Potassium Chloride-Assisted Synthesis of Hollow Carbon Spheres from Pure or Mixed Polyolefins Containing Silica Templates

The use of plastics as carbon source to synthesize carbon nanomaterials is one of potential ways for recycling of waste plastics. Herein, a method for synthesizing hollow carbon spheres (HCSs) was reported by using polyolefins as carbon source, silica as templates and KCl as additives. The presence of KCl can effectively decline the thickness and improved graphitization degree of HCS. Besides, the introduction of KCl made the method universal to pure or mixed polyolefin carbon source. The HCSs were characterized by Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD), Raman spectroscopy, Thermal gravimetric analysis (TGA) and N-2 sorption. It was demonstrated that the addition of 2 wt% of KCl into PP/20%SiO2 blend decreased the thickness of carbon shell of final HCSs from 20 nm to 7 nm, and enhanced the graphitization degree and porosity of HCSs. An application for the HCSs from polypropylene was investigated for removal of methylene blue (MB) from water. Finally, the possible KCl-assisted mechanism was analyzed. The KCl-assisted approach might provide a potential route to recycling plastic wastes into value-added HCS materials.