| 摘要 |
1,149,743. Regeneration of aqueous solutions of salts of chelating acids. GENERAL DYNAMICS CORP. 18 May, 1966 [24 May, 1965], No. 22190/66. Heading C2C. [Also in Division C7] Spent aqueous electrolytes resulting from the electrolytic descaling of surfaces of metals (which metals form hydroxides which are insoluble in aqueous solutions of pH 10À5 and above, said aqueous electrolyte being a solution of pH 3-7 of an alkali metal or nitrogen base salt of a chelating acid (said acid being soluble in water and forming complexes which are stable at pH 3-7, but unstable at a pH of 10À5 or above) are reclaimed by contact with an alkali metal water-soluble hydroxide in sufficient amount to raise the pH of the spent electrolyte to at least 10À5, separating any precipitated solids and contacting the resultant solution with at least one cation exchange resin to reduce the pH to 3-7 when reclaiming an alkali metal salt of the chelating acid, or 1-2 when reclaiming a nitrogen base salt of the chelating acid and, in the latter instance, raising the pH to 3-7 by addition of a nitrogenous base. It is preferred to heat the solution obtained at the precipitation step in order to drive off volatile components, e.g. NH 3 , and coagulate the precipitate. Specified chelating acids are gluconic, tartaric, diglycolic, glycolic and citric acid. Preferred electrolytes for regeneration are ammonium, sodium and potassium citrates. Preferred soluble hydroxides are NaOH and KOH. The process is illustrated by reference to a flow chart (not shown). |
