BigPatents India

The invention relates to a method for producing N-phosphonomethylglycine from an aqueous mixture containing N-phosphonomethylglycine, ammonium halogenides and alkali halides or earth alkali halides and optionally, organic impurities in a dissolved form. According to the invention, (a) the pH-value of the mixture is regulated to a value of 2 - 8, (b) the mixture is separated by means of a selective nano-filtration membrane, to obtain a retentate rich in N-phosphonomethylglycine and poor in halogenides and a permeate rich in halogenides and poor in N-phosphonomethylglycine and (c) the N-phosphonmethylglycine is prepared from the retentate. The inventive method enables the production of N-phosphonomethylglycine by simultaneously separating the halogenide salts thereof.