Low-cost activated carbon from the pyrolysis of post-consumer plastic waste and the application in CO2 capture

Abstract

Chemical recycling by pyrolysis of plastic waste has been considered a potential approach. However, little attention has been paid to the reuse of the char residue generated. The preparation of materials from char residue obtained from the pyrolysis process has become an essential task. The purpose of this work is the preparation of activated carbons from the resulting char from the pyrolysis of a dirty and wet mixture of post-consumer plastic waste. The porous materials have been applied to the adsorption of CO2. Both physical and chemical activation methods were investigated to modify the surface texture properties. The properties of the developed activated carbons were characterized by diverse techniques such as elemental and proximate analysis, Fourier Transform Infrared Spectroscopy (FTIR), adsorption-desorption isotherms with N2, and Scanning Electron Microscopy (SEM). Among all synthesized samples, the activated samples prepared by chemical activation with KOH (char: KOH ratio 2:1; surface area, 487.0 m2·g−1) exhibited the highest CO2 adsorption uptake (∼49 mg·g−1). The activation temperature was explored within 680–840 ºC. For physical activation, an increase in the activation temperature decreases the adsorption uptake of the samples. For chemical activation, the adsorption increased as activating temperature rise to a maximum value, subsequently decreasing with further temperature rise. Increasing the amount of the chemical activating agent significantly decreases the adsorption capacities. The best-activated carbon was chosen, and several parameters were investigated on CO2 adsorption, C: KOH mass ratio (6:1–1:4), and adsorption temperature (15–60 °C). The highest adsorption of CO2 achieved was 62.0 mg·g−1 for activated carbon operating at the lower adsorption temperature (15 ºC).