Disseny de dispositius basats en membranes d’inclusió polimèrica amb líquids iònics per a la determinació de mercuri

Abstract

Mercury, Hg, is toxic heavy metal that is present in the environment because of natural and anthropogenic sources. Due to its high toxicity and its presence in aquatic systems, it is important to develop methodologies to control its existence in the environment. This work tends to evaluate the extraction efficiency of mercury with ionic liquid (ILs) such as trioctylmethylammonium thiosalicylate (TOMATS) and trioctylmethylammonium salicylate (TOMAS), in extraction systems with solvents and with polymer inclusion membranes (PIMs). It has been performed liquid-liquid extraction efficiency studies and elution with these two ILs depending on the pH and media that the mercury is found. It has been observed that TOMATS IL extracts mercury more efficiently than TOMAS LI and that it is not affected by the pH, but it is affected by the presence of high chloride concentrations. The best mercury extraction for the thiosalicylate derivate is due to the stronger interaction that presents this metal for the molecules with sulphur atoms. The elution of the metal-extracted is been possible using cysteine as an eluent for the case of IL with thiosalycilate anion, while in the case of the IL with salycilate anion, EDTA also allowed the metal recuperation. It has been designed a separation system based on PIMs. With this aim, 50% CTA + 50% IL (TOMATS or TOMAS) membranes have been used. In the same way that in liquid-liquid studies, the TOMATS IL was more effective in the metal extraction than TOMAS. When this membrane was implemented in a device in order to allow the metal preconcentration, using a 0,001 M cysteine as receptor phase, it was showed the correct efficiency of the system. It has been possible to transport between 70-80% of the metal present in natural water samples. In addition, it has been observed that there is a lineal tendency between mercury concentration in the aqueous phase and the recuperated one in the receptor phase. This fact shows the possibility of using this device as a passive mercury sampler in natural water