The influence of hydrothermal carbonization parameters on the textural and physicochemical properties of highly porous activated carbons derived from garlic peel biowaste

The parameters associated with the pyrolysis and chemical activation processes of a hydrochar prepared by hydrothermal carbonization (HTC) have been thoroughly studied to produce porous carbon materials. To date, there are very few references on how to modulate the textural and physicochemical properties of the final material by tunning the HTC parameters. This research work succeeds in studying the effect of particle size, carbonization temperature, on different properties of the resulting activated carbon, as for instance, the surface area values, micro– and mesopore ratio, and nitrogen content. This allows the production of porous carbon materials with controlled and tunable characteristics to be obtained through a sustainable HTC and pyrolysis processes using K₂CO₃ and urea as green activation agents, allowing the valorization of agri-food derived biowaste. It is demonstrated how the use of a dry biomass such as garlic peel is suitable for obtaining a high carbon yield hydrochar that, after its chemical activation aided by pyrolysis, allows obtaining a series of carbon materials with a well-developed and adjusted porosity (2000–2700 m²/g), high CO₂ adsorption (4.9–5.9 mmol/g at 293 K) and a variable nitrogen (1–3.5 wt%) and oxygen (5.4–10.8 wt%) content.