Evaluation of Polyethylene Terephthalate Microplastic Removal in Water System Using Porphyridium cruentum Microalgae

ABSTRACT This study evaluated the ability of the red microalga Porphyridium cruentum in removing polyethylene terephthalate (PET) microplastics (MPs) from aquatic systems through a hetero‐aggregation mechanism mediated by exopolysaccharides (EPS). Results showed that PET MPs exposure to microalgae at concentrations of 100, 200, and 300 mg/L for 30 days notably reduced microalgae growth at higher concentrations. Conversely, increased PET MPs concentration increased EPS production by microalgae as a defense response to oxidative stress. The highest EPS production was obtained at a 300 mg/L PET MPs exposure, concentration of 4.349 g/L. FTIR analysis showed EPS was rich in negatively charged carboxyl and sulfate groups, electrostatically interacting with positively charged PET MPs, forming stable flocculating hetero‐aggregates. The removal efficiency of PET MPs reached 95.8%–97.5%, with the highest efficiency obtained at a concentration of 200 mg/L PET MPs, demonstrating the effectiveness of P. cruentum in removing PET MPs from water environment. SEM analysis confirmed the formation of a solid EPS matrix encasing the MPs particles and the absence of markedly structural changes in the EPS post‐interaction confirmed through FTIR. These findings underscore the potential of microalgae as an eco‐friendly and energy‐efficient biological solution for MPs remediation in aquatic environments.