<p>Hydroxyl radical (•OH) formation from Fe(II)-bearing clay mineral oxygenation in the shallow subsurface has been well documented under moderate environmental conditions. However, the impact of freezing processes on the •OH production capability of Fe(II)-bearing clay minerals for organic contaminant degradation, particularly in seasonally frozen soils, remains unclear. In this study, we investigated the influence of pre-freezing durations on the mineral proprieties, •OH production, and phenol degradation during the oxygenation of reduced Fe-rich nontronite (rNAu-2) and Fe-poor montmorillonite (rSWy-3). During the freezing process of reduced clay minerals (1 mM Fe (II)), the content of edge surface Fe and Fe(II) decreased by up to 46% and 58%, respectively, followed by a slight increased as clay mineral particles aggregated and subsequently partially disaggregated. As the edge surface Fe(II) is effective in O₂ activation but less effective in the transformation of H₂O₂ to •OH, the redistribution of edge surface Fe(II) leads to that •OH production and phenol degradation increased initially and then decreased with pre-freezing durations ranging from 0 to 20 days. Moreover, the rate constants of phenol degradation for both the rapid and slow reaction phases also first increase and then decrease with freezing time. However, pre-freezing significantly influenced the rapid phase of phenol degradation by rNAu-2 but affected the slow phase by rSWy-3 due to the much higher edge-surface Fe(II) content in rNAu-2. Overall, these findings provide novel insights into the mechanism of •OH production and contaminant degradation during the freeze-thaw processes in clay-rich soils.</p>