Polyphenol-SiO2 hybrid biosorbent for heavy metal removal. Yerba mate waste (Ilex paraguariensis) as polyphenol source: kinetics and isotherm studies.

A low-cost biosorbent hybrid material ready for application was obtained in this work. Yerba mate (Ilex paraguariensis) milling residual dust was used as a polyphenol source by ethanolic extraction. Polyphenols were immobilized within a SiO(2) matrix to form an interpenetrated polymer after glutaraldehyde cross-linking. Pb(II), Cr(III) and Cr(VI) were chosen as model metals for adsorption. The hybrid materials were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and Nitrogen Adsorption Isotherms. Adsorption experimental data were analysed using Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, Redlich-Peterson, Sips and Toth isotherm models along with the evaluation of adsorption energy and standard free energy (ΔG°). The adsorption was observed to be pH dependent. The main mechanism of metal adsorption was found to be a spontaneous charge associated interaction. Electron Spin Resonance (ESR) spectroscopy confirmed that Cr(VI) adsorption was an adsorption-coupled reaction and the adsorbed specie was Cr(V). The hybrid matrix probed its adsorption capacity of Cr(III) in a non-treated tannery wastewater.

Arsenic intoxication, a hemorheologic view.

Arsenic (As) is a toxic semi-metal of wide distribution in nature. People living in regions where drinking water contains large quantities of arsenic, have an unusually high likelihood of developing blood-vessel diseases, but little is known about the mechanisms involved, i.e. the blood rheologic alterations that would contribute to the circulatory obstruction. Erythrocytes are the main target cells for arsenic compounds systemically absorbed and their cell membrane is the first place against the toxic. In this paper we have examined the in vitro effect of arsenic (As(V)) on the rheologic properties of human erythrocytes in relation with membrane fluidity and internal microviscosity. According to our present results, As(V) treatment produces oxidative degradation of membrane lipids and alteration of internal microviscosity. These red blood cells (RBCs) membrane and cytoplasmic structural damage consequently alters RBCs rheologic properties: an alteration of the RBCs discoid shape to stomatocytes, a diminution of erythrocyte deformability and an enhancement of osmotic fragility and cell aggregability. These effects impaired blood fluid behaviour that contribute to obstruct peripheral circulation and provides anemia, both clinic evidences typical of arsenic cronic intoxication.

Nitric oxide increases in the rat retina after continuous illumination.

Continuous illumination (CI) of the retina induces an oxidative stress followed by the degeneration of photoreceptors. This phenomenon may be partially related to the excessive production of nitric oxide (NO). In order to confirm this hypothesis, the aims of this work are to determine NO levels during the illumination of the retina by electron paramagnetic resonance (EPR), and if an increase of NO is found, to characterize the NOS isoform responsible of the increment by using Western blot. Sprague-Dawley rats were continuously illuminated with white light (12,000 lux) for 2, 24, 48 h, 5 and 7 days while control rats were maintained at light/dark cycles of 12/12 h. Using EPR, an increase of NO signal was observed in the light exposed retinas peaking at 24 h of CI. Western blot analysis showed the expression of iNOS in the illuminated retinas with a peak after 24 h of CI, but did not show significant differences of nNOS among illuminated and control retinas. In summary, there is an increase of NO during CI. Further studies will reveal whether this mechanism is responsible for light induced photoreceptor degeneration.