The surfactant liquid membrane extraction (SLM) is very promising for environmental uses but its application to industrial effluents is very reduced due to the complexity of the transfer phenomena. A more accurate comprehension of them will lead hopefully to an industrial development of this process. The single drop method has been used to study the transfer of zinc from an hydrochloric solution into a W/O emulsion containing a tertiary amine. The main result is a surprising amount of extraction during the drop formation. Both extraction reactions (during the drop formation and during its rise in the column) have been carefully studied leading to the identification of the limiting steps. During the drop formation zinc transfer is controlled by an interfacial chemical reaction involving two extractant molecules; on the contrary during the drop rise, the extraction regime is mixed, suggesting a diffusion limitation in addition to the chemical reaction. These original results can be used to design new contactors for SLM extraction, better adapted than the classical solvent extraction devices commonly used.
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