Abstract
The concentration of CO2 in Earth’s atmosphere has been gradually increasing since the Industrial Revolution, primarily as a result of the use of fossil fuels as energy sources. Although coal and oil have been vital to the development of modern civilization, it is now recognized that atmospheric CO2 levels must be reduced to avoid the serious effects of climate change, including natural disasters. Consequently, there is currently significant interest in developing suitable methods for the fixation of CO2 in the air and in exhaust gases. The present work demonstrates a simple yet innovative approach to the chemical fixation of extremely low and very high CO2 concentrations in air, such as might result from industrial sources. This process is based on the use of aqueous solutions of the water-soluble compounds NaOH and CaCl2, which react with CO2 to produce the harmless solids CaCO3 (limestone) and NaCl (salt) via intermediates such as NaHCO3 and Na2CO3. The NaCl generated in this process can be converted back to NaOH via electrolysis, during which H2 (which can be used as a clean energy source) and Cl2 are produced simultaneously. Additionally, sea water contains both NaCl and CaCl2 and so could provide a ready supply of these two compounds. This system provides a safe, inexpensive approach to simultaneous CO2 fixation and storage.
Highlights
The concentration of CO2 in Earth’s atmosphere has been gradually increasing since the Industrial Revolution, primarily as a result of the use of fossil fuels as energy sources
The CO2 concentration in a 2-L bottle made of poly(ethylene terephthalate) (PET) was monitored to determine whether a solution containing 0.05 N NaOH and 0.05 M CaCl2 reduced the level of CO2
At a high CO2 concentration of approximately 15%, the addition of 50 mL of a solution containing 0.05 N NaOH and 0.05 M CaCl2 followed by vigorous shaking of the 2-L bottle for 30 s by hand reduced the CO2 concentration to 10% (Fig. 3c)
Summary
The concentration of CO2 in Earth’s atmosphere has been gradually increasing since the Industrial Revolution, primarily as a result of the use of fossil fuels as energy sources. In the present work, CO2 was bubbled through an initially clear solution (Fig. 1a) containing 0.05 N NaOH and 0.05 M CaCl2 to form an immediate white precipitate (Fig. 1b). Solutions with lower NaOH concentrations (from 0.05 to 0.1 N NaOH) together with 0.05 M C aCl2 remained clear, while the addition of CO2 bubbles produced a white precipitate (Fig. 2a).
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