초록 ▼

An improved process for the electrodialysis of aqueous NaCl which operates at high current efficiency and low unit cell voltage drop to produce high strength, high purity Na2CO3 and either high purity HCl or CaCl2 by utilizing cation permselective, anion permselective and bipolar membranes wherein t

An improved process for the electrodialysis of aqueous NaCl which operates at high current efficiency and low unit cell voltage drop to produce high strength, high purity Na2CO3 and either high purity HCl or CaCl2 by utilizing cation permselective, anion permselective and bipolar membranes wherein the solutions on both sides of the anion permselective membrane are acidic.

대표청구항 ▼

A process for the electrodialysis of aqueous NaCl in an electrodialytic cell having anode and cathode compartments separated by acid, salt and base zones respectively which comprises the steps of: (a) feeding an aqueous HCl stream to said acid zone of said electrodialytic cell located between the ca

A process for the electrodialysis of aqueous NaCl in an electrodialytic cell having anode and cathode compartments separated by acid, salt and base zones respectively which comprises the steps of: (a) feeding an aqueous HCl stream to said acid zone of said electrodialytic cell located between the cation face of a bipolar membrane and one side of a weakly basic anion permselective membrane; (b) feeding an aqueous NaCl stream to said salt zone located between the other face of said weakly basic anion membrane and one face of a strongly acidic cation permselective membrane; (c) feeding an aqueous Na2CO3 stream to said base zone located between the other face of said cation permselective membrane and the anion face of a bipolar membrane; (d) passing a direct electric current through said electrodialytic cell, thereby effecting an increase in H+concentration in said HCl stream, an increase in OH-concentration in said Na2CO3 stream, the transfer of Cl-from said NaCl stream to the acid-enriched HCl stream and the transfer of Na+from said NaCl stream to the OH--enriched Na2CO3 stream; (e) maintaining a pH of streams on both faces of said anion permselective membrane at a value less than about 7; (f) withdrawing a portion of the partially depleted NaCl stream from said salt zone; (g) withdrawing the HCl-enriched stream from said acid zone; (h) withdrawing NaOH-enriched Na2CO3 stream from said base zone; (i) contacting said NaOH-enriched Na2CO3 stream from step (h) with a carbonating agent thereby forming additional Na2CO3; and (j) withdrawing at least a portion of said Na2CO3 stream as product.