Comparison of Hydrodchar and Pyrochar made from Cellulose, Lignin, and Cornhusk: Physiochemical Properties and removal of Cd(Ⅱ) from Aqueous Solution

In this study, hydrochar and pyrochar were made from cellulose, lignin (components of biomass), and corn husk (a type of biomass) through hydrothermal carbonization at 300 ℃ and pyrolysis at 300 ℃ and 500 ℃. Their physiochemical properties and Cd(Ⅱ) adsorption performances were then compared. Additionally, characteristics of hydrochar and pyrochar generated by each process were analyzed, including char generation yield, proximate & ultimate analysis, specific surface area (BET surface area) & porosity analysis, SEM & EDS (Scanning Electron Microscope & Energy Dispersive Spectrometer), FT-IR, pHpzc, and so on. The pyrochar generated at the same temperature (300 ℃) had higher char generation yield, ash content, and oxygen content with more oxygen functional groups than hydrochar. However, pyrochar had a lower specific surface area and pore volume than hypercar. By type of biomass, lignin showed the highest char generation yield. Regarding pHpzc, corn husk had the highest value, followed by lignin and cellulose. Cd(Ⅱ) adsorption characteristics in hydrochar and pyrochar were more suitable for the Langmuir adsorption model. It was found that the Cd(Ⅱ) adsorption amount (116.8 mg/g) was the highest in PC-CH-500, which had high pHpzc and inorganic content. As a result, electrostatic adsorption and cation exchange were the main mechanisms of Cd(Ⅱ) adsorption under the condition of pH solution < pHpzc.