Study on the effect of modified Fe3O4@SiO2@PAC magnetic seeds on magnetic flocculation separation of ballast water sediments

ABSTRACT In this study, modified Fe3O4@SiO2@PAC magnetic seeds were prepared to explore the separation efficiency and mechanism of algae and particles in high-turbidity ballast water under different influencing factors. The results showed that when the mass ratio of Fe3O4@SiO2 and PAC was 1:3, the removal rate of algae and turbidity was increased by 20 and 15.7% compared with the unmodified magnetic seed. When the dosage of magnetic seed was 217.5 mg/L, the stirring time was 129.2 s, the stirring speed was 211.6 r/min, and the pH was 8, the removal rates of turbidity and algae were 83.23 and 97.85%, respectively. The removal rates of algae and turbidity by the secondary magnetic seeds after compounding reached 97.8 and 96.57% of the first utilisation. Through scanning electron microscopy, transmission electron microscopy, and the adsorption kinetics model, it was found that the magnetic seed removed algae and turbidity through electrostatic adsorption generated by PAC. Among them, the role of SiO2 as an intermediate layer is to make PAC a better composite on the magnetic seed so that it can play the greatest role.