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.
- potassium nitrate
- magnesium nitrate