Striking influence of Fe2O3 on the “catalytic carbonization” of chlorinated poly(vinyl chloride) into carbon microspheres with high performance in the photo-degradation of Congo red

Abstract

A one-pot approach was demonstrated to effectively synthesize carbon microspheres through “catalytic carbonization” of commercial chlorinated poly(vinyl chloride) (CPVC) microspheres by Fe2O3 at 700 °C. Without Fe2O3, a “sponge-like” carbon lump was obtained. However, after adding Fe2O3 (even 0.5 g per 100 g CPVC) into CPVC, carbon microspheres with octahedral Fe3O4 microcrystals uniformly embedded on the surface (Fe/CMS) were synthesized. The influence of Fe2O3 on the carbonization of CPVC microspheres was investigated. It was found that Fe2O3 significantly accelerated the dehydrochlorination of CPVC into polyene before the melting of the CPVC microsphere surface. As a result, the microspheres of raw CPVC showed a “shape-duplicate” carbonization behaviour. The resultant Fe/CMS showed high photo-degradation efficiency of Congo red under UV irradiation via a heterogeneous photo-Fenton process with high recyclablity, reusability and long-term stability. This indicated that the resultant Fe/CMS has a potential application in wastewater treatment. Therefore, the initial catalytic substance could be effectively used as a catalyst twice in the carbonization of CPVC microspheres and in the subsequent application of Fe/CMS. More importantly, the strategy of “catalytic carbonization” offers a new potential way to largely convert charring polymers into functional carbon and carbon-based materials with various morphologies.