Adsorption of PFAS onto secondary microplastics: A mechanistic study

Omobayo A Salawu; Christopher I Olivares; Adeyemi S Adeleye

doi:10.1016/j.jhazmat.2024.134185

Adsorption of PFAS onto secondary microplastics: A mechanistic study

J Hazard Mater. 2024 May 15:470:134185. doi: 10.1016/j.jhazmat.2024.134185. Epub 2024 Mar 31.

Authors

Omobayo A Salawu¹, Christopher I Olivares¹, Adeyemi S Adeleye²

Affiliations

¹ Department of Civil and Environmental Engineering, University of California, Irvine, CA 92697-2175, USA; The Water-Energy Nexus Centre, University of California, Irvine, CA 92697-2175, USA.
² Department of Civil and Environmental Engineering, University of California, Irvine, CA 92697-2175, USA; The Water-Energy Nexus Centre, University of California, Irvine, CA 92697-2175, USA; Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027-6623, United States. Electronic address: asa2296@columbia.edu.

PMID: 38579582
DOI: 10.1016/j.jhazmat.2024.134185

Abstract

Microplastics (MPs) are abundant in aquatic systems. The ecological risks of MPs may arise from their physical features, chemical properties, and/or their ability to concentrate and transport other contaminants, such as per- and polyfluoroalkyl substances (PFAS). PFAS have been extracted from MPs found in natural waters. Still, there needs to be a mechanistic investigation of the effect of PFAS chemistry and water physicochemical properties on how PFAS partition onto secondary MPs. Here, we studied the influence of pH, natural organic matter (NOM), ionic strength, and temperature on the adsorption of PFAS on MPs generated from PET water bottles. The adsorption of PFAS to the MPs was thermodynamically spontaneous at 25 °C, based on Gibb's free energy (ΔG = -16 to -23 kJ/mol), primarily due to increased entropy after adsorption. Adsorption reached equilibrium within 7-9 h. Hence, PFAS will partition to the surface of secondary PET MPs within hours in fresh and saline waters. Natural organic matter decreased the capacity of secondary PET MPs for PFAS through electrosteric repulsion, while higher ionic strength favored PFAS adsorption by decreasing electrostatic repulsion. Increased pH increased electrostatic repulsion, which negated PFAS adsorption. The study provides fundamental information for developing models to predict interactions between secondary MPs and PFAS.

Keywords: Fluorochemicals; Forever chemicals; Plastics; Water chemistry.