Preparation Of Superfine Anhydrous Magnesium Carbonate Powder

Anhydrous magnesium carbonate(MgCO3)is a novel inorganic functional material with wide application prospects.A green process route is successfully explored to prepare superfine MgCO3 powder with industrial grade caustic-burned magnesia powder as raw material.The two-step route combined Rotor-Stator Reactor(RSR)and hydrothermal synthesis method.RSR is introduced to intensify the preparation processes of precursor nesquehonite whiskers(MgCO3�3H2O);NaHCO3 was used as additive in the hydrothermal treatment of MgCO3�3H2O to obtain the final product MgCO3.XRD,SEM,dynamic thermogravimetric analysis(TG),chemical analysis method were introduced to investigate the character of product;the effect of process parameters on product were investigate to obtain the optimal process conditions;the growth mechanism of MgCO3 was preliminarily discussed.High purity Mg(HCO3)2 solution was prepared by hydration,carbonation,purification process.Mg(HCO3)2 solution and air were pumped into RSR to intensify the desorption of CO2,promoting the decomposition of Mg(HCO3)2.The study shows that RSR significantly improved the reaction rate,reduced the crystal size.MgCO3�3H2O product with an average diameter of 1?m and an average length of 10?m was obtained.Optimal operating parameter of RSR:temperature at 20?,time of 1h,Mg(HCO3)2 concentration of 0.3mol/L,RSR rotate speed of 900rpm,material circulation speed of 200L/h,air speed of 2m3/h.MgCO3 was obtained by hydrothermal treatment of as-prepared MgCO3�3H2O;temperature,material concentration,types of additives and the amount of additive were investigate.The study shows that the addition of NaHCO3 significantly improved the reaction speed,reduced the particle size of MgCO3.Optimal hydrothermal condition:temperature at 160?,time of 1h,MgCO3�3H2O concentration of 15%wt,NaHCO3 additive amount of 10%wt.As-prepared MgCO3 is rhombohedra crystal with uniformity crystal structure,smooth surface and clear edge.Laser particle analyzer shows that the average diameter of as-prepared MgCO3 is 1.267?m with a narrow size distribution and good dispersity.TG analysis shows MgCO3 decomposed into MgO and CO2 at 410?550?.The quality of product surpassed national standard GB/T 27814-2011.