Comment on ”Mechanistic investigation of salt precipitation induced by supercritical CO2 in saline aquifers” by Wang et al. (2025)

Wang et al. (2025) report mechanisms of salt precipitation during supercritical CO2 exposure in saline aquifers based on static high-temperature, high-pressure soaking experiments. We identify fundamental flaws in their thermodynamics, chemical stoichiometry, experimental design, and data interpretation that render their mechanistic conclusions invalid. First, their brine remains below halite saturation throughout experiments, making NaCl precipitation thermodynamically impossible. Second, their treatment of chloride as both a conservative tracer and a precipitating species represents a logical impossibility, compounded by Na+/Cl- removal ratios that violate halite precipitation stoichiometry. Third, all analyses were performed on dried samples, without distinguishing between in situ precipitation and post-experiment evaporative crystallization, which is a critical temporal attribution failure. Fourth, their claim that salt precipitation transforms micropores into mesopores violates mass conservation. Fifth, wettability changes attributed to salt crusts contradict surface chemistry, as all identified salts are highly hydrophilic. We demonstrate that all observations are more consistently explained by acidification-driven mineral dissolution during soaking, followed by evaporative crystallization during sample preparation—requiring no thermodynamically implausible water extraction or chemically impossible mechanisms.