Patent ID: 6607651
Filing Date: 2003-08-19
Classification: B01J,C25D,Y10S

Abstract:
A method for treating an aqueous solution discharged from an ion exchanger during a flushing thereof wherein an acidic aqueous flushing solution is caused to flow through said exchanger to increase a hydrogen ion content of said exchanger and wherein the resulting aqueous discharge solution is acidic and comprises metal ions from structures being electroplated in an electroplating bath, metal ions from electrodes used in the electroplating bath, and metal ions from the plating metal in said electroplating bath, said method comprising:adding a pH raising agent having a cation with a valence of at least 2 to said discharge solution to raise the solution's pH such that hydroxyl ions in the discharge solution (i) bond with the metal ions from the structures being plated in said electroplating bath to form a first precipitate; (ii) bond with the metal ions from said electrodes to form a second precipitate; and (iii) bond with the metal ions from the plating metal to form a third precipitate; affecting separation of said first, second and third precipitates from said discharge solution; aerating the discharge solution with carbon dioxide, such that said cation from said pH raising agent reacts with said carbon dioxide to form a carbonate precipitate; and separating said carbonate precipitate from said solution such that the solution consists essentially of water; wherein adding said pH raising agent comprises: adding a first pH raising agent having a cation with a valence of at least 2 to said discharge solution to raise the solution's pH such that hydroxyl ions in the discharge solution bond with the metal ions from the structures being plated in said electroplating bath to form at least said first precipitate; adding a second pH raising agent having a cation with a valence of at least 2 to said discharge solution to raise the solution's pH such that hydroxyl ions in the discharge solution (i) bond with the metal ions from the structures being plated in said electroplating bath to further form said first precipitate; (ii) bond with the metal ions from the electrodes to form said second precipitate; and (iii) bond with the metal ions from the plating metal to form a third precipitate; wherein said affecting separation of said first, second and third precipitates is formed by collectively separating said precipitates from the discharge solution after adding said first and second pH raising agents.