The hydrothermal (HT) conversion of mixed biomass and plastic waste to hydrochar adsorbents has attracted significant attention
however, factors controlling the structure and adsorption properties of hydrochar remain still poorly understood. Herein, HT treatment of the marine biomass waste (crab shells (CR) and fishery waste-derived chitin (CT) and chitosan (CS)) mixed with plastic waste (polyethylene (PE) and polyethylene terephthalate (PET)) at temperatures of 200-250 °C and residence times of 4-12 h was conducted to prepare hydrochars for screening their adsorption characteristics towards ketoprofen, a pharmaceutical pollutant. PET underwent efficient degradation when processed with marine biomass, particularly in mixtures with CS, which facilitated PET depolymerization through an aminolysis reaction. Hydrochars derived from PET mixed with CS demonstrated adsorption capacities for ketoprofen of ca. 25 mg/g due to the presence of the amine, amido, and aromatic groups providing sites for electrostatic interactions, hydrogen bonding, and π-π interactions with ketoprofen. The ketoprofen adsorption was best described by the pseudo-second-order kinetic model and Freundlich-type isotherm. On the other hand, no significant decomposition of PE was observed during the HT treatment of PE and biomass mixtures even in the presence of H