Study On The Distribution Of Lanthanum And Ammonium In The Electric Double Layer On The Surface Of Ionic Rare Earth Ore Particles

Ion type rare earth resources have attracted much attention due to their unique strategic significance.The research on the occurrence of rare earth ions mostly focuses on the macro level,and studies are carried out from the aspects of metallogenic mechanism,adsorption/desorption characteristics,and occurrence forms.There is little research on the occurrence position of ions from the micro level.Therefore,it is of great significance to study the specific occurrence position of rare earth ions and ammonium ions in rare earth ore for the efficient leaching of ionic rare earth and the treatment of residual ammonium in tailings.In this paper,the leaching process of ionic rare earth was studied based on the double layer theory,and the proportion of ions in the double layer was calculated by using the particle surface charge density model.The adsorption/desorption experiments of lanthanum chloride and ammonium chloride solutions with different initial concentrations on different types of rare earth ores were carried out.Combined with the experimental results and the model calculation results,the conclusions are as follows.(1)The adsorption capacity of the sample for cations was not directly related to the specific surface area,but positively correlated with the surface potential of the sample.This is related to the charged surface of ore particles.The particle surface charge density model was used to calculate the proportion of ions in the interlayer of the double layer of the three rare earth mines,which was 1.61%of Xunwu,1.3%of Anyuan and 1.12%of Xinfeng.The analysis shows that the cation adsorption capacity is proportional to the proportion of ions.The stronger the cation adsorption capacity is,the larger the proportion of ions in the Helmholtz layer outside the electric double layer is.(2)The adsorption capacity of lanthanum ions on kaolin increased in a"ladder"way,but there was no similar phenomenon in the process of lanthanum ions saturated adsorption,and the maximum adsorption capacity was reached when the concentration of lanthanum chloride was 0.4g·L^-1.it was inferred that this phenomenon was caused by the unsaturation of lanthanum ions adsorption on kaolin.The adsorption characteristics of lanthanum ions in the three rare earth ores are different.The order of total adsorption amount is Xunwu>Xinfeng>Anyuan.The adsorption capacity of fixed and ionic lanthanum ions in Xunwu mine is more than that in Anyuan mine and Xinfeng mine,indicating that Xunwu mine has stronger affinity for lanthanum ions,which may be related to rare earth enrichment and mineralization.Comparing the ion proportion with the desorption test results of saturated adsorption raw ore lanthanum,it is found that the calculated value of ion proportion is different from the test results.The water-soluble lanthanum accounts for 1-10%of the total adsorption amount,and the ionic lanthanum accounts for 33-93%of the total adsorption amount.In addition,there is the production of fixed lanthanum in the adsorption process,and the fixed La³⁺will enter and exist in the Stern layer.(3)At the concentration of 30 mmol·L^-1,the adsorption of ammonium on rare earth ore reached the maximum adsorption capacity.The adsorption characteristics of rare earth minerals on ammonium in different regions are different,which shows the difference of ammonium adsorption amount in different forms.This is determined by the metallogenic causes of rare earth minerals,rare earth taste,mineral composition and electrochemical properties.The extraction of rare earth ions mainly depends on ionic ammonium,the ratio is not simple 3:1,but related to the physical and chemical properties of ore samples and the average valence of rare earth.The results of ion proportion show that only 2%of the ions occur in the diffusion layer,which is inconsistent with the results of ammonium desorption test of tailings.The leaching test of tailings showed that the water-soluble ions did not cause significant fluctuation of Zeta potential,and the absolute value of Zeta potential increased.Due to the controversy over the definition position of the sliding surface,the calculation results of ion proportion deviate from the actual desorption resultsThe results show that the water-soluble ions occur in the diffusion layer and the ionic ions occur in the outer Helmholtz layer.