Magnesium Hydroxide Extracted from a Magnesium-Rich Mineral for CO sub(2) Sequestration in a Gas-Solid System

Magnesium hydroxide extracted from magnesium-bearing minerals is considered a promising agent for binding CO sub(2) as a carbonate mineral in a gas-solid reaction. An efficient extraction route consisting of hydrothermal treatment on serpentine in HCl followed by NaOH titration for Mg(OH) sub(2) precipitation was demonstrated. The extracted Mg(OH) sub(2) powder had a mean crystal domain size as small as 12 nm and an apparent surface area of 54 m super(2)/g. Under one atmosphere of 10 vol% CO sub(2)/N sub(2), carbonation of the serpentine-derived Mg(OH) sub(2) to 26% of the stoichiometric limit was achieved at 325 degree C in 2 h; while carbonation of a commercially available Mg(OH) sub(2), with a mean crystal domain size of 33 nm and an apparent surface area of 3.5 m super(2)/g, reached only 9% of the stoichiometric limit. The amount of CO sub(2) fixation was found to be inversely proportional to the crystal domain size of the Mg(OH) sub(2) specimens. The experimental data strongly suggested that only a monolayer of carbonates was formed on the crystal domain boundary in the gas-solid reaction, with little penetration of the carbonates into the crystal domain.