Microplastics as carriers of iron and copper nanoparticles in aqueous solution

In recent years, microplastics have attracted a lot of attention due to their excessive spread in the environment, especially in aquatic ecosystems. By sorbing metal nanoparticles on their surface, microplastics can act as carriers of these pollutants in aquatic environments and thus cause adverse effects on the health of living organisms and humans. This study, investigated the adsorption of iron and copper nanoparticles on three different microplastics i.e. polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS). In this regard, the effects of parameters such as; pH, duration of contact and initial concentration of nanoparticle solution were investigated. By using atomic absorption spectroscopic analysis, the amount of adsorption of metal nanoparticles by microplastics was measured. The maximum amount of adsorption occurred at pH = 11, after a duration time of 60 min and at the initial concentration of 50 mg L−1. Scanning electron microscope (SEM) images showed that microplastics have different surface characteristics. The spectra obtained from Fourier transform infrared analysis (FTIR) before and after the adsorption of iron and copper nanoparticles on microplastics were not different, which showed that the adsorption of iron and copper nanoparticles on microplastics was physically and no new functional group was formed. X-ray energy diffraction spectroscopy (EDS) showed the adsorption of iron and copper nanoparticles on microplastics. By examining Langmuir and Freundlich adsorption isotherms and adsorption kinetics, it was found that the adsorption of iron and copper nanoparticles on microplastics is more consistent with the Freundlich adsorption isotherm. Also, pseudo-second-order kinetics is more suitable than pseudo-first-order kinetics. The adsorption ability of microplastics was as follows: PVC > PP > PS, and in general copper nanoparticles were adsorbed more than iron nanoparticles on microplastics.