Heterogeneous Catalytic Peroxide Oxidation Inducing Surface Reactions Toward Flotation Extraction of Hazardous Poly(Vinyl Chloride) From Waste Plastics

Low separation efficiency is a stumbling block for the recycling of heterogeneous waste plastics, which initiates the invasion of hazardous plastic pollutants, such as microplastics. The froth flotation controlled by wettability regulation strategies has become a promising remediation scheme and separation technology for plastic mixtures. Herein, this research proposed a wettability regulation for waste plastics from advanced oxidation processes (AOPs) that was heterogeneous Fenton reactions catalyzed by green tea extract-reducing iron nanoparticles (GTFe(0) NPs). In the heterogeneous catalysis system (GTFe(0) NPs/H2O2), the GTFe(0) NP catalyst excited HO center dot production and the reactive HO center dot was a major species for plastic oxidation. Besides, surface reactions on plastics were illustrated to explain the hydrophilic pattern of acrylonitrilebutadiene-styrene (ABS), polystyrene (PS), and polycarbonate (PC). HO center dot radicals can attack olefinic double bonds, abstract alkane protons, and scissor carbonate groups, anchoring hydroxyl and carboxyl groups on polymer surfaces. The flotation process separated hydrophilic ABS, PS, and PC plastics from hydrophobic hazardous poly(vinyl chloride) (PVC) plastics. The recovery and purity of PVC could reach 100 and 97.6%. The mild modification temperature, wide pH value, and low oxidant concentration determined its potential application in separating hazardous plastics. Simplifying the plastic composition benefits plastic recycling and prevents environmental risks.

Automated summary

This research proposed a froth flotation method controlled by wettability regulation strategies to separate heterogeneous waste plastics, especially the separation of hydrophilic plastics from hydrophobic hazardous plastics. By introducing the catalysis of green tea extract-reducing iron nanoparticles, successful separation and recovery of the waste plastics were achieved.