The Research On Metastable Properties Of Rare Earth In Sodium Carbonate Solution

When rare earth is precipitated from ionic rare earth leaching solution with carbonate,the dissolution of rare earth occurs in carbonate solution.In order to study the dissolution of rare earth in carbonate solution,the solution of rare earth chloride was added to sodium carbonate solution to explore the dissolution behavior,stability and occurrence form of rare earth in sodium carbonate solution.In order to investigate the dissolution behavior of rare earth in sodium carbonate solution,the solution of rare earth chloride was added to sodium carbonate solution for dissolution experiment.It was found that the dissolution amount of rare earth increased first and then decreased with the increase of rare earth feeding amount,which resulted in a certain saturated feeding amount of rare earth in sodium carbonate solution,such as the maximum of 10 g/L praseodymium chloride solution in 25 mL 2 mol/L sodium carbonate solution.The instantaneous solubility is 0.0168 mol/L;Under the same experimental conditions,when the concentration of sodium carbonate solution is reduced to 1.0 and 1.5 mol/L,the maximum instantaneous solubility is reduced to0.0053 and 0.0101 mol/L,respectively.If the concentration of praseodymium chloride solution is changed,it is found that the solubility of rare earth increases first and then decreases.When the concentration of praseodymium chloride solution is 18 g/L,the maximum solubility is 0.022 mol/L.8 mol/L.Under the same experimental conditions,the solubility of rare earth elements increases with the increase of atomic number of rare earth elements.The saturated solubilities of Ce,Pr,Gd,Dy,Ho and Yb are 0.0125,0.0168,0.0240,0.0318,0.0350 and 0.0410 mol/L,respectively.On the basis of dissolution experiment,the stability of Rare Earth-Sodium carbonate solution was studied.It was found that the solution of Rare Earth-Sodium carbonate under saturated feeding condition was extremely unstable,and precipitated rare earth in a short time.At the same time,the solubility of rare earth showed a rapid downward trend.In contrast,the solution of rare Earth-Sodium carbonate under unsaturated feeding condition had metastable properties,which could be in metastable period.The stability of rare earth in sodium carbonate solution of 2 mol/L is better than that in sodium carbonate solution of 1.0 and 1.5 mol/L.In order to explore the occurrence forms of rare earth ions in rare Earth-Sodium carbonate solution,the molecular dynamics calculation of rare Earth-Sodium carbonate solution was carried out by using Material Studio software on the basis of previous experiments.The results show that rare earth ions in solution can coordinate with CO_#^$%and form RECO₃⁺,RE?CO₃?₂^-plasma complexes.From this point of view,it is explained that rare earth ions can be dissolved in the solution.At the same time,the calculation results show that the coordination number of rare earth ions with CO_#^$%in unsaturated rare Earth-Sodium carbonate solution is higher than that in saturated feeding condition,which corresponds to the results of stability experiment.Finally,the complexation morphology of other rare earth elements in sodium carbonate solution was studied.It was found that the main form of light rare earth element Pr was RECO₃⁺,and the main form of heavy rare earth element Yb was RE?CO₃?₂^-.