METHOD FOR RECOVERING ALKALI FROM ALKALI ETCHING LIQUID

PROBLEM TO BE SOLVED: To provide a method for recovering alkali comprised in an alkali etching liquid of aluminum with a compact apparatus as the precipitation of alumina (Al2O3) is evaded and the storage of NaCO3and heavy metals is evaded. SOLUTION: As a first stage, an alkali etching liquid of aluminum is introduced into a first electrolytic tank, and is passed through an ion exchange membrane, so as to separate Na+to the cathode side, and the Na+ is coupled with OH-generated by cathode reaction, so as to obtain NaOH. Next, as a second stage, the liquid on the anode side in the first stage is fed to a neutralization tank 6, jointly, an anolyte in a second electrolytic tank 9 is fed to the neutralization tank 6, in the neutralization tank, AlO2-ions in the anolyte in the first electrolytic tank are neutralized with H+ions generated by anode reaction in the second electrolytic tank, so as to separate Al3+ions as Al(OH)3, thereafter, this liquid is introduced into the second electrolytic tank, so as to separate Na+to the cathode side through an ion exchange membrane, and the Na+is coupled with the OH-generated by cathode reaction, so as to obtain NaOH. COPYRIGHT: (C)2007,JPO&INPIT