Characteristic Parameters Of Equilibrium Leaching Ion Adsorption Rare Earth By Electrolyte Solutions And Process Optimization

Ion adsorption rare earth(IARE)is a strategic resource.However,the commonly used ammonium sulfate in-situ leaching process is gradually restricted due to its environmental problems.It is urgent to develop new leaching reagent and process to solve the problems of low leaching rate of IARE and high risk of soil erosion and landslide.In this paper,a continuous titration leaching(CTL)method was used to measure characteristic parameters such as Zeta potential of clay minerals,rare earth leaching concentration,p H value and conductivity in equilibrium leaching solution of IARE by various electrolytes.The changes of characteristic parameters and the optimization of column leaching process of IARE by leaching with sodium citrate + inorganic salt solution and aluminum salt + low valent inorganic salt solution were studied systematically.Firstly,the dependence of characteristic parameters such as Zeta potential,leaching efficiency(LE)of IARE,p H value and electrical conductivity on the concentration of leaching agent when leaching IARE with organic acid and inorganic salt and the following washing process of tailings was studied.The results showed that the LE of IARE by three organic acids was in the order of sodium citrate >sodium tartrate > sodium acetate,and can reach more than 90% by using only a small amount of sodium citrate.At the same time,it is found that the seepage rate of sodium citrate solution in the ore layer decreases with the leaching process,and it is difficult to extract the solution.Therefore,the characteristic parameters of CTL with sodium citrate in inorganic salt solution and with sodium citrate as lead reagent were compared respectively.The leaching effect is good when sodium citrate is added to the leaching agent,but the concentration of inorganic salts is high.The general trend of Zeta potential is that the clay is more charged,the suspension becomes better,and the risk of soil erosion and landslide increases.In the process of sodium citrate +calcium chloride leaching,the rare earth leaching efficiency reached more than 95%at low concentration of calcium chloride solution.Inorganic salt was used to restore the Zeta potential and p H of clay minerals to reduce the risk of soil erosion and landslide.Therefore,the conditions of continuous drip leaching ion adsorption of rare earth with sodium citrate and 15 inorganic salts were optimized,and the stability of tailings was evaluated.The results showed that when sodium citrate was used as the lead,the rare earth leaching efficiency of other inorganic salts except zinc salt and iron salt could reach about 95%,and the absolute value of Zeta potential of tailings were all low,which was beneficial to the stability of tailings.Moreover,the p H value of tailings leached by mono-valent and bivalent inorganic salts was close to neutral,and no subsequent adjustment of p H value was needed.The tailings after leaching of trivalent salt are acidic and need to be neutralized with lime water.The column leaching experiment verified the results of Zeta potential continuous titration experiment.During the column leaching,sodium citrate could effectively leach rare earth in advance,and the leaching was completed at the liquid solid ratio of 0.2-0.3:1.Adding calcium chloride to adjust the Zeta potential of the ore soil,the seepage rate was accelerated,and the p H value of the leaching solution was stable above 6.5,so there was no need to carry out tailings protection work.Secondly,in order to ensure the leaching rate of rare earth and reduce the consumption of leaching reagent,the leaching performance of aluminum salt and low valent inorganic salt solution on ion-adsorbed rare earth was systematically studied,and the synergistic effect of aluminum salt and low valent inorganic salt was verified.The optimum leaching conditions for ion-adsorbed rare-earth ore samples were determined by the column leaching experiment,and the optimum leaching conditions for magnesium salt and aluminum salt were 8:2.The concentration of0.24 N was used.The feasibility of the synergic enhancement leaching method was verified through the column leaching method of the production mode.It was proved that the synergic enhancement leaching method of aluminum salt and low valentinorganic salt could reduce the concentration of aluminum ions in the leaching solution and the absolute value of Zeta potential of tailings,increase the p H,enhance the stability of tailings,and significantly reduce the concentration of leaching agent and the amount of pollutants as well as the subsequent enrichment and separation pressure.Reduce the difficulty of follow-up tailings treatment.