Patent ID: 6221225
Filing Date: 2001-04-24
Classification: B01D,C01C,C01D,C02F,C07C,C12P,C25B

Abstract:
A process for converting an incoming feed of a salt of a monovalent cation and a weak acid anion into an acidified product stream which is reduced in its monovalent cation content, said process comprising the steps of:(a) obtaining an input feed stream which is freed of suspended solids;(b) passing the feed stream of step (a) through a salt/acid compartment of a two compartment electrodialysis cell containing at least a bipolar membrane and two cation membranes, said bipolar membrane having a cation side and an anion side, said salt/acid compartment being located between said cation side of the bipolar membrane and one of said cation membranes, the other of said two compartments being a base compartment coupled in a base loop extending directly from an output of said base compartment through an ion exchange column to an input of said base compartment, said base compartment being located between said anion side of the bipolar membrane and the other of said cation membranes;(c) supplying a liquid including water to the base compartment of the cell, said base compartment having an output stream in constant communication with said ion exchange column in said base loop, said column being packed with a material capable of removing multivalent cations that may enter the base loop whereby a first portion of an output stream from said base compartment passes through said ion exchange column for further refinement of said stream in said base compartment,(d) passing a direct current through the electrodialysis cell for causing an acidification of the feed salt and a concurrent transport of monovalent cations to the base loop;(e) producing a base product through a combination of the transported cation with a hydroxyl ion generated by the bipolar membrane in the base loop; and(f) withdrawing a second portion of said output stream from said base compartment which comprises the acidified feed and the base product.