First Insights into Photocatalytic Degradation of HDPE and LDPE Microplastics by a Mesoporous N–TiO2 Coating: Effect of Size and Shape of Microplastics

Brenda Estefanía Llorente-García,Cristina Siligardi,Antonio Alberto Zaldívar-Cadena,Erika Iveth Cedillo-González,Juan Manuel Hernández-López

doi:10.3390/coatings10070658

Brenda Estefanía Llorente-García, Cristina Siligardi + Show 3 more

Open Access

https://doi.org/10.3390/coatings10070658

Copy DOI

Abstract

Microplastics (MPs), which are small plastic debris of ≤5 mm size, are polluting the oceans with negative consequences for their biota. In this work, visible-light photocatalysis of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) MPs in aqueous medium using a mesoporous N–TiO2 coating is proposed as an alternative for fighting MP pollution. Spherical primary HDPE MPs were extracted from commercially available facial scrubs, while film-shaped secondary LDPE MPs were obtained from a plastic bag. For each plastic, two different sizes were tested. Degradation was measured by mass-loss and carbonyl-index (CI) calculation. The results obtained reveal that the photocatalytic degradation of HDPE and LDPE MPs using an N–TiO2 coating was affected by the size and shape of the MPs. Smaller MPs led to higher degradation, while film-shaped MPs led to lower degradation that was related to a poorly illuminated and oxygenated reaction medium. These results set the basis for further investigation on the on the design of more effective photocatalytic-reaction systems for decreasing MP inputs to the environment.

Highlights

Microplastics (MPs), defined as water-insoluble, solid polymer particles smaller than 5 mm [1], are polluting the environment
The band at 1630 cm−1 corresponds to the stretching and bending vibration of water and O–H groups adsorbed in the surface of the photocatalyst [50,51,52]
Bands around 1450, 1340, 1252, and 1104 cm−1 were attributed to the vibrations of the N–Ti–O and Ti–O–N bonds [39,51,52], suggesting that the N species were successfully incorporated into the TiO2 lattice

Summary

Introduction

Microplastics (MPs), defined as water-insoluble, solid polymer particles smaller than 5 mm [1], are polluting the environment. MPs in the form of beads, fibers, flakes, debris or films [1] are present in rivers, lakes, oceans, coastal areas, groundwater, frozen ice, air and soils [2,3,4,5,6,7]. They are consumed by fauna causing false satiation, blocking of feeding appendages, pathological stress, reproductive complications, blocked enzyme production, reduced growth rate of oxidative stress, as well as become embedded in tissues [6,7]. It was found that MPs are present in the Coatings 2020, 10, 658; doi:10.3390/coatings10070658 www.mdpi.com/journal/coatings

Objectives

Methods

Results

Conclusion