Humic Substances of Hydrochar and soils Amazon Dark Earth: Interactions with Macro and Micronutrients

Abstract

Humic substances (SH) are complex macromolecules resulting from the chemical and biological degradation of plant and animal wastes. They are widely distributed in soils, natural waters and sediments. The soils Amazon Dark Earth (TPI) are soils typically known to have high fertility, which has been attributed to the high content of humified organic matter, recalcitrant and nutrient richness. Studies have shown that hydrothermal carbonization (CHT) of biomass produces a carbon-rich material, called hydrothermal coal. The process employs gentle temperatures of at most 300 ° C, humid biomass and self-generated pressures. The morphological, structural and chemical characteristics of the material suggest that it may have similarities with some fractions of TPI, such as humic substances. Therefore, the objective of this work is to evaluate the complexing capacity of humic substances as well as the nutrient exchange constants for SH extracted from hydrothermal coal compared to the humic substances released from TPI. In this work the CHT will be conducted using by-products from the sugar-energy sector, sugarcane bagasse and vinasse. The CHT will be carried out at 232 ° C using a mixture of sugarcane bagasse and vinasse with addition of 1% and 4% sulfuric acid percentages. Humic substances will be extracted from hydrothermal carbon following the recommendation of the International Humic Substances Society. The total metal concentration Co, Mg, Ca, Al, Fe, Mn, Cu, Zn and Ni in SH of hydrothermal coal and TPI will be determined using an Atomic Absorption Spectrophotometer with Flame Atomization. The complexing capacity between SH and metals and the exchange constants with Co, Cu and Fe metals will be done employing a Tangential Flow ultrafiltration system. The aim of this study is to evaluate the potential of the use of hydrothermal coal produced from bioenergy residues for agricultural purposes based on the evaluation of the similarities between the complexing capacity of SH extracted from hydrothermal coal and the humic substances extracted from the TPI, as well as their release of macro and micronutrients, which are important for the growth of plants. (AU)