Activated carbon from waste leaves of Japanese leeks: Preparation and <i>p</i>-cresol adsorption capacity

In Japan, the tips of Japanese leek leaves are typically trimmed and discarded during harvesting, resulting in considerable waste. In this study, the discarded leaves were repurposed as a raw material for the production of activated carbon (AC). To prepare the AC, beet sugar syrup was added to precarbonized leaves, followed by carbonization and physical activation with CO2 gas. The specific surface area, along with the micropore and mesopore volumes, increased as activation time increased. The maximum specific surface area was 1852.7 m2/g after 3 h of activation. The AC produced had a high adsorption capacity for p-cresol, with Langmuir adsorption isotherms indicating a maximum adsorption capacity of 401.5 mg/g—approximately 2.0 and 1.7 times higher than those of commercial coal-based and coconut shell ACs, respectively.