Activated carbon from hydrochar produced by hydrothermal carbonization of wastes

Hydrothermal carbonization (HTC) is a thermo-chemical process for recovery and valorization of biomass and organic waste that uses sub-critical liquid water as a reaction medium for converting feedstock into valueadded products.. HTC treatment produces a carbonaceous solid, named hydrochar, with attractive characteristics that can be used in a variety of applications, such as activated carbon or soil amendment. In this study, activated carbons were prepared by KOH chemical activation of hydrochars obtained from hydrothermal carbonization of green waste and municipal solid waste. The effects of precursors and different KOH/char mass ratios on physical characteristics of the activated carbon were investigated. Methylene blue and iodine numbers were determined to evaluate the adsorption properties of obtained activated carbons. The results have shown a significant increase of porosity and a change in hydrochar structure by KOH activation method. The amount of mesopores and micropores increase with increasing KOH/char ratio. In particular, the sample by treatment of hydrochar from green waste activated with a 2:1 KOH/char weight ratio presented good mesoporosity, with a methylene blue number of 385 mg/g, and a well-developed micropore structure, with iodine number of 747 mg/g. Therefore, the application of KOH activated hydrochar as activated carbon appears to be promising.