Preparation and characterization of porous cationic poly[styrene-co -(N ,N ′-dimethylaminoethyl methacrylate)] nanoparticles and their adsorption of heavy metal ions in water

Adsorption of As(III) by microplastics coexisting with antibiotics

Although recent studies have been conducted on the pollution and toxicity of microplastics with heavy metals or antibiotics, it is necessary to further investigate the coexistence of antibiotics and heavy metals on the surface of microplastics. In this study, the mechanisms of As(III) adsorption by polystyrene (PS) and polyamide (PA) microplastics in the presence of antibiotics (ciprofloxacin, CIP) were investigated. Adsorption behavior was investigated using kinetic and isotherm models, and the effects of microplastic particle size, aging, ion concentration, pH, xanthic acid (FA), and tannic acid (TA) were considered. Adsorption kinetics and isotherm models showed that the kinetics of As(III) adsorption on PS were consistent with a pseudo-first-order model; the kinetics of adsorption on PA were more consistent with segmented linear regression. The Freundlich model is consistent with the adsorption isotherms of As(III) on PS and PA. The smaller the microplastic particle size and the longer the aging time, the better the adsorption of As(III). Increasing NO3-significantly inhibited the adsorption of As(III) by PS, while it first promoted and then inhibited the adsorption by PA. The effect of pH was similar to that ofNO3-. The adsorption of As(III) by PS was significantly promoted by FA and TA, regardless of the presence of CIP; the adsorption of As(III) by PA was inhibited. Scanning electron microscopy (SEM) was used to characterize microscopic morphology of pristine and aged PS and PA microplastics; Fourier transform infrared (FTIR) and X-ray absorption spectroscopy (XPS) revealed changes in surface functional groups of PS and PA, while demonstrating the importance of different functional groups in exogenous additives (CIP and dissolved organic matter, DOM) in the adsorption of As(III). This study provides new insight into adsorption behaviors and interaction mechanisms between ternary pollutants.

Sorption behaviour of tebuconazole on microplastics: kinetics, isotherms and influencing factors

Microplastics (MPs) and pesticides are two classes of environmental pollutants and have become global challenges. MPs could adsorb substantial environmental pollutants, which may affect their transportation, distribution and cause combination toxicity. Therefore, the study of sorption properties and mechanisms is the basis of the ecological risk assessment of co-exposure of pesticides and MPs. In this research, typical triazole fungicide tebuconazole (TEB) is selected as a model pollutant, and its sorption behaviour was investigated by kinetic and isotherm models. Meanwhile, a series of environmental influencing factors, like pH, salinity, and metals were conducted. Results showed that the sorption of TEB on MPs could reach equilibrium at 24 h, and the sorption capacity followed the order of PA (polyamide) > PS (polystyrene) > PP (polypropylene). The pseudo-second-order model was the most appropriate model to describe kinetic data, and the Freundlich model was well fit for PA sorption isotherms, in contrast the Langmuir model is better for PP and PS. Additionally, the pH of the solution, salinity, and metals have an important effect on sorption. Combined with Fourier Transform Infrared Spectroscopy and environmental influencing factors, the sorption mechanisms were mainly electrostatic interaction and hydrogen bond for PA and PP, and hydrophobic force, intermolecular force, and electrostatic force for PS, respectively.

Adsorption behavior of the antibiotic levofloxacin on microplastics in the presence of different heavy metals in an aqueous solution

In recent years, the composite pollution of microplastics with organic pollutants and heavy metal ions in the water environment, including their combined toxicity, has received increasing attention. However, the mechanism underlying the joint effect of antibiotics and heavy metals on the surface behavior of microplastics has not been reported. The primary purpose of this article was to analyze the adsorption of levofloxacin (OFL) onto polyvinyl chloride (PVC) in an aqueous solution. The adsorption behavior was studied using kinetics, thermodynamics, and isotherm models, and the effects of several environmental factors, such as ionic strength, fulvic acid, and heavy metals, were determined. The adsorption kinetics and isotherms models indicated that the whole adsorption process was controlled by both intraparticle and outer diffusion, as well as chemical adsorption, which was the dominant mechanism. Based on the results of the thermodynamic experiment, the adsorption process was a nonspontaneous and exothermic reaction process. Furthermore, the presence of Cu²⁺, Zn²⁺, and Cr³⁺ ions significantly promoted the adsorption of OFL, but the presence of Cd²⁺ and Pb²⁺ ions inhibited its adsorption. At the same time, the presence of the ionic strength and fulvic acid remarkably restricted the adsorption process. These findings confirmed that electrostatic interactions, ion exchange, intermolecular hydrogen bonds, and halogen bond cooperation were the main adsorption mechanisms. This paper mainly discusses the interaction between combinations of pollutants with microplastics, which provides theoretical guidance for the interface behavior, migration and transformation of marine microplastics in the actual environment.