China Nonferrous Metallurgy

In this work, the green and ammonium-free leaching agents for ion-absorbed rare earth ore in southern China were explored. The effects of leaching agent concentration, liquid-solid ratio and pH value on rare earth leaching by ammonium sulfate, magnesium sulfate and SAK (a complex salt of aluminum and potassium) were investigated, and the leaching effects were compared among these three leaching agents. The results showed that the leaching efficiency of rare earth and impurities including Fe, Si, Al and Ca increased and then became flat with the increase of the leaching agent concentration or liquid-solid ratio, and decreased with the increase of the pH value. Under the leaching conditions (leaching agent concentration of 2%, liquid-solid ratio of 06∶1, pH value of 50 for ammonium sulfate and magnesium sulfate, and pH value of 30 for SAK). The leaching efficiency of impurity Al followed the order of ammonium sulfate ＞ magnesium sulfate ＞ SAK, and the leaching efficiency of Fe, Si, and Ca was in the order of SAK ＞ ammonium sulfate ＞ magnesium sulfate. At the same time, the leaching velocity of ammonium sulfate and SAK were significantly higher than that of magnesium sulfate, the volume of washing water dropped sharply comparing with magnesium sulfate. And SAK was determined as the new kind of leaching agent based on environmental protection and leaching effect. The optimal leaching behavior with SAK can be obtained at the leaching agent concentration of 2%, liquid-solid ratio of 06∶1, as well as pH value of 30, with corresponding leaching efficiency of RE and impurity Al of 9693% and 1378%, respectively.