Patents

The invention provides a process for selective extraction of potassium from aqueous solution, e.g., bittern to produce Sulphate of Potash (SOP) and co-generate ammonium sulphate using magnesium hydroxide (or magnesium carbonate), ammonia and sulphuric acid as the other raw materials. The process comprises, among other steps, the selective precipitation of potassium from bittern as  potassium bitartrate, reacting the potassium bitartrate with calcium carbonate and calcium sulphate to produce precipitate of calcium  tartrate aqueous solution of potassium sulphate, treating the potassium depleted bittern with calcium carbonate to precipitate  calcium tartrate, digesting all the calcium tartrate with sulphuric acid to obtain solution of tartaric acid, recycling the solution of  tartaric acid in potassium extraction reaction, evaporating the solution of potassium sulphate to produce Sulphate of Potash (SOP) fertilizer, reacting the part of the gypsum precipitated in the digestion reaction of calcium tartrate with ammonia and carbon dioxide  generated during calcium tartrate precipitation reactions to produce additional quantity of ammonium sulphate, recycling the calcium  carbonate precipitated during the reaction of gypsum, ammonia and carbon dioxide to calcium tartrate precipitation reactions. Except for the potassium depleted bittern, the process does not generate any effluent.