Partial electro-neutralisation of D-alpha-p-hydroxyphenylglycine in sulphuric acid medium

In the industrial synthesis of D-alpha-p-hydroxyphenylglycine the separatio n of amino acid is carried out by precipitation. During this process, a mot her liquor is produced with a high salt content (2 M phosphates and sulphat es) and an amino acid concentration of 0.11-0.12 M. The disposal of this mo ther liquor causes an environmental problem and an economic loss. The salt content of this mother liquor can be reduced in 70% of the initial by means of an electrodialysis process previously carried out by us, with only an a mino acid loss of 15% of the initial. To improve and simplify this process, an electro-electrodialysis process (a membrane electrolysis process; the e lectrode processes and the transport process across the membrane are used) has been developed in which as a first step, the electro-neutralisation of solutions containing sulphuric acid and D-alpha-p-hydroxyphenylglycine is s tudied. The sulphuric acid content is reduced to 87% of the initial, withou t detected loss of amino acid, The final solution is posteriorly neutralise d by working up the pH of the solution for precipitating the amino acid, an d a mother liquor with approximately 0.10M D-alpha-p-hydroxyphenylglycine a nd a low salt content (0.08 M Na2SO4) is produced. This mother liquor with low salinity can be recirculated again to a new electro-electrodialysis pro cess. (C) 2000 Elsevier Science B.V. All rights reserved.