Chlorine Gas Removal by H2 Treated Red Mud for the Potential Application in Waste Plastic Pyrolysis Process

Abstract

In the process of pyrolyzing waste plastics, the generation of Cl2 gas can pose a problem. During the pyrolysis processing, incomplete combustion of organic compounds containing chlorine can lead to the formation of toxic chemicals, which can cause issues in subsequent processing stages. Therefore, an adsorbent plays an important role in removing Cl2 in the dechlorination process, and alkaline adsorbents and metal oxides are generally used. Waste red mud is composed of Fe metal oxide and alkaline components, so it is intended to be used as a Cl2 adsorbent. The Cl2 removal ability of red mud with different redox status of iron oxides was assessed. Hydrogen treatment was performed at various temperatures to control the reduction potential of the Fe in the metal oxides, and phase changes in the Fe oxide component of red mud were confirmed. In the case of red mud hydrogenated at 700 °C, most of the Fe2O3 structure could be converted to the Fe3O4 structure, and the Fe3O4 structure showed superior results in Cl2 adsorption compared to the Fe2O3 structure. As a result, red mud at an H2 treatment temperature of 700 °C showed about three times higher Cl2 adsorption compared to red mud without H2 treatment.