Study On Purification Of A Low-Grade Hydromagnesite Ore In Tibet Area

China has abundant hydromagnesite resources,which has excellent flame retardancy and is widely used in the field of inorganic flame retardancy.It is also one of the important raw materials for the preparation of magnesium oxide and magnesium carbonate.However,there are relatively few studies on the purification and application of hydromagnesite in China,therefore,it is so important to investigate the purification and significant utilization of the hydromagnesite.The reverse flotation was used for purifying a low-grade hydromagnesite from Tibet,Under the conditions of particle size 50.5%-0.074 mm,pulp density 16.67%,slurry p H about 5.5,modifier(sodium hexametaphosphate)dosage 150g/t,collector(LKD)dosage 90g/t,the one stage rougher-two stage cleaning-reverse flotation process was conducted using the feed which contain Ma O of 91.83%,Si O2 of 0.52%,Ca O of 2.70%,Al2O3 of 0.12%,and Fe2O3 of 0.25%,and the results shown that the Ma O grade and recovery were 95.54% and 69.90%,respectively.Infrared spectroscopy analysis showed that after adding collector LKD and modifier sodium hexametaphosphate to the slurry,N-H and P=O stretching vibration absorption peaks appeared,indicating that hydromagnesite interact with LKD and sodium hexametaphosphate in the form of chemisorption,and the addition of sodium hexametaphosphate can promote the adsorption of hydromagnesite and LKD.The prepare high-purity magnesia was used for a low-grade hydromagnesite from Tibet.Through the hydromagnesite roasting,ammonium chloride leaching,ammonia precipitation,and magnesium hydroxide roasting.The grain size of the hydromagnesite is-2mm,the calcination temperature is 900°C,the holding time is 3h;the reaction temperature is 70°C,when the ammonium chloride is leached.reaction time 70 min,ammonium chloride solution concentration 4mol/L,stirring speed 500r/min;ammonia hydromagnesite reaction temperature 45°C,reaction time 60 min,ammonia solution concentration 7mol/L,stirring speed 500r/min;magnesium hydroxide Magnesium oxide products with a Mg O content of 99.88% were finally obtained under the experimental conditions of calcination temperature of 500°C and holding time of 40 min.Analysis of the mechanism for the preparation of high-purity magnesia shows that hydromagnesite basically decomposes at 799.34°C,the characteristic peaks of hydromagnesite Mg-O disappear completely at 900°C,and hydromagnesite completely decomposes.At 600-800?,aragonite gradually decomposes into Ca O,and the characteristic diffraction peak of quartz gradually becomes thinner.When it rises to 900°C,the characteristic diffraction peak of Ca O gradually weakens,and the characteristic diffraction peak of quartz disappears completely.