Valorization of bamboo and cedar bark residues for the production of biochars as adsorbents of CO2 and radionuclides

Abstract

The escalating issues of rising CO2 emissions and radioactive pollution, specifically from isotopes like 232U and 241Am, present critical global environmental challenges. This study utilized bamboo and Japanese cedar as biomass sources for biochar production, aiming to investigate the influence of carbonization temperature on the biochars capacity to adsorb CO2 and radionuclides. The biochars were produced at 500, 600 and 700oC and underwent a comprehensive structural and material property analyses employing electron microscope, gas adsorption isotherms, and spectroscopy methods. Characterization revealed that the biochar samples predominantly consisted of micropores, whereas the Japanese cedar biochars exhibited elevated mesoporous surfaces compared to bamboo-derived biochars, along with the presence of oxygen-containing moieties on their surface. Remarkably, the results indicate a positive correlation between carbonization temperature and adsorption capacity for both CO2 and the radionuclides. Notably, biochars produced at 700 °C exhibited the highest CO2 adsorption capacity of 2.21 mmol g−1. While both bamboo and cedar biochars exhibited comparable adsorption behavior against CO2, Japanese cedar biochars demonstrated superior capacity for adsorbing 232U and 241Am compared to bamboo biochars. JC700 showed the optimum adsorption behavior, achieving 91 and 88% removal of 232U and 241Am at pH 4, respectively. These findings highlight the potential of both bamboo and Japanese cedar biochars as effective adsorbents for mitigating CO2 emissions and radioactive pollution.