A kinetic model for abiotic pyrite reduction in aqueous solutions under low temperature conditions

In this study, a kinetic model was developed to describe the process of abiotic pyrite reduction (APR) in aqueous solution under low temperature conditions. Using PHREEQC, a reactive transport model was built to analyze the reaction rates and understand the mechanisms behind the mineral dissolution and precipitation in the presence of hydrogen. The results obtained revealed that the rate of pyrite reduction and H 2 S formation strongly depends on the temperature. At 90°C, hydrogen consumption is limited to 2.4%, while at 150°C, it increases dramatically to 46.5%. Similarly, the amount of H 2 S in the gas phase follows an exponential trend with temperature, reaching up to 0.49 gmole at 150°C. In addition, by fitting the PHREEQC model to experimental data, the activation energy and pre-exponential factor (A OH ) of the pyrite reduced with H + were estimated to be 58.3471 KJ/gmole and 0.1799 gmole/(m 2 .s), respectively. These values for pyrrhotite reduction with H + are 53.0434 KJ/gmole and 0.122 gmole/(m 2 .s), respectively. Huge uncertainty was observed in the results due the variability of pyrrhotite stoichiometry and unknown role of different ions in the reaction kinetics. These results have important implications for underground hydrogen storage as they highlight the potential for substantial hydrogen loss and H 2 S formation, which can influence gas quality, reduce storage efficiency, and increase the risk of corrosion in storage infrastructure. Comprehensive assessment of mineralogical composition, coupled with temperature and chemical control approaches, is essential to ensure safe, efficient, and sustainable hydrogen storage. • Developed a kinetic model for abiotic iron-mineral reduction in H 2 storage sites • Validated reactive transport simulations with existing experimental data • Identified strong temperature dependence of H 2 loss and H 2 S formation in reservoirs • Highlighted the need for thermal control to ensure safe underground H 2 storage