CaCO3 Precipitation and Polymorph Forms During CO2 Sequestration from the Atmosphere: Effects of the Basic Buffer Components

CO2 sequestration and polymorph selection was achieved by CaCO3 precipitation via the reaction of calcium ions and atmospheric CO2 in a basic buffer, in a process that mimicked geological sedimentation. Precipitation proceeded in yield exceeding 80% in the presence of basic buffers at room temperature over 10 h. Calcite formed mainly during the early stages of precipitation, within less than 5 h, followed by needle-like aragonite precipitation between 5 and 10 h of aging. The aragonite polymorph selection increased in the presence of carbonic anhydrase and at high solution temperatures. We found that the deposited CaCO3 polymorphs depended on the rate of calcium ion consumption and precipitation as well as the ionic strength of the basic buffer and the solution pH. We developed a method for depositing high-purity aragonitic CaCO3 crystals in solutions with temperatures exceeding 60 degrees C in the presence of basic buffer, using CO2 from the atmosphere without the need for seed crystals or metal ions.