Enhancement of polystyrene microplastic removal by near dissolved organic matter microfiltration (NDOM MF) coupled with cold plasma treatment

Various sizes of microplastics (MPs) have been found in water bodies these days. Among them, small MPs (<1 μm) are known to threaten human health. Accordingly, it is necessary to prevent MPs from being discharged into the aquatic environment. For that reason, many researchers have attempted to remove MPs via several approaches including advanced oxidation processes. However, there have been a number of occasions when the size of MPs was reduced at best, which is not the ultimate solution. Herein, we demonstrated that MPs could be efficiently removed via near dissolved organic matter microfiltration (NDOM MF) coupled with cold plasma (CP) treatment. CP treatment increased the particle size of MPs from 1.1 μm to 3.5 μm by setting off a chain of coagulation process including the increased nitrate concentration, increased ionic strength, and reduced thickness of the electrical double layer. Such coagulated MPs enabled NDOM MF to exhibit 124% higher water flux than the existing MF while maintaining a 99.9% removal rate. Furthermore, given that the performance improvement was achieved without secondary contamination arising from adding coagulants, it was expected that NDOM MF coupled with the CP process could provide a sustainable and eco-friendly approach to removing MPs.