Fouling behavior heterogeneity of typical nanoplastics in widely used polyvinylidene fluoride ultrafiltration membranes

The similarity between the particle size of nanoplastics (NPs) and the pore size of membranes used in water treatment plants may cause overlooked NPs to become potential bothers of membrane processes. Also, various NPs may impact membrane processes differently. Here, fouling behaviors of typical polyvinylidene fluoride ultrafiltration membranes induced by two typical NPs were investigated in environmentally relevant conditions. Results manifested adverse effects of diverse NPs on membranes differed. The flux descent rates of diverse NPs feed solutions-fouled membranes ranged from 9% to 36% over 2 h at 0.10 MPa in the dead-end filtration system. Polystyrene nanoplastics caused severer membrane fouling and greater cleaning difficulty than polyethylene nanoplastics did, and the fouling and the cleaning difficulty were both exacerbated with divalent cations present. Also, the incipient fouling was the chief driver. The obtained fouling behavior and cleaning efficiency were compared to the interaction energy data calculated by DLVO theory to better understand underlying fouling mechanisms. Significant correlations were observed between them. Overall, our findings demonstrated the negative impact and its heterogeneity of different NPs on membrane processes, elucidated their mechanisms, and provided scientific bases for NPs membrane fouling control. ● The negative impact of different NPs on membrane processes was demonstrated. ● PSNPs caused severer membrane fouling and greater cleaning difficulty than PENPs did. ● The fouling and the cleaning difficulty were both exacerbated with Ca 2+ /Mg 2+ present.