Increasing attention is being paid to hydrothermal carbonization (HTC) of waste biomass, due to energy shortages, environmental crises and developing customer demands. However, most research has been dedicated to the production of bio-oil, with few studies focusing on the application of hydrothermal carbon (hydrochar), a solid residue from HTC of biomass. In this study, a novel porous carbon (PC) was prepared from hydrochar, via pyrolysis at different temperatures (300-700 degrees C), the characteristics of PC as well as tetracycline (TC) adsorption behavior were investigated. The hydrochar and PC samples showed a remarkable range of surface properties, as characterized by Boehm titration, the Fourier transform infrared spectra and nuclear magnetic resonance spectra. The changes in characteristics suggested that the PC samples produced at high activation temperature (500-700 degrees C) were well carbonized and exhibited a high surface area (>270 m(2)/g). Linear relationships were obtained between Freundlich adsorptive capacity (K-F) and elemental atomic ratios, surface area and pore volume. The high adsorption capacity of PC samples can be attributed to its low polarity and high aromaticity, surface area and pore volume. The molecular variations among the hydrochar and PC samples translated into differences in their ability to adsorb TC.