Eletrodo Modificado com [CoO(OH)] Coloidal Aplicado na Detecção de Ácido Oxálico

In this work, we used a chemically modified electrode with cobalt oxyhydroxide in colloidal form as an electrochemical sensor for oxalic acid. Initial experiments were performed in different electrolytes (LiOH, NaOH e KOH), that better defined electrochemical response in medium NaOH solution [0.5 mol.L-1]. From measurements of cyclic voltammetry and square wave voltammetry for quantification of oxalic acid responses electroanalytical was obtained for concentrations in order 10-5-10-6 mol L-1. The detection limits (2.52x10-5 mol.L-1) and quantification (7.55x10-6 mol.L-1) were significantly better for measurements performed by square wave voltammetry. The CME-Co has potential application as a sensor for the measurement of oxalic acid and redox species. DOI: http://dx.doi.org/10.17807/orbital.v7i2.57

Mixed oxides with corundum-type structure obtained from recycling can seals as paint pigments: color stability.

peer reviewedGreen chromium and red iron oxides are technically important pigments due to their high color intensity, good dispersibility in paints, and superior hiding power. We report on the synthesis of colored pigments of mixed oxides with a corundum-type structure. The pigments are obtained via the addition of coloring ions to boehmite from recycled metallic aluminium. X-ray diffractometry (XRD) and Raman spectroscopy confirmed the crystallographic phase. Additionally, the oxidation state 3+ responsible for the greenish (chromium) and reddish (iron) coloration of the mixed oxides was confirmed by XPS and visible-light absorption measurements. The colorimetric stability of the oxides in acid and alkaline environments was evaluated. After 240 h of exposure to harsh environments, both pigments demonstrated stability and showed no strong color difference.12. Responsible consumption and productio

Synthesis of Blue Gahnite (ZnAl2O4:Co, Nd): A Cost-Effective Method for Producing Solar-Reflective Pigments for Cool Coatings.

peer reviewedDeveloping 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

Synthesis of Periclase Phase (MgO) from Colloidal Cassava Starch Suspension, Dual Application: Cr(III) Removal and Pigment Reuse

peer reviewedThis study aimed to synthesize magnesium oxide (MgO) using a colloidal starch method for two primary purposes: the removal of chromium (III) ions from synthetic wastewater and the subsequent use of the chromium-containing material as synthetic inorganic pigments (SIPs) in commercial paints. The synthesis used to obtain the oxide (St-MgO) is a promising method for using plants, such as cassava, as green fuels due to their abundance, low cost, and non-toxicity. With this, the oxide showed greater porosity and alkalinity, compared to commercial magnesium oxide (Cm-MgO). The MgO samples were subjected to structural characterization using XRD and FTIR, surface area and pore volume study by B.E.T. and SEM, and chemical composition by ICP-OES and thermogravimetric analysis (TGA). The crystalline periclase phase was identified for both samples, but the brucite phase was shown to be a secondary phase for the commercial sample. After the removal of chromium ions, the brucite crystalline phase became the majority phase for the samples, regardless of the concentration of ions removed. The pigments were characterized by color measurements and discussed in terms of colorimetric parameters using the CIELab method and electron spectroscopy (VIS-NIR). This study also evaluated the colorimetric stability of green pigments in aggressive environments (acidic and alkaline) over a 240 h exposure period, demonstrating minimal color difference. This study aims to develop materials for the decontamination of wastewater containing chromium and its reuse as a synthetic inorganic pigment, using an innovative and sustainable synthesis method

SUCRALOSE CoO(OH)-ASSISTED ELECTROCHEMICAL DETECTION IN ALKALINE MEDIA. THE THEORETICAL ANALYSIS OF AN INTERESTING POSSIBILITY

The sucralose electrochemical determination, assisted by cobalt (III) oxyhydroxide, has been theoretically evaluated. The mathematical model, describing the electroanalytical process, has been developed. The analysis of the model by linear stability theory and bifurcation analysis has shown that CoO(OH) may be applied as an efficient electrode modifier in the sucralose determination in neutral and lightly alkaline media. The electrochemical response has to be clear and easy to interpret. The oscillatory and monotonic instabilities may occur due to double electric layer influences of the electrochemical process

Synthesis and Characterization of Boehmite Particles Obtained from Recycling: Water Disinfection Application.

peer reviewedWe 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

THE POSSIBILITY OF NALBUPHIN CoO(OH)-ASSISTED ELECTROCHEMICAL DETECTION AND ITS MATHEMATICAL DESCRIPTION

The possibility of nalbuphin electrochemical determination over a CoO(OH)-modified electrode has been studied from the theoretical point of view. The correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis. It was shown that CoO(OH) may be applied as an efficient electrode modifier in the detection of nalbuphin in neutral and lightly alkaline media. The electrochemical response has to be clear and easy to interpret. The possibility of the oscillatory and monotonic instabilities has also been verified

Antiviral Properties against SARS-CoV-2 of Nanostructured ZnO Obtained by Green Combustion Synthesis and Coated in Waterborne Acrylic Coatings

peer reviewedThe COVID-19 pandemic has increased the need for developing disinfectant surfaces as well as reducing the spread of infections on contaminated surfaces and the contamination risk from the fomite route. The present work reports on the antiviral activity of coatings containing ZnO particles obtained by two simple synthesis routes using Aloe vera (ZnO-aloe) or cassava starch (ZnO-starch) as reaction fuel. After detailed characterization using XRD and NEXAFS, the obtained ZnO particles were dispersed in a proportion of 10% with two different waterborne acrylic coatings (binder and commercial white paint) and brushed on the surface of polycarbonates (PC). The cured ZnO/coatings were characterized by scanning electron microscopes (SEM) and energy-dispersive X-ray spectroscopy (EDS). Wettability tests were performed. The virucidal activity of the ZnO particles dispersed in the waterborne acrylic coating was compared to a reference control sample (PC plates). According to RT-PCR results, the ZnO-aloe/coating displays the highest outcome for antiviral activity against SARS-CoV-2 using the acrylic binder, inactivating >99% of the virus after 24 h of contact relative to reference control

Synthesis and Characterization of Ag/ZnO Nanoparticles for Bacteria Disinfection in Water.

peer reviewedIn this study, two green synthesis routes were used for the synthesis of Ag/ZnO nanoparticles, using cassava starch as a simple and low-cost effective fuel and Aloe vera as a reducing and stabilizing agent. The Ag/ZnO nanoparticles were characterized and used for bacterial disinfection of lake water contaminated with Escherichia coli (E. coli). Characterization indicated the formation of a face-centered cubic structure of metallic silver nanoparticles with no insertion of Ag into the ZnO hexagonal wurtzite structure. Physicochemical and bacteriological analyses described in "Standard Methods for the Examination of Water and Wastewater" were used to evaluate the efficiency of the treatment. In comparison to pure ZnO, the synthesized Ag/ZnO nanoparticles showed high efficiencies against Escherichia coli (E. coli) and general coliforms present in the lake water. These pathogens were absent after treatment using Ag/ZnO nanoparticles. The results indicate that Ag/ZnO nanoparticles synthesized via green chemistry are a promising candidate for the treatment of wastewaters contaminated by bacteria, due to their facile preparation, low-cost synthesis, and disinfection efficiency