Extraction And Separation Of Rare Earth From Nitric Acid-decomposing Phosphate Rock System

As a new separation and purification technology,emulsion liquid membrane?ELM?separation technology has several key advantages,such as high efficiency,high selectivity,maximum permeability.This paper mainly presents a comprehensive study on the extraction of rare earth ions(RE³⁺)from phosphate leach solution using emulsion liquid membrane?ELM?in concentrated nitric acid medium.The extraction rate of RE³⁺ was examined under different chemical factors,such as surfactant,stripping phase and carrier that can be evaluated through the extraction rate.The distribution of rare earth element?REE?in phosphate ore was monitored with ICP-MS,the analytical data shows that La,Ce,Y,and Nd constituted 84.92% of the REE in phosphate ore.The ELM was prepared using polyisocrotyl succinimide?T154?as surfactant,di?2-ethylhexly?phosphate?D2EHPA?,MX-1 and MX-2 as carriers,and were diluted with sulfonated kerosene.Research was focused on the concentrations of the surfactant and phosphoric acid,volume ratio of the emulsion phase to the rare earth solution,volume ratio of organic phase to internal phase and carrier types and concentrations.Results demonstrated that in a condition with c?H⁺?= 1.5 mol/L,RE³⁺ concentration of feed solution containing 306 mg/L,the solution with optimum condition contains 12%?V/V?carrier,8% T154,80% sulfonated kerosene as organic phase,85% H₃PO₄ as internal phase,1:1 volume ratio of organic phase to internal phase,1:10 volume ratio of the emulsion phase to the feed solution,stirring speed of 4000 r/min,and stirring time of 20 min.The ELM with MX-1 has a considerably higher extraction efficiency than the ELM with D2 EHPA as carrier.The extraction efficiency of the former reached 82.68%,whereas the latter only reached 60%.MX-1can become a high efficiency,useful carrier to exaction RE³⁺.In summary,ELM with MX-1 was able to extract RE³⁺ from phosphate leach solution with high acidity.When the external phase which containing 300 mg/L rare earth oxide?REO?in the solution,and the the pH were studied in the range of-0.1 1.0.The extraction rate of RE³⁺ was examined under different pH and different factors,such as surfactant,stripping phase and carrier using the same method to extract RE³⁺.The experimental results indicated that the extraction rate of ELM on RE³⁺ was also a corresponding increase with the pH of external phase increased.When pH= 1,the optimum ELM system has been found to contain 12%?V/V?MX-1,8% T154,80% sulfonated kerosene as organic phase,organic-to-internal phase volume ratio of 1:1,the internal phase of 85% H₃PO₄,stirring speed of 4000 r/min,and stirring time of 20 min.During extraction,the emulsion-to-external phase volume ratio is 1:10,and the extraction rate of RE³⁺ from the phosphate leach solution is 87.44%.This research not only use the extraction rate to evaluate the effect of carrier,but using physical methods and combinative methods to demulsificate the emulsion which is the best formular for the external phase c?H⁺?= 1.5 mol/L of phosphate leaching solution,rare earth ions concentration of 306 mg/L.The results showed that the best demulsification method was with centrifugal time of 120 min,at temputure of 90?,the demulsification rate up to 59%.