Enhanced Leaching-efficient Aluminum Removal Process Of Ionic Type Rare Earth Ore With Magnesium Salt-acetic Acid System

Ionic type rare earth ores have a complete rare earth composition,abundance in medium-and-heavy rare earth elements,and high exploitation value in industries.It is considered a valuable and strategic mineral resource in China.However,no matter magnesium sulfate or ammonium sulfate is used to leach ion-type rare earth ore,there are problems of low rare earth leaching rate and poor leaching selectivity.At the same time,the loss of rare earth in the subsequent leaching process reaches more than 8%,resulting in serious waste of rare earth resources.In this paper,acetic acid was introduced into the leaching and enrichment process of ion-type rare earth ore,and the enhanced leaching technology of ion-type rare earth ore with magnesium salt-acetic acid system and high efficiency aluminum removal was proposed,which could realize the enhanced leaching of ion-phase rare earth and anti-impurity leaching of aluminum ion.At the same time,the loss of rare earth can be effectively reduced in the process of neutralization and removal of aluminum.In this paper,the intensive leaching and anti-impurity leaching of ion-type rare earth ore with magnesium salt-acetic acid system,and the neutralization and removal of aluminum in the leach solution of ion-type rare earth ore were studied,so as to realize the efficient utilization of rare earth resources and the separation of rare earth and aluminum,and provide guidance for the high-quality development of ion-type rare earth ore.The research contents and results are as follows:（1）The species balance calculation of RE/Al-acetic acid solution alone and compound system showed that:In Al₂（SO₄）₃-HAc and Al₂（SO₄）₃-RE₂（SO₄）₃-HAc systems,Al³⁺and acetic acid form Al OH-Ac⁺complexes,which leads to the delay of Al³⁺precipitation p H,and the precipitation rate of Al³⁺decreases at the same p H.In the system of RE₂（SO₄）₃-HAc and Al₂（SO₄）₃-RE₂（SO₄）₃-HAc,RE³⁺and acetic acid form REAc²⁺complex,the content of RE³⁺is more than 20%,resulting in the increase of rare earth hydroxide precipitation p H.Acetic acid-acetate buffer system exists in Al₂（SO₄）₃-RE₂（SO₄）₃-HAc system.（2）The thermodynamics and kinetics of leaching of magnesium salt-acetic acid from ionic rare earth ore were studied.The thermodynamic results show that the addition of acetic acid can promote the leaching of rare earth ore.The kinetics results showed that the leaching kinetics of Mg SO₄ and Mg SO₄-acetic acid were controlled by internal diffusion,and the addition of acetic acid could improve the leaching rate.The results of the study on the leaching behavior of Al show that the acetic acid buffer solution makes the leaching system p H higher,resulting in the hydrolysis of most Al in the complex leaching system,thus inhibiting the leaching of Al.Through factor experiments,under the optimal leaching conditions,the extraction rate of rare earth is98.40%,and the concentration of aluminum ion is 89.17 mg/L.Compared with ammonium sulfate,the extraction rate of rare earth is more than 6%,and the concentration of aluminum ion is 31.02 mg/L.Finally,FT-IR,SEM and EDS tests were conducted on the tailings.The results showed that Al hydrolyzed to form aluminum hydroxide attached to the surface of clay minerals in the tailings of the composite leaching system.（3）The results show that the loss of rare earth includes adsorption and co-precipitation,and adding acetic acid can reduce the adsorption loss of rare earth.Through FT-IR,potential,XPS and other tests,it is found that the reason why acetic acid reduces the loss rate of rare earth may be:Acetate ions exchange ligand with OH-on the surface of aluminum hydroxide,and chemically adsorb on the surface of aluminum hydroxide,which increases the Zeta potential of aluminum hydroxide and leads to the weakening of the electrostatic attraction between the hydroxyl group and La/Y on the surface of aluminum hydroxide,thus inhibiting the adsorption of aluminum hydroxide on La/Y.In addition,the addition of acetic acid can increase the particle size of aluminum hydroxide,reduce the specific surface area,reduce the adsorption site,reduce the adsorption of aluminum hydroxide to rare earth,so as to reduce the loss rate of rare earth.（4）Taking ionic rare earth leaching solution as the research object,Mg O has the best aluminum removal effect in the process of Mg O,Ca O,NH₄HCO₃ and Na OH precipitators.Through the optimization of the process conditions,under the optimal conditions,the removal rate of aluminum reaches 98.47%and the loss rate of rare earth is 2.62%.Compared with the blank precipitation,the loss rate of rare earth is reduced by 5.59%,and the acetic acid in the solution has no effect on the subsequent enrichment process of rare earth.The causes of rare earth loss were analyzed by XRD,FT-IR,SEM-EDS and BET tests.It was found that the formation of inner spherical complex between acetic acid and aluminum hydroxide inhibited the adsorption of aluminum hydroxide to rare earth and reduced the loss of rare earth.