From Nano-(Micro)-Plastics to Value-Added Fuels and Chemicals: A Review of Mechanisms and Future Perspectives on Sonication-Assisted Photocatalytic Upgrading

Abstract

Micro(nano)plastic pollution poses a critical and growing environmental challenge due to its persistence, widespread presence, and significant ecological and health risks. This Review provides a comprehensive overview of advanced transformation strategies focusing on photocatalytic and sonocatalytic processes, particularly emphasizing sonication-induced transformations. It starts by outlining the fundamental principles of photocatalysis and key catalytic materials that enable efficient breakdown of these resistant polymers. Building on this foundation, the review explores ultrasound-assisted valorization techniques, emphasizing the crucial role of acoustic cavitation and the impact of ultrasonic power parameters in promoting polymer disintegration. The synergistic mechanical, thermal, and chemical effects of sonocatalysis are examined to elucidate the underlying mechanisms of microplastic decomposition under ultrasonic irradiation. The environmental impacts of microplastic contamination are critically assessed, highlighting the urgent need for effective remediation technologies. Recent advancements in sonocatalysis and the emerging field of sonophotocatalysis are discussed, showcasing enhanced transformation efficiencies and a broader application potential. Additionally, the economic feasibility and scalability of these catalytic methods are evaluated with attention to challenges such as energy demand, catalyst durability, and integration into large-scale systems. The review concludes by proposing future research directions focused on optimizing catalyst design, improving reaction kinetics, and ensuring environmental safety of the valorization byproducts. By synthesizing mechanistic insights, technological progress, and practical considerations, this Review offers a holistic resource aimed at advancing sustainable and innovative sonication-driven catalytic solutions for mitigating micro- and nanoplastic pollution.