Leaching Ioy Adsorption Rare Earths By Aluminum Sulfate Solution For Increasing The Efficiency

The efficient green extraction of ion-adsorption rare earths is a very important issue.Ammonium sulfate leaching is the best process at present,but there are still some problems such as low efficiency,large waste water and high risk of landslide in situ leaching.This paper focuses on the relationship between the extraction efficiency and the zeta potential of tailings using high valance of electrolyte solution as leaching reagent,so as to find a new leaching reagent with better leaching efficiency and smaller environmental impact.On this basis,the scientific and reasonable extraction process is determined.Specific development include:The leaching efficiency of ion adsorption rare earths,zeta potential of clay minerals and residual electrolyte in tailings leached by 8 inorganic salt electrolytes with different concentrations were comparatively studied.It is found that there is a linear relationship between leaching efficiency and zeta potential of clay.The slope of the linear relationship is positive for aluminum salts and negative for magnesium and calcium salts,indicating that it is dominated by cations.It is proved that the behavior of aluminum ions in leaching rare earths is significantly different from that of calcium,magnesium and monovalent ions.The highest negative zeta potential of the tailings after leaching refers to sulfate for a particular cation,indicating that the sulfate is more easily adsorbed by the positive charge districts on the surface of the clay.This adsorption facilitates the exchange leaching of rare earths by increasing the number of cations entering the dense layer of the double layer.The results show that the stability of ions in tailings leaching with aluminum salt is higher than that with calcium and magnesium salt,but their zeta potential is negative with the increase of washing times,which is different from that of monovalent ions.Based on the double layer model and hydration theory of clay minerals in water,the contribution and mechanism of anion to leaching efficiency are discussed.The adsorption properties of rare earth,magnesium and aluminum ions on ammonium adsorption clay in sulphate medium were studied.The order of adsorption ability by ammonium adsorption clay for cations is: aluminum > rare earth >magnesium.The adsorption isotherms of aluminum and rare earth are in accordance with Freundlich and Langmuir adsorption equations,respectively,while the adsorption isotherms of magnesium ions at pH 4-5 and 7-9 respectively accord with Freundlich and Langmuir adsorption equations.Based on the results above,a new multi-stage leaching process using aluminum sulfate to improve the leaching efficiency of rare earth and reduce the loss of residual electrolyte in tailings is proposed.The ore was firstly leached with ammonium sulfate,followed by aluminum sulfate,and by water leaching and lime water protection.In the second stage,aluminum sulfate leaching can completely exchange the residual rare earth and ammonia nitrogen in the tailings,which not only improve the rare earth yield,but also eliminates the waste water produced by the residual ammonium loss.The pH of the tailings reaches 6-7,Zeta potential approaches near to zero,and the aluminum ion is stably adsorbed,which can not only reduce the emission of pollutants,but also reduce the landslide risk of tailings.