Adsorption mechanism of cadmium on polystyrene microplastics containing hexabromocyclododecane

Abstract

There are few studies on the adsorption of heavy metals by microplastics containing additives in water environment. The present study investigated the adsorption mechanism of Cd(II) on polystyrene microplastics containing hexabromocyclododecane (PS-HBCD MPs). In the experiments, the effects of pH value, salinity, particle size and dissolved organic matter derived from PS-HBCD MPs on the adsorption capacity were analyzed. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the properties of PS-HBCD MPs and adsorption behavior of Cd(II) onto MPs. The adsorption kinetics and isotherms of Cd(II) onto PS-HBCD MPs can be described well by the pseudo-second-order kinetics model and Langmuir isotherm model, respectively. Solution pH, salinity, dissolved organic matter derived from MPs and particle size have a greater impact on the adsorption behavior of cadmium on microplastics. The results of this study highlight the importance of C-Br bonds of PS-HBCD MPs in controlling the adsorption of Cd(II). • Cd(II) adsorption onto PS-HBCD MPs was dominated by electrostatic interaction. • The C-Br bonds of PS-HBCD MPs controlled the adsorption of Cd(II). • DOM derived from MPs inhibited the adsorption of Cd(II) on PS-HBCD MPs