Purification and regeneration of a spent chemical nickel plating bath comprises a protonation stage and a demineralization stage involving removal of orthophosphite ions from the bath by using an ion-exchange membrane

摘要

Purification and regeneration of a chemical nickel plating bath containing hypophosphite, orthophosphite and nickel ions and at least one dissociated weak acid involves a protonation stage, in which the pH of the bath is changed, and a demineralization stage, in which orthophosphite ions are removed from the bath by using an ion-exchange membrane at 15-50 deg C. The protonation stage can carried out by adding a strong acid, preferably HCl, directly to the bath, or by using an ion-exchange membrane which allows transfer of protons from an acidic solution to the spent chemical nickel plating bath. The demineralization stage is carried out at 15-50 deg C for 1-150 minutes. Preferably, the process comprises a third stage involving the addition of at least one nickel salt selected from nickel sulfate, nickel acetate, nickel carbonates, nickel fluoride, nickel sulfonate and nickel hypophosphite. Independent claims are given for: (a) application of the above process to a chemical nickel plating bath that also includes sulfate ions; and (b) an installation for regenerating a chemical nickel plating bath. The installation includes a first unit including: (1) insoluble cathode (C) and insoluble anode (A) (2) anode (9) and cathode (2) compartments containing electrolyte in direct contact with the anode (A) and cathode (C), respectively; (3) a side compartment separate from the cathode compartment (5) be an anion-exchange membrane (A56); and (4) a stack of at least one electrodialysis cell (7) for receiving the spent bath containing molecular weak acids and a compartment (8) for recovery of orthophosphite ions next to the electrodialysis cell (7). The electrodialysis cell (7) is defined on the cathode side by a cation exchange membrane (C67) and separated from the orthophosphite ion recovery compartment (8) by an anion exchange membrane (A78). The orthophosphite ion recovery compartment (8) is defined on the anode side by a cation exchange membrane (C89).