Process for recovering caustic alkali from spent alkali liquor

摘要

A process for recovering caustic alkali from spent alkali liquor, in which a spent alkali liquor and iron oxide are roasted to obtain a product containing alkali ferrate and the product of roasting is hydrolyzed at a temperature over 110 DEG C. and under pressurized conditions where liquid phase is retained, thereby recovering caustic alkali in the form of an aqueous solution of a concentration higher than approximately 15 wt% containing dissolved iron in an extremely small concentration.