A Calculation Method Of Leaching Agent Dosage In Ion-adsorption Type Rare Earth Based On DED Model

Ion-adsorbed rare earth minerals rich in medium and heavy rare earth are important strategic resources in China.However,the amount of leaching agent is the main factor affecting the leaching effect of ion adsorption rare earth.Too little amount of leaching agent will lead to low leaching efficiency of rare earth and loss of resources.If the amount of leaching agent is too much,it will cause a large amount of residual of leaching agent,mainly ammonium sulfate,which will cause a serious burden on the ecological environment.Therefore,it is of great significance to accurately calculate the amount of leaching agent to realize green and efficient mining of ion-adsorbed rare earth.According to the form of ammonium ions in clay minerals,the adsorption of ammonium ions on ore can be divided into two parts: reversible adsorption and irreversible adsorption.According to the analysis of leaching mechanism,the consumption of ammonium ion in leaching can be divided into three parts: ion exchange consumption,obligate adsorption consumption and the consumption of maintaining the concentration of leaching agent.The reversible adsorption part of dualequilibrium desorption(DED)model was improved by Kerr model.The physicochemical process of leaching was described by the DED model and the improved DED model respectively.On this basis,two calculation methods of leaching agent dosage were proposed.Finally,the accuracy,advantages and disadvantages of the two methods are evaluated through the column leaching test of double-ion ore and raw ore.Combined with the occurrence form of ammonium ions and leaching mechanism,the physical and chemical process of leaching was directly described by DED model.The isothermal adsorption lines of ammonium ions were obtained through adsorption/desorption experiments of ammonium sulfate with different concentrations in two kinds of raw ores.The corresponding parameters in the model were determined by isothermal adsorption lines and numerical fitting.Considering the influence of main impurity aluminum ion in leaching,the calculation method of leaching agent dosage is obtained.In order to reflect the difference of leaching of rare earth and aluminum ions by ammonium ions in the leaching process,Kerr model was used to improve the reversible adsorption part of DED model.Through isothermal adsorption experiments of ammonium ions on two kinds of single-ion ores of rare earth and aluminum,the chemical equilibrium constants of ammonium ion exchange rare earth and aluminum ions are obtained respectively,where KRE = 140.0×10-9(L /g)2,KAl = 15.9×10-9(L /g)2.It is proved that the ability of ammonium ion to exchange rare earth is stronger than that of aluminum for the test ore,and the calculation method of leaching agent dosage under the improved DED model can more accurately calculate the consumption of aluminum ion to leaching agent.In view of the proposed two calculation methods,the column leaching experiments of lanthanum-aluminum double-ion ore and raw ore were carried out to evaluate the calculation methods.Evaluate accuracy of two methods.The target leaching rates of rare earth are set at85.0%,90.0% and 95.0%.For the double-ion ore,the calculation method under the improved DED model is used to determine the dosage of leaching.The relative error between the actual leaching rate of rare earth and the target leaching rate is less than 2.5%,and the method has good accuracy for the double-ion ore.For raw ore,the calculation method under DED model is used to determine the dosage of leaching.The relative error between actual and target leaching rate of rare earth is less than 1.5%,and the method has good accuracy for raw ore.Evaluate the advantages and disadvantages of two methods.The unit consumption of the actual leaching rate of rare earth was used to determine the calculated dosage,and the relative absolute error between calculated dosage and actual dosage was used to evaluate the advantages and disadvantages of two methods.For the double-ion ore,the error of the calculation method under the improved DED model is less than 13.0%.For raw ore,the error of the calculation method under DED model is less than 21.0%.The modified DED model can better reflect the leaching difference,and it is expected that when the influence of cations other than aluminum ions is considered in the model,the leaching agent dosage can be more accurately calculated.