A comprehensive study on the performance and mechanism of microplastics removal by enhanced coagulation methods

Abstract

Drinking water is probably the main route for microplastics (MPs) to enter the human body. However, due to factors such as density and volume, MPs are difficult to remove during coagulation. Accordingly, the purpose of this paper is to study the removal efficiency of MPs in water supply treatment. Parameter optimization during coagulation, as well as the pre-oxidation process and addition of coagulant aids were investigated to explore the sedimentation efficiency of polyethylene terephthalate (PET) and polystyrene (PS) MPs. The experimental results showed that the extension of stirring time, the increase of PAC dosage, and the addition of pre-oxidation could not significantly improve the removal of MPs, while the addition of cationic/anionic PAM can effectively improve the low removal rate of MPs (removal rates were PET: 60.5 %, PS: 40.5 %, and PET: 67.9 %, PS: 67.5 % when cationic PAM and anionic PAM were added respectively). Characterization results showed that pre-oxidation, coagulation, and the addition of cationic PAM mainly played the role of double-layer compression. The anionic PAM had a strong adsorption effect and the efficiency was further improved through enmeshment by a precipitate. In summary, coagulant aids may be an effective method for the removal of MPs and are worth further studying.