EXTRACTION OF AMPHOTERIC AMINO-ACIDS BY AN ELECTROMEMBRANE PROCESS - PH AND ELECTRICAL STATE CONTROL BY ELECTRODIALYSIS WITH BIPOLAR MEMBRANES

Electrodialysis (ED) with bipolar membranes (BPM) was applied for the extraction of amino acids in an electrically neutral form. Under volta ge, BPM split water, generating hydroxyl ions at the anodic side and p rotons at the cathodic side. The use of these membranes represents a n ewer method to convert neutral species into electrically charged speci es that are able to cross homopolar ED membranes. The ED operations we re performed using a laboratory cell with a membrane area of 50 cm(2). A mixture containing five amino acids (Gly, Ser, Ala, Val, Phe) was e xamined. The concentration of each amino acid was 100 mmol dm(-3). The current density and pH in the feed and receiver compartments were var ied. Extraction degrees and current efficiencies were calculated and c ompared under different experimental conditions. (C) 1998 Society of C hemical Industry.