Supported liquid membranes technologies in metals removal from liquid effluents

Abstract

The generation of liquid effluents containing organic and inorganic residues from industries present a potential hazardousness for environment and human health, being mandatory the elimination of these pollutants from the respective solutions containing them. In order to achieve this goal, several techniques are being used and among them, supported liquid membranes technologies are showing their potential for their application in the removal of metals contained in liquid effluents. Supported liquid membranes are a combination between conventional polymeric membranes and solvent extraction. Several configurations are used: flat-sheet supported liquid membranes, spiral wounds and hollow fiber modules. In order to improve their effectiveness, smart operations have been developed: non-dispersive solvent extraction, non-dispersive solvent extraction with strip phase dispersion and hollow fiber renewal liquid membrane. This paper overviewed some of these supported liquid membranes technologies and their applications to the treatment of metal-bearing liquid effluents. KeywordsSupported liquid membranes; Metals; Extractants; Ionic liquids; liquid effluents; Environment. Tecnologías de membranas líquidas soportadas en la eliminación de metales de efluentes líquidos ResumenLa generación, por parte de las industrias, de efluentes líquidos conteniendo sustancias orgánicas e inorgánicas, es un peligro potencial tanto para los humanos como para el medio ambiente, siendo necesaria la eliminación de estos elementos tóxicos de las disoluciones que los contienen. Para conseguir este fin, se están aplicando diversas técni-cas y entre ellas las tecnologías de membranas líquidas soportadas, están demostrando sus aptitudes para la eliminación de metales contenidos en efluentes líquidos. Las membranas líquidas soportadas, resultan de la unión de las membranas poliméricas y de la tecnología de extracción líquido-líquido. Este tipo de membranas se pueden utilizar en diversas configuraciones: plana, módulo en fibra hueca y módulo en espiral y para aumentar su efectividad se están desarrollando las llamadas operaciones avanzadas: extracción no dispersiva, extracción no dispersiva con dispersión de la fase de reextracción y empleo del módulo de fibra hueca, con renovación de la membrana líquida. En este trabajo se revisan estas operaciones de membranas líquidas soportadas y algunas de las aplicaciones de las mismas, en el tratamiento de efluentes líquidos conteniendo metales. Palabras claveMembranas líquidas soportadas; Metales; Agentes de extracción; Líquidos iónicos; Efluentes líquidos; Medio ambiente.

Inorganic Micropollutants Removal by Means of Membrane Processes - State of the Art

“…Thus, the use of liquid membranes has gained a general interest in the treatment of effluents where solute concentrations are low and large volume solutions must be processed, and if possible, without generating any secondary waste [57][58][59]. There are two types of liquid membranes, unsupported and supported liquid membranes.…”

“…At present, there are few, if any, large scale operations of supported liquid membranes basically due to their apparent lack of stability under long term operation. Normally, this decreasing in stability is due to the loss of the organic phase filling the membrane pores as well as the loss of membrane stability by a decreasing in the membrane permeation coefficient or the membrane flux [59].…”

“…There are two types of liquid membranes, unsupported and supported liquid membranes. Nonsupported liquid membranes, ie bulk liquid membranes and emulsion liquid membranes, are considered not very attractive for practical use due to various problems that they present under operation [59]. Supported liquid membranes (SLMs) are very effective for the removal and recovery of metals from wastewaters and process streams since they combine extraction and stripping, into one step.…”

“…The pores of the solid membrane are completely filled with the organic and/or carrier phase and this impregnation process makes relatively stable and heterogeneous solid-liquid membranes. [59]. Often, the solid supports are hydrophobic in nature, which facilitates wetting by the organic solution and the reject of the aqueous phases.…”

Liquid-liquid extraction of cadmium(II) by TIOACl (tri-iso-octylammonium chloride) ionic liquid and its application to a TIOACl impregnated carbon nanotubes system

“…solidsupported liquid membrane configuration, where the performance of the separation is enhanced by the combination of extraction and stripping processes in one step (De Agreda et al, 2011). Also there is the potential application of using these extraction systems on other solid supports such as being carbon nanotubes.…”