Characterization of activated composite membranes by solute transport, contact angle measurement, AFM and ESR

In this article, various characterization techniques are used to determine the structural membrane properties of various activated composite membranes (ACMs), which have been developed in the last years in our laboratories of the Universitat Autònoma de Barcelona (UAB). The mentioned ACMs were developed in an attempt to enhance the stability and lifetime of the well-known selective liquid membranes, for their application on selective transport of heavy metals and organic species, such as chiral compounds. Four different characterization techniques have been investigated with the aim to reach an actual microscopic information of the ACMs, and in that way, ascertain their future applications, by modifying their preparation methodology when needed. The characterization techniques here employed are: solute transport, contact angle measurement, atomic force microscopy (AFM) and electron spin resonance (ESR). The simultaneous employment of these techniques provide evidence of the presence, dimension and distribution of pores in membrane surface, as well as useful information about its hydrophilic properties, and confirmation of the immobilization of selective carriers into the membrane. Actual values of pores size and distribution on the membrane surfaces were reached by comparison of the different techniques, and the presence of the selective transport agents checked was detected.