Wettability and spreading behavior of organic extractant and its effect on formation of gas bubble supported organic liquid membrane for large-phase-ratio extraction

Our previous works suggested a novel method by spreading and covering a layer of organic extractant on the surface of gas bubbles to perform gas bubble-supported organic liquid membrane extraction at large aqueous-to-organic phase ratios. However, details about wettability and spreading kinetic behavior of organic extractant within the annular gaps between the internal gas and the external oil needles in the injector was not dear, and so did its effect on formation of gas bubble-supported organic liquid membrane. In present work, spreading of P507 organic extractant on surface of two kinds of typical solid substrates, glass and PVC, with different hydrophilic-hydrophobicity is investigated. It is found that the spreading empirical coefficient k is a simple mathematical function of three crucial operation parameters in the process of gas bubble-supported organic membrane extraction: P507 concentration, saponification degree of P507, and pre-loading amount of rare earths in the organic phase. A feasible mathematical model is suggested for theoretical prediction of the spreading rate. Calculation based on the new model is more convenient than de Gennes's model. The present work provides a scientific foundation for the design of hydrophilic-hydrophobicity of the materials for making the internal gas and the external oil needles in the injector.