Interaction of polyhalite K2SO4•MgSO4 • 2CaSO4 • 2H2O with sodium chloride solutions

The interaction rate of polyhalite K2SO4 center dot MgSO4 center dot 2CaSO(4) center dot 2H(2)O with sodium chloride solutions and the composition of the resulting solid phases were studied as functions of the temperature, sodium chloride concentration, polyhalite particle size, and solid-to-liquid (S : L) phase ratio. The experiments were carried out at 10, 25, and 40 degrees C; sodium chloride concentrations of 10, 15, and 25 wt %; polyhalite particle sizes of <= 0.1 and 2-3 mm; and polyhalite-to-NaCl solution (S : L) ratios of I : 20 and I : 50. Gypsum CaSO4 center dot 2H(2)O was the solid reaction product under the specified conditions. The maximal reaction rate was observed for the 15 wt % NaCl solution, 40 degrees C, and polyhalite particle sizes of <= 0.1 mm. More than 90% of the polyhalite in 6 h under these conditions decomposed to gypsum. Comparative analysis of our data and related literature revealed the features of the polyhalite reaction with water and aqueous NaCl solutions at various temperatures, S : L ratios, and solution concentrations.