In situ Fe3O4 nanoparticles coating of polymers for separating hazardous PVC from microplastic mixtures

Poly(vinyl chloride) (PVC) poses great challenges to the recycling of plastic wastes since it highly deteriorates the properties of other plastics and induces the formation of hazardous chlorinated dioxins and furans. For the first time, we developed a novel hydrophilization method of polymers, the in situ magnetite (Fe3O4) nanoparticles (NPs) coating, to facilitate the flotation separation of PVC from microplastic mixtures. A homogeneous Fe3O4 NPs layer was selectively fabricated on the surface of non-PVC microplastics via a facile in situ coprecipitation method. This obviously decreased the contact angle of non-PVC microplastics by approximately 30 degrees due to the plenty of hydroxyl groups on the surface of Fe3O4 NPs. However, the fabrication was not observed on the surface of PVC due to the weak interaction between Fe3+/Fe2+ and the surface of PVC. In this regard, the application of in situ Fe3O4 NPs coating in the flotation separation of PVC was systematically optimized using Box-Behnken design of response surface methodology. Quadratic models were generated to predict the floatability of microplastics, ascertain the effect of independent and interacted parameters, and numerically optimize the separation efficiency. Under optimum conditions, the Removal rate, Purity, and Recovery of PVC were 100.0%, 99.6%, and 100.0%, respectively. This study provides novel insights into the surface hydrophilization of polymers and shows promising prospects for facilitating the recycling of plastic wastes.

Automated summary

This study introduces a novel method of hydrophilization by coating non-PVC microplastics with Fe3O4 nanoparticles to facilitate the flotation separation of PVC from microplastic mixtures, resulting in efficient recycling of PVC.