Resumo Os efluentes líquidos de algumas indústrias apresentam traços de metais nocivos que possuem propriedade bioacumulativa, o que contribui para o aumento de sua toxicidade. Tendo em vista o crescimento industrial, e o consequente aumento de emissões de contaminantes em efluentes líquidos, a adsorção está entre as operações aplicadas para diminuir as concentrações dos metais a fim de atender a regulamentação ambiental vigente. A biomassa residual vem ganhando destaque no tratamento desses efluentes por se um material renovável e de baixo custo, quando comparado com os adsorventes convencionais. O objetivo deste trabalho é avaliar a eficiência da cinza do bagaço da cana-de-açúcar (CBC) na adsorção dos íons metálicos Cu2+ e Cr3+ por meio de ensaios de isoterma de adsorção. A CBC foi caracterizada quanto a sua microestrutura, composição química, área de superfície específica e morfologia, e o adsorbato foi analisado por absorção atômica de chama. A CBC apresentou-se de maneira eficaz como um bioadsorvente para ambas as soluções sintéticas, contendo os íons Cu2+ e Cr3+, presentes nos efluentes líquidos. As isotermas de adsorção apresentaram um perfil crescente, indicando a eficiência na remoção média de 97,3% para o Cr3+ e 96,4% para o Cu2+, podendo este material ser aplicado como adsorvente em efluentes industriais.
Magnesium aluminates (MgAl2O4) with Mn substituting sites A and B were synthesized by the microwave-assisted combustion method applying high power (900 W) using Aloe Vera as a green chelating agent. The study evaluated the effect of the presence of Aloe Vera and the subsequent heat treatment on the structural characteristics of spinel powders by X-ray diffraction (XRD). The effect of heat treatment was evaluated in two ways: with and without calcination. The results showed that the substitutes occurred forming the following phases: Mg0.21Mn2.36Al0.43O4, Mg0.13Mn2.63Al0.25O4, Mg0.31Mn2.06Al0.63O4 substituting site A; and MgMn1.88Al0.13O4 and MgMn1.75Al0.25O4 substituting site B. The presence of Mn and Aloe Vera ions affected the spinel crystal structure. The crystallinity degree is less intense when the magnesium aluminate was substituted by the Mn ion due to the amount of deformations in the crystal system induced by the substituent ion. However, the calcination of the powders increased the crystallinity degree in all scenarios. Furthermore, the substitution caused alteration in the lattice parameters due to the difference between the ionic radius of the substituent and the Mg2+ or Al3+ ion evidenced in the positions of 2θ. The spinel cubic phase was found in most materials, although the tetrahedral phase was observed in some Mn-substituted structures. The crystallite sizes of the powders were influenced by the presence of phytochemicals present in Aloe Vera. A decrease in crystallite size was observed when the materials were calcined as a result of the gasification of biomolecules from the plant extract. However, these biomolecules help in dissociating precursors, albeit slowly, which prevented crystallite growth. The use of Aloe Vera as a chelating agent proved to be efficient in the synthesis of magnesium aluminate spinels, pointing out the synthesized material as a promising route for the green synthesis field.
Ionic liquids (ILs) are good electrical conductors and organic liquid compounds at room temperature, with potential applicability in water electrolysis for H2 generation. The objective of this work is to describe the synthesis, characterization and study of the feasibility of ionic liquid 1-methyl-3-(2,6-(S)-dimethyloct-2-ene)-imidazolium tetrafluoroborate (MDI-BF4) as electrolyte to produce hydrogen through electrolysis of water. The synthesized MDI-BF4 was characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), mid-infrared spectroscopy with Fourier Transform by method of attenuated total reflectance (FTIR-ATR), nuclear magnetic resonance spectroscopy of hydrogen (NMR 1H) and cyclic voltammetry (CV). The yield of the synthesis were calculate by the TGA and DSC. From the results: The infrared spectroscopy identified the functional groups of the compound and the B-F bond at 1053 cm-1. The NMR 1H analyzed and compared with literature data confirms the structure of MDI-BF4. The yield of the synthesis of MDI-BF4 which was 88.84%. The current density achieved by MDI-BF4 in the voltammogram shows that the IL can conduct electrical current regardless the concentration of water, indicating that the MDI-BF4 is a potential electrolyte for hydrogen production from water electrolysis.
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