Enrichment And Separation Of Four Rare Earth Element Ions By Solvent Sublation And High-Speed Countercurrent Chromatography

Rare Earth elements,with their unique electromagnetic and optical properties,are of great strategic significance in the world development of science and technology.The production of rare earth elements is inevitably accompanied by a large number of low concentration rare earth wastewater.At present,China’s rare earth industry produces more than 20 million tons of wastewater every year,rare earth ions content of about 0-500 mg/L.Industrial wastewater enrichment in rare earth ions is also named as secondary rare earth resources.How to effectively enrich and recover these rare earth ions is the key to achieve a rational and effective use of resources.The solvent sublation with many advantages,such as high concentration multiple,large sample size,less solvent needed,wide application range,simple installation,convenient for industrial production and large-scale continuous operation,has showed great advantage in low concentration rare earth solution enrichment.High-speed countercurrent chromatography for its advantages of large loading,good tolerance to samples and simple pretreatment is suitable for separation and purification of rare earth elements.In this paper,the method of enriching low concentration rare earth ions by solvent sublation in low concentration rare earth solution was studied,and the low concentration rare earth solution was enriched and separated by carbon dots assisted high-speed countercurrent chromatography.The main contents are as follows:1.Under the model of“Floatation Complexation Extraction”,a general method of concentrating low concentration rare earth ions by solvent sublation was established.The optimum conditions were determined such as P507concentration 0.15 mol/L,flotation time 10 min,N₂flow rate 30 m L/min,p H=8.Under the optimum conditions,the recovery of single rare earth ion flotation was more than 90%,which is La（Ⅲ）92.33%,Ce（Ⅲ）93.43%,Gd（Ⅲ）93.70%,Er（Ⅲ）96.30%.The results of mixed rare earth ions solvent sublation showed that under suitable condition,the separation of light rare earth ions La（Ⅲ）,Ce（Ⅲ）from heavy rare earth ions Gd（Ⅲ）,Er（Ⅲ）was achieved by controlling p H.At p H=8,the four rare earth ions all showed high recovery.The results of selective experiments showed that,under optimum conditions,solvent sublation could realize the selective separation of rare earth ions La（Ⅲ）,Ce（Ⅲ）,Gd（Ⅲ）,Er（Ⅲ）from gangue ions such as Ca（II）and Mg（II）.2.The high-speed countercurrent chromatography was used to separate La（Ⅲ）,Ce（Ⅲ）,Gd（Ⅲ）and Er（Ⅲ）from low concentration rare earth solution enriched by solvent sublation.Using petroleum ether as diluent,acid phosphorus extractant P507 as organic phase and carbon dots as modifier,four rare earth ions(La（Ⅲ）,Ce（Ⅲ）,Gd（Ⅲ）and Er（Ⅲ）were separated at 0.05mol/L P507（PE）-0.05 mol/L HNO₃-C2 CDs（1:1:0.01,v/v/v）.