Alan J Stacey

US Patent:

41167813, Sep 26, 1978

Filed:

Apr 19, 1977

Appl. No.:

5/788836

Inventors:

Martin M. Dorio - Mentor OH
Alan J. Stacey - Parma OH

Assignee:

Diamond Shamrock Corporation - Cleveland OH

International Classification:

C25B 120
C25B 126
C25B 1508
C25B 1308

US Classification:

204 98

Abstract:

Chlor-alkali cells of the membrane type are highly susceptible to multivalent metallic impurities in the brine feeds. As the impurity concentration builds up on and/or in the membrane material, cell voltage increases and current efficiency is lost. By the practice of the instant invention the membrane is rejuvenated and the current efficiency of the cell increased by intermittently replacing the normal brine feed thereto with a brine which is of relatively high purity with respect to the multivalent metallic impurities found in the normal brine feed. Generally, the pure brine feed should have little or no hardness (calcium and magnesium level) or, if present, the hardness should be completely complexed by a phosphate treatment. The other multivalent metallic impurities should be present in the "pure" brine at less than 2 milligrams per liter in total and preferably less than 1 milligram per liter thereof, while each individual other metallic contaminant should not exceed 0. 5 milligrams per liter and preferably it would be below 0.