Investigation of the reaction of roasted serpentine ore with some ammonium salts

The reaction between roasted serpentine ore and ammonium sulfate was studied at the range of temperature 250-1000 degrees C using different molar ratios to determine the maximum extraction of magnesia and also to characterize the different reaction products. The maximum extraction of MgO from the roasted ore reached 92.4% at 400 degrees C. It was found from XRD that ammonium magnesium sulfate [(NH4)(2)Mg-2(SO4)(3)] was produced as the main product at 400 degrees C, which decomposes to magnesium sulfate at 500-600 degrees C. The last compound decomposes to magnesium oxide at 900-1000 degrees C. Thermal analysis of the reaction mixture confirmed the results obtained by XRD. Extraction of magnesia by ammonium chloride at 300-400 degrees C showed low percentage of extraction (7.8%). Comparison was made between using ammonium chloride instead of sulfate taking into consideration the thermal decomposition products of both ammonium salts. Extraction of magnesia from the roasted ore by aqueous ammonium sulfate or ammonium chloride showed good results.