Review of starch-based coagulants for water treatment: Mechanisms, extraction and surface modification

As the UN Sustainable Development Goal 6 emphasizes, sustainable and equitable access to clean water is paramount to improving public health and minimizing waterborne disease transmission. Due to rapid urbanization and population growth, freshwater resources are depleted, and approximately two-thirds of the world’s population will experience severe water scarcity by 2050. The coagulation-flocculation method demonstrates a viable solution for water treatment due to the minimal technical requirements, short treatment duration, and low material cost. Recently, starch-based coagulants have garnered significant attention due to their non-toxic nature, abundance, and cost-effectiveness. However, the coagulation efficiency of starch can be further enhanced through surface modification. The performance efficiency of starch-based coagulants largely depends on the modification technique, as it may influence the density of the surface charge. This review paper comprehensively discusses the coagulation mechanism of starch-based coagulants and the distinct methods for starch extraction. The removal efficacy of starch-based coagulants primarily depends on various physicochemical properties such as surface functional groups, zeta potential, and the elemental and morphological properties of the coagulant. Tailoring these properties is essential for developing a promising starch-based coagulant capable of effectively removing pollutants from water. Finally, the future prospects of starch-based coagulants are provided to highlight the exciting opportunities for sustainable water treatment and alignment with circular economy principles.