Study on the process of two-step digestion and calcination of dolomite for extracting calcium and magnesium
This article uses ammonium chloride solution to directly digest and calcine dolomite powder.By examining factors such as calcination temperature,ammonium chloride concentration,ammonium chloride dosage,reaction temperature,stirring intensity,and time,a two-step method of"extracting calcium first and then magnesium"is adopted to achieve the separate extraction of calcium and magnesium.The experimental results show that the weight loss rate of dolomite reaches its highest when calcined at 950℃ for 90 minutes;In the first step of calcium extraction,the molar ratio of ammonium chloride to dolomite calcium oxide is 2.3∶1,the digestive temperature is 100℃,the ammonium chloride concentration is 0.5M,the time is 1.5 hours,the stirring intensity is 1000r·min-1,the calcium extraction rate reaches over 99.8%,and there are almost no magnesium ions present in the solution;In the second step of magnesium extraction,the molar ratio of ammonia to magnesium is greater than 2.07,the temperature is 100℃,the ammonium chloride concentration is 0.5M,the time is 1 hour,the stirring intensity is 1500r·min-1,and the magnesium element extraction rate is 50.96%.Prepare calcium carbonate and magnesium hydroxide from digested dolomite solution,and characterize and analyze calcium and magnesium products through SEM and XRD.
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