Due to their unique physicochemical properties, PFAS used in numerous industrial applications pose a problem regarding their accumulation in groundwater. This situation highlights the need for innovative treatment technologies aimed at minimizing PFAS levels in effluents. Various methods (thermal, biological, chemical) have been investigated, but they suffer from drawbacks such as high energy consumption or the generation of toxic secondary effluents. In this context, hydrothermal oxidation (HTO) offers a promising alternative, achieving PFAS mineralization rates exceeding 99.9% at temperatures of 600°C and above. Under these conditions, water becomes a reaction medium conducive to the mineralization of organic compounds. However, applying such operating conditions at an industrial scale presents a technological challenge due to significant heat loss and the *in situ* formation of HF, which can cause corrosion issues. This thesis aims to investigate the HTO process using a co-fuel and the *in situ* use of a silica-based material designed to sequester all fluoride ions. Defining the process's operating regime requires a detailed understanding of mass balances as well as the mechanisms of PFAS oxidation. Elucidating these mechanisms will require the implementation of a precise and rigorous analytical protocol to quantify all residual organofluorine compounds. Modeling high-pressure/high-temperature phase equilibria for fluorinated species can be performed using PhreeQC and Prosim Simulis software. Finally, the process's versatility regarding other organofluorine waste streams will also be considered. The candidate will work within the Supercritical Processes and Decontamination Laboratory, in collaboration with the Measurement, Safety, and Environment Laboratory (LITEN/Grenoble) and in interaction with technicians, engineers, and doctoral students. They will benefit from the expertise of these laboratories in hydrothermal processes and the analysis of perfluorinated compounds. The skills acquired during the PhD will open up numerous career opportunities in academic research and industrial R&D within the fields of chemistry and the environment..