A comprehensive review of coagulation as a technique for microplastics removal from water

The presence of microplastics (MPs) in marine, terrestrial, and atmospheric ecosystems, as well as in drinking water, has become a major environmental and public health concern. Coagulation has emerged as one of the most widely investigated techniques for removing MPs from water systems. Recent advancements in coagulation-based removal are summarized with emphasis on the various classes of coagulants and the mechanisms that govern MP separation. Key factors influencing removal efficiency and overall treatment performance are highlighted, including coagulant type, MP characteristics, and operational conditions. Evidence demonstrates that inorganic coagulants, synthetic organic coagulants, and natural bio-coagulants each offer distinct advantages in enhancing MP removal performance. Proper post-treatment management is crucial to prevent separated MP particles from re-entering the environment, and several approaches for recovering and reusing coagulants and the resulting water treatment sludge (WTS) are explored. Methods such as acid digestion, alkalization, ion exchange, and membrane separation enable efficient recovery of coagulants, while WTS can be repurposed for uses including adsorbent materials, constructed wetland substrates, and construction products. Future research directions for enhancing coagulation-based MP removal technologies are also outlined. By consolidating the current knowledge and identifying research gaps, this review contributes to the advancement of MP treatment technologies and outlines future directions for optimizing coagulation as a viable method for mitigating MP pollution in water.