Obtenção de complexos organominerais a partir de substâncias húmicas e nutrientes essenciais as plantas

Abstract

One of the main challenges of the fertilizer industry is to create in a single product that contains two essential ingredients for an efficient plant’s development, which are organic matter and mineral nutrients. The release of these components should occur in a controlled way to the plants, avoiding the environmental impacts caused by its excess. Therefore, the objective of the work was to synthesize and characterize the complexes formed between the humic (HA) and fulvic acids (FA) derived from poultry waste, with the metal ions Cu2+, Fe2+, Zn2+ and Ce3+. The metal release of these complexes in a buffer solution that simulated the soil solution in which the plants are inserted was evaluated. The synthesized compounds were characterized by analytical techniques such as Vibrational Spectroscopy in the Fourier Transform Infrared (FTIR), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), Flame Atomic Absorption Spectroscopy (FAAS), X-ray diffraction (XRPD) and Thermogravimetry (TGA/DTG). From the complexes formed were studied the structural characteristics such as the degree of aromaticity, functional groups present in the structures, resistance to thermal degradation, metallic ion release capacity, and influence of the metallic ions on the structures of the Humic Substances. The spectra of HA and FA infrared after complexation with the metallic ions showed changes in the absorption bands, which are related to the changes in the humic structure, indicating the complexation of the metallic ions mainly with phenolic and carboxylic groups. The obtained diffractograms helps the aromaticity determination of these structures and in the characterization of these structures with the metals. Thermogravimetric analysis showed that the complexed metals decrease the thermal stability of Humic Substances (HSs). The analysis by atomic absorption and ICP-OES showed that the release of metals caused by humic fractions is directly related to the sample origin, type of metal interaction with the humic structure and the environment conditions in which the complex is inserted. The complex that fits the profile of slow/controlled release fertilizers was the complex of humic acid and iron.