Síntese de micropartículas magnéticas visando adsorção de urânio

Abstract

Some chemical species, even in low concentrations in the environment, raise concerns about the health risk due to their toxicity. Uranium is an element associated with possible damage to the urinary, skeletal, nervous systems in the population surrounding the mines, through the contamination of water and vegetation, motivating the study of groundwater in these regions. In order to recover the uranium present in low concentrations, 3 sulfonated polymeric resins of styrene-divinylbenzene (without magnetite - Sty-DVB, with uncoated nanostructured magnetite - Sty-DVB/Mag, with nanostructured magnetite coated with oleic acid - Sty-DVB/Mag-AcOl) were synthesized in order to obtain a magnetizable adsorbent material with the potential to capture uranium cations. The chemical availability of uranium was studied through simulations in PHREEQC software considering the degradation of organic matter (MO) and disregarding it, for different experimental conditions. The concentration data for the input elements was provided by the partnership with the University of Salamanca and the University of Extremadura. Among the results obtained by the factorial planning carried out by them (3k, with k = 4, taking into account moisture content, incubation time, suction pressure and soil particle size), which constitute 81 water samples that were in contact with the soil of the same mine region (Villar de la Yegua, Salamanca, Spain), the 5 with the highest uranium content were selected to explore the chemical species present through simulation. The results showed that disregarding the OM, the predominant species are U (VI), with emphasis on the concentrations of UO2PO4-, UO2HPO4, UO2(OH)2, UO2(CO3)22-; considering the OM, the predominant species becomes U(OH)4 and Uraninite is supersaturated. The results made it possible to propose an ideal solution for studying the influence of pH (values 3, 5 and 7) on uranium species, highlighting the predominance of cations in pH=3 and anions in pH=7. Ion exchange tests were carried out for the synthesized resins with 0.1N NaOH, 0.05M MnCl2 and 0.05M CuSO4 solution, repeating the same procedure with commercial Dowex MSC-1 resin. The results showed that for Sty-DVB, Sty-DVB/Mag- AcOl and Dowex MSC-1 the values in NaOH are similar, of 4meq/g dry resin, whereas for Sty-DVB/Mag the result is 6meq/g. For MnCl2, similar values are obtained for all resins tested, of 1.2meq/g, the same happening for CuSO4 (0.6meq/g). The characterization of the synthesized resins was made regarding the distribution of the average particle size (from 41μm to 64μm before sulfonation), apparent density, surface area (the synthesized materials are mesoporous, and the specific area increased with the addition of magnetite , ranging from 0.41m2/g (Sty-DVB) to 1.86m2/g (Sty-DVB / Mag-AcOl)), optical microscopy (showed the spherical morphology of the particles and it was possible to visualize the iron oxide in the polymerized resins), Mössbauer spectroscopy (provided comparative data for the iron oxide structures present in the resin with and without oleic acid), and X-ray Diffraction. For future work, it is proposed to repolymerize the particles with magnetite and explore other functionalities (anionic) for the resin, in addition to adsorption/desorption tests with uranium.