Optimized preparation of multi-matrix activated carbon for CO2 capture by response surface methodology: The advantages of co-pyrolysis of biomass and plastics

In this paper, low-cost activated carbons (ACs) using apple tree pruning waste and waste polyethylene terephthalate (PET) plastic bottles as precursors were prepared by a two-step chemical activation, and the synergistic mechanism between the two precursors during carbonization was investigated. Response surface methodology (RSM) was employed to analyze the impact of PET ratio and carbonization conditions (carbonization temperature, heating rate) on the pore structure and CO2 adsorption performance of the activated carbon. The results demonstrate that the PET ratio and carbonization conditions significantly influence the pore structure and CO2 adsorption performance of the activated carbon. By optimizing the preparation conditions, the RSM-predicted CO2 uptake at 1 bar and 25 °C closely matches the experimental value, both reaching 4.49 mmol/g. Additionally, at 1 bar and 0 °C, the CO2 uptake of the activated carbon was found to be 7.03 mmol/g. The activated carbon AC0.2-8-515 exhibits exceptional characteristics, including a highly developed specific surface area of 1808 m2/g and a significant microporous volume of 0.67 cm3/g. It also demonstrates good selectivity for CO2/N2 (13.44) and exhibits ease of regeneration with excellent cycling stability even after multiple cycles. The isotherm data obtained from experimental measurements are fitted using Langmuir, Freundlich, and Toth isotherm equations. Among these models, the Toth isotherm equation provides the best fit to the data. Furthermore, the co-pyrolysis process contributes to an increased yield of PET pyrolysis fixed carbon. This study presents a novel solution to address the issues of carbon dioxide capture and white pollution, offering promising prospects for future development.