A Comprehensive Review of Natural Polymer-Based Adsorbents for Microplastic Removal

Abstract

Microplastics (MPs) have emerged as pervasive environmental contaminants, posing rising risks to aquatic ecosystems and human health. Adsorption-based approaches have been widely explored as effective strategies for MPs removal because they are operationally simple and compatible with diverse materials. Natural polymers and their composites have attracted increasing attention as MPs adsorbents because they are renewable, often biodegradable, and structurally tunable. This review summarizes recent advances in MPs adsorption using representative natural polymers, including chitosan (CS), sodium alginate (SA), cellulose, and pectin. The relationships between material structure, surface functionality, and MPs adsorption behavior are critically analyzed, with emphasis on particle-surface interactions such as physical interception, hydrophobic interactions, electrostatic attraction, and hydrogen bonding. Reported MPs removal performances span a wide range, with capacities typically from tens to several hundred mg g⁻¹ and removal efficiencies often above 90%, depending on polymer type, surface modification, and MPs properties. In addition, the applicability of adsorption models and evaluation metrics is discussed. This review aims to provide practical guidance for selecting and applying natural polymer-based adsorbents for MPs removal in water treatment systems. Finally, current challenges and future perspectives are proposed to guide the rational design of efficient and sustainable natural polymer-based adsorbents for MPs removal.