Dr. Salgado-Mendoza, Pablo

The present study reports on phenolic compounds profile of Eucalyptus globulus leaf extracts and exhibiting their role in obtaining silver nanoparticles (AgNP) by a green method on paper and fabric supports with or without addition of NaOH. To know the mechanism involved in the formation of AgNP, FTIR, UV–Visible spectrophotometry and UHPLC-QTOF-MS analyzes were carried out of E. globulus extracts before and after the synthesis of AgNP. The FTIR, UV–Visible spectrophotometry analyzes identified phenolic compounds, and to a lesser extent reducing sugars mainly participate as reducing agents in the formation of AgNP, while phenolic compounds would participate as stabilizing agents. UHPLC-QTOF-MS analyzes identified derived from gallic acid play an important role in AgNP formation. AgNPs were characterized in their morphology and structure by SEM-EDS, TEM-SAED, XRD, UV–Vis diffuse reflectance and TGA. The results indicate the formation of Ag and/or Ag2O nanoparticles depending on the influence of NaOH in the reaction system. Furthermore, the support used (paper or fabric), it would influence the concentration of AgNPs formed, the consumption of phenolic compounds, the antibacterial activity and band-gap of AgNPs synthesized. This study provides evidence of a simple process to support AgNP on cellulose and providing key information towards the definitive clarification of the mechanism of formation of AgNP by green synthesis.

In this work, the Fenton technology was applied to decolorize methylene blue (MB) and to inactivate Escherichia coli K12, used as recalcitrant compound and bacteria models respectively, in order to provide an approach into single and combinative effects of the main process variables influencing the Fenton technology. First, Box–Behnken design (BBD) was applied to evaluate and optimize the individual and interactive effects of three process parameters, namely Fe2+ concentration (6.0 × 10−4, 8.0 × 10−4 and 1.0 × 10−3 mol/L), molar ratio between H2O2 and Fe2+ (1:1, 2:1 and 3:1) and pH (3.0, 4.0 and 5.0) for Fenton technology. The responses studied in these models were the degree of MB decolorization (D%MB), rate constant of MB decolorization (kappMB) and E. coli K12 inactivation in uLog units (IuLogEC). According to the results of analysis of variances all of the proposed models were adequate with a high regression coefficient (R2 from 0.9911 to 0.9994). BBD results suggest that [H2O2]/[Fe2+] values had a significant effect only on D%MB response, [Fe2+] had a significant effect on all the responses, whereas pH had a significant effect on D%MB and IuLogEC. The optimum conditions obtained from response surface methodology for D%MB ([H2O2]/[Fe2+] = 2.9, [Fe2+] = 1.0 × 10−3 mol/L and pH = 3.2), kappMB ([H2O2]/[Fe2+] = 1.7, [Fe2+] = 1.0 × 10−3 mol/L and PH = 3.7) and IuLogEC ([H2O2]/[Fe2+] = 2.9, [Fe2+] = 7.6 × 10−4 mol/L and pH= 3.2) were in good agreement with the values predicted by the model.