Study On Calculation Method Of Rare Earth Ion' Breakthrough Curve In The Column Leaching Process

The geotechnical problems in the mining environment have attracted more and more attention from the national society.The mining of ionic rare earth ores has problems such as excessive use of ammonium sulfate and serious ammonia and nitrogen pollution.The in-situ leaching process of ionic rare earth is the process of sulfate ammonium ion exchange rare earth ion and sulfate ammonium ion and rare earth ion migration in ore body.Therefore,it is necessary to study the ion exchange and migration law during leaching to reduce the impact of rare earth mining on the surrounding environment.Based on the results of small-scale column leaching experiment,this paper presents a method for calculating the breakthrough curve of small-scale column leaching process.On this basis,based on theoretical plate and CDE equation,the breakthrough curve of large-scale column leaching process are calculated,and compared with those of indoor large-scale column leaching experiment,the optimum model describing the breakthrough curve of large-scale column leaching process is determined.The results show that:?1?The small-scale column leaching experiment with column heights of 2.5 cm?5.0 cm?7.5 cm?10.0 cm was carried out.Based on the experimental data,the empirical model:?=exp?a-b/t²?was used to describe the relationship between leaching percentage and time.Considering the soil column as a unit body,the calculation method of the parameter a is established by the idea of continuous cup leaching.The relationship between parameter b and soil parameters is established by dimensional analysis method.At the same time,considering the leaching percentage and the leaching period,the established model is used to optimize the concentration of the injection.The results show that the relationship between the rare earth grade and the optimal ammonium sulfate concentration is:C_op=7.36?+0.2.?2?The large-scale column leaching experiment with a column height of 50.0cm was carried out,and the soil column was regarded as a lot of unit bodies.Based on the theoretical plate,the equation for the concentration of rare earth ions under the same pipe diameter is established,and distribution range of pipe diameter was determined according to Q-t curve.The breakthrough curves of rare earth ions in column leaching process were obtained by combining the curves of the concentration of rare earth ions with the number of pipe diameter.Compared with the experimental results,the correlation coefficients of two groups of experiment were 0.964 and 0.957,respectively.?3?According to the seepage velocity of column leaching process and the breakthrough curve of non-reactive solute obtained from column leaching experiment,the hydrodynamic dispersion coefficient in CDE equation was calculated by least square method.Based on ion exchange model,t the convection dispersion equation considering the sources and exports is established to describe the penetration curve in column leaching process.The calculated results were compared with two groups of experimental data.The correlation coefficients were 0.847 and 0.876,respectively.?4?Compared with the CDE equation,the parameters contained in theoretical plate are easier to obtain,and the correlation coefficient between the calculated results of theoretical plate and those obtained from column leaching experiment is higher.Therefore,theoretical plate is adopted to describe the breakthrough curve of large-scale column leaching process.