The Dow Chemical Company

Harry S Burney

Bobby R Ezzell

Walter L Vaughn

Marius W Sorenson

Donald W Calvin

Robert D Spradling

Gary R Gantt

Robert R Frable

Hardness values (Ca.sup.++ and Mg.sup.++) and other polyvalent metal cations are removed from alkali metal brines (esp. NaCl) by using a high surface area ethylene/carboxylic acid polymer (esp. porous ethylene/acrylic acid copolymers).

Brine treatment using ethylene carboxylic acid polymers

Used or contaminated pieces of fluoropolymer membrane or sheet materials are salvaged for re-use by particulating the materials into powders, granules, or fibers, or otherwise reforming it, treating the particulated material, as desired, to cleanse or modify the material, and utilizing the material in subsequent applications.

Re-use of fluoropolymer membranes

Method for reducing electrical energy consumption increase of ion-exchange membranes over long term use which comprises electrolyzing an alkali metal chloride solution which contains no more than about 75 ppm 'carbonate' whether such low 'carbonate' solution is achieved by removing excess carbonate previously added to the solution to reduce the hardness or not.

Membrane cell brine feed

Methods of membrane regeneration of permselective ion-exchange membranes of a brine electrolysis cell are greatly improved when the cells are fed brine which contains little or no carbon dioxide, carbonate anions or bicarbonate anions during normal electrolysis and when the methods of membrane regeneration are those wherein at least one liquid solution contacts the membrane and the pH of that solution is below that of the pH of the electrolyte in contact with the membrane during normal electrolysis.

Operation and regeneration of permselective ion-exchange membranes in

Electrolytic cell ion-exchange membranes, comprising fluoropolymers having pendant sulfonic acid functional groups and/or carboxylic acid functional groups, are treated with primary, secondary, and/or tertiary amines to provide dimensional stability and other improvements to the membranes. The treatment with amines provides easily-disassociable amines salts which are leached out by an aqueous leachant, e.g., cell electrolyte, thereby providing sulfonic acid groups and/or carboxylic acid groups to function as ion exchange sites in the membrane during subsequent cell operation.

Electrolytic cell ion-exchange membranes

Improvements in electrolytic chlor-alkali membrane cells, operated with cell-to-cell catholyte series flow, are obtained by the use, as membranes, of fluoropolymers containing pendant functional groups on the cathode side which are less hydrophilic than sulfonic acid groups. Preferably the functional groups on the catholyte side of the membrane absorb about 5 to about 12 moles of H.sub.2 O per functional group whereas the functional groups on the anolyte side of the membrane absorb more, generally, about 15 to about 30 moles of H.sub.2 O per functional group.

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Clute, TX, United States of America

Harry S Burney