Recovery by means of electrodialysis of an aromatic amino acid from a solution with a high concentration of sulphates and phosphates

In the industrial synthesis of D-alpha-p-hydroxyphenylglycine the separation of the amino acid is carried out by precipitation. During this process, a mother liquor is produced with a high salt content (phosphates and sulphates) and an amino acid concentration of approximately 0.12-0.15 M. The disposal of this mother liquor not only causes an environmental problem due its high salinity and COD (chemical oxygen demand) content but also an economic loss due to the high price of the unrecovered amino acid. To avoid this problem an electrodialytic process has been developed that allows the recovery of 85% of the amino acid in the form of a low salinity stream with a salt content 70% lower than that of the initial mother liquor. This low salinity stream can be incorporated into the main process and in this way the amino acid can be recovered. (C) 1998 Elsevier Science B.V.