Hydrogen solubility in water and brine: A simplified Henry’s law method verified against experimental data

Hydrogen solubility in water and brine plays a key role in (geo)chemical and microbial processes associated with underground hydrogen storage (UHS) and surface applications. This study presents a Henry’s law-based approach that integrates non-idealities due to high pressure and salinity through vapor-phase fugacity coefficients, the Poynting factor, and liquid-phase activity coefficients. A robust databank covering wide ranges of pressure, temperature, and salinity is compiled, enabling stepwise parameter optimization to account for these effects. Testing Henry’s constants from different sources revealed deviations, with NIST-recommended values underpredicting solubility. A constant (pressure-independent) liquid molar volume for hydrogen (19.95 cm 3 /mol) is recommended for simple Poynting factor calculations to avoid complex fitted models. Fugacity coefficients were evaluated using various EOS, including PR and SRK (with and without volume shift) and GERG-2008, an advanced EOS for natural gas mixtures. GERG-2008 delivered the best accuracy, followed by SRK and PR-VolumeShift, while other cubic EOS forms introduced considerable errors. For salinity effects, a simplified salinity-based correction was proposed and optimized, reducing prediction errors to acceptable levels, with errors mostly confined to − 10 % to + 9 % and a corresponding MAD of 4.4 % . Neglecting salting-out effects can lead to errors exceeding 200%. Overall, this work provides a new and straightforward framework for predicting hydrogen solubility in water and brine, and also identifies gaps and discrepancies in published experimental data, offering directions for future research.