Processing of "secondary products" from the production of KNO3

Potassium nitrate can be prepared by the reaction of KCl and Mg(NO3)(2). Cooling of the solution containing K+, Mg2+, Cl and NO3- ions results in KNO3 crystallization. After filtration out of potassium nitrate crystals from the system, the mother liquor still contains reasonable amount of potassium cations. By evaporation of the mother liquor, carnallite (MgCl2.KCl.6H(2)O) with admixture of MgCl2.6H(2)O crystallizes out. Decomposition of carnallite with cold water makes it possible to separate potassium chloride from this compound. When this KCl is returned back to the process of KNO3 making, utilization of potassium as high as 97 % can be achieved.