Process and system for treating the discharge stream from an ion exchanger

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 solution (i) bond with the metal ions from the structures being plated in said electroplating bath to form said first precipitate;
• and (ii) bond with the metal ions from the electrodes to form said second precipitate;
• adding a second pH raising agent having a cation with a valence of at least 2 to said discharge solution to further raise the solution's pH such that said hydroxyl ions bond with the metal ions from the plating metal to form said third precipitate;
• and
• wherein said affecting separation is performed by separating said first and second precipitates after adding said first pH raising agent and then separating the third precipitate separately from the first and second precipitates.

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 chromium (VI) ions from the plating metal in said electroplating bath, said method comprising:

• adding a reducing agent to the discharge solution to reduce the chromium (VI) ions to chromium (III) ions;
• adding 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 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 chromium (III) ions to form a third precipitate of chromium (III) hydroxide;
• and
• 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 precipitate and water;
• and
• separating said precipitate from said discharge solution such that the discharge solution consists essentially of water;
• wherein said adding said pH raising agent comprises:
• adding a first pH raising agent having a cationic valence of at least 2 to said discharge solution to raise the solution's pH such that hydroxyl ions in the 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 cationic valence of at least 2 to said discharge solution to raise the solution's pH such that hydroxyl ions in the 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 said electrodes to form said second precipitate;
• and (iii) bond with the chromium (III) ions to form said third precipitate of chromium (III) hydroxide.

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 chromium (VI) ions from the plating metal in said electroplating bath, said method comprising:

• adding a reducing agent to the discharge solution to reduce the chromium (VI) ions to chromium (III) ions;
• adding 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 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 chromium (III) ions to form a third precipitate of chromium (III) hydroxide;
• and
• 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 precipitate and water;
• and
• separating said precipitate from said discharge solution such that the discharge 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 solution (i) bond with the metal ions from the structures being plated in said electroplating bath to form said first precipitate;
• and (ii) bond with the metal ions from the electrodes to form said second precipitate;
• adding a second pH raising agent having a cation with a valence of at least 2 to said discharge solution to further raise the solution's pH such that said hydroxyl ions bond with the chromium (III) ions to form said third precipitate of chromium (III) hydroxide;
• and
• wherein said affecting separation is performed by separating said first and second precipitates after adding said first pH raising agent and then separating the third precipitate separately from the first and second precipitates.