Slow-release permanganate (MnO4-) gel (SRP-G) is a hyper-saline KMnO4 solution that can be used for treating large, dilute, or deep plumes of chlorinated solvents in groundwater. Ideally, the SRP-G injected into aquifers will slowly gelate to form MnO4- gel in situ, and the gel will slowly releases MnO4-. Objectives of this study were to develop SRP-G using colloidal silica as gelling solution, characterize its gelation and release kinetics, and delineate its dynamics in a saturated sandy media.The SRP-G exhibited a two-phase increase in viscosity: a lag phase characterized by little increase in viscosity followed by a short gelation phase. Gelation lag times of SRP-G solutions increased (from 0.5h to 13d) with decreasing KMnO4 concentrations (from 25 to 8gL−1). Permanganate release from gelated SRP-G increased with increasing KMnO4 concentrations, and was characterized as asymptotic release with initial peak (0.9–2.2mgmin−1) followed by more attenuated release. Gelation lag times of SRP-G flowing in sands (linear velocity=2.1md−1) increased (1, 3, and 6h) with decreasing KMnO4 concentrations (25.0, 23.0, and 22.9gL−1). Permanganate release from gelated SRP-Gs continued for up to 3d and was characterized as asymptotic release with an initial peak release (∼1.2gmin−1) followed by more attenuated release over 70h. Dilution of SRP-G by dispersion in porous media affects gelation and release kinetics. Increasing the silica concentration in the SRP-G may facilitate gelation and extend the duration of MnO4- release from emplaced SRP-G in porous media.