Preparació i caracterització de membranes d’inclusió polimèrica (PIMs) amb nous líquids iònics com a extractants: estudis d’estabilitat i eficiència de transport

Abstract

Nowadays, there are a variety of techniques or separation processes in both small and large scale allowing us to treat different kind of waste or samples according to the needs of each case. Some of these separation methods are based on the use of membranes. There are different types of membranes, such as polymer inclusion membranes, or PIMS, and are the ones used in this work. PIMs normally consist on a polymeric support in which the extracting agent is placed. Such membranes have a wide variety of applications (in the laboratory) in both the extraction and transport of metals and anions. In the present work, new types of PIMS have been prepared using cellulose triacetate (CTA) as a polymer, and using as extractant the commercial reagent Aliquat 336 (or A336), which is a room temperature ionic liquid (IL), or derivatives thereof. New IL have prepared in the laboratory by exchanging the chloride anion of the commercial extractant by a series of anions such as SCN-, NO3-, ClO4- and thiosalycilate. These new extractants have been used to prepare the corresponding PIM and the stability of membranes has been evaluated in both water and saline solutions. In addition, another parameter that has been studied is the ability of new PIMs to extract metals. For that, the extraction of Cr(VI) has been investigated. Another study that has been done is to assess the lifetime of a PIM prepared with 50% and 50% of CTA Aliquat 336 (commercial IL) when used to transport As (V) to a sample of well water to a solution of NaCl 0.1M. Our studies have revealed that the most stable PIM is the one containing A336- (thiosalycilate), while those prepared with A336-(Cl) and A336-(NO3-) are the best in terms of Cr(VI) extraction at pH = 4. However, the PIM with A336-(NO3-) is the best in terms of stability and efficiency. Thus, PIM was used to evaluate different parameters affecting the transport system such as the content of the IL and the composition of the receiving phase. The most favourable results were obtained with a PIM composition of 60% CTA and 40% A336-(NO3-) and 0.1M HNO3 as stripping phase. From our results using a PIM 50%CTA and 50% A336-(Cl) (which is the less stable) for As(V) transport, we have observed that even the permeability decreases when the membrane is reused, the system efficiency is acceptable after long time contact