Utilização da fibra de poliéster para determinação de Cádmio em amostras de águas

Abstract

Toxic metals, often from pollution due to improper disposal, reduce biodiversity in the ecosystem and can reach the food chain causing harm to human health, for example, exposure to cadmium is linked to cancer in the kidneys, lungs and reproductive system. Therefore, it is essential to monitor the levels of these metals in different samples, for example water. Conventional analytical techniques, such as Atomic Absorption Spectrometries with Flame Atomization, do not always have adequate detectability for the determination of toxic metals, thus, supporting techniques such as solid phase extraction (SPE) are of great value to improve the performance of the techniques. analytics. In this context, the investigation of new materials for SPE has been growing. In the present work, pet wool was evaluated as an adsorbent in SPE, which is made up of 100% polyester and its main use is as thermoacoustic insulation in civil engineering. PET (Polyethylene terephthalate) is a thermoplastic polymer resulting from the chemical reaction between terephthalic acid and ethylene glycol, these polymers are mainly used in the form of polyester fibers (pet wool). In the present work, a flow analysis system (FIA) was proposed for the pre-concentration and determination of cadmium, in water samples, by Flame Atomic Absorption Spectrometry (FIA- FAAS), using pet wool as material. adsorbent. The procedure is based on the sorption of cadmium ions in a mini column (diameter = 0.5 cm, length = 5.0 cm) filled with PET wool. The characterization of the adsorbent was performed through Infrared Spectroscopy with which it was possible to deduce the main functional groups (carbonyl and hydroxyl) that constitute the possible adsorptive sites responsible for the interaction of Cadmium ions. With Thermogravimetry it was concluded that the material has a good thermal stability decomposing at 420 o C. The FIA-FAAS- SPE system was optimized with chemometric tools (factorial design and Doehlert matrix) and the conditions obtained were sample pH 7.37, flow rate of 4.4 mL min-1, the eluent used for desorption was HNO3 at the concentration of 0.1 mol L-1. A linear response range was obtained between 1 and 20 µg L-1 (r = 0.99551), pre-concentration factor of 81, LD 0.1 µg L-1 and LQ 0.25 µg L-1. The proposed method has a good precision with relative standard deviation (RDS) < 5%, the accuracy was checked through addition and recovery tests which varied between 96% and 115%. Finally, the methodology was applied in the determination of 6 water samples from different sources, it is a low-cost alternative, fast and with adequate precision and accuracy for monitoring cadmium levels.