Micro- and nanoplastics removal from water and solid matrices: Technologies, challenges, and future perspectives

Plastic contamination in wastewater and sludge is an emerging environmental challenge, with microplastics (MPs) and nanoplastics (NPs) increasingly requiring effective mitigation strategies. A bibliometric analysis (2015-2025) reveals a rapid growth in research activity, initially dominated by studies on MPs, which accounted for nearly 90% of early publications. This review critically evaluates current technologies for the removal and degradation of micro- and nanoplastics across aqueous and solid matrices. In water treatment systems, most processes primarily transfer particles to solid residues rather than achieving true elimination, with more than 95% of retained particles accumulating in sewage sludge. Conventional treatments such as filtration, coagulation-flocculation, sedimentation, and flotation frequently achieve MPs removal efficiencies above 80%, although their effectiveness for NPs remains poorly validated. Advanced oxidation processes (AOPs) have shown strong potential for polymer degradation, with mineralization levels exceeding 80-99% under controlled conditions; yet, most studies rely on simplified matrices, limiting extrapolation to real effluents. In soils, sediments, and sludge-amended systems, research has largely focused on extraction and quantification rather than remediation. Emerging thermochemical and biological approaches show promise but remain at an early stage of development. Future work should prioritize scalable degradation technologies validated under realistic conditions and integrated treatment strategies capable of preventing the transfer of micro- and nanoplastics between water and solid matrices.