Preparation of potassium nitrate from potassium chloride and magnesium nitrate in a laboratory scale using industrial raw materials

Preparation of potassium nitrate from magnesium nitrate and potassium chloride was investigated. Prepared potassium nitrate contains less than 0.5 % chlorides and it can be applied as environmentally friendly fertilizer in hydroponic systems. After filtration out potassium nitrate crystals from the reciprocal system K⁺, Mg²⁺//Cl^-, NO₃^- - H₂O, the mother liquor still contains reasonable amount of potassium cations. By evaporation of the mother liquor, carnallite (MgCl₂・KCl・6H₂O) with admixture of MgCl₂・6H₂O 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.