The development of hydrothermal carbonization process using seaweed-contained water as the reaction environment and analysis of its impact on adsorption

To enhance the product performance of the traditional hydrothermal carbonization process, this study proposes and adopts a self-intrinsic water hydrothermal carbonization process for the value-added treatment of seaweed raw materials. The hydrothermal carbonization process of seaweed with self-intrinsic water production exhibits a more complex porous structure, with pore sizes mainly distributed between 1.65 and 20.14 nm, and demonstrates excellent performance in morphology and structure. It has a lower defect level and higher carbonization degree. Compared with traditional techniques, the steady values of the thermogravimetric curve of carbon materials produced by the self-intrinsic water hydrothermal carbonization process under the same conditions are reduced by 2.12–30.41 %. Under the same processing conditions, the cost per kilogram decreased by approximately 81.72 %, with a profit of around 0.62 ¥/g. -OH, N-O and C-O groups contribute to spontaneous adsorption of hydrochar, and the maximum adsorption capacity can reach 9.02 mg/g. The adsorption process is controlled by electrostatic adsorption and ion exchange adsorption, and the adsorption is stable. The study confirms the advantages of the seaweed self-intrinsic water hydrothermal carbonization process and the theoretical feasibility of its product in adsorbing ammonium ions.