Electrolytic method for preparing potassium dihydrogen phosphate

Abstract

The invention discloses an electrolytic method for preparing potassium dihydrogen phosphate, and is characterized in that a saturated or nearly saturated potassium chloride solution and a dipotassium hydrogen phosphate solution with a concentration of 1-8 mol / L, or a mixed solution of potassium dihydrogen phosphate and dipotassium hydrogen phosphate, or a mixed solution of dipotassium hydrogen phosphate and tripotassium phosphate, or a mixed solution of tripotassium phosphate and potassium hydroxide, are added into an electrolytic tank; under the conditions of a reaction temperature being 40-100 DEG C and an electrolyzing voltage being 2.1-5 V, continuous electrolysis is carried out to obtain a cathode complete solution; through concentration separation, a solid (or a heavy paste) is recycled into the electrolysis system; after a clear solution neutralizes a phosphoric acid, evaporation concentration, cooling crystallization, filtering, and drying are carried out to obtain a product potassium dihydrogen phosphate; a mother solution is neutralized by a catholyte after the electrolysis, and then returns to the electrolytic tank to undergo electrolysis; and at the same time, a chlorine gas and a hydrogen gas are by-products. The method of the invention overcomes the deficiencies of a high reaction temperature, high corrosion of equipment, high environmental pollution of the extraction method, a high material cost, and the like in the traditional complex decomposition method.

Description

technical field

[0001] The invention relates to a method for preparing potassium dihydrogen phosphate by electrolysis, belonging to the field of preparation of potassium phosphate. technical background

[0002] At present, there are many methods for producing potassium dihydrogen phosphate, including neutralization method, double decomposition method, conversion method, solvent extraction method, electrolysis method and so on.

[0003] The simplest method is the neutralization method, such as neutralizing phosphoric acid with potassium hydroxide or potassium carbonate to obtain potassium dihydrogen phosphate. This method has the advantages of simple process flow and mature process technology, etc., but the disadvantages are large investment in raw materials and high production costs, and it is not suitable for large-scale production.

[0004] Metathesis method, with potassium chloride and phosphoric acid, KCl and MH 2 PO 4 (Wherein M is Na or NH4) is the double decomposit...