Removal of polystyrene and polyethylene microplastics using PAC and FeCl3 coagulation: Performance and mechanism

As a new type of potentially threatening pollutant, microplastics are widely distributed in water and may come into contact with the humans through tap water. The removal behaviors of microplastics in water treatment plants coagulation are not completely clear. In this paper, the removal performance and mechanism of polystyrene (PS) and polyethylene (PE) microplastics using PAC and FeCl coagulation were studied. Results showed that PAC was better than FeCl in removal efficiency of PS and PE microplastics. Charge neutralization occurred in the coagulation process. The figures of scanning electron microscope (SEM) illustrate that agglomeration adsorption occurred in PS system, and the Fourier transform infrared spectroscope (FTIR) spectra demonstrates that new bonds were formed during the interaction between PS microplastics and coagulants. In addition, the hydrolysis products of coagulants played a major role rather than the hydrolysis process in both PS system and PE system. The removal efficiency of microplastics in alkaline conditions was higher than that in acidic conditions. Cl had little effect on the removal efficiency of microplastics, while SO and CO had inhibitory and promoting effects respectively. The increase of stirring speed could improve the removal efficiency of microplastics. This paper can provide a reference for the study of microplastics treated by coagulation.