Abstract: Solubility of CO2 in media formed one-or-more of four forms of inorganic carbon species: carbonic acid, aqueous carbon dioxide, bicarbonate, and carbonate and generated hydrogen ion affecting the medium pH. The saturated TIC and pH were studied using RO water, RO+, GM and GM+ with air (0.038%), 0.5%, 1.0%, 1.5%, 2.0% and 10% CO2 under atmospheric pressure at temperatures of 25, 35, 45, and 55C. Chemical species existing in the media formed additional inorganic carbon species functioning as a buffer, resulting in raising the medium pH. The NaOH boosted the TIC holding capacity of the media and improved the saturated pH. At a specific CO2-enriched air and medium, the saturated pH linearly increased with respect to increased temperature, which implied the decreasing of TIC. However, the saturated TIC concentration nonlinearly decreased with respect to temperature. At a specific medium and temperature, the saturated pH nonlinearly decreased with respect to increased CO2 concentration whereas the TIC concentration linearly increased with respect to increased CO2-enriched air. At a specific CO2-enriched air, medium and temperature, increasing of TIC concentration decreased the medium pH. The saturated TIC and pH became stable at a same period of time; however, the correlation of the TIC and pH was invalid. The saturated pH can be used to specify the saturation condition of TIC.

Keywords: Solubility of CO2, Total inorganic carbon, saturated pH, Algal Growth