Research On Preparation Technolody Of Lanthanum Carbonate By Multistage Continuous Precipitation

Rare earth carbon precipitation production line,whose production operation has been in the state of complete manual operation and single tank precipitation production process for a long time,has low output of single tank precipitation and high water consumption,resulting in low labor productivity.Oxalic acid is used as precipitator in rare earth solution.The conditions for the formation of crystalline rare earth carbonate from solid rare earth sulfate and bicarbonate in sulfuric acid solution containing rare earth have been studied.The permissible concentration of sulfuric acid and its relationship with the solubility of rare earth sulfate have been determined for copper sulfate,sulfuric acid ornament,sulfuric acid ornament,mixed copper sulfate ornament and conversion of copper sulfate to carbonate.It is proved that the addition of high solubility rare earth sulfate can break through the concentration limitation of sulfuric acid when low solubility copper sulfate and sulfuric acid ornament react with bicarbonate to form crystalline rare earth carbonate,and obtain high concentration of sulfuric acid as mother liquor,which makes it possible to recover sulfuric acid at low cost.Ammonia water and calcium sulfate residue are obtained by treating sulphuric acid solution with hydrated lime.The clarified liquid can be recycled as the bottom liquid of the solid phase conversion reaction mentioned above,and the residual calcium is only one thousandth of rare earth carbonate.In this paper,lanthanum carbonate was prepared by using ammonium bicarbonate of industrial grade as precipitator and by controlling the concentration of feed solution,sodium carbonate concentration,reaction temperature and reaction time.In the preparation process,with the increase of feed concentration,reaction temperature and reaction time,the effects of cl^-,SO₄^2-,CaO and MgO in lanthanum carbonate solution were studied.The crystallinity and morphology of cerium carbonate were analyzed by XRD and SEM,and the optimum preparation conditions of low chloride cerium carbonate were determined.The concentration of lanthanum chloride solution is 110 g/L.The best feeding method is that the reaction tank is fed at two stages at the same time.The concentration of precipitator ammonium bicarbonate is 280 g/L.The feeding method of ammonium bicarbonate solution is multi-stage and different flow rate.The precipitation reaction temperature is 55?,the reaction is uninterrupted,and the continuous operation of 24hours is realized.Finally,the solid-liquid separation is carried out in the slurry tank.The separation and precipitation time is at least 1.5 h,the first five stages of stirring speed is 80r/min,and the solid-liquid separation tank is 20 r/min.The total precipitated rare earth of lanthanum carbonate is 46.36%and the average particle size is 45.92?m,fully meet the product quality requirements.Through the precise measurement of process parameters such as PH value,feed-liquid flow rate and concentration by the new equipment,the feeding mode of each stage is controlled separately,and each stage is re-adjusted separately,thus ending the long-term operation of manual single tank in rare earth production.Continuity and automation of industrial production can stabilize production line parameters and reduce people.In order to improve the quality of products,reduce the consumption of raw and auxiliary materials and production costs,and improve the core competitiveness of enterprises,it is the only way for modern enterprises to survive and develop.