硫酸镁和硫酸铵浸矿对离子吸附型稀土与重金属的释放与影响机理

Release and Influence Mechanism of Magnesium Sulfate and Ammonium Sulfate Leaching on the Ionic Adsorption Rare Earth and Heavy Metals

传统的硫酸铵与新型的硫酸镁是目前离子吸附型稀土矿原位浸矿主要的浸矿剂,除了关注稀土的浸取效率,稀土浸取过程中是否会引起伴生重金属的释出而对地下水环境造成影响是值得关注的问题。为此,以江西龙南稀土矿为研究对象,对比研究硫酸镁和硫酸铵浸矿剂条件下,pH、固液比及浸矿剂浓度对稀土及Pb、Mn、Cd等金属离子释放与变化的影响。结果表明:稀土浸出率和重金属受pH影响较大,其次是固液比和浸矿剂浓度。pH对浸出液中金属释放影响程度从大到小为:Pb>Mn>Cd。根据微观表征,浸出前后稀土矿中的主要矿物相组成未发生明显变化,高岭石、钾长石等矿相表面的Mn、Fe等重金属通过离子交换作用进入浸出液。整体上,硫酸铵较硫酸镁对RE 3+的释放迁移影响更显著,可能加剧重金属离子的释放,造成地下水中重金属的超标。

Traditional ammonium sulfate and new magnesium sulfate are the main leaching agents for in-situ leaching of ion-adsorption rare earth ores.In addition to paying attention to the leaching efficiency of rare earths,whether the leaching process of rare earth will cause the release of associated heavy metals and affect the groundwater environment is worthy of attention.Therefore,taking the Longnan rare earth mine in Jiangxi province as the research object,the effects of pH,solid-liquid ratio and leaching agent concentration on the release and change of rare earth and metal ions such as Pb,Mn and Cd were studied,under the condition of magnesium sulfate and ammonium sulfate as leaching agent.The results showed that the leaching rate of rare earth and heavy metals were greatly affected by pH,followed by the solid-liquid ratio and leaching agent concentration.The effect of pH on the release of metals in the leaching solution was Pb>Mn>Cd.The results of microscopic characterization showed that the phase composition of the main minerals in the rare earth ore did not change significantly before and after leaching,and the heavy metals such as Mn and Fe on the surface of kaolinite and potassium feldspar entered the leaching solution through ion exchange.On the whole,ammonium sulfate had a more significant effect on the release and migration of RE 3+than magnesium sulfate,which may aggravate the release of heavy metal ions in ore and cause excessive heavy metals in groundwater.