Insights into the degradation mechanism of PET and PP under marine conditions using FTIR

Sarra N Dimassi; John N Hahladakis; Mohamed Nejib Daly Yahia; Mohammad I Ahmad; Sami Sayadi; Mohammad A Al-Ghouti

doi:10.1016/j.jhazmat.2023.130796

Insights into the degradation mechanism of PET and PP under marine conditions using FTIR

J Hazard Mater. 2023 Apr 5:447:130796. doi: 10.1016/j.jhazmat.2023.130796. Epub 2023 Jan 14.

Authors

Sarra N Dimassi¹, John N Hahladakis², Mohamed Nejib Daly Yahia³, Mohammad I Ahmad⁴, Sami Sayadi⁵, Mohammad A Al-Ghouti⁶

Affiliations

¹ Environmental Science Program, Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, P.O. Box: 2713, Doha, Qatar; Food-Energy-Water-Waste Sustainability (FEWWS) program, Center for Sustainable Development, College of Arts and Sciences, Qatar University, P.O. Box: 2713, Doha, Qatar.
² Food-Energy-Water-Waste Sustainability (FEWWS) program, Center for Sustainable Development, College of Arts and Sciences, Qatar University, P.O. Box: 2713, Doha, Qatar; Chemistry and Earth Sciences Department, Qatar University, College of Arts and Sciences, P.O. Box: 2713, Doha, Qatar. Electronic address: ichachladakis@qu.edu.qa.
³ Environmental Science Program, Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, P.O. Box: 2713, Doha, Qatar.
⁴ Central Laboratories Unit, Qatar University, P.O. Box: 2713, Doha, Qatar.
⁵ Biotechnology Program, Center for Sustainable Development, College of Arts and Sciences, Qatar University, P.O. Box: 2713, Doha, Qatar.
⁶ Environmental Science Program, Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, P.O. Box: 2713, Doha, Qatar. Electronic address: mohammad.alghouti@qu.edu.qa.

PMID: 36669417
DOI: 10.1016/j.jhazmat.2023.130796

Abstract

Plastics possess diverse functional properties that have made them extremely desirable. However, due to poor waste management practices, large quantities eventually end up in the oceans where their degradation begins. Hence, it is imperative to understand and further investigate the dynamics of this process. Currently, most relevant studies have been carried out under benign and/or controlled weather conditions. This study investigates the natural degradation of polypropylene (PP) and polyethylene terephthalate (PET) in more extreme environments. Simulated and real marine conditions, both in the laboratory (indoors) and outdoors were applied for a duration of 140 days and results were assessed using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis. SEM micrographs revealed variations in the morphologies of both plastic types. Degradation signs were shown in both plastic types, under all conditions. Findings indicated that microplastics (MPs) degraded faster than macroplastics, with PP MPs having higher weight loss (49%) than PET MPs (1%) when exposed to outdoor marine conditions. Additionally, the degradation rates of MPs-PP were higher than MPs-PET for outdoor and indoor treatments, with 1.07 × 10^-6 g/d and 4.41 × 10^-7 g/d, respectively. FTIR combined with PCA was efficient in determining the most degraded plastic types.

Keywords: Degradation; FTIR; Fragmentation; Marine litter; Plastic waste.