro/nanoplastics in the aquatic environment. Sci Total Environ 694:133643 Yu F, Li Y, Huang G, Yang C, Chen C, Zhou T, Ma J (2020) Adsorption behavior of the antibiotic levofloxacin on microplastics in the presence of different heavy metals in an aqueous solution. Chemosphere 260:127650 Yu F, Yang C, Huang G, Zhou T, Zhao Y, Ma J (2020) Interfacial interaction between diverse microplastics and tetracycline by adsorption in an aqueous solution. Sci Total Environ 721:137729 Zhang H, Liu FF, Wang SC, Huang TY, Li MR, Zhu ZL, Liu GZ (2020) Sorption of fluoroquinolones to nanoplastics as affected by surface functionalization and solution chemistry. 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Sci Total Environ 646:29–36 Supplementary Files SupplementaryMaterial.docx Cite Share Download PDF Status: Published Journal Publication published 31 Oct, 2024 Read the published version in Environmental Science and Pollution Research → Version 1 posted Editorial decision: Major Revision 08 Aug, 2024 Reviewers agreed at journal 11 Jun, 2024 Reviewers invited by journal 11 Jun, 2024 Editor invited by journal 27 May, 2024 Editor assigned by journal 10 May, 2024 First submitted to journal 09 May, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4370552","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":313208936,"identity":"16d7663f-62e8-4445-8c94-65f33ad717da","order_by":0,"name":"Jie Yang","email":"","orcid":"","institution":"Taiyuan University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Jie","middleName":"","lastName":"Yang","suffix":""},{"id":313208937,"identity":"70c3c3f1-514f-4090-a187-c6120e113d7b","order_by":1,"name":"Wei Ji","email":"","orcid":"","institution":"Taiyuan University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Ji","suffix":""},{"id":313208938,"identity":"e6d4d0f4-a3f4-4056-9d1b-5cb1fc1dbddd","order_by":2,"name":"yanan Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0ElEQVRIiWNgGAWjYBACPmYILQflMxPWwgZVY8zDwMDYQJwWKJ3YQ7wWdh7DzwU1d9L3S+SYP2CosE5sYD97gIDDeIylZxx7ltsjkWPYwHAmPbGBJy+BkBYDaR62wxAtjG2HExskeAwI2vKb59/hdB6wln/EaTGT5m07nADR0kCUFrYya96+w4Y9Z54Vzkg4lm7cxpODXws//+HNt3m+HZZnb0/e8OFDjbVsP/sZ/FoYGDigCgQSGBgSGBAxhQewP4Dad4Cw2lEwCkbBKBiZAACJJTwQ0zBOCgAAAABJRU5ErkJggg==","orcid":"","institution":"Taiyuan University of Technology","correspondingAuthor":true,"prefix":"","firstName":"yanan","middleName":"","lastName":"Li","suffix":""},{"id":313208939,"identity":"0eb0cd9b-4a48-46b3-9660-2c874853b5cb","order_by":3,"name":"Yaning Wu","email":"","orcid":"","institution":"Taiyuan University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yaning","middleName":"","lastName":"Wu","suffix":""},{"id":313208940,"identity":"96688eed-cea4-4cc8-9f92-776bc2fde684","order_by":4,"name":"Meijing Yao","email":"","orcid":"","institution":"Taiyuan University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Meijing","middleName":"","lastName":"Yao","suffix":""},{"id":313208941,"identity":"34a59547-eb53-48da-b86e-c559104ebace","order_by":5,"name":"Weiqin Wu","email":"","orcid":"","institution":"Taiyuan University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Weiqin","middleName":"","lastName":"Wu","suffix":""},{"id":313208942,"identity":"71970157-ef12-44a4-9cbf-95498800d343","order_by":6,"name":"Kangjian Jing","email":"","orcid":"","institution":"Taiyuan University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Kangjian","middleName":"","lastName":"Jing","suffix":""},{"id":313208943,"identity":"9324d13d-0e4e-4d5a-9c0f-5dcf39bd9b98","order_by":7,"name":"Guokai Zhang","email":"","orcid":"","institution":"Chinasea Group Co., LTD.","correspondingAuthor":false,"prefix":"","firstName":"Guokai","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2024-05-05 06:46:42","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4370552/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4370552/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11356-024-35457-2","type":"published","date":"2024-10-31T16:20:31+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":59163819,"identity":"9a6b6371-5be7-49e7-80d8-f3c859e6b99f","added_by":"auto","created_at":"2024-06-27 06:13:00","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":533685,"visible":true,"origin":"","legend":"\u003cp\u003eThe SEM morphology of PS (a), PS-COOH (b) and PS-NH\u003csub\u003e2\u003c/sub\u003e (c) ; the particle size distribution of PS (d), PS-COOH (e), PS-NH\u003csub\u003e2\u003c/sub\u003e (f) ; zeta potential diagram (g)\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/52150c8ce3251150c07252fc.jpeg"},{"id":59163814,"identity":"75e2799a-f068-47da-ba18-84eb7b78df22","added_by":"auto","created_at":"2024-06-27 06:13:00","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":187683,"visible":true,"origin":"","legend":"\u003cp\u003ePS、PS-COOH、PS-NH\u003csub\u003e2 \u003c/sub\u003eadsorption kinetic model fitting: Pseudo first order kinetic (a) pseudo second order kinetic (b) , intra-particle diffusion model (c)\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/77fe0db413d27418bb675c31.jpeg"},{"id":59164085,"identity":"fde4df45-6c87-424e-81cf-82b53279bf0d","added_by":"auto","created_at":"2024-06-27 06:21:00","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":403389,"visible":true,"origin":"","legend":"\u003cp\u003eFitting the adsorption isotherms of PS(a),PS-COOH(b) and PS-NH\u003csub\u003e2\u003c/sub\u003e(c)\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/2099998915c65bee6955bc51.jpeg"},{"id":59163816,"identity":"46c2b17f-ef55-409e-bebd-bdbc9e714065","added_by":"auto","created_at":"2024-06-27 06:13:00","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":186279,"visible":true,"origin":"","legend":"\u003cp\u003e(a\u003cstrong\u003e) \u003c/strong\u003eEffect of solution pH on adsorption capacity, (b) The morphology of GAT at different pH.\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/ddeccae588ede0870b95de14.jpeg"},{"id":59163811,"identity":"db6a3dab-34c3-4110-bf03-fb257d613611","added_by":"auto","created_at":"2024-06-27 06:12:59","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":433125,"visible":true,"origin":"","legend":"\u003cp\u003e(a)Effect of NaCl concentration on adsorption capacity, (b) Effect of alginic acid concentration on adsorption capacity,(c,d) Effect of heavy metal ion concentration on adsorption capacity\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/c0c1f3447bbb769a34ae64e5.jpeg"},{"id":59163809,"identity":"1d815bd0-3bf0-40f6-b73d-9f717ebe485f","added_by":"auto","created_at":"2024-06-27 06:12:59","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":605440,"visible":true,"origin":"","legend":"\u003cp\u003eFourier transform infrared spectra of PS(a), PS-COOH(b) and PS-NH\u003csub\u003e2\u003c/sub\u003e(c) before and after adsorption\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/0aa6e53798777b4cfc11ed83.jpeg"},{"id":59163812,"identity":"400cd13a-1be2-4040-a5d0-1671b53918d7","added_by":"auto","created_at":"2024-06-27 06:13:00","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":919135,"visible":true,"origin":"","legend":"\u003cp\u003eGAT(a); PS(b, c); PS-COOH(d); PS-NH\u003csub\u003e2\u003c/sub\u003e(e, f) surface electrostatic potential distribution, PS-NH\u003csub\u003e2\u003c/sub\u003e (g,), PS-COOH (h) and GAT van der Waals penetration position. The yellow dot in the electrostatic potential distribution diagram represents the extreme point of positive potential, and the blue dot represents the extreme point of negative potential.\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/ae338ee1997544d146a2b496.jpeg"},{"id":59163810,"identity":"9f9175f1-5981-4341-983f-fb6bcb7f0e19","added_by":"auto","created_at":"2024-06-27 06:12:59","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1028110,"visible":true,"origin":"","legend":"\u003cp\u003eReduced density gradient (RDG) analysis. (a,c)GAT and PS-NH\u003csub\u003e2\u003c/sub\u003e, (b,d)GAT and PS-COOH\u003c/p\u003e","description":"","filename":"floatimage8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/0f0f61e8c00b731e74c8d475.jpeg"},{"id":68207171,"identity":"52f1b4d9-1417-4f1c-a33b-19ea90b791d4","added_by":"auto","created_at":"2024-11-04 16:35:36","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5010979,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/60ff5adf-9e5d-48e4-ad0f-9af8ec83a8fc.pdf"},{"id":59163818,"identity":"06d373e3-4205-47ea-9d34-81e873285206","added_by":"auto","created_at":"2024-06-27 06:13:00","extension":"docx","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":7680085,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-4370552/v1/8def64c30105525f509de014.docx"}],"financialInterests":"","formattedTitle":"Adsorption behavior and quantum chemical analysis of surface functionalized polystyrene nano-plastics on gatifloxacin.","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe production of plastic has grown exponentially since the 1950 s all over the word (Ostle et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), about 8\u0026nbsp;million tons of plastic eventually flows into the sea every year, most of which come from land, and plastic has become a global pollutant (Baeta et al., 2021). Plastics have been reported to be found in many sampling sites from high mountains to the seafloor, and bulk plastics in the environment can be decomposed into microplastics (MPs, 1 \u0026micro;m\u0026thinsp;\u0026lt;\u0026thinsp;MPs particle size\u0026thinsp;\u0026lt;\u0026thinsp;5 mm), including PP, PA, PS, PVC, et al., by physical, chemical and biological actions. For example, the concentration of microplastics in rivers is about 1.6\u0026ndash;41 mg/L (Moore et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Part of microplastics can be further degraded into nano-plastics (1 nm\u0026thinsp;\u0026lt;\u0026thinsp;NPs particle size\u0026thinsp;\u0026lt;\u0026thinsp;1 \u0026micro;m) (Vandermeersch et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Andrady et al., 2011; Lambert et al., 2016) with smaller particle size under the action of photodegradation, mechanical wear and biodegradation. micro / nano plastics will age and produce functional groups, such as amino group and carboxyl group, on their surface. Moreover, the micro / nano plastics can adsorb various heavy metal ions and organic pollutants, like lead ions, cadmium ions, antibiotics, pesticides and so on (Yu et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Xu et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Bao et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Dong et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). However, due to the difficulties of current sampling and analysis strategies of granular plastics, it is difficult to evaluate their real exposure to humans or biota at a given location and their harm to human and biological health (Vandermeersch et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Bergmann et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Bergmann et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWith the development of pharmaceutical industry, more and more antibiotics are used to treat microbial infections in people (Lage et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Fluoroquinolones have ranked first in the use of all kinds of antibiotics since 2002, and the consumption of fluoroquinolones in 2013 was estimated to be as high as 27300 tons (Zhang et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Especially, the output and dosage of fluoroquinolone antibiotics such as pefloxacin, ciprofloxacin and norfloxacin reached the maximum (Yu et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). However, the treatment efficiency of fluoroquinolone antibiotics was only 56\u0026ndash;75% (Carvalho et al., 2016), with the concentration of antibiotics in the wastewater at the effluent of pharmaceutical factories even reached 30 mg/L (Aus et al., 2016), and antibiotics were also detected in many water bodies, such as East Dongting Lake, Pearl River Estuary, etc. (Yu et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ma et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eVarious behaviors of micro / nano plastics and antibiotics, such as aggregation and dispersion, adsorption, migration and deposition, may affect their compound pollution toxicity and ecological effect. The previous studies on the adsorption behavior of micro or nano plastics to antibiotics mainly included the adsorption of amoxicillin, tetracycline, ciprofloxacin, sulfadiazine, pefloxacin and levofloxacin by polystyrene (PS), polyethylene (PP), polyvinyl chloride (PVC) and polyamide (PA), mostly focusing on the kinetics, isotherm and pH, temperature, salt ions, etc., on the adsorption (Yu et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Li et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Atugoda et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The adsorption of antibiotics by microplastics was mainly physical or chemical adsorption, which was jointly controlled by external and intra-particle diffusion, and the main mechanisms included hydrogen bonding, electrostatic interaction, van der Waals forces (vdW), hydrophobic interaction and so on (Li et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Atugoda et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Chen et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). For example, electrostatic interaction was the main mechanism of pH affecting the adsorption of polyethylene to antibiotics (Chen et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), and due to the competitive adsorption and ion exchange among pollutants, the increase of dissolved organic matter concentration and ion strength will reduce the adsorption amount (Yu et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eCompared with micron plastics, nano-plastics had larger specific surface area, higher surface hydrophobicity and better adsorption effect for heavy metals, polychlorinated biphenyls, antibiotics and other pollutants (Li et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Da Costa et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). In particular, the saturated adsorption capacity of nano-plastics for antibiotics is higher than that of microplastics for antibiotics, the former 20-50mg/g, the latter concentrated within 10 mg/g or less. Interestingly, PS-COOH adsorbed antibiotics better than PS because of the polarity between them, and for norfloxacin and levofloxacin, the adsorption capacity of PS-COOH was 54.9% and 69.6% higher than PS, respectively (Zhang et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Yilimulati et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). However, there is still a lack of data on the interaction between functionalized nano-plastics and antibiotics. Therefore, in this paper, 400 nm polystyrene microspheres (PS), carboxyl modified PS (PS-COOH) and amino modified PS (PS-NH\u003csub\u003e2\u003c/sub\u003e) were selected as the research objects to explore their adsorption mechanism for gatifloxacin (GAT), a typical fluoroquinolone antibiotic. The effects of physical and chemical conditions, including pH, temperature, ionic strength, heavy metal ions and dissolved organic matter, on the interaction were investigated, and the interaction mechanism and theory between nano-plastics and antibiotics were clarified, which will provide theoretical guidance for the transformation and removal of micro-nano plastics in practical environment.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials, reagents and instruments\u003c/h2\u003e \u003cp\u003eNano-polystyrene microspheres (PS, 400 nm, 2.5% (w/v)), carboxyl nano-polystyrene microspheres (PS-COOH, 400 nm, 2.5% (w/v)), amino nano-polystyrene microspheres (PS-NH\u003csub\u003e2\u003c/sub\u003e, 400 nm, 2.5% (w/v)) were purchased from Jiangsu Zhijie Technology Co., Ltd, and Gatifloxacin (GAT, powder, 98%) were purchased from Shanghai McLean biochemical Technology Co., Ltd.\u003c/p\u003e \u003cp\u003eThe resistivity of Milli-Q water in the experiment was 18.2 MΩ\u0026middot;cm, obtained by Milli-Q water purification system, and the polystyrene colorimetric cell (FIS14-955125) used in the measurement of potential and particle size was purchased from Fisherbrand Company of USA. The 0.22\u0026micro;m cellulose acetate membrane used in filtration was purchased from Corning Company of New York, USA.\u003c/p\u003e \u003cp\u003eThe instruments used in the adsorption experiment included constant temperature oscillator (THZ-C, Taicang Haocheng Experimental instrument Manufacturing Co., Ltd.), pH meter (PHS-3C, Shanghai instrument Co., Ltd.), Ultrasonic Cleaner (KQ5200E, Kunshan Ultrasonic instrument Co., Ltd.), dynamic light scattering (DLS, Zetasizer Nano ZS90, Malvern instrument Co., Ltd.), high performance liquid chromatograph (HPLC, G711A, Agilent Technology Co., Ltd.), microelectrophoresis instrument (JS94H2, Shanghai Zhongchen Digital Technology equipment Co., Ltd.), scanning electronic micromirror (SEM, Czech Tescan MIRA LMS), fourier transform infrared spectrometer (FTIR, American Thermo Scientific Nicolet iS20).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Experimental methods\u003c/h2\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.2.1 Solution preparation and adsorption experiment\u003c/h2\u003e \u003cp\u003eAccurately weighed 100 mg of Gatifloxacin (GAT) and make up a 100 mg \u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e stock solution. The solution was stored in a 500 mL brown volumetric bottle and kept in dark in 4℃ refrigerator. The experimental steps of adsorption kinetics, adsorption isotherm and adsorption thermodynamics were shown in Text S1, S2, S3.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.2.2 Experiment on the effect of solution pH\u003c/h2\u003e \u003cp\u003eThe 10 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e PSNPs were added to 50mL GAT solution of 10 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, in 100mL conical bottles, adjusting pH to 3\u0026ndash;9. The conical bottles were then placed in an oscillator and oscillate in dark. The oscillator temperature was set at 298K and the rev was 150 r\u0026middot;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The samples were taken 24 hours later, and filtered quickly with 0.22\u0026micro;m acetate fiber filter membrane. The concentration of GAT in the samples was measured.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.2.3 Effects of NaCl, alginic acid and Cu\u003csup\u003e2+\u003c/sup\u003e, Zn\u003csup\u003e2+\u003c/sup\u003e\u003c/h2\u003e \u003cp\u003eTo assess the impact of environmental factors, a series concentration of NaCl (0.1\u0026ndash;0.5 mol\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), dissolved organic alginic acid (1\u0026ndash;20 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), Cu\u003csup\u003e2+\u003c/sup\u003e (1\u0026ndash;20 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and Zn\u003csup\u003e2+\u003c/sup\u003e (1\u0026ndash;20 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) were selected to prepare antibiotic solution (mass concentration 10 mg\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and mixed with nano plastic solution. The conical bottles were oscillated in a constant temperature oscillator. The temperature of the oscillator was 298K and the rotational speed was 150 r\u0026middot;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. After 24 hours, the samples were quickly filtered with 0.22\u0026micro;m cellulose acetate membrane, and then the concentration of antibiotics was determined.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Analysis and detection methods\u003c/h2\u003e \u003cp\u003e(1) Particle morphology analysis.\u003c/p\u003e \u003cp\u003eScanning electronic micromirror (SEM) was used to analyze the particle morphology. A few nanoparticles were added to 50% anhydrous ethanol solution of 20 mL to form a dilute solution, which was then observed under scanning electron microscope after ultrasound.\u003c/p\u003e \u003cp\u003e(2) Functional group and mechanism analysis.\u003c/p\u003e \u003cp\u003eThe nanoparticles before and after adsorption were freeze-dried, and then placed in a Fourier transform infrared spectrometer (FTIR) instrument for infrared spectrum analysis after treating by KBr tablet method. The test range was 400\u0026ndash;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with 32 times scanning.\u003c/p\u003e \u003cp\u003e(3) Particle size and electric potential analysis\u003c/p\u003e \u003cp\u003eDynamic light scattering (DLS) was used for particle size potential analysis. The samples were prepared by using ultra-pure water with different pH values, and placed in a special dish equipped with the nanoparticle size potentiometer. The particle size and its distribution and potential of the nanoparticles were measured separately.\u003c/p\u003e \u003cp\u003e(4) Analysis of GAT concentration\u003c/p\u003e \u003cp\u003eBy high performance liquid chromatograph (HPLC) to determine the concentration of GAT. The chromatographic column was InfinityLab Poroshell 120, the mobile phase was 80% acetonitrile and 20% formic acid water (\u003cem\u003ew\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.1%), the injection volume was 50 \u0026micro;L, the flow rate was 0.8 mL\u0026middot;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the GAT detection wavelength was 291 nm.\u003c/p\u003e \u003cp\u003e(5) Quantum chemistry calculation\u003c/p\u003e \u003cp\u003eThe surface electrostatic potential distribution of nano-plastics was calculated by Gaussian 09 and GaussView 6.0 software (Gaussian Inc., USA). B3LYP/6-31G(d) was used for structural optimization, and M062X/6-31G(d) was used for energy calculation. Multiwfn 3.8 and Visual Molecular Dynamics (VMD 1.9.3) software (University of Illinois) (Humphrey et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Lu et al., 2012) were used to further process the above calculation results, including reduced density gradient (RDG) analysis, etc. The surface electrostatic potential distribution and van der Waals force penetration of the complex were calculated by using the compound formed by the connection of two nano-plastic monomers, and the strength of the interaction force between GAT and nano-plastics was quantitatively analyzed.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Characterization of nano-plastics\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, b and c are the SEM morphologies of PSNPs. They were all spherical particles with smooth and uniform surface. The particle size distribution of the three kinds of nanoparticles was shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed, e and f. The average particle size of PS particles, PS-COOH particles and PS-NH\u003csub\u003e2\u003c/sub\u003e measured by DLS were 395.33\u0026thinsp;\u0026plusmn;\u0026thinsp;27.59 nm, 458.73\u0026thinsp;\u0026plusmn;\u0026thinsp;62.63 nm and 480.6\u0026thinsp;\u0026plusmn;\u0026thinsp;26.4 nm, respectively, and the dispersion index was 0.036, 0.064 and 0.055, respectively. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg shows the variation of Zeta potential of PSNPs with pH, the surfaces of PSNPs are all negatively charged. the surface negative charge gradually increased when the pH increased, and the electronegativity also increased. The negative charge of PS-NH\u003csub\u003e2\u003c/sub\u003e was the highest, with its electronegativity the strongest, followed by that of PS-COOH, and the negative charge of PS was the lowest.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Adsorption kinetics\u003c/h2\u003e \u003cp\u003eThe change of adsorption amount of GAT by PSNPs with adsorption time was studied at 298K, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. PSNPs all showed rapid adsorption to GAT at the initial stage, and then the adsorption slowed down and finally reached the adsorption equilibrium at 12 h. Adsorption sites on the particle surface affected the adsorption capacity, and the initial number was large, when the adsorption amount increased, the adsorption sites gradually decreased, and the adsorption amount also decreased. The equilibrium trend and equilibrium time point of PS and PS-COOH were almost the same, while the equilibrium time of PS-NH\u003csub\u003e2\u003c/sub\u003e was relatively short. The modified PS exhibited significantly stronger adsorption capacity for GAT than PS. The existence of carboxyl and amino groups increased the polarity of the modified nano-plastic surface and made it more hydrophilic, easier to adsorb GAT (Zhang et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The adsorption of PS-NH\u003csub\u003e2\u003c/sub\u003e to GAT was better than that of PS-COOH, which may be due to the fact that the amino group was more likely to form hydrogen bonds with water molecules than the carboxyl group, which made PS-NH\u003csub\u003e2\u003c/sub\u003e more hydrophilic.\u003c/p\u003e \u003cp\u003eThe adsorption processes of GAT on PSNPs conformed to the pseudo-first-order and pseudo-second-order kinetic models in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the results showed that the adsorption of GAT on the surface of nano-plastics was influenced by both physical and chemical mechanisms.. The fitting results of Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec showed that none of the lines pass through the origin, indicating that the main control mode of adsorption was not intra-particle diffusion, and the external diffusion may happen (Sun et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). To sum up, the adsorption of GAT by PSNPs was controlled by both external and intra-particle diffusion.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eFitting results of kinetic equation\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eNano-plastic type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003epseudo-first-order kinetic\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003epseudo-second-order kinetic\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eQe\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eQe\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(mg/g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(mg/g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e(g/mg\u0026middot;h)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e77.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.134\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.937\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e86.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.957\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePS-COOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e96.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.096\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.954\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e103.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.994\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePS-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e248.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.168\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.910\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e283.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.963\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Adsorption isotherm\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e showed the adsorption amount of PSNPs for GAT. the adsorption amount of GAT by PSNPs increased when the concentration of GAT increased, and finally became saturated. In Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Langmuir and Freundlich models were fitted to the experimental data of adsorption isotherm. The correlation coefficient R\u003csup\u003e2\u003c/sup\u003e fitted by Langmuir model was 0.935\u0026ndash;0.996 and by Freundlich model was 0.92\u0026ndash;0.986, which indicated that Langmuir model fitted better, suggesting that the adsorption of GAT on nano-plastics tended to be monolayer adsorption. \u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e and 1/n values indicated that PS-NH\u003csub\u003e2\u003c/sub\u003e had a stronger affinity for GAT than PS-COOH and PS in the Freundlich model. The 1/n were all 0\u0026ndash;1, indicating that the three nano-plastics had good adsorption effect on GAT at different temperatures.\u003c/p\u003e \u003cp\u003eCompared with PS, the adsorption amount of PS-NH\u003csub\u003e2\u003c/sub\u003e and PS-COOH was obviously larger and the adsorption effect was better. On the one hand, in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e, the modification of carboxyl and amino groups increased the molecular polarity index (MPI), and thus increased the polarity of the particle surface (Zhang et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In addition, PS-COOH and PS-NH\u003csub\u003e2\u003c/sub\u003e formed hydrogen bonds with GAT, which promoted adsorption. Previous studies showed that hydrogen bonding was an important mechanism by which aging microplastics adsorb antibiotics (Zhang et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), and the N-H functional group contained in PS-NH\u003csub\u003e2\u003c/sub\u003e may further promote adsorption, resulting in the adsorption better effect of PS-NH\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLangmuir and Freundlich isotherm fitting results of GAT adsorption by PS and PS-COOH\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNano-plastic type\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTemperature\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e \u003cp\u003eLangmuir isotherm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c8\" namest=\"c6\"\u003e \u003cp\u003eFreundlich isotherm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eQ\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003ef\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003en\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003ePS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e283K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e92.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.418\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.952\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e26.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.967\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e298K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e119.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.144\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.954\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e28.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.182\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.942\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e313K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e148.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.874\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.996\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e66.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.617\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.961\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003ePS-COOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e283K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e90.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.988\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.917\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.986\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e298K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e95.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.268\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.935\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e43.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.767\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.926\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e313K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e148.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.750\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.996\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e65.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.183\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.948\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003ePS-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e283K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e205.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.351\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.981\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e53.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.745\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.980\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e298K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e268.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.127\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.964\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e77.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.295\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.969\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e313K\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e287.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.452\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.989\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e92.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.348\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.920\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Adsorption thermodynamics\u003c/h2\u003e \u003cp\u003eAccording to the formula (6)\u0026ndash;(8) in Text S3, the ΔH\u003csup\u003e0\u003c/sup\u003e, ΔS\u003csup\u003e0\u003c/sup\u003e and ΔG\u003csup\u003e0\u003c/sup\u003e were calculated, and the results were shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. All the free energy changes were less than 0, suggesting that the adsorption of GAT on PSNPs was spontaneous. The free energy changes decreased as the temperature increases, indicating that the lower the ΔG\u003csup\u003e0\u003c/sup\u003e, the stronger the adsorption driving force (Chen et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The enthalpy change ΔH\u003csup\u003e0\u003c/sup\u003e of the adsorption of GAT on PSNPs was greater than 0, showing that PSNPs adsorbed GAT was an endothermic process. It was reported that physical adsorption dominated when the adsorption enthalpy change was less than 40 kJ\u0026middot;mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Wang et al., 2018), and it mainly included electrostatic interaction and valence bond force action (Chen et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Zhou et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Therefore, the adsorption process of PSNPs to GAT was a spontaneous physical adsorption process. Moreover, all the adsorption entropy changes were positive, implicating that the degree of confusion of the adsorption system increased, which was a typical entropy increase reaction (Ahmed et al., 2014; Zhang et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAdsorption thermodynamic parameters of GAT adsorbed by PS, PS-COOH and PS-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNano-plastic type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eΔH\u003csup\u003e0\u003c/sup\u003e(kJ/mol)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eΔS\u003csup\u003e0\u003c/sup\u003e(J/mol\u0026middot;K)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003eΔG\u003csup\u003e0\u003c/sup\u003e(kJ/mol)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e283K\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e298K\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e313K\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e16.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e32.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-5.738\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-6.912\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-8.095\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePS-COOH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e18.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e33.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-5.851\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-7.240\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-8.413\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePS-NH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e18.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e93.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-7.741\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-9.850\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-10.56\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Environmental factors\u003c/h2\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e3.5.1 pH\u003c/h2\u003e \u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, When the pH increased, the adsorption amount of PSNPs to GAT showed the same trend, that was, it increased at first and then decreased. The adsorption effect of PS and PS-NH\u003csub\u003e2\u003c/sub\u003e in neutral and weak acid conditions was better than that in strong acid and strong alkaline conditions, while the adsorption effect of PS-COOH in neutral and alkaline conditions was significantly better than that in acid conditions, showing that pH was one of the key factors affecting adsorption amount.\u003c/p\u003e \u003cp\u003eIt can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e that PSNPs all had negative charges on their surfaces, and their absolute zeta potential values were positively correlated with pH. The ionic forms of nanoparticles PSNPs and GAT all changed with the change of pH. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, under acidic conditions, when the pH of the solution was less than 6, GAT molecules mainly existed in a positively charged form. When the pH increased, the negative charges on the surface of PSNPs gradually increased, therefore, the electrostatic interaction between particles gradually increased as well, resulting in the increase of the adsorption amount of nanoparticles, with the maximum value at pH 6. When the pH was greater than 6, GAT mainly neutral molecules. Subsequently, the alkalinity gradually increased, and the proportion of negatively charged form of GAT gradually increased, and GAT and PSNPs surface electrostatic repulsion also increased, leading to the decrease of adsorption amount. In conclusion, electrostatic interaction was one of the main mechanisms of the adsorption process.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e3.5.2 NaCl\u003c/h2\u003e \u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, when NaCl concentration increased, the adsorption capacity of PSNPs to GAT decreased, indicating that NaCl inhibited the adsorption (Ge et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Yu et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The reasons were as follows: (1) the existence of ionic strength reduced the negative charge of PS and PS-COOH, thus weakening the electrostatic interaction. The increase of NaCl concentration compressed the double electric layer, resulting in weaker and weaker electrostatic attraction, thus reducing the adsorption amount (Wu et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). (2) NaCl competes with GAT for action sites on PSNPs, thereby inhibiting adsorption amount (Yu et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). (3) When NaCl increased to a certain concentration, PSNPs will agglomerate, and the aggregation products will reduce the action sites, thus inhibiting the adsorption (Li et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Yu et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The critical aggregation concentration of micron grade polystyrene plastics in NaCl solution was 14.9mM (Li et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). (4) When NaCl concentration increased, the viscosity and density of the solution increased accordingly, so that the transfer of mass from water to solid phase (PS, PS-NH\u003csub\u003e2\u003c/sub\u003e, PS-COOH) was restrained, and the adsorption amount decreased (Wu et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e3.5.3 Dissolved organic matter\u003c/h2\u003e \u003cp\u003eAlginic acid is a kind of dissolved organic matter, and it could combine with various cations in seawater to form various kinds of alginate, which widely existed in seawater, and are found in lakes and rivers, therefore the effect of alginic acid concentration on the adsorption capacity of PSNPs on GAT adsorption was studied, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb. The adsorption amount of PSNPs on GAT was negatively correlated with alginate concentration. It has been reported that as the concentration of fulvic acid increases, the adsorption amount of PS and PS-COOH for norfloxacin and levofloxacin decreased (Zhang et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), and the adsorption capacity of PS, PE and PBS for norfloxacin was negatively correlated with the concentration of fulvic acid (Sun et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). This showed that the existence of dissolved organic matter might inhibit the adsorption. The first, alginic acid produced competitive adsorption with GAT, thus making the adsorption amount decrease (Wan et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The second, dissolved organic matter can also adsorb antibiotics through ion exchange, hydrogen bonding and so on, resulting in the reduced GAT adsorption amount on PSNPs (Feng et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003e3.5.4 Cu\u003csup\u003e2+\u003c/sup\u003e, Zn\u003csup\u003e2+\u003c/sup\u003e\u003c/h2\u003e \u003cp\u003eCu\u003csup\u003e2+\u003c/sup\u003e, Zn\u003csup\u003e2+\u003c/sup\u003e are common heavy metal ion in water environment. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, d, as the concentration of Cu\u003csup\u003e2+\u003c/sup\u003e increases, the adsorption amount of PSNPs to GAT decreased, indicating that Cu\u003csup\u003e2+\u003c/sup\u003e could inhibit the adsorption. It may be because Cu\u003csup\u003e2+\u003c/sup\u003e was adsorbed by PSNPs through electrostatic interaction and ion exchange, occupying the adsorption sites of PSNPs, which reduced the adsorption amount (Yu et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The possible reason for the significant inhibition of PS-NH\u003csub\u003e2\u003c/sub\u003e adsorption by Cu\u003csup\u003e2+\u003c/sup\u003e was that the amino groups in PS-NH\u003csub\u003e2\u003c/sub\u003e were heavy metal coordination groups, which can form chelates with heavy metals, preventing hydrogen bonds from forming, and further inhibiting the adsorption of GAT on PS-NH\u003csub\u003e2\u003c/sub\u003e. Notely, at low concentration, Cu\u003csup\u003e2+\u003c/sup\u003e slightly promoted the adsorption of GAT by PS and PS-COOH, which may be due to the formation of metal bridging effect between GAT and PS and PS-COOH surface caused by Cu\u003csup\u003e2+\u003c/sup\u003e to promote adsorption (Zhou et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAs the concentration of Zn\u003csup\u003e2+\u003c/sup\u003e increases, the adsorption amount of PS and PS-NH\u003csub\u003e2\u003c/sub\u003e to GAT decreased at first and then increased. The reasons for the inhibition may be that Zn\u003csup\u003e2+\u003c/sup\u003e was adsorbed by PS and PS-NH\u003csub\u003e2\u003c/sub\u003e through electrostatic interaction and ion exchange (Sun et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), occupying the adsorption sites of PS-NH\u003csub\u003e2\u003c/sub\u003e and PS, or that a complex reaction happened between -NH\u003csub\u003e2\u003c/sub\u003e in PS-NH\u003csub\u003e2\u003c/sub\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e (Song et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). When the Zn\u003csup\u003e2+\u003c/sup\u003e concentration was further increased, Zn\u003csup\u003e2+\u003c/sup\u003e helped to form a metal bridge on the surface of PS, PS-NH\u003csub\u003e2\u003c/sub\u003e and GAT (Zhou et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), which weakened the inhibition effect and increased the adsorption amount. Whereas the adsorption amount of PS-COOH for GAT decreased gradually, might resulting from the complex reaction between the carboxyl group contained in PS-COOH and Zn\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Adsorption mechanisms\u003c/h2\u003e \u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the adsorption mechanism of PSNPs on GAT was clarified by FTIR analysis. The characteristic peak benzene ring of PS was found to be transferred from 1703 to 1601 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, show that PS adsorbed GAT mainly through π-π interaction (Sun et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Xiong et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). There were no other functional groups before and after adsorption, indicating that the adsorption of GAT by PS was physical adsorption (Zhang et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The characteristic peak C-O group of PS-COOH was transferred from 1227 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 1247 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the intensity of the stretching vibration peak of O-H decreased at 3445 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e after adsorption, indicating that the mechanism of PS-COOH adsorption to GAT included π-π interaction and hydrogen bond (Sun et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). No other functional groups appeared before and after adsorption, indicated that the adsorption of GAT by PS-COOH was physical adsorption as well. The O-H peak of PS-NH\u003csub\u003e2\u003c/sub\u003e at 3443 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e becomes stronger after adsorption, indicating that the main adsorption mechanism of PS-NH\u003csub\u003e2\u003c/sub\u003e to GAT is hydrogen bond (Mamtimin et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eGAT, PS, PS-COOH and PS-NH\u003csub\u003e2\u003c/sub\u003e all contained benzene ring structure, and there was π-π interaction mechanism between benzene rings. The addition of carboxyl functional groups was reported to weaken the electron supply capacity of PS-COOH, thus weakening the π-π interaction (Lavrinenko-Ometsinskaya et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Therefore, the π-π interaction of PS-COOH was weaker. However, it was found in this study that the ability of PS-COOH to adsorb GAT was stronger than that of PS, which showed that π-π interaction was not the main adsorption mechanism of PS-COOH. In conclusion, the main mechanism of adsorption of GAT by PS was π-π interaction, and the main mechanism of adsorption of GAT by PS-NH\u003csub\u003e2\u003c/sub\u003e and PS-COOH may be vdW and hydrogen bond (Mamtimin et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo further clarify the adsorption mechanism of PSNPs to GAT, the electrostatic potentials, one of the main driving forces of GAT adsorption (Wang et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), on the surfaces of PSNPs were calculated by Gaussian 09 (B3LYP/6-31g (d)) density functional theory and analyzed by Multiwfn 3.8 and VMD software. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea-f and Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e, the highest electrostatic potential (41.49 kcal\u0026middot;mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) on the surface of GAT corresponded to -H on the carboxyl group, which was conducive to the formation of electrostatic guided hydrogen bonds between GAT and nano-plastics, while the lowest potential (-68.84 kcal\u0026middot;mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) corresponded to =\u0026thinsp;O on quinoline and =\u0026thinsp;O on the carboxyl group. The electrostatic potential of PS ranged from \u0026minus;\u0026thinsp;19.81 kcal/mol to 12.87 kcal/mol, which made PS have stable chemical properties (Wang et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In Fig. S2, through the analysis of van der Waals force penetration position and interaction region indicator (IRI), it can be seen that the interaction between PS and GAT was mainly carried out through π-π interaction (green part). The surface electrostatic potential of PS-COOH ranged from \u0026minus;\u0026thinsp;35.28 to 46.57 kcal\u0026middot;mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, with the highest and lowest potential appearing at -H and =\u0026thinsp;O of -COOH, respectively, and the surface electrostatic potential of PS-NH\u003csub\u003e2\u003c/sub\u003e ranged from \u0026minus;\u0026thinsp;32.22 to 33.74 kcal\u0026middot;mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, with the lowest potential appearing at N of -NH\u003csub\u003e2\u003c/sub\u003e. It can be seen that the range of surface electrostatic potential of PS-NH\u003csub\u003e2\u003c/sub\u003e and PS-COOH was obviously larger than that of PS. Moreover, according to the analysis by the reduced density gradient method (RDG), shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, hydrogen bonds were formed between -H on the carboxyl group of GAT and N on the -NH\u003csub\u003e2\u003c/sub\u003e of PS-NH\u003csub\u003e2\u003c/sub\u003e, =O on GAT quinoline and -H on the carboxyl group of PS-COOH, and the vdW existed between them were significant. The theoretical calculation results showed that the surface functionalized PS was easier to adsorb GAT than the PS, which was echoed with the experimental results. Interestingly, the maximum penetration distance of van der Waals (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eg,h, Fig.S2,S3, Table S2) was calculated as GAT-PS-NH\u003csub\u003e2\u003c/sub\u003e (1.20 \u0026Aring;)\u0026thinsp;\u0026gt;\u0026thinsp;GAT-PS-COOH (1.06 \u0026Aring;)\u0026thinsp;\u0026gt;\u0026thinsp;GAT-PS (0.63 \u0026Aring;), showing that the interaction force between GAT and PS-NH\u003csub\u003e2\u003c/sub\u003e was greater than that between GAT and PS-COOH. It's theoretically proved that the adsorption amount of PS-NH\u003csub\u003e2\u003c/sub\u003e to GAT was particularly higher than that of PS-COOH. In addition, -NH\u003csub\u003e2\u003c/sub\u003e (weakly acidic) and-COOH (weakly basic) on GAT may also react slowly to form amide groups to bind them together.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe experimental results of the adsorption kinetics of PSNPs to GAT showed that the adsorption was influenced by both physical and chemical mechanisms, and the adsorption rates were controlled by both intraparticle diffusion and external diffusion, physical adsorption was dominant. Isothermal adsorption, the adsorption thermodynamics experiment results showed that the adsorption process of GAT was spontaneous, entropy increase reaction. Density functional theory showed that the interaction between PS and GAT was mainly through π-π interaction and electrostatic interaction, and the interaction between PS-COOH, PS-NH\u003csub\u003e2\u003c/sub\u003e and GAT was mainly through electrostatic interaction, hydrogen bond and vdW, the maximum penetration distance of van der Waals was GAT-PS-NH\u003csub\u003e2\u003c/sub\u003e (1.20 \u0026Aring;)\u0026thinsp;\u0026gt;\u0026thinsp;GAT-PS-COOH (1.06 \u0026Aring;)\u0026thinsp;\u0026gt;\u0026thinsp;GAT-PS (0.63 \u0026Aring;). The equilibrium adsorption capacity of functionalized PS to GAT was greater than that of PS, and the adsorption amount of PS-NH\u003csub\u003e2\u003c/sub\u003e to GAT was particularly higher than that of PS-COOH. pH affected the adsorption of PSNPs to GAT by changing the surface charge of nano-plastics. NaCl inhibited adsorption through electrostatic interaction and aggregation of nanoparticles. Alginate and heavy metal ions inhibited adsorption by competitive adsorption and metal bridging. Since the amino functional group was a heavy metal coordination group, it could form chelates with heavy metals to prevent the formation of hydrogen bonds, so the inhibition of metal ions on PS-NH\u003csub\u003e2\u003c/sub\u003e was particularly obvious. The experiment is of great significance for understanding the interaction between nano-plastics and GAT in water environment.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cstrong\u003eEthical approval\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent to participate\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCompeting interests\u003c/strong\u003e \u003cp\u003eThe authors declare no competing interests\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis work was supported by the Research Project Supported by Shanxi Scholarship Council of China (No. 2023-054), the Applied Basic Research Project of Shanxi Province, China (No. 20210302123121), and the National Natural Science Foundation of China (No. 52170045).\u003c/p\u003e\u003ch2\u003eAuthor contribution\u003c/h2\u003e \u003cp\u003e \u003cb\u003eJie Yang\u003c/b\u003e: Conceptualization, Formal analysis, Investigation, Methodology, Data curation, Writing - original draft. \u003cb\u003eWei Ji\u003c/b\u003e: Validation, Writing \u0026ndash; review \u0026amp; editing. \u003cb\u003eYanan Li\u003c/b\u003e: Conceptualization,Funding acquisition, Supervision. \u003cb\u003eYaning Wu\u003c/b\u003e: Investigation. \u003cb\u003eMeijing Yao\u003c/b\u003e: Investigation. \u003cb\u003eWeiqin Wu\u003c/b\u003e: Investigation. \u003cb\u003eKangjian Jing\u003c/b\u003e: Investigation. \u003cb\u003eGuokai Zhnag\u003c/b\u003e: Investigation.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAhmed MJ, Theydan SK (2014) Fluoroquinolones antibiotics adsorption onto microporous activated carbon from lignocellulosic biomass by microwave pyrolysis. 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Sci Total Environ 646:29\u0026ndash;36\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"nano-polystyrene, functionalization, gatifloxacin, adsorption, quantum chemical calculations","lastPublishedDoi":"10.21203/rs.3.rs-4370552/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4370552/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMicro / nano plastics will age and produce a variety of functional groups, but there are few studies on the interaction behavior of surface-functionalized nano-plastics with antibiotics. In this paper, 400 nm polystyrene microspheres (PS), amino modified PS-NH\u003csub\u003e2\u003c/sub\u003e, carboxyl modified PS-COOH (PSNPs) and gatifloxacin (GAT) were selected as research objects. The adsorption of GAT by PSNPs was comparatively studied by both experimental and theoretical calculations, and the adsorption mechanism of nano-plastics to antibiotics were revealed. The equilibrium adsorption capacity of PSNPs to GAT was PS-NH\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;PS-COOOH\u0026thinsp;\u0026gt;\u0026thinsp;PS, and adsorption capacity of PS-NH\u003csub\u003e2\u003c/sub\u003e was the largest, which was 236 mg/g. The adsorption kinetics of GAT showed that adsorption was controlled by both physical and chemical mechanisms, and the intra-particle diffusion and external diffusion jointly controlled the adsorption rate. All of Na\u003csup\u003e+\u003c/sup\u003e, alginic acid, Cu\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e inhibited the adsorption, and the inhibition effect of Cu\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e on PS-NH\u003csub\u003e2\u003c/sub\u003e adsorption of GAT was the most significant., which may be related to the inhibition of hydrogen bond formation by chelates formed by amino functional groups and heavy metals. The theoretical calculation results showed that π-π interaction and electrostatic interaction were the main interactions between PS and GAT, and electrostatic interactions, hydrogen bonds and van der Waals forces (vdW) were the main interactions between PS-COOH, PS-NH\u003csub\u003e2\u003c/sub\u003e and GAT. The surface electrostatic potential of PS-COOH and PS-NH\u003csub\u003e2\u003c/sub\u003e was significantly larger than PS, and the maximum penetration distance of van der Waals was GAT-PS-NH\u003csub\u003e2\u003c/sub\u003e (1.20 \u0026Aring;)\u0026thinsp;\u0026gt;\u0026thinsp;GAT-PS-COOH (1.06 \u0026Aring;)\u0026thinsp;\u0026gt;\u0026thinsp;GAT-PS (0.63 \u0026Aring;). The results provided a theoretical basis for the migration and synergistic removal of antibiotics and micro-nano-plastics.\u003c/p\u003e","manuscriptTitle":"Adsorption behavior and quantum chemical analysis of surface functionalized polystyrene nano-plastics on gatifloxacin.","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-27 06:12:52","doi":"10.21203/rs.3.rs-4370552/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2024-08-08T04:11:05+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-06-11T17:02:51+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-06-11T14:59:26+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2024-05-27T16:40:06+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-10T05:04:53+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2024-05-09T08:12:37+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"d10f8edd-f576-4477-bf9d-5b57c4d61475","owner":[],"postedDate":"June 27th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-11-04T16:28:33+00:00","versionOfRecord":{"articleIdentity":"rs-4370552","link":"https://doi.org/10.1007/s11356-024-35457-2","journal":{"identity":"environmental-science-and-pollution-research","isVorOnly":false,"title":"Environmental Science and Pollution Research"},"publishedOn":"2024-10-31 16:20:31","publishedOnDateReadable":"October 31st, 2024"},"versionCreatedAt":"2024-06-27 06:12:52","video":"","vorDoi":"10.1007/s11356-024-35457-2","vorDoiUrl":"https://doi.org/10.1007/s11356-024-35457-2","workflowStages":[]},"version":"v1","identity":"rs-4370552","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4370552","identity":"rs-4370552","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}