Leaching Experimental Study For Ion-adsorption Rare Earth Ore With Magnesium Chloride Compound Leaching Agent

After a long time of extensive mining,ion-adsorption rare earth ore resources of our country were depleted.The extensive usage of ammonium salt resulted to exceed ammonia in the water of the surrounding area and the further leaching loss of nutrient elements?such as calcium and magnesium?of the tailings which crop need.It is not conducive to the repair of environment.Therefore,to reduce the ammonia pollution in the leaching process of ion-adsorption rare earth ore and try to make the nutrient of the leaching tailings meet plant growth become the important consideration.In the Southern China,the existing general lack of magnesium in soil.So magnesium sulfate became the main objects of researchers.However,there are few studies on magnesium chloride and its complex leaching agents in China.In this paper,ion-adsorption rare earth ore in Wuping County of Fujian Province were used as the sample.Firstly,the leaching process of magnesium chloride were studied and the parameters of the process were optimized through column leaching in laboratory,containing the influence of leaching agent concentration,leaching agent flow rate,pH value,the amount of leaching agent,the water content,top water and ore loading height.Secondly,the compound leaching agents were studied,containing the two system of magnesium chloride-ammonium chloride and magnesium chloride-calcium chloride,three system of magnesium chloride-ammonium chloride-calcium chloride.By changing the ratio,the effect of different proportions of leaching agent on the leaching rate of rare earth and calcium and magnesium elements in tailings were explored.The final compound leaching agents were chosen due to the rare earth leaching rate was high and the calcium and magnesium were meet the demand of the soil.In the following,the further exploration was studied the flow patterns and relationships of rare earth ions,magnesium ions,aluminum ion and pH value.The following conclusions were made:?1?The larger the concentration of leaching agent,the slower the flow rate,the lower the pH value,the lower the moisture content,the higher the ore loading height,the rare earth leaching rate is higher.But the buffer will destroy by too low pH value.However,ore loading height is too high,the leaching period would be more long.If the moisture content is much great,the rare earth leaching rate will be significantly reduced.?2?While the ratio of calcium chloride was low,the content of calcium and magnesium could not meet the nutrition demand of soil.Unless the ratio of calcium chloride was the high,the available calcium content would be increased.The ratio of15:25:60 magnesium-ammonium-calcium three element leaching agent,the tailings is consistent with soil nutrient requirements and the rare earth leaching rate is the highest,about 85%,the concentration is about 766mg/L.?3?When the proportion of three element leaching agent is 15:25:60,the leaching rare earth,calcium ion,magnesium ions and aluminum ions outflow are in a certain extent accordance with normal distribution.The collection of post peak fluid should be guaranteed as far as possible.The outflow curve of aluminum ions lagged slightly behind the outflow of rare earth.The lower pH value is favorable to the leaching of rare earth and impurities Al³⁺.In summary,in the ion-adsorption rare earth leaching process of 15:25:60 ratio of magnesium-ammonium-calcium three element composite leaching agent,the rare earth leaching rate can keep high,and the content of available calcium and magnesium in tailings can be regulated,they are conducive to the latter part of the soil restoration.