Desenvolvimento de uma metodologia de extração em ponto nuvem modificada para determinação de Cd(II) utilizando as cascas das sementes de moringa oleífera magnética como adsorvente

Abstract

The combination of analytical sample preparation techniques is highlighted for contributing to alternative methodologies, using low volumes of reagents, contributing to the environment, in addition to circumventing limitations of well-established techniques within analytical chemistry. A modified cloud point extraction (CPE) methodology was combined with magnetic solid phase extraction (MSPE) for cadmium ion extraction in aqueous samples. Triton X-100 was used as non-ionic surfactant and magnetized Moringa oleifera as solid phase. For this, the natural adsorbent had its surface modified with ferromagnetic fluid, giving it magnetic characteristics. The adsorbent material was characterized by pH at the point of zero charge (pHPCZ), infrared (IR), Scanning Electron Microscopy (SEM-EDS) and X-Ray Diffraction (XRD). The ideal pH for extraction and the mass of the adsorbent were studied in a univariate way and their values were fixed at pH 6 and 20.0 mg. Subsequently, a 24 factorial design, with a central point, was carried out, evaluating four variables, concentrations of surfactant Triton x-100 and HNO3, sonication time and water bath time. Values for surfactant concentration and eluent concentration were set at 1% and 1.0 mol L-1 respectively, and in a univariate manner later, the ultrasound and heating time was set at 5 and 6 min respectively. In addition, the cloud point extraction technique and the solid phase extraction technique were evaluated separately and together, and it can be seen that the method proposed in this work results in greater analytical signals, proving that the combination of techniques is efficient. in the extraction of Cd(II). The selectivity evaluation was carried out from a fractional factorial design, analyzing seven metallic ions, Cu2+, Cr3+, Co2+, Pb2+, Fe3+, Mn2+ and Ni2+, where the ions that do not interfere in the system are Co(II), Fe(III ), Mn(II), Ni(II) and the others interfere. The stability of the adsorbent was evaluated from successive analyzes using the same portion of adsorbent, being possible to notice that this one has a low stability. The analytical performance of the method was evaluated, obtaining a sensitivity of 1,8. 10-3 , linear working range 0.25 to 2000.0 μg L-1 , precision at 7.71% and limits of detection and quantification, 3.45 and 11.5 μg L-1 , with a pre-concentration of 4 and coefficient of determination 0.9998. In addition, precision was evaluated in terms of repeatability and reproducibility, which was 5.12% and 2.56%. Thus, the modified CPE procedure, using the combination with solid phase extraction, is a promising and viable method with regard to the extraction and pre-concentration of Cd(II) using magnetic Moringa oleifera as adsorbent.