Carbon dioxide (CO2) gas is the main contributor to climate change. CO2 storage in underground brines and oil-field brines by mineral trapping has been considered as a promising alternative in order to reduce CO2 emissions. However, permanent storage of CO2 in stable carbonate minerals is greatly dependent on brine pH, being favored over an alkaline pH. The effect of alkaline additives (NaOH, KOH, CaO) and buffer solutions (NaHCO3/NaOH, Na2HPO4/NaOH, NH4Cl/NH4OH) on the mineral trapping of CO2 under mild conditions using a synthetic brine is investigated. The results indicate that both NaOH+NH4Cl/NH4OH and KOH+NH4Cl/NH4OH mixtures promote precipitation mainly of calcium carbonate (CaCO3).