Recent advances in mechanistic insights into microplastics mitigation strategies via emerging advanced oxidation processes: Legislation, challenges, and future direction

Microplastics (MPs) pollution has emerged as a global environmental concern due to its detrimental impacts on ecosystems. Conventional wastewater/water treatment methods are inadequate for MPs removal due to their diminutive size ranging from micrometers to nanometers. Advanced oxidation processes (AOPs) have gained attention as a promising green strategy for the efficient and safe elimination of MPs from aqueous systems. In recent years, various AOPs, including direct photo-degradation, photocatalytic oxidation, electrochemical oxidation, sono-chemical oxidation, ozonation, as well as sulfate radicals-based AOPs (SR-AOPs), and the use of hybrid systems have all been extensively investigated for MP elimination. However, the molecular mechanisms of MP polymer chain scission by AOPs have not been thoroughly studied so far. In this review, we have attempted to provide a thorough overview of molecular mechanisms and highlighted recent advances in the degradation of commonly used MP by AOPs. The characteristics and limitations of each technique are thoroughly examined. Additionally, current policies and legislation on plastic pollution are discussed, emphasizing the need for regulatory frameworks to support effective MPs mitigation strategies. To advance the practical application of AOPs for MPs removal, future research direction should address the transition from controlled laboratory environments to complex field conditions, assess the sustainability of AOPs in terms of catalytic material design, selection of effective oxidants, power consumption, and operational costs. Given these challenges, recommendations for future research directions are proposed based on knowledge gaps in the reported literature. This review could offer a coherent summary of the molecular mechanisms involved in different MP elimination techniques, aiding in the advancement of more dependable AOPs technology with superior removal and degradation efficiency.