Assessment of removal technologies for microplastics in surface waters and wastewaters

Microplastics and the even more elusive nanoplastics are now recognized as ubiquitous, persistent, and potentially toxic contaminants in surface waters and wastewaters. Despite growing attention, real-world mitigation remains limited. This critical review interrogates the performance, scalability, and lifecycle implications of the principal removal technologies reported between 2016 and 2025. Although the size-exclusion membranes remain the benchmark for absolute removal efficiency (>95% for MPs <0.5 µm), they incur the highest unit-energy demand and chronic fouling. High-affinity sorbents, including Zr-based metal–organic frameworks, graphene-oxide hybrids, and engineered biochars, achieve 90–97% removal at far lower energy input, yet their lifecycle viability hinges on closed-loop regeneration and avoidance of polymer desorption. Magnetic composites (e.g. Fe₃O₄-ZIF-8) deliver near-quantitative capture (∼98%) within minutes, but field-scale demonstrations and robust magnet-recovery protocols are still lacking. Coagulation and electrocoagulation offer the most cost-effective high-throughput solutions (77–98%) but shift the plastic burden into metal-rich sludges. Advanced oxidation processes uniquely mineralize plastics (≤98.4%) albeit at high reagent and energy cost, while nature-based strategies (microbial consortia, hyperthermophilic composting, constructed wetlands) deliver 40–90% removal over longer residence times and remain highly sensitive to environmental variability. Across all classes, nanoplastic (<100 nm) retention is the weakest link, underscoring the need for standardized detection, nanoscale-selective materials, and pilot-scale validation. To support effective implementation, we identify key research priorities, including fouling control, sorbent regeneration, sludge valorization, catalyst stability, and risk assessment, and propose an integrated treatment hierarchy that couples low-energy bulk removal with targeted polishing and safe end-of-life management.