Grantee Research Project Results
Physicochemical degradation of microplastics
EPA Grant Number: SU840573Title: Physicochemical degradation of microplastics
Investigators: Fakhraei, Habibollah
Institution: Southern Illinois University - Carbondale
EPA Project Officer: Cunniff, Sydney
Phase: I
Project Period: August 1, 2023 through July 31, 2024
Project Amount: $25,000
RFA: 19th Annual P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet Request for Applications (RFA) (2022) RFA Text | Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources
Description:
Occurrence and accumulation of plastic materials in the environment have recently become a major environmental threat. These accumulated plastics undergo fragmentation into microplastics (MPs) and nanoscale plastics (NPs) through different environmental factors. This has become a concern due to limited information on their behavior and fate in the environment and in the human body. The potential for negative impacts from MPs may depend upon their extent of degradation in the environment. This is heavily influenced by MPs type, size, additive chemicals, etc. and various environmental parameters. Increasing usage of synthetic textiles (polyester, acrylics, etc.) is also a concerning issue from an environmental perspective. These synthetic textiles are shedding microfibers during washing and drying of these fabrics and are considered a potential source of MPs in the environment. These fibers can pass through the wastewater treatment plant (WWTP) and eventually be transported into soil and water bodies.
Plastics are used by people globally for their numerous benefits, but unfortunately, improperly disposed plastics often end up in the aquatic environment and cause global plastic pollution. These macroscopic plastics eventually degrade into smaller sized MPs (size < 5 mm) through physical, biological, and chemical processes. Some recent studies have demonstrated the existence of these tiny plastics in drinking water, tap water, seafood, beer, and sea salt. There is considerable risk as these tiny plastics have the potential to cause serious threats to human health as well as to the aquatic and terrestrial environment. Moreover, recent studies have shown that effluent water from laundry machines is also a major source of MP pollution in the environment. Cloth fabrics made of plastic produce microfibers during laundering. There is a significant knowledge gap on how fast these released plastics degrade to smaller sizes and are transported along different media in the environment. At present, research into degradation of MPs mainly focuses on biodegradable plastics and their enzymatic degradation.
Objective:
Degradation by physicochemical factors which are prevalent in the environment are relatively underrepresented in this field of study. In the current study, we propose to investigate the degradation mechanism of MPs and microfibers under visible light irradiation and hydrolysis processes. The goal of this project will be to understand the degradation mechanism of plastics and to observe the resulting size variation of produced MPs and even smaller NPs. This would help us ascertain the size of plastics that might enter WWTP from the environment. This information will be beneficial for modifying the existing pretreatment and primary treatment systems in WWTPs. Thus, the removal of MPs within WWTPs can be enhanced before they enter the environment via discharge into surface waters. Controlling the discharge of MPs will benefit the aquatic environment and mankind. Modification of existing treatment technologies may be an inexpensive alternative for those communities who do not have access to more advanced or tertiary treatment systems for their WWTP to remove MPs.
Approach:
In this study, the degradation process of microfibers released from fabrics and virgin MPs will be observed under visible light irradiation and base-catalyzed hydrolysis processes. Degradation of common microfibers in the environment (polyester, acrylic) and virgin plastic (polystyrene) will be studied. Most previous studies reported the degradation behavior of virgin plastics that do not represent the actual MPs found in environment, which originate from commercially used plastics. Degradation of the MPs will be studied in synthetic surface water, ground water and seawater (ocean water) to observe the degradation rates of different plastics under varying environmental conditions. Fragmentation and physical changes to the material surfaces will be studied using scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDX). Chemical characterization will be conducted with spectroscopic techniques such as Fourier transformed infrared spectroscopy (FTIR). In addition, mass change of the material during degradation will be observed at the nanoscale level using a quartz-crystal microbalance (QCM) following deposition of plastic thin films onto the QCM sensors. The mass of surface-bound plastic will be measured prior to degradation, and the mass change will be monitored in situ during visible light degradation and hydrolysis.
Expected Results:
Expected outcomes include an improved understanding of how microplastics degrade under visible light and hydrolysis in the aquatic environment. Furthermore, in depth studies of MPs by measuring their mass change during degradation at the nanoscale level will enable fundamental studies to understand the kinetics and mechanism of degradation. Expected results can be utilized in the pretreatment and primary treatment systems in WWTP for the removal of MPs. Moreover, understanding the release pattern of MPs and their subsequent degradation in the environment can increase awareness of MPs pollution and plastic degradation among the public and WWTP personnel. The results will be shared with local/state water policymakers to address the current plastics problem in WWTP and to the community through oral/poster presentations and publications.
Contribution to Pollution Prevention or Control:
Plastic pollution is a global concern since we use plastic in household and consumer products as well as packaged goods. However, another major source of such pollution is clothing, which contains polyester, nylon, acrylic, and other synthetic fibers. When washed in the laundry they shed numerous microfibers, also a form of MPs. These degrade into progressively smaller pieces of plastic which are even more difficult to remove within WWTP. However, many people might be unaware of their contribution to this global problem and how to control it. This study will be useful for understanding how microfibers are generated during laundering and subsequent degrade in the environment from different physical and chemical factors. Moreover, the results can be utilized for future research and be implemented to modify current water treatment technologies. In addition, this study should help to increase public awareness and engagement in addressing this environmental challenge.
Supplemental Keywords:
UVA irradiation, nanoscale interactions, water treatmentThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.