There are three different separation methods that can be employed for recovering
citric acid from the fermentation broth. These are Precipitation, Ion Exchange and
Solvent Extraction. Precipitation is the most commonly used method. It is more
economical to remove citric acid as calcium citrate by lime precipitation than by ionexchange
treatment. The ion exchange method may be used for treating lime juice
rather than filtered acid juice. Solvent extraction is a possible alternative to the
classical method but because the available solvents tend to extract some of the
impurities too, it is easier to apply to products from glucose or alkane based substrates.
The advantage of this process is that it avoids the use of lime and sulfuric acid and the
concomitant problem of gypsum (calcium sulphate) disposal. Gypsum is produced as a
waste product during the purification process of citric acid and its disposal is a
complicated issue.