Hydrothermal Carbonization of Corncob and Characterization of the Obtained Hydrochar

The hydrothermal carbonization (HTC) is a thermochemical process of biomass conversion that uses water as the reaction medium, which does not have any toxicity and categorizes the method as an environmentally friendly process. The solid product obtained by this process is commonly called hydrochar, and has many applications: it can be used for energy purposes, for soil amendment processes, also by producing activated carbon adsorbents, catalysts, and nanostructured materials. In this investigation was used as lignocellulosic biomass milled corncob, which was sieved before the process. For the experimentation were used three-quarter parts of the capacity of a Parr reactor of 25 ml, adding a volumetric relation of biomass: distilled water of 1:3. The hydrothermal carbonization was applied in a temperature range between 180 and 350 degrees C under subcritical water conditions and during the same period: four hours. These resulting hydrochars, were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), adsorption analysis, thermogravimetric analysis (TGA) and scanning electron microscopy. The results of this characterization showed that after the hydrothermal carbonization, the functional groups from fresh biomass were preserved, as evidenced in the IR analysis. Appreciable changes in carbon densification, which increases with increasing HTC temperature, improved the potential properties as a solid fuel of this material; the Higher Heating Values obtained are comparable to the values reported for fossil fuels such as carbon which indicates that a replacement thereof can be performed by hydrochar in industrial processes. In addition, the adsorption capacity was observed in samples hydrotreated at low temperature, which generates adsorptive properties and makes it able to be used in processes for removal of dyes, metals and water. The results presented indicate that treatment of hydrothermal carbonization is a low-cost waste management of lignocellulosic biomass with economic feasibility, which generates a versatile solid product with diverse applications, making HTC an excellent way to take advantage of this kind of renewable resources.