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US 4,065,270 AGranted
Process for purifying sodium hydroxide
AssigneeAsahi Glass Company, Limited
InventorsKeiichi Nakaya, Suekazu Hirata, Kunio Sato
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Abstract
An aqueous solution of sodium hydroxide containing soluble impurities such as a concentrated catholyte produced by a diaphragm electrolysis is cooled by a coolant or a heat-exchanger to form a slurry containing sodium hydroxide hydrate crystals and fine impurity crystals. The fine impurity crystals are adsorbed on bubbles which are formed by vaporizing a dissolved coolant or introducing a gas in the slurry and separated from the slurry.
Claims17
A process for purifying sodium hydroxide which comprises:
- cooling an aqueous solution of sodium hydroxide containing soluble impurities to form a slurry containing sodium hydroxide hydrate crystals and the fine impurity crystals;
- forming bubbles in said slurry, whereby said impurity crystals are adsorbed on the bubbles and float upward therewith to form a foamed scum on said slurry;
- and
- removing said scum from said slurry, thereby separating the impurity crystals from the sodium hydroxide crystals.
1 more element
Dependencies are inferred from the claim text.