Preparation of hydrochar by one‐step hydrothermal carbonization with potassium ferrate‐assisted activation for the removal of tetracycline in water

Abstract BACKGROUND Woody biomass has a low hydrothermal‐carbonization (HTC) degree and the hydrolysis process of some of its components is similar to that of saccharides. To improve the adsorption performance of wood‐chips hydrothermal char (hydrochar) for tetracycline in water, molasses and potassium ferrate (K 2 FeO 4 ) were added to its HTC process; K 2 FeO 4 catalyzed the carbonization of raw materials and the surface of wood chips and saccharides in molasses, along with the iron ions mutually polymerized, added more reactive‐oxygen functional groups to the hydrochar surface. The effects of K 2 FeO 4 and molasses on the morphology, pore structure, surface oxygen‐containing functional groups, and tetracycline‐adsorption properties of hydrothermal carbon were investigated. RESULTS The strong oxidizing properties of K 2 FeO 4 promoted the hydrolysis of raw material. The modified hydrochar formed more oxygen‐containing functional groups and produced FeO bonds with an increased specific surface area. For the adsorption of tetracycline in water, the pseudo‐second‐order kinetic model and Freundlich isotherm were more consistent with the hydrochar‐adsorption process. The adsorption mechanism favored a combination of physical and chemical adsorption, with chemisorption being predominant. The maximum tetracycline‐adsorption capacity of HTC–0.15Fe was 119.7 mg g −1 , which is significantly higher than that of unmodified hydrochar HTC‐C (56.4 mg g −1 ). Furthermore, molasses addition effectively improved the hydrochar structure, forming carbon‐coated iron‐core particles on its surface, which increased adsorption performance. CONCLUSION K 2 FeO 4 ‐catalyzed hydrochar produced from wood chips and sugarcane molasses is an effective adsorbent for tetracycline removal from water. This work provides innovative insights into the recycling and effective use of wood chips and molasses for environmental remediation and waste treatment. © 2023 Society of Chemical Industry (SCI).