Partial electro-neutralisation of -α-p-hydroxyphenylglycine in sulphuric acid medium

In the industrial synthesis of -α-p-hydroxyphenylglycine the separation of amino acid is carried out by precipitation. During this process, a mother liquor is produced with a high salt content (2 M phosphates and sulphates) and an amino acid concentration of 0.11–0.12 M. The disposal of this mother 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 amino acid loss of 15% of the initial. To improve and simplify this process, an electro-electrodialysis process (a membrane electrolysis process; the electrode 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 -α-p-hydroxyphenylglycine is studied. The sulphuric acid content is reduced to 87% of the initial, without detected loss of amino acid. The final solution is posteriorly neutralised by working up the pH of the solution for precipitating the amino acid, and a mother liquor with approximately 0.10 M -α-p-hydroxyphenylglycine and 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 process.