To understand the capture of elemental mercury (Hg-0) on potassium iodide-impregnated clays, a variety of kinetic models including pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models were used to analyze the experimental data and discuss the mechanism. A strong correlation was observed between the pseudo-second-order kinetic model and the experimental data for a range of parameters (KI loading, adsorption temperatures, and O-2 concentrations). This suggests that chemisorption may be a rate-limiting mechanism during the adsorption process on KI clays. Further, the results of the pseudo-first-order model and the intraparticle diffusion model both indicate that mass transfer limitations should not be ignored during the initial stage of adsorption. Thermodynamic investigation shows that the adsorption reaction of Hg-0 on the KI clays is inherently spontaneous and endothermic, corresponding to a process involving both physisorption and chemisorption, and the chemisorption is the dominant adsorption.