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.