Production of low-cost adsorbents with tunable surface chemistry by conjunction of hydrothermal carbonization and activation processes

We report a new methodology to produce activated carbons from biomass-derived hydrothermal carbons using air and carbon dioxide. The activation step is crucial to develop porosity in the hydrothermal carbons. Additionally different surface functionalities are also introduced on the surface of the final materials. Our method based on initial hydrothermal carbonization of lignocellulosic biomass (walnut shell, sunflower stem and olive stone) represents a more energy-efficient tactic as compared with the traditional pyrolysis. The final yield is higher and the initial hydrothermal treatment allows a better control over the resulting porosity. The produced activated carbons show a higher porosity development when activated with carbon dioxide. The activation with air produced carbon materials with acidic surface chemistry.

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► Adsorbents were prepared via a novel method based on hydrocarbonization followed by activation.
► This method is more energy efficient, cheap and simple than traditional physical activation.
► The acidity of the hydrochars offers the possibility of tailoring the adsorbent surface chemistry.