Claudia Maria Branco de Freitas Maia

Molecular and morphological characterization of hydrochar produced by microwave-assisted hydrothermal carbonization of cellulose

The objective of this work was to characterize the morphology and molecular composition of the hydrochar produced by microwave-assisted hydrothermal carbonization of cellulose. The produced hydrochar consists mainly of aggregate microspheres with about 2.0 µm in diameter, with aliphatic and aromatic structures and the presence of carbonyl functional groups. The aromatic groups are formed mainly by benzofuran-like structures, being chemically different from common cellulose char. Microwave-assisted hydrothermal carbonization yields a functionalized carbon-rich material similar to that produced by the conventional hydrothermal process.

Context and importance of biochar research

In the context of global warming, major changes are expected in the worldwide energy matrix in the near future. Biomass, a renewable source, as a raw material for energy production, is fundamental in this process. By definition, biochar is any source of biomass previously heated in the absence or at low concentrations of oxygen with the purpose of application to the soil (Maia et al., 2011). The production of biomass for energy (biofuels) requires, above all, soil resources, in terms of occupied land and soil productivity. There are different ways of producing energy from biomass, and the resulting biochar may vary in its physical and chemical composition depending on the kind of biomass and on the conditions of pyrolysis. The technologies that produce biochar as the main product or byproduct of a pyrolysis process are the only ones, among the available biofuel technologies, that may contribute to the improvement or maintenance of soil properties, and, therefore, to the sustainable production of energy and food.

Biochar na composição de substratos para a produção de mudas de teca

The objective of this work was to evaluate the development and quality of clonal seedlings of teak (Tectona grandis) grown in substrate with two types of biochar. The assay was carried out in a randomized complete block design, with ten treatments and four replicates: CS, commercial substrate, composed of pine bark and vermiculite at a ratio of 4:1; NS, nursery substrate composed of carbonized rice husk and coconut fiber at 1:1; and the remaining treatments were composed of the inclusions of biochar (BC) or activated biochar (BCA) in the CS, at the proportions of 25, 50, 75, and 100%. The development and quality parameters of seedlings were evaluated 90 days after striking the minicuttings in the substrates. BCA substrate additions at 25, 50, and 100% allowed for a development of height and stem diameter comparable to that of the NS. Biochar without the activation procedure does not improve quality parameters of seedlings, in comparison with the commercial substrate. The use of 25% activated biochar added to the commercial substrate is enough to improve seedling growth performance to the same level as that provided by the already validated NS.

Spectroscopic Characterization of Organic Structures and Organic‐Inorganic Interactions in Paper Mill Sludge

The organic composition and organic-inorganic interaction in paper mill sludge (PS) solvent extracts (hexane, ethyl acetate, acetone and ethanol) and humic fractions, humic acid (HA) and humin (HU) were studied by electron paramagnetic resonance spectroscopy (EPR), proton and carbon-13 nuclear magnetic resonance spectroscopy ( 1 H NMR; 13 C NMR), Fourier-transformed infrared spectroscopy (FTIR), and ultraviolet-visible spectroscopy (UV-vis). The strategy of fractionating the PS, sequentially, with organic solvents of increasing polarity is a reliable analytical procedure for humic substance sample separation because it results in more purified fractions. FTIR, 1 H NMR and 13 C NMR results showed that hexane extract consisted mainly of aliphatic hydrocarbon structures. Their contents in the extracts decreased as the polarity of the extracting solvent increased and the content of oxygen functional groups increased. Carboxylic and carboxylate functional groups were found in the acetone extract, and ester and ether functions were predominantly found in the ethanol extract. EPR spectra revealed some Fe 3+ complexes with rhombic structure (g 1 = 4.3; g 2 = 9.0) in the humic fractions and in all solvent extracts, except hexane. Quasi-octahedral Fe 3+ complexes (g = 2.3; ΔH pp ≤400 G) were found in the HU fraction and in the acetone extract. The organic free radical content in the HA fraction was higher than the non-fractionated PS sample and HU fraction.