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Carbonatation is a slow process that occurs in concrete where lime (CaO, or Ca(OH) 2 ) in the cement reacts with carbon dioxide (CO 2) from the air and forms calcium carbonate. The water in the pores of Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5.
As lime in the form of limewater is added to raw water, the pH is raised and the equilibrium of carbonate species in the water is shifted. Dissolved carbon dioxide (CO 2) is changed into bicarbonate (HCO − 3) and then carbonate (CO 2-3). This action causes calcium carbonate to precipitate due to exceeding the solubility product.
Each mole of CO 2 (44 g) reacts with one mole of calcium hydroxide (74 g) and produces one mole of water (18 g). The reaction can be considered as a strong-base-catalysed, water-facilitated reaction. [5] The reaction mechanism of carbon dioxide with soda lime can be decomposed in three elementary steps:
A study found the mean concentration of sodium in softened water to be 278 mg/L. [24] In 2 liters of water—the amount of drinking water typically suggested for an average adult, this constitutes about 22% of the recommended sodium intake by the US CDC and may make a difference to those who need to significantly limit their sodium consumption.
When the masonry has been laid, the slaked lime in the mortar slowly begins to react with carbon dioxide to form calcium carbonate (limestone) according to the reaction: Ca(OH) 2 + CO 2 → CaCO 3 + H 2 O. The carbon dioxide that takes part in this reaction is principally available in the air or dissolved in rainwater [9] so pure lime mortar ...
However, in dry injection or spray drying operations, the SO 2 is first reacted with the lime, and then the flue gas passes through a particulate control device. Another important design consideration associated with wet FGD systems is that the flue gas exiting the absorber is saturated with water and still contains some SO 2. These gases are ...
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As it hydrates, an exothermic reaction results and the solid puffs up. The hydrate can be reconverted to quicklime by removing the water by heating it to redness to reverse the hydration reaction. One litre of water combines with approximately 3.1 kilograms (6.8 lb) of quicklime to give calcium hydroxide plus 3.54 MJ of energy.