CaCO<sub>3</sub> Precipitation and Polymorph Forms
During CO<sub>2</sub> Sequestration from the Atmosphere: Effects of
the Basic Buffer Components
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Abstract
CO<sub>2</sub> sequestration and
polymorph selection was achieved
by CaCO<sub>3</sub> precipitation via the reaction of calcium ions
and atmospheric CO<sub>2</sub> 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 CaCO<sub>3</sub> 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 CaCO<sub>3</sub> crystals
in solutions with temperatures exceeding 60 °C in the presence
of basic buffer, using CO<sub>2</sub> from the atmosphere without
the need for seed crystals or metal ions