The exchange behaviors of hydrogen isotopes between protonated lithium metal compounds anddeuterated water or tritiated water were investigated. The various protonated lithium metal compoundswere prepared by acid treatment of lithium metal compounds with different crystal structures and metalcompositions. The protonated lithium metal compounds could more effectively reduce the deuteriumconcentration in water compared with the corresponding pristine lithium metal compounds. The Hþ inthe protonated lithium metal compounds was speculated to be more readily exchangeable with hydronsin the aqueous solution compared with Liþ in the pristine lithium metal compounds, and the exchangedheavier isotopes were speculated to be more stably retained in the crystal structure compared with thelight protons. When the tritiated water (157.7 kBq/kg) was reacted with the protonated lithium metalcompounds, the protonated lithium manganese nickel cobalt oxide was found to adsorb and retain twiceas much tritium (163.9 Bq/g) as the protonated lithium manganese oxide (69.9 Bq/g) and the protonatedlithium cobalt oxide (75.1 Bq/g) in the equilibrium stat