Neodymium naphthenate-loaded organic phase stripping using sodium oxalate

Abstract

Neodymium naphthenate-loaded organic phase stripping using sodium oxalate solution was studied to explore the feasibility of synchronous rare earth-loaded organic phase stripping, rare earth precipitation, and blank organic phase saponification. Experimental results show that loaded organic phase stripping, rare earth precipitation, and blank organic phase saponification can be realized simultaneously. When using 20% excess of sodium oxalate over the stoichiometry with the volume ratio of organic phase to aqueous phase of 1:1 at 25 °C for 40 min, the single stage stripping rate and saponification value are about 40% and 0.29 mol/L, respectively. After 16 stages of countercurrent continuous stripping, the stripping rate of neodymium can reach 99%, the saponification value is 0.42 mol/L, the Nd3+ concentration in saponified organic phase is less than 0.0020 mol/L, and the main phase in precipitation is Nd2(C2O4)3·10H2O. Afterwards, this saponified organic phase can be used in the extraction of NdCl3 solution, and then the loaded organic phases (neodymium naphthenate) with 0.16 mol/L Nd3+ can be retrieved. The morphology, particle size distribution, and composition of the Nd2(C2O4)3·10H2O products are similar to those of the current direct precipitation products. The neodymium oxide prepared by continuous calcination of neodymium oxalate meets the national standard of China (GB/T 5240−2015). These results prove the feasibility of stripping neodymium naphthenate-loaded organic phase by using sodium oxalate solution. Sodium oxalate can serve as a stripping agent, a saponifier, and a precipitator, thereby simplifying rare earth extraction and separation. This study provides theoretical and technical support for the development of a novel method for rare earth extraction and separation.