Features of Heavy Metals Sorption by Microplastics in Environmentally Relevant Conditions

Abstract

The sorption capacity of microplastic in respect of heavy metals (Co, Ni, Cu, Cd, Pb) in the natural water of Lake Onego was investigated. Microplastic particles of polyethylene terephthalate were obtained by grinding a plastic bottle aged in natural conditions. The type of polymer used to produce microplastics and the degree of its destruction were investigated using Scanning electron microscopy with energy dispersive X-ray spectroscopy, Raman spectroscopy and micro Fourier Transform infra-red Spectroscopy. The concentrations of metal additives in the model aqueous solutions for the construction of isotherms were close to those in Lake Onego and its tributaries. Obtained isotherms of metals sorption on the surface of microplastics in natural waters differed from those widely reported in the literature for model solutions based on distilled water. Conventional Langmuir and Freundlich models were able to describe sorption processes in Lake Onego water only within certain ranges of element concentrations, what is primarily due to the presence of natural organic matter and Fe and Mn hydroxides in the water of Lake Onego.