1 research outputs found
Quantification of the Dissolved Inorganic Carbon Species and of the pH of Alkaline Solutions Exposed to CO<sub>2</sub> under Pressure: A Novel Approach by Raman Scattering
Dissolved
inorganic carbon (DIC) content of aqueous systems is
a key function of the pH, of the total alkanility (TA), and of the
partial pressure of CO<sub>2</sub>. However, common analytical techniques
used to determine the DIC content in water are unable to operate under
high CO<sub>2</sub> pressure. Here, we propose to use Raman spectroscopy
as a novel alternative to discriminate and quantitatively monitor
the three dissolved inorganic carbon species CO<sub>2</sub>(aq), HCO<sub>3</sub><sup>–</sup>, and CO<sub>3</sub><sup>2–</sup> of alkaline solutions under high CO<sub>2</sub> pressure (from <i>P</i> = 0 to 250 bar at <i>T</i> = 40 °C). In
addition, we demonstrate that the pH values can be extracted from
the molalities of CO<sub>2</sub>(aq) and HCO<sub>3</sub><sup>–</sup>. The results are in very good agreement with those obtained from
direct spectrophotometric measurements using colored indicators. This
novel method presents the great advantage over high pressure conventional
techniques of not using breakable electrodes or reference additives
and appears of great interest especially in marine biogeochemistry,
in carbon capture and storage and in material engineering under high
CO<sub>2</sub> pressure