Material innovations and challenges in adsorption-based nanoplastic removal for water purification: A comprehensive review of efficacy, mechanisms, performance factors, and future perspectives

Nanoplastics (NPs <100nm) are increasingly recognized as high-risk pollutants due to their ability to penetrate biological barriers, transport co-contaminants, and persist in aquatic ecosystems. While conventional remediation techniques struggle with particles in this size range, adsorption has emerged as a promising alternative due to its efficiency, affordability, and operational simplicity. This review critically examines recent advances in adsorption-based NP removal, with a specific focus on the underexplored 20-100nm range. Adsorbents are categorized into sponge/hydrogel/aerogel-based, metal-based, biochar/activated carbon, and multifunctional composites. Key adsorption mechanisms - including electrostatic attraction, hydrogen bonding, hydrophobic effects, and π-πstacking - are discussed alongside performance-influencing factors such as pH, coexisting pollutants, and NP morphology. The review further highlights critical challenges, including low adsorption efficiency of ultra-small NPs (< 20nm), interference from coexisting pollutants, and concerns over adsorbent regeneration, scalability, and environmental safety. Technological innovations - such as stimuli-responsive adsorbents, microrobotic scavengers, and AI-guided material optimization - are also discussed for their potential to overcome these barriers. This review offers a forward-looking roadmap for developing scalable, efficient, sustainable, and field-deployable NP remediation technologies by integrating mechanistic insights with real-world applicability.