Synergistic Leaching Of Ion Adsorption Rare Earth By Aluminum Salts And Low Valence Of Inorganic Salts

In the mining of ion adsorption rare earth,there are many problems in the current process,such as ammonia nitrogen pollution,water and soil loss,etc.It is urgent to develop a green and efficient leaching method.The selection of leaching agent is particularly critical.In this study,aluminum salt was selected as the main leaching agent and combined with other reagents to construct a new type of composite leaching agent to improve the efficiency of rare earth leaching and reduce reagent consumption.Therefore,a continuous titration leaching method that can determine the leaching characteristics of ion adsorption type rare earth and optimize the leaching conditions was adopted.This method can be used to evaluate various leaching reagents and the leaching capacity of their different concentrations on rare earth ores,as well as the stability and environmental impact of tailings,and to optimize the leaching conditions.The effects of the leaching agent concentration on the leaching efficiency,Zeta potential of clay mineral particles,suspension p H,and electrical conductivity of ionic adsorption type rare earths from mixed solutions of aluminum salt and several low valent inorganic salts with different concentration ratios were emphatically studied.The synergistic leaching effect of aluminum salt and several low valent non-ammonium inorganic salts such as magnesium salt,sodium salt,potassium salt and calcium salt on the ion adsorption type rare earth leaching are found and determined for the first time.The maximum synergistic leaching coefficient occurs when the ratio of the normal concentration of cations to Al³⁺:Mⁿ⁺(low valent cations,Mⁿ⁺=Na⁺,K⁺,Ca²⁺,Mg²⁺)is 1:2.The rare earth leaching efficiency,Zeta potential and p H in this situation are between the values of the two pure salt solutions,and it is closer to the value during aluminum salt leaching.The synergistic leaching effect can be attributed to the fact that the addition of the low valent inorganic salts can increase the negative Zeta potential during aluminum salt leaching and strengthen the leaching kinetics.The addition of a small amount of aluminum salt can not only exert the thermodynamic strong leaching effect of aluminum ion on rare earth ions,but also make the equilibrium p H of the low valent inorganic salts leaching close to the peak value of 4.Because the leaching efficiency of rare earth depends on the ionic potential of cations,the dispersion of mineral particles（related to the surface Zeta potential）and the appropriate p H range（generally with a maximum peak between 3-4）.Based on this,a new method of co-leaching ion adsorption rare earth by aluminum salt and low valent inorganic salts is proposed.The results of elution on the column also prove that under the condition of the same total normal concentration of cations,the mixed leaching agents could make the rare earth outflow peak move forward and higher.To achieve the same rare earth leaching efficiency,the new method can lower the electrolyte concentration,enhance the stability of tailings,improve the leaching effect and shorten the leaching time more than the single low valent inorganic salt leaching.This new method can also reduce the cost of subsequent enrichment and recovery,realize the recycling of mine aluminum,and solve the problem of ammonia nitrogen pollution.