Activated persulfate (Na(2)S(2)O(8)) regeneration of methyl tert-butyl ether (MTBE) and chloroform-spent GAC was evaluated in this study. Thermal-activation of persulfate was effective and resulted in greater MTBE removal than either alkaline-activation or H(2)O(2)-persulfate binary mixtures. H(2)O(2) may serve multiple roles in oxidation mechanisms including Fenton-driven oxidation, and indirect activation of persulfate through thermal or ferrous iron activation mechanisms. More frequent, lower volume applications of persulfate solution (i.e., the persulfate loading rate), higher solid/solution ratio (g GAC mL(-1) solution), and higher persulfate concentration (mass loading) resulted in greater MTBE oxidation and removal. Chloroform oxidation was more effective in URVGAC compared to F400 GAC. This study provides baseline conditions that can be used to optimize pilot-scale persulfate-driven regeneration of contaminant-spent GAC. Published by Elsevier B.V.