Hydrothermal carbonization has been proven as one of the simplest and most efficient technologies to produce a variety of carbon-based hydrochars with various applications. Like other types of biochars, hydrochar has reactive, functionalized/aromatic surfaces. Those properties make hydrochar a potential low-cost adsorbent for water purification and soil remediation. In order to increase its ability to remove heavy metal contaminants from aqueous solutions, chemical modification/activation of hydrochar surface using KOH has been suggested. The presented FT-IR spectroscopy analysis of hydrochars obtained from grape pomace and miscanthus (Miscanthus×giganteus) showed that KOH modification increased the oxygen-containing functional groups on hydrochar surfaces and its aromaticity. As a result, activated hydrochars may demonstrate enhanced sorption efficiency.

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