Study On Removal Of Iron From Rare Earth Chloride Solution By Goethite Method

In the process of separating rare earth concentrates to extract rare earth elements,iron impurities can enter the solution with water washing,acid leaching and other processes,resulting in the product,mixed rare earth chloride solution,containing iron impurities,which harm the subsequent extraction and separation process of rare earths.N eutralization hydrolysis is the main traditional method for iron removal.Although the method has a good effect on iron removal,it has some disadvantages such as difficult to deal with neutralization products and easy to entrap too much rare earth.In this paper,the crystal formation conditions were firstly explored using Fe SO₄ solution and Fe Cl₃ solution as raw materials,and then the goethite iron removal was carried out for rare earth chloride solution.The main research contents and results are as follows:（1）Optimize the preparation process of goethite crystals.The ferrous sulfate solution was used as the initial material and the hydrogen peroxide oxidation method was adopted.When the hydrogen peroxide dosage is 1.2 times the theoretical dosage,almost all ferrous ions are oxidized to ferric iron,and the oxidation rate is above 99.5%.When the reaction temperature is 85°C,the reaction time is 3h,the stirring speed is 300r/min,and the molar ratio of ferric hydroxide colloid to ferric iron is 0.6,the obtainedα-Fe OOH crystal has the best phase.Using the ferric chloride solution as the initial material,the uniform precipitation method can obtain theβ-Fe OOH crystal with a good degree of crystallization when the reaction temperature is 80°C,the reaction time is 2h,and the molar ratio of ferric to urea is 1:4.5.The crystal particles obtained by the hydrogen peroxide oxidation method are not uniform,and the particles are larger and form polygonal blocks;while the crystal particles obtained by the uniform precipitation method are uniform in size,high in crystal ization,and irregular spheres.（2）Experimental study on iron removal by goethite method.In the ferrous oxidation stage in rare earth chloride solution,under the conditions of hydrogen peroxide concentration of 3%,oxidation temperature of 25°C,oxidation time of 30 min,and stirring speed of 250r/min,the oxidation rate of ferrous iron in rare earth chloride solution reaches99.7%.In the iron removal stage of the goethite method,when t he p H value is about 3.5,the reaction temperature is 85°C,the aging time is 120min,the feeding rate is 2.5m L/min,and the goethite seed crystal addition amount is 10%,the average iron removal rate reaches99.60%,the loss rate of rare earth is 3.4%,which is better than the iron removal result of neutralization method.（3）Treating mixed rare earth chloride solution by goethite method can produce iron removal slag with less harmful elements,less slag amount and environment-friendly.The iron in rare earth chloride mainly producesβ-Fe OOH,and the loss of rare earth is mainly Ce,which is absorbed by goethite in the form of bastnaesite and bastnaesite,while Al,Th,Ca and other elements in the solution are absorbed in the form of N ioboeschynite and Allanite.At the same time of iron removal,F element can also be partially removed,and the defluorination amount can reach about 55%under optimal conditions.