Process for regenerating alkali metal citrates from spent aqueous citrate dispersions

摘要

1,125,062. Regenerating alkali metal citrates. GENERAL DYNAMICS CORP. 20 Feb., 1967 [3 March, 1966], No. 8052/67. Heading C2C. Alkali metal citrates are regenerated from spent aqueous citrate dispersions by contacting the spent dispersion with an alkali metal hydroxide sufficient to raise the pH of the spent dispersion to at least 10À5, separating the precipitated solids, evaporating the resultant solution to dryness, leaching the resultant solid with an organic solvent that is capable of dissolving the alkali metal hydroxide but not the alkali metal citrate until an aqueous solution of a portion of the solid gives a pH from 8À5 to 9, and thereafter drying the remaining solid. Preferred alkali metal hydroxides are sodium and potassium hydroxide and a preferred organic solvent is methanol. Insoluble material is suitably removed from the spent citrate prior to treatment with the alkali metal hydroxide, the precipitated solids obtained during the process are preferably coagulated by heating prior to their separation and the organic solvent and the alkali metal hydroxide may be reclaimed from the solution obtained in the leaching step. The spent aqueous citrate dispersion may be one derived from an electrolytic descaling of metal with a citrate solution, or from a citrate solution that has been used for the removal of metallic scale from a surface.