Extraction of neodymium by ,-dibutylacetamide (DBAc) has been investigated using a single hollow porous fiber pertraction device. It consists of a polypropylene hydrophobic fibre maintained in a cylindrical glass calender. The Nd loaded aqueous phase flows inside the porous fiber. The organic phase flows outside in the calender and fills the pores of the membrane. Neodymium is extracted by DBAc, transported through the membrane by molecular diffusion and collected in the solvent flow. DBAc was chosen taking into account its efficiency with regard to the extraction of rare earths, estimated initially by liquid–liquid extraction, and because of its low variation of viscosity with metal concentration. Accurate measurements of diffusion coefficient of neodymium in the solvent by Taylor Dispersion Analysis (TDA) confirmed the low influence of the neodymium concentration on its diffusivity. These results, combined with the determination of the distribution coefficient of Nd in DBAc, gave good agreement between experimental and simulated data of pertraction test. Nevertheless, the results showed a high resistance of mass transfer mainly due to the diffusion in membrane. A possible explanation was that the distribution coefficient of Nd was not high enough to ensure a sufficient gradient of concentration along the thickness of the membrane filled by the solvent. To prove it, a second pertraction experiment was performed using HDEHP at 1 mol L in n-dodecane as extractant. In this case, the distribution coefficient of Nd is 3 times higher than for DBAc. Good fitting of experimental data with simulated extraction of neodymium has been obtained and confirm the aforementioned hypothesis which assumes that high mass transfer rate requires high distribution and diffusion coefficients.

中文翻译：

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使用中空纤维穿孔装置提取稀土时的传质效率


使用单个中空多孔纤维牵引装置研究了通过 ,-二丁基乙酰胺 (DBAc) 提取钕。它由保持在圆柱形玻璃压延机中的聚丙烯疏水纤维组成。负载 Nd 的水相在多孔纤维内部流动。有机相在压延机中流出并填充膜的孔隙。钕被 DBAc 萃取，通过分子扩散穿过膜并收集在溶剂流中。选择 DBAc 是考虑到其在稀土萃取方面的效率（最初通过液-液萃取估计），并且由于其粘度随金属浓度变化较小。通过泰勒色散分析（TDA）精确测量了溶剂中钕的扩散系数，证实了钕浓度对其扩散率的影响很小。这些结果与 DBAc 中 Nd 分配系数的测定相结合，表明拉伸试验的实验数据与模拟数据非常吻合。然而，结果表明传质的高阻力主要是由于膜中的扩散造成的。一种可能的解释是，Nd 的分配系数不够高，无法确保沿溶剂填充的膜厚度有足够的浓度梯度。为了证明这一点，使用 1 mol·L HDEHP 在正十二烷中作为萃取剂进行了第二次萃取实验。在这种情况下，Nd 的分配系数比 DBAc 高 3 倍。实验数据与模拟的钕萃取得到了良好的拟合，并证实了上述假设，即假设高传质速率需要高分布和扩散系数。