Sustainable Adsorption of Polystyrene Microplastics in Aqueous Media Using PET-C Synthesized from Plastic Waste: DFT and Experimental Studies

Abstract

This study transformed polyethylene terephthalate (PET) waste into activated carbon (PET-C) by means of direct carbonization and subsequent KOH activation, without inert gases. PET-C was characterized and evaluated for microplastic (MP) removal, specifically targeting polystyrene (PS). Adsorption experiments revealed a maximal adsorption capacity of 139.57 mg·g^–1(0.5 g/L, 12 h, 298 K), and monolayer chemical adsorption was indicated by the Langmuir isotherm and pseudo-second-order kinetics fitting. The process occurred spontaneously and exothermically with robust pH stability. Removal mechanisms included π–π interactions, hydrogen bonding, hydrophobic interactions, and electrostatic interactions supported by Fourier transform infrared spectroscopy (FTIR), X-Ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. PET-C demonstrated high efficiency in diverse water matrices with minimal anion interference and >80% removal efficiency retention after five cycles. This work offered a sustainable strategy for transforming PET waste into a high-performance adsorbent, addressing plastic waste management and microplastic pollution for environmental remediation and wastewater treatment.