Kinetics and Size Effects on Adsorption of Cu(II), Cr(III), and Pb(II) Onto Polyethylene, Polypropylene, and Polyethylene Terephthalate Microplastic Particles

Xiaoxin Han,Xue Yu,Xueqiang Lu,Lin Zhu,Jianfeng Feng,Lifang Zhai,Weiqi Ma,Rolf D Vogt,Shiyu Wang

doi:10.3389/fmars.2021.785146

Abstract

Due to its small size, large specific surface area and hydrophobicity, microplastics, and the adsorbed contaminants may together cause potential negative effects on ecosystems and human beings. In this study, kinetics and size effects on adsorption of Cu(II), Cr(III), and Pb(II) onto PE, PP and PET microplastic particles were explored. Results indicated that the PE and PET microplastics have the higher adsorption capacity for Cu(II), Cr(III), and Pb(II) than that for PP microplastic. The adsorption capacity was affected by microplastic types and metal species. Among the three metals, Pb(II) had the largest adsorption amount on microplastic particles, especially on PET particles. Moreover, the adsorption capacities of microplastics increase with the decrease of particle size. The metal adsorption capacity of &lt;0.9 mm microplastics is greater than that of 0.9–2 mm and 2–5 mm microplastics. The size effect on metal adsorption was largest for PE microplastic. More attention should be paid in case of the coexistence of heavy metals and tiny PE and PET microplastics in the environment.

Highlights

Microplastics have already posed potentially risk for human health through transmission and accumulation in food chain (Yang et al, 2015; Xu et al, 2019) as they have already been widely detected in food (Liebezeit and Liebezeit, 2013, 2014; Yang et al, 2015)
The adsorption rates and adsorption capacities followed the orders of polyethylene terephthalate (PET) > PE > PP for Cu(II), and PE > PET > PP for Cr(III) and Pb(II)
It may be attributed to no functional group on PP microplastic compared with PET microplastic and the smoother surface of PP microplastic than PE microplastic (Figure 3)

Summary

INTRODUCTION

Microplastics have already posed potentially risk for human health through transmission and accumulation in food chain (Yang et al, 2015; Xu et al, 2019) as they have already been widely detected in food (Liebezeit and Liebezeit, 2013, 2014; Yang et al, 2015). Microplastics will be further fragmented into smaller part due to environmental dynamics, thereby affecting the adsorption capacity of heavy metals on microplastics (Gao et al, 2019; Zhang et al, 2020). Polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET), which are three mostly used and typical types of plastics in the world (The Essential Chemical Industry (ECI), 2016a,b, 2017), are selected to study the adsorption kinetics and size effect for the three typical metal ions of Cu(II), Cr(III), and Pb(II) to test the hypotheses: (a) different temporal change in metal adsorption for different microplastics; and (b) larger metal adsorption for smaller microplastic particles

MATERIALS AND METHODS

RESULTS AND DISCUSSION

DATA AVAILABILITY STATEMENT