The separation and storage of CO 2 in geological form as mineral carbonates has been seen as a viable method to reduce the concentration of CO 2 from the atmosphere. Mineralization of CO 2 to mineral salts like calcium carbonate provides a stable storage of CO 2 . Reversible hydration of CO 2 to carbonic acid is the rate limiting step in the mineralization process. We report catalysis of the reversible hydration of CO 2 using nickel nanoparticles (NiNPs) at room temperature and atmospheric pressure. The catalytic activity of the NiNPs is pH independent and as they are water insoluble and magnetic they can be magnetically separated for reuse. The reaction steps were characterized using X-ray photoemission spectroscopy and a possible reaction mechanism is described.

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Hydration reaction of CO2is one of the rate limiting steps for CO2absorption (in aqueous solutions) and aqueous CO2mineralization. The catalytic activity of nickel nanoparticles (NiNPs) for CO2hydration is studied at different temperatures, pH, and low CO2partial pressures to mimic the true flue gas conditions. Results show that NiNPs can work as active catalyst for hydration of CO2in applications such as CO2separation and CO2mineralization. The NiNPs display optimum activity within 20–30°C and at pH value <8. NiNPs show catalytic activity even at low CO2partial pressures (12 vol%). In 50 wt% K2CO3solution, an enhancement of 77% is observed in the rate of CO2absorption with NiNPs. Commercially, CO2saturated K2CO3solutions are usually regenerated at 150°C; at these conditions, NiNPs show no considerable surface oxidation. They still exhibit catalytic activity for hydration reaction of CO2. CO2absorption and mineralization (as CaCO3) in DI water are three times higher in presence of NiNPs. Calcite (CaCO3) particles precipitated in presence of NiNPs are spherical in morphology.

In this work, wavy nickel nanowires (NiNWs) were immobilized on mesoporous silica (SiO2) aerogels by the sol–gel method. We measured the catalytic activity of pure NiNWs and NiNW–SiO2 aerogel composites toward the CO2 hydration reaction (CHR) when they are in water. Dynamic vapor sorption (DVS) analysis was performed at levels of 50% CO2 and 50% H2O vapor for SiO2 aerogels, immobilized nickel nanoparticles (NiNPs) on silica aerogel and NiNW–SiO2 aerogel composites, in order to determine catalytic activity for CHR in the gaseous phase. The results from DVS analysis (gaseous phase) and CHR (aqueous phase) showed that NiNW–SiO2 aerogel composites are good heterogeneous catalysts for CHR in both gaseous and aqueous phases but they are less active than NiNP–SiO2 aerogel composites.