SYNTHESIS, CHARACTERIZATION AND FIXATION OF NANOSTRUCTURED SELENIUM IN POLYURETHANE SPONGES

SYNTHESIS, CHARACTERIZATION AND FIXATION OF NANOSTRUCTURED SELENIUM IN POLYURETHANE SPONGES

ABSTRACT

The objective of the present work is to synthesize and fix selenium nanostructures in polyurethane sponges for further laboratory tests, aiming a better removal of low concentration metalloids. Synthetic sponges of polyurethane (PU) exhibit important characteristics, such as reversible compressibility, high porosity and high capability of adsorption. Nanotechnology can be used to remove environmental pollutants, including the metalloids: arsenic, mercury and cadmium. Selenium nanostructures show great affinity for these metalloids. First, Se-Nano were synthesized in a liquid solution with BSA (150 mM) and sodium selenite (23 mM) in autoclave, for 20 minutes at 121°C and 1 Kgf, and then characterized in the Scanning Electron Microscope (SEM). PU sponges were acquired at the local commerce, cut to the same size and placed into the solution (in the conditions described above) for 7 days under agitation. Tests were carried out in the sponges to confirm the fixation/liberation of Se in the PU. The PU sponges with Se-Nano fixed in their structures were placed in contact with cadmium chloride solutions (1 mM and 0.5 mM), for 48 hours, and then the samples were sent to Neutron Activation Analysis (NAA) to confirm the adsorption/desorption of Cd in the Nano-SePU. The first tests showed that the nanoparticles were synthesized, fixed in the PU, and the liberation of selenium in water was insignificant. The Se-Nano synthesized present two different morphologies. With the SEM images it was possible to observe the formation of spherical nanoparticles with diameters ranging from 600 to 700 nm. It was also observed nanotubes with nanometric sizes in one dimension and micrometric in the other one. The analysis of the sponge with Se-Nano shows that the nanoparticles were fixed both on the surface and in the pores of the PU. NAA tests revealed that the Nano-SePU can adsorb significant amounts of Cd in their structures. It was also shown that part of the adsorbed Cd can be released when in contact with water. The preliminary results indicated that the PU with Nano-Se can be considered a new alternative to be studied for metalloid pollutants removal.

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