Sustainable\nRemoval of Microplastics and Natural Organic\nMatter from Water by Coagulation–Flocculation with Protein\nAmyloid Fibrils

Water contamination is a global threat\ndue to its damaging effects\non the environment and human health. Water pollution by microplastics\n(MPs), dissolved natural organic matter (NOM), and other turbid particles\nis ubiquitous in water treatment. Here, we introduce lysozyme amyloid\nfibrils as a novel natural bio-flocculant and explore their ability\nto flocculate and precipitate the abovementioned undesired colloidal\nobjects. Thanks to their positively charged surface in a very broad\nrange of pH, lysozyme amyloid fibrils show an excellent turbidity\nremoval efficiency of 98.2 and 97.9% for dispersed polystyrene MPs\nand humic acid (HA), respectively. Additionally, total organic carbon\nmeasurements confirm these results by exhibiting removal efficiencies\nof 93.4 and 61.9% for purifying water from dispersed MPs and dissolved\nHA, respectively. The comparison among amyloid fibrils, commercial\nflocculants (FeCl₃ and polyaluminumchloride), and native\nlysozyme monomers points to the superiority of amyloid fibrils at\nthe same dosage and sedimentation time. Furthermore, the turbidity\nof pristine and MP-spiked wastewater and lake water decreased after\nthe treatment by amyloid fibrils, validating their coagulation–flocculation\nperformance under natural conditions. All these results demonstrate\nlysozyme amyloid fibrils as an appropriate natural bio-flocculant\nfor removing dispersed MPs, NOM, and turbid particles from water.