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Aging and Transformation of Polyethylene Microplastics in UASB Effluents Treated with O 3 and O 3 /H 2 O 2 : Physicochemical Changes and Toxicity Assessment

ACS ES&T Water 2025 1 citation ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Diego Aparecido Silva de Brito, Thalita Ferreira da Silva, Priscila Sabioni Cavalheri, Antonio Kaique Canatto, Eugenio de Miguel, Fernando Jorge Corrêa Magalhães Filho, Lincoln Carlos Silva de Oliveira, Gleison Antônio Casagrande, Amílcar Machulek

Summary

Scientists tested a wastewater treatment method using ozone and hydrogen peroxide to break down tiny plastic particles (microplastics) before they leave treatment plants and enter rivers or farmland soil. The good news: this process broke down the plastic's surface without creating toxic byproducts, based on tests with small aquatic organisms. However, the leftover plastic fragments actually became more heat-resistant, meaning we still need more research to understand how these altered particles might behave once they're out in the environment.

Polymers

High Resolution Image Download MS PowerPoint Slide Wastewater treatment plants (WWTPs) represent a pathway for microplastics (MPs) to enter the environment, through direct discharge via effluents into surface waters or indirect release via sewage sludge applied to agricultural soils. This study demonstrates the effectiveness and safety of an O 3 /H 2 O 2 process for aging polyethylene microplastics (PE-MPs) directly within a complex UASB reactor effluent. A characteristic FTIR peak at 1714 cm –1 confirms the formation of carbonyl groups, which indicates that the treatment caused significant surface degradation under optimal conditions (52.00 mg L –1 O 3 and 100.00 mg L –1 H 2 O 2 for 110 min). Crucially, the byproducts produced showed no acute toxicity to Artemia salina, demonstrating that the process was environmentally sound. Additionally, thermogravimetric analysis (TGA) revealed a counterintuitive increase in the polymer’s thermal stability, suggesting complex structural reorganization potentially driven by the removal of low-molecular weight fractions or cross-linking. Treated PE exhibited increased thermal stability, increasing from 436.18 to 449.35 °C, indicating that the remaining fragments are more thermally resistant and could therefore alter their subsequent fragmentation behavior. This work, therefore, validates a robust and safe strategy for MP remediation in realistic scenarios.

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