Optimization Of The Extraction Process Of Low-grade Ionic Rare Earth By Response Surface Methodology

Because of the long-term export,the rare earth resource reserves have obviously decreased,so it is urgent to increase the utilization rate of the existing rare earth.And the factory cannot establish corresponding mathematical models to guide the actual production.The utilization rate of rare earth is still low due to the problems in extraction process.Therefore,this paper studied the extraction process of rare earth in longnan low grade ionic rare earth,and optimized the extraction process with response surface method.This paper choose the condition of rare earth ions had a greater influence on the leaching rate of factors(p H,concentration of ammonium sulfate,ammonium sulfate leaching velocity)and the reasonable value range by combining rare earth leaching of the processing results of single factor experiment.On the basis of process parameters for the best,using the method of the CCD response surface method to design the experiment,finally determining the weathering crust leaching of ionic type rare earths best process parameters.The experimental results showed that the concentration of ammonium sulfate was the most important for the leaching process,followed by the leaching volecity and the solution p H.The relative error between the predicted leaching rate and the actual value of the rare earth predicted by the response surface method is less than 5%,which indicates that the leaching model(R2=0.9464)is suitable and effective.The results of XRD,XPS and FT-IR detection of the ore and the post-leaching tailings show that the concentration of ammonium sulfate can enhance the ion exchange rate,and the leaching process does not change the internal crystal structure.The experimental results and the process parameters optimized by the response surface method is proved for the best,the realization of the aim of the rare earth leaching process is optimized,which has a certain guiding significance to this kind of ionic rare earth leaching process.In order to reduce the impurity ion content in leaching liquor,the removal process was optimized.The results showed that the best effect was ammonia,followed by ammonium bicarbonate,and sodium sulfide was the least effective.The experimental results show that except the solution p H value has great influence on the removal of the mixed results.Under the condition of optimal removal of hybrid process parameters,the loss rate of rare earth was 5.81%,and the removal rate of aluminum was 96.72%,which was notable for the removal of aluminum.Optimization experiments were conducted by combining the single factor experiment of rare earth precipitation crystallization.The optimization experiment chooses the factors that influence the rare earth precipitation crystallization(REE concentration,aging time,crystal dosage)and reasonable value range.The experiment was designed by response surface method(CCD).The optimal precipitation crystallization parameters of rare earth were determined,and the maximum influence of the three factors on the precipitation crystallization was the concentration of liquor,the second was the amount of the crystal,and the least influence was the aging time.The relative error between the grain size and the actual value predicted by the response surface method is less than 8%,which indicates that the model(R2=0.894)is suitable and effective.Precipitation product of scanning electron microscope,XRD,FT-IR detection results show that rare earth to obtained are rare earth carbonate,it also verifies the best technological parameters obtained by the response surface method are optimum,grain size and large crystal shape is quite good.The realization of the aim of the rare earth precipitation crystallization process was optimized,the test results proved that the optimization experiment have certain guiding significance on the crystallization process of rare earth.