A New Type Of Leaching Agent Selected And Leaching Process Research Of Ion-absorbed Rare Earth Deposits

The in-situ leaching process which uses ammonium sulfate as leaching agent has beingwidely used to extract the rare earth of ion-absorbed rare earth deposits in industry at present, andthe rare earth resource recovery rate is over70%. This process neither reduces the destruction ofvegetation, nor leads to the accumulation of tailings, but produces a lot of ammonia nitrogenwastewater which pollute the environment. To solve these problems, this paper carries out theselection study of new non-ammonia nitrogen leaching agent and rare earth precipitant, andsimulates the in-situ leaching process through the column leaching process.Magnesium sulfate is selected as a new type of leaching agent by the selection experiment,and it is concluded by small-scale column leaching experiments that the optimal conditions ofcolumn leaching process are that column leaching temperature is25℃(room temperature), pHvalue is5.0(the pH value of Magnesium sulfate solution), magnesium sulfate dosage is1:1thevolume mass ratio of liquid to solid, water dosage is1:1the volume mass ratio of liquid to solidand the mass fraction of magnesium sulfate is2%. For rare earth ore of Guangdong (A#) and rareearth ore of Jiangxi xunwu (B#), the leaching effect of rare earth is very good and the leachingrates of them reach99.70%and99.46%respectively under the optimal condition of the process.Through the study of leaching process, it is found that rare earth ions in mother liquor arere-adsorbed by circular column leaching method and44.79%of them are re-adsorbed after theprimary circulation.Three equilibriums of water、rare earth ions、leaching agent and the behavior of impuritiesare studied in column leaching process. The results show that the water absorption of perkilogram rare earth ore is about333mL, the rare earth leaching rate is99.80%and increasesabout17%than that82.50%of traditional ammonium sulfate process, the balance rate of rareearth is99.95%, the balance rate of magnesium is98.76%, compared with the leaching agent,magnesium ions of leach liquor increase about4.7%and are barely consumed, the balance rateof sulfate ions is102.66%and the leaching rates of aluminum、iron、silicon impurities are lowerand are respectively0.0154%、0.03%、0.117%.It is found that by optimizing the leaching process when the rare earth concentration ofleachate reached the peak in the column leaching process, the rare earth ions of adsorption on theclay mineral are largely exchanged, at this time directly injecting the top water to wash the rareearth ions into the leaching liquid and not need to continue to inject magnesium sulfate leachingagent, compared with the original process, magnesium sulfate is less injected into54%, but the leaching rate still reachs99.05%and is basically consistent with the original process.It is concluded by the magnesium hydroxide precipitation experiment that the optimalconditions are that the precipitation temperature is25℃(room temperature), the stirring rate is200rpm, the percentage content of magnesium hydroxide theoretical value is140%and thesettling time is4h. Under the optimal conditionof the process, the average precipitation rate ofrare earth stabilizes at98.61%, the average precipitation rates of iron and aluminum both are0.4%and the content of rare earth oxide is83.5%of the sediment.