Hierarchical porous composites derived from spent tire char for CO2 capture: K-N co-doped, process intensification and thermodynamic analysis

Abstract

Spent tire is a kind of solid waste with large production, accumulation and great pollution. Spent tire char is the primary product of tire harmless disposal. Its commercial value is enhanced by modification. In this study, K-N co-doped activated carbon was prepared by using spent tire char as raw material, KOH and melamine as activator and dopant to enhance CO2 capture. In comparison with traditional process, the reasons for the decrease in specific surface area and pore volume caused by K doped have been identified, and a potential doped mechanism has been proposed. It was determined that pyridine nitrogen in the amino functional group played a key role in CO2 adsorption. Meanwhile, the synergistic intensification of CO2 adsorption by potassium phenolic and pyridine nitrogen was verified by simplified model simulation. The precise K-N doping significantly intensify the CO2 adsorption capacity of spent tire char from 0.45 to 2.60 mmol/g (1 bar, 0℃), an increase of 4.78 times. Thermodynamic studies have demonstrated that the Langmuir model accurately describes the adsorption process, and the adsorption reaction takes place spontaneously at temperatures below 80.52 °C. This work presents an efficient process for upgrading spent tire char, and a novel method of co-treating waste and CO2.