Preparation of activated carbon from ginkgo leaves by steam activation for adsorption application with isotherm and kinetics

Abstract

Biomass is a useful resource for maintaining carbon neutrality and sustainability. Ginkgo leaves, considered waste biomass, can be converted into high-value-added compounds through additional processes such as pyrolysis. This study produced activated carbon from ginkgo leaves through steam activation, and their pyrolysis characteristics were studied using thermogravimetric analysis (TGA). Ginkgo leaves showed a higher heating value (HHV) of 19.69 MJ/kg and ash content of 11.67 wt%. Among the inorganic matters in ginkgo leaves, Ca was the main component, with 311,000 ppm. The differential thermogravimetric (DTG) profile from TGA was deconvoluted to separate into individual peaks of moisture, tannin, pectin material, hemicellulose, cellulose, lignin, cutin, and inorganic compounds. Using the Friedman isoconversional model, activation energies were calculated in the range of 66.71 and 361.21 kJ/mol. It was found that the activation energy increased with the conversion level. A yield of 33.95±0.27 wt% was obtained through the carbonization of ginkgo leaves at 500 °C for 2 h. The activated carbon (AC) produced under the activation condition at 700 °C for 1 h at a steam flow rate of 3.0 mL/g-char⋅h showed the highest methylene blue adsorption capacity of 111.63 mg/g and BET specific surface area of 503.05 m2/g. As a result of introducing various adsorption isotherms, it was confirmed that the adsorption step is dominated by physisorption. Among the three adsorption kinetic models, the experimental data correlated best with the Elovich model. Through the results of the pyrolysis characteristics of ginkgo leaves and the performance of produced AC, this study suggested the recyclability of ginkgo leaves treated as waste biomass.