Calcium carbonate can be used as well (Heding and Gupta, 1975).
The precipitated citrate can be filtered off, thus separating it from
most impurities and water. However, not all citric acid is recovered,
due to the aqueous solubility of calcium citrate. The solubility value of
0.96 g/L given in Table 11 corresponds to 0.57 g/L citric acid, which is
less than 0.5% of the amount produced by fermentation and acceptable
as loss. However, solubility product calculations should be used to determine
the exact solubility of citrate as function of pH and added
amount of calcium ion