Abstract Gas bubble supported organic extractant liquid membrane exhibits a promising potential in enhanced extraction and separation of low-concentration rare earths from the in-situ leaching solutions of ion-adsorption ores. However, instability of organic liquid membrane on the surface of gas bubbles might result in dissolution loss of organic extractant in the flowing-out aqueous raffinates and bring serious organic pollution if the raffinates are recycled for re-leaching of rare-earth ores. The present work focuses on the mechanism of the instability of organic extractant P507 liquid membrane on the surface of bubbles during rare-earth extraction. Various effects, including volume flow rate of aqueous feed solution, initial aqueous pHs and concentrations of co-existing impurity ions, saponification degree of P507 and pre-loaded concentration of rare earths in organic phase, on the stability of organic liquid membrane are discussed. Experimental results reveal that the stability of organic liquid membrane depends on three kinds of forces exerting on the surface of bubbles, i.e., the shear force Fs, the interface tension Ft and the dispersion force Fd. The occurrence of Ft and Fd are benefit for the stability, but Fs is not. The competition of the two component forces of Fs respectively with Ft and Fd will result in instability of organic liquid membrane and an increase in the concentration of total organic phosphorus in the flowing-out raffinates. The present work provides a theoretical basis about how to control the stability of organic extractant liquid membrane on the surface of gas bubble. Based on the suggested new technique by bubble supported organic liquid membrane extraction, a green and environmentally friendly strategy is suggested for replacing the traditional ammonium bicarbonate precipitation to extract low-concentration rare earths from in-situ leaching solutions of ion-adsorption ores.

中文翻译：

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气泡支撑有机液膜在离子吸附矿原位浸出液中提取低浓度稀土的不稳定性行为

摘要 气泡支撑的有机萃取剂液膜在离子吸附矿石原位浸出液中强化萃取分离低浓度稀土方面具有广阔的应用前景。然而，气泡表面有机液膜的不稳定性可能导致流出的含水萃余液中有机萃取剂的溶解损失，如果将萃余液回收用于稀土矿的再浸出，会带来严重的有机污染。目前的工作重点是有机萃取剂P507液膜在稀土萃取过程中气泡表面不稳定的机理。各种影响，包括含水进料溶液的体积流速、初始水溶液 pH 值和共存杂质离子的浓度，讨论了P507的皂化度和稀土在有机相中的预载浓度，对有机液膜稳定性的影响。实验结果表明，有机液膜的稳定性取决于作用在气泡表面的三种力，即剪切力Fs、界面张力Ft和分散力Fd。Ft 和 Fd 的出现有利于稳定性，而 Fs 则不然。Fs 的两个分力分别与 Ft 和 Fd 竞争，将导致有机液膜不稳定，流出液中总有机磷浓度增加。该工作为如何控制有机萃取剂液膜在气泡表面的稳定性提供了理论依据。