Recyclable regenerant for weak acid ion exhange resins

A process for regenerating spent polyacrylic acid cation exchange resin having associated polyvalent cations obtained from softening hard water, comprising the steps of:

• a) contacting the spent polyacrylic acid cation exchange resin with a regenerant solution containing one or more sodium or potassium salts of a carboxylic acid selected from a group consisting of .alpha.-hydroxy carboxylic acids and hydroxylated benzoic acids, thereby producing charged polyacrylic acid cation exchange resins;
• b) separating said charged polyacrylic acid cation exchange resin from an effluent solution containing a mixture of monovalent and polyvalent cationic salts of said carboxylic acid;
• c) precipitating said effluent solution with the addition of sodium or potassium carbonate, thereby generating a slurry containing precipitates of said polyvalent cations;
• d) separating said slurry into said precipitates of said polyvalent cations and a filtrate containing soluble sodium and potassium salts of said carboxylic acid;
• e) concentrating said filtrate by removing excess water;
• f) utilizing said concentrated filtrate containing said soluble sodium and potassium salts of said carboxylic acid to react with the additional spent polyacrylic acid cation exchange resin;
• and
• g) employing said removed excess water as a rinse in said separation step.