Process for the concentration of sulfuric acid
AssigneeHoechst Aktiengesellschaft
InventorsHeinz Kau, Jurgen Russow
Life of this patent
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Abstract
A process is described for increasing the sulfuric acid concentration of solutions containing an alkali metal sulfate, sulfuric acid and alkaline earth metal ions. The solutions to be worked up are introduced into the anode compartment of an electrolysis cell. The anode compartment and the cathode compartment of the cell are each bounded by a cation exchange membrane. A center chamber is located between the two membranes. This center chamber is filled with an aqueous solution containing alkali metal ions. The concentration of alkaline earth metal ions in the solution in the center chamber must be kept below 5 mg/l during the electrolysis.
Claims10
A process for increasing the sulfuric acid concentration of a solution containing an alkali metal sulfate, sulfuric acid and alkaline earth metal ions, by electrolysis in a cell which comprises a plurality of cation exchange membranes which demarcate an anode compartment, a cathode compartment and a center chamber being present between said cathode and anode compartments, in which process the solution, the sulfuric acid concentration of which is to be increased, is introduced into the anode compartment of the cell, the center chamber is filled with a solution containing aqueous alkali metal ions, alkaline earth metal ions migrate from the anode compartment into the center chamber and the concentration of alkaline earth metal ions in the center chamber is kept below 5 mg/l during electrolysis.
The process for the production of regenerated cellulose, in which an alkaline cellulose solution containing sodium ions and small amounts of alkaline earth metal ions is brought into contact with a sulfuric acid solution and the cellulose is thereby precipated, the regenerated cellulose is passed through at least one further acid bath in order to remove completely sodium ions adhering to it, the regenerated cellulose is washed with water, the solution of the precipitation bath is fed into the anode chamber of an electrolysis cell which is bounded by a cation exchange membrane, the acid solution is electrolyzed in the cell and, in the course thereof, its concentration of free sulfuric acid is increased and its content of sodium ions is reduced, which comprises carrying out the electrolysis in a 3-chamber cell, the cathode chamber also being bounded by a cation exchange membrane, and, during the electrolysis, any content of alkaline earth metal ions in the center chamber of the cell being kept below 5 mg/l.
Dependencies are inferred from the claim text.