RESUMO
Co-abietate and Cu-abietate complexes were obtained by a low-cost and eco-friendly route. The synthesis process used Pinus elliottii resin and an aqueous solution of CuSO4/CoSO4 at a mild temperature (80 °C) without organic solvents. The obtained complexes are functional pigments for commercial architectural paints with antipathogenic activity. The pigments were characterized by Fourier-transform infrared spectroscopy (FTIR), mass spectrometry (MS), thermogravimetry (TG), near-edge X-ray absorption fine structure (NEXAFS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and colorimetric analysis. In addition, the antibacterial efficiency was evaluated using the minimum inhibitory concentration (MIC) test, and the antiviral tests followed an adaptation of the ISO 21702:2019 guideline. Finally, virus inactivation was measured using the RT-PCR protocol using 10% (w/w) of abietate complex in commercial white paint. The Co-abietate and Cu-abietate showed inactivation of >4 log against SARS-CoV-2 and a MIC value of 4.50 µg·mL-1 against both bacteria Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The results suggest that the obtained Co-abietate and Cu-abietate complexes could be applied as pigments in architectural paints for healthcare centers, homes, and public places.
RESUMO
Developing strategies for the green synthesis of novel materials, such as pigments for protection from solar radiation, is a fundamental research subject in material science to mitigate the heat island effect. Within this perspective, the current study reports on the synthesis of blue pigments of ZnAl2O4:M (M = Co2+ and Co2+/Nd3+) using recycled metallic aluminum (discarded can seal) with reflective properties of Near-infrared radiation. The pigments were characterized by XRD, SEM, XPS, UV-Vis, NIR diffuse reflectance spectroscopy, and CIE-1976 L*a*b* color measurements. The wettability of the coatings containing the synthesized pigments was also evaluated. The structural characterization showed that the pigments present the Gahnite crystalline phase. Colorimetric measurements obtained by the CIEL*a*b* method show values correlated to blue pigments attributed to Co2+ ions in tetrahedral sites. The pigments exhibit high near-infrared solar reflectance (with R% ≥ 60%), with an enhancement of nearly 20% for the pigment-containing neodymium when applied in white paint, indicating that the prepared compounds have the potential to be energy-saving color pigments for coatings.
RESUMO
The present study described three synthesis routes using different natural polysaccharides as low-cost non-toxic fuels and complexing agents for obtaining MgO. Cassava starch, Aloe vera leaves (mainly acemannan) gel, and citric pectin powder were mixed with magnesium nitrate salt and calcined at 750 °C for 2 h. The samples were named according to the polysaccharide: cassava starch (MgO-St), citrus pectin (MgO-CP), and Aloe vera (MgO-Av). X-ray diffraction identified the formation of a monophasic periclase structure (FCC type) for the three samples. The N2 adsorption/desorption isotherms (B.E.T. method) showed an important difference in textural properties, with a higher pore volume (Vmax = 89.76 cc/g) and higher surface area (SA = 43.93 m2/g) obtained for MgO-St, followed by MgO-CP (Vmax = 11.01 cc/g; SA = 7.01 m2/g) and MgO-Av (Vmax = 6.44 cc/g; SA = 6.63 m2/g). These data were consistent with the porous appearance observed in SEM images. Porous solids are interesting as adsorbents for removing metallic and molecular ions from wastewater. The removal of copper ions from water was evaluated, and the experimental data at equilibrium were adjusted according to the Freundlich, Langmuir, and Temkin isotherms. According to the Langmuir model, the maximum adsorption capacity (qmax) was 6331.117, 5831.244, and 6726.623 mg·g-1 for the adsorbents MgO-St, MgO-Av, and MgO-CP, respectively. The results of the adsorption isotherms indicated that the synthesized magnesium oxides could be used to decrease the amount of Cu2+ ions in wastewater.
RESUMO
We report on the synthesis of boehmite aluminum oxide hydroxide particles with lamellar structure (γ-AlO(OH)) obtained from the recycling of metallic can seals, with the addition of silver nanoparticles (Ag-NPs) reduced by Aloe Vera extract. X-ray diffractometry (XRD) confirmed the γ-phase, and scanning electron microscopy (SEM) showed the presence of Ag-NPs on the boehmite particle surface, confirming the efficiency of the synthesis to obtain the composite material. The samples were used to treat lake water, according to the Standard Methods for the Examination of Water and Wastewater. The results indicated that the elimination of total coliforms and Escherichia coli occurred, with excellent efficiency for the Ag-boehmite sample. The tests show the possibility of reuse (5×) of the sample, as it maintained the efficiency of disinfection for E. coli. The preparation, use, and reuse of boehmite obtained from metallic waste is a case of a circular economy, focused on sustainability and green chemistry.
RESUMO
The synthesis of structured MgO is reported using feedstock starch (route I), citrus pectin (route II), and Aloe vera (route III) leaf, which are suitable for use as green fuels due to their abundance, low cost, and non-toxicity. The oxides formed showed high porosity and were evaluated as antimicrobial agents. The samples were characterized by energy-dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The crystalline periclase monophase of the MgO was identified for all samples. The SEM analyses show that the sample morphology depends on the organic fuel used during the synthesis. The antibacterial activity of the MgO-St (starch), MgO-CP (citrus pectin), and MgO-Av (Aloe vera) oxides was evaluated against pathogens Staphylococcus aureus (ATCC 6538P) and Escherichia coli (ATCC 8739). Antifungal activity was also studied against Candida albicans (ATCC 64548). The studies were carried out using the qualitative agar disk diffusion method and quantitative minimum inhibitory concentration (MIC) tests. The MIC of each sample showed the same inhibitory concentration of 400 µg. mL-1 for the studied microorganisms. The formation of inhibition zones and the MIC values in the antimicrobial analysis indicate the effective antimicrobial activity of the samples against the test microorganisms.