Conversion of Calcium Citrate to Citric Acid with Compressed CO(2)

[Image: see text] Citric acid is mainly produced in the fermentation industry, which needs complex processes and produces a high amount of CaSO(4) as waste. In this study, CO(2) has been used to convert calcium citrate to citric acid and CaCO(3) by controlling the reaction parameters (reactants ratio, temperature, and pressure). The CaCO(3) produced in this conversion could further be used in the fermentation industry for citric acid production. The transformation condition has been optimized by controlling temperature, pressure, reaction time, and mass ratio of calcium citrate and water. The highest conversion could reach up to 94.7% under optimal experimental conditions of 18 MPa of pressure, 65 °C of reaction temperature, 4 h of reaction time, and 2 g/L of calcium citrate/water suspension solution. This method features simple process, easy separation of citric acid, and environmentally friendly process, which could be a potentially alternative route for downstream treatment in fermentation production of citric acid.