Conversion of Calcium Citrate to Citric Acid with Compressed CO2

Citric acid is mainly produced in the fermentation industry, which needs complex processes and produces a high amount of CaSO4 as waste. In this study, CO2 has been used to convert calcium citrate to citric acid and CaCO3 by controlling the reaction parameters (reactants ratio, temperature, and pressure). The CaCO3 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 degrees 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.

Automated summary

In this study, citric acid has been converted from calcium citrate using CO2, which can be further utilized in the fermentation industry for citric acid production. The method shows high conversion rate and environmentally friendly characteristics, providing a potentially alternative route for downstream treatment in fermentation production of citric acid.