Process Control Of Neodymium Chloride Solutions Precipitated By Magnesium Bicarbonate

At present,chemical liquid deposition is one of the most important preparation technologies for rare earth oxides in industry.The key point of this technology is the selection of precipitant,the traditional precipitant such as oxalic acid,ammonium bicarbonate and sodium carbonate.Because of its precipitation process,a large amount of wastewater containing acid,ammonia nitrogen and high salt is produced.It is difficult to recover and cause serious environmental pollution.Therefore,the development of new green environmental rare earth precipitation preparation technology has important practical significance.In the light rare earth carbonate,neodymium carbonate is the most difficult to crystallize.Because of its difficult crystallization and long production cycle in industrial production,it is necessary to study the precipitation of neodymium carbonate.In this paper,the high purity magnesium bicarbonate(Mg(HCO3)2)solution was prepared from MgCl2 wastewater and industrial dolomite produced during the extraction and separation of rare earth,and neodymium oxide products were prepared with Mg(HCO3)2 solution as precipitant.The main research results were as follows:(1)The stability of Mg(HCO3)2 solution at 25 ?-80 ? temperature range was studied.It is found that the decomposition rate of Mg(HCO3)2 or the solid content in the solution increases with time,especially the decomposition rate above 50 ?,and the decomposition rate of Mg(HCO3)2 in 25 ? and 40 ? is 24 hours and 10 hours respectively,then the decomposition rate is basically stable.Mg(HCO3)2 is decomposed 10%in half an hour under 50 ?.The decomposition product is MgCO3 · 3H2O,and its chemical properties are relatively stable.The suitable reaction conditions for precipitation of magnesium bicarbonate were determined to be below 50 ? and below.(2)The process of preparation of neodymium carbonate with Mg(HCO3)2 solutions as precipitant was explored,and the effects of feeding method,[HCO3-]/[Nd3+]ratio,feeding speed,reaction temperature,aging time and other factors were investigated.The results show that when the reaction temperature is 50 ?,[HCO3-]/[Nd3+]ratio is 3.0,the feeding speed of Mg Mg(HCO3)2 is 10mL/min,and when the aging time is 2 hours,the dumbbell type neodymium carbonate precursor can be prepared.The produced neodymium oxide after roasting is in accordance with the industrial application standard of chemical raw materials,where MgO content of is below 0.020%,and the yield is higher than 99.5%.In summary,neodymium oxides with large particle size and uniform distribution was prepared by using Mg(HCO3)2 solution as precipitant.During the production process,no ammonia wastewater is produced.The preparation technology will be broadly applied in the rare earth industry for its green environmental protection.