Process for the preparation of potassium nitrate

A process for the preparation of potassium nitrate comprising:

• (a) feeding an anolyte consisting essentially of a saturated aqueous solution of potassium chloride to an anodic compartment of a membrane cell, said cell containing an anode and a cathode separated by a permselective cation-exchange membrane to thereby form said anodic compartment and a cathodic compartment;
• (b) feeding a catholyte consisting essentially of an aqueous solution of potassium carbonate and potassium bicarbonate to said cathodic compartment;
• (c) electrolyzing said anolyte inside said anodic compartment to thereby generate chlorine gas at the anode and to generate potassium ion which migrates from said anodic compartment to said cathodic compartment through said membrane;
• (d) discharging a depleted anolyte from said anodic compartment;
• (e) resaturating said depleted anolyte with potassium chloride and recycling said resaturated anolyte to said anodic compartment;
• (f) electrolyzing said catholyte in said cathodic compartment to thereby generate hydrogen at the cathode and to transform at least a portion of the potassium bicarbonate into potassium carbonate;
• (g) discharging a potassium-carbonate enriched catholyte from said cathodic compartment;
• (h) treating a portion of said enriched catholyte with nitric acid to thereby form an aqueous solution of potassium nitrate and carbon dioxide gas;
• and
• (i) contacting a second portion of said enriched catholyte with carbon dioxide gas to thereby at least partially convert the potassium carbonate into potassium bicarbonate and recycling said second portion to said cathodic compartment.