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In the present work, phosphogypsum (PG) waste was used as a calcium source, and integrated with 2-hydroxyphosphonoacetic acid (HPA) doping, modified inorganic-organic amorphous calcium phosphate hybrid composite was prepared, to remove Cd2+ and Co2+in aqueous solution. The study demonstrated that when pH=8, the equilibrium adsorption capacity of hydroxyapatite (HAP) for Cd2+ and Co2+ can reach 275.84 mg/g and 70.63 mg/g, respectively. After modification with HPA, the adsorption capacity of 20HPA-HAP for Cd2+ and Co2+ was higher at 468.92 mg/g and 171.38 mg/g, respectively. Regeneration experiments show that the adsorbent has good recycling performance, and the adsorbent has a good adsorption effect on low-concentration cadmium and cobalt ions in the actual hard gold electroplating wastewater. Meanwhile, the adsorption mechanism of 20HPA-HAP for Cd2+ and Co2+ was vividly visualized through Multiwfn wavefunction program and VMD program. Therefore, the reason why doping HPA greatly improves the adsorption performance of amorphous calcium phosphate on heavy metal ions was revealed from the atomic point of view. The findings suggest a promising approach for the effective utilization of discarded PG and the effective treatment of heavy metal pollution in industrial wastewater, highlighting the dual benefit of waste material repurposing and pollution control, which was an innovative strategy of turning waste into treasure. [Display omitted] • HPA/HAP was firstly to prepare by PG waste as calcium source and HPA as dopant. • HPA/HAP composite has excellent adsorption properties for Cd2+ and Co2+. • The interaction of HPA with two metal ions was vividly visualized and compared. • This work realized the resource of PG waste and the immobilization of Cd2+ and Co2+. [ABSTRACT FROM AUTHOR]

Using alumina (Al2O3) as the adsorbent, a static adsorption experiment was carried out in this study. It comprehensively evaluated the factors including Al2O3 dosage, adsorption temperature, and pH that influence the adsorption capability of three tetracyclines (TCs), namely, tetracycline hydrochloride (TC), chlortetracycline hydrochloride (CTC) and oxytetracycline hydrochloride (OTC). The results demonstrate that the adsorption efficiency increases with Al2O3 dosage. In addition, low-acid or natural solution is benefit for the adsorption. The adsorption behavior is more reasonably described with the Freundlich isotherm, and fits well with the pseudo-second-order kinetic model (R2 > 0.999). The results of molecular dynamics (MD) simulation show that the structures of TCs deformed during the combining process. The values of binding energy of TCs follow the order as: CTC (88.45 kcal/mol) > OTC (73.54 kcal/mol) > TC (54.28 kcal/mol). The MD simulation results agree well with the adsorption experimental results, which indicates that the MD simulation is reliable and reasonable. The MD simulation will provide theoretical knowledge in understanding the adsorption mechanism and environmental behavior of TCs. [ABSTRACT FROM AUTHOR]

Adsorption characteristics of tetracycline (TC) onto alumina were investigated according to batch adsorption experiments, and the mechanism was dissected at molecular level by molecular dynamics (MD) simulation. Results indicated that the adsorption was influenced by alumina dosage, temperature, and oscillating frequency. The optimal temperature was 25°C. By increasing the alumina dosage from 0.1 to 2.0 g/L, the removal efficiency of TC increased from 53.73 to 86.44%. With the increase in oscillation frequency from 90 to 200 r/min, the removal efficiency of TC increased by 28.78%, indicating that the increase of frequency could enhance the adsorption of TC. The adsorption behavior fitted well with the pseudo-second-order model (R2 > 0.99). MD simulations revealed that TC molecule structure was deformed when it clung to the alumina crystal. The magnitude of deformation energy (99.893 kcal/mol) was far less than that of non-bond energy (319,643.811 kcal/mol). Analysis of radial distribution function showed that TC could be adsorbed effectively by alumina mainly through non-bond interaction. [ABSTRACT FROM PUBLISHER]

Microplastics could act as a carrier for pesticides in the water environment and pose a potential risk. This study mainly investigated the effects of reaction time, microplastics dosages, pH, and NaCl salinity on the adsorption characteristics of three pesticides (Imidacloprid, Buprofezin, Difenoconazole) on polyethylene (PE) microplastics in aqueous solution. The results showed that high pH and low NaCl salinity were conducive to the adsorption. The adsorption data were well fitted by the Freundlich isotherm model and the pseudo-first-order kinetics, indicating that it was mainly controlled by physical function. The adsorption capacity of three pesticides on PE microplastics followed the order of Difenoconazole > Buprofezin > Imidacloprid. The thermodynamic study indicated the adsorption of all pesticides as spontaneous and exothermic processes, and the elevated temperature was favorable to the adsorption. SEM-EDS and FTIR results verified that pesticides were adsorbed on the microplastics but the adsorption process was mainly controlled by intermolecular Van Der Waals Force and the microporous filling mechanism. Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation results indicated that surface adsorption was the exclusive mechanism for the adsorption of pesticides on microplastics, and the final adsorption configurations revealed that there were complex interactions between the pesticide molecules and the C, H atoms in PE molecules. The results of this study illustrated that PE microplastics are potential carriers for pesticides in the water environment. Image 1 • Adsorption behavior and mechanism of pesticides on PE microplastics were investigated. • Adsorption capacity followed the order of Difenoconazole > Buprofezin > Imidacloprid. • High pH and low NaCl salinity were conducive to the pesticide adsorption. • Adsorption was a spontaneous and endothermic process. • Surface adsorption was the exclusive mechanism for the pesticide adsorption. [ABSTRACT FROM AUTHOR]

Nanomaterials were widely used as efficient adsorbents for environmental remediation of tetracycline pollution. However, the separation of the adsorbents posed the challenge to their practical applications. In this study, we grew magnetic MnFe2O4 nanoparticles on the reduced graphene oxide (rGO) to form MnFe2O4/rGO nanocomposite with a one-step method. When used as the absorbent of Tetracycline, it exhibited an adsorption capacity of 41 mg/g. The adsorption kinetics and isotherm were fitted well with the pseudo-second order model and Freundlich model, respectively. The MnFe2O4/rGO nanocomposite could be easily extracted from the solution with the external magnetic field and regenerated with acid washing. [ABSTRACT FROM AUTHOR]

Microplastics are a kind of new organic pollutant in the environment. In this study, the adsorption of tetracyclines (TCs), including tetracycline hydrochloride (TC), chlortetracycline hydrochloride (CTC) and oxytetracycline hydrochloride (OTC) onto polyethylene (PE) microplastics in aqueous solutions were investigated. The mechanism of the adsorption behavior was preliminarily explored by adsorption kinetics, isotherms, and thermodynamics, in combination with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). In addition, molecular dynamics (MD) simulation was applied to investigate the adsorption processes of TCs on PE at a molecular level. It was found that the adsorption behaviors of TCs reached an equilibrium state within 30 h. The experimental data showed that adsorption capacities of TCs onto PE were as follows: OTC (64.40 ± 2.38 μg/g)>CTC (63.36 ± 4.92 μg/g)>TC (53.52 ± 3.43 μg/g). TC sorption onto PE increased with pH, peaking at around pH 6 and then decreased. The increase of ionic strength in the solution led to the reduced adsorption capacity of TC onto PE. The results indicated that the experimental data were well fitted by the pseudo-second-order model and the Freundlich isotherm model, indicating both monolayer and multilayer coverage of TCs onto the surface of PE. The results of MD simulation showed that PE can effectively adsorb the TCs molecule mainly through non-bond interactions, and PE exhibited the highest affinity for CTC and OTC, followed by TC. Image 1 • TCs adsorption on PE microplastics investigated by experiments and molecular dynamics simulation. • TCs adsorption onto PE fitted well with Freundlich and pseudo-second-order model. • TCs adsorption onto PE could be influenced by pH and salinity. • TCs adsorption onto PE was mainly controlled by intermolecular van der Waals force. [ABSTRACT FROM AUTHOR]

Straw will degrade into segment, powder and crystalline cellulose, while the agricultural film will degrade into microplastics (MPs) in farmland soils. The specific surface area of these micro-particles increases and many new functional groups are formed in the degradation process, which can be a good vector of pesticides. To more accurately and truly analyze the risk of main imported substances and their degradation products against pollutants in soil, the adsorption behavior and mechanism of four commonly used pesticides on aged polyethylene microplastics (APE), wheat straw segment (WSS), wheat straw powder (WSP), and straw crystalline cellulose (SCC) were analyzed and compared through batch adsorption experiments and infrared spectrum. The adsorption kinetics of four pesticides on MPs and straw degradation products tended to be pseudo-second-order kinetics; the adsorption isotherms of pesticides on APE and SCC tended to fit the Freundlich model, while on WSP and WSS tended to fit the Langmuir model. The adsorption was a spontaneous endothermic increase process, suggesting that the main adsorption force of pesticides on MPs and straw degradation products was hydrophobic diffusion. The adsorption of pesticides against WSP and WSS still had a certain π-π conjugation and electrostatic interaction. And the adsorption amount on the straw degradation products followed the order of WSP > WSS > APE > SCC, presumably related to the specific surface area and pore volume of the adsorbent. As WSP, WSS could adsorb more pesticides, the straw returning to the field can be used for slow-release of pesticides to reduce the dosage of pesticides. [Display omitted] • Hydrophobic force mainly contributes to the adsorption. • π-π conjugation and electrostatic interaction also play a role in adsorption. • The adsorption amount followed the order of WSP > WSS > APE > SCC. • The straw returning to the field can be used for slow-release of pesticides. [ABSTRACT FROM AUTHOR]