Study On The Mechanism Of Impurity Suppression And Leaching Of Ionic Rare Earth Ore Based On PH Influence

As we all know,ionic rare earth mineral resources are non-renewable resources.At present,chemical leaching method is used for mining.During the mining process,pH value is one of the important factors affecting the leaching rate.When the pH value is too high,the rare earth leaching rate is low,which affects the product recovery rate and causes waste of resources.If the pH value is too low,the impurity content in the leaching solution is high,which affects the product quality and increases the production cost.At the same time,the ore body itself has acidbase buffering properties,and the pH value of the leaching agent solution is easily affected during the leaching process.Therefore,in order to improve the utilization rate of rare earth resources,the actual mining situation of ionic rare earth mines was investigated,and the influence of pH value on the adsorption and desorption of rare earth and impurity elements on clay minerals was studied.Based on this,the leaching agent solution was improved,the pH control technology of leaching was developed,and the optimum pH conditions for impurity suppression and leaching in the leaching process were studied.In this study,the rare earth content before and after leaching of an ionic rare earth ore was investigated.Through the adsorption and desorption experiments of lanthanum and aluminum on kaolin,the desorption mechanism of rare earth and impurity elements on clay minerals was studied.Finally,based on the principle of conjugated acid-base pairs,the leaching agent solution was improved to study the mechanism of pH inhibition and leaching of ionic rare earth ore.The results show that:(1)The rare earth grade of water-soluble phase,ionic phase and colloidal phase in an ionic rare earth ore and tailings in Fujian was measured by step-by-step desorption,so as to obtain the leaching and residual rules of three kinds of adsorbed phase rare earth under empirical injection:1)ionic phase rare earth leaching rate ηI(71.23%-93.64%)>total rare earth leaching rate ηT(68.44%-92.64%)>colloidal phase rare earth leaching rate ηC(33.23%82.31%)>water-soluble phase rare earth leaching rate ηW(-212.19%-31.32%);2)The total residual amount of rare earth in tailings increased with the increase of depth,and the residual effect of colloidal rare earth kc(2.70-5.84)was greater than that of ionic rare earth kI(0.81-0.88).3)The residual amount of rare earth in colloidal phase is positively correlated with the pH value of ore body in tailings,and the pH value increases significantly with the increase of pH value after 5.1.This shows that the exploitable space of gelatin phase rare earth is worthy of further study,and pH value is one of the influencing factors.(2)When the concentration of lanthanum ion CLa is higher than 2.5 mmol/L,the adsorption of ionic phase lanthanum on kaolin is saturated,up to 5.381 umol/g,and the colloidal phase lanthanum begins to adsorb on kaolin.With the increase of colloidal aluminum ion solution cA1,the adsorption capacity of colloidal aluminum increases linearly,and with the increase of pH value to 5.5,the slope of the linear fitting equation approaches 3.Based on the adsorption law of colloidal lanthanum and aluminum on kaolin,pH=4.5 is the best acid-base condition to meet the precipitation of impurity aluminum in ore body and inhibit the hydrolysis of rare earth lanthanum.(3)As a leaching agent,acetic acid-ammonium acetate buffer solution can reduce the influence of soil acid-base buffering performance on the pH of leaching agent.The linear fitting slope of pH value before and after leaching is k=0.998.With the increase of pH value from 4.1 to 4.9,the leaching rate of rare earth and aluminum ions can be improved,and the maximum values are 96.60%and 94.44%respectively.The leaching effect is determined by the ratio of rare earth to aluminum leaching amount of equal quality raw ore.When the pH value is 4.5～4.6,the N value is the largest(up to 64.07～64.54),the rare earth leaching rate is 89.73%～92.51%,and the aluminum leaching rate is 72.22%～75.00%.Compared with 2%ammonium sulfate(pH=4.5 and 5),the leaching rate of rare earth is slightly lower by 0.54%～1.61%,but the leaching rate of impurity aluminum is greatly reduced by 16.67%～19.45%.This indicates that the acetic acid-ammonium acetate buffer solution can play a pH control role,and the solution pH value between 4.5～4.6 is the best.