Influence of Technical Parameters of the Pyrolysis Process on the Surface Area, Porosity, and Hydrophobicity of Biochar from Sunflower Husk Pellet

Biochar is a product that has been of interest to many researchers in recent years. The use and positive effect of biochar depend on its properties, which in turn result primarily from the type of substrate used for production and the technical parameters of the pyrolysis process used. From the point of view of sustainable development, agricultural raw materials, such as sunflower husks, are good materials for biochar synthesis. The research aimed to determine the effect of changing the technical parameters of the pyrolysis process (i.e., temperature, heating rate, and residence time) on the properties of biochar obtained from sunflower husk pellets. The pellets were heated to 480 °C, 530 °C, and 580 °C. The applied heating rate for 480 °C was 4.00 and 7.38 °C·min−1, for 530 °C it was 4.42 and 8.15 °C·min−1 and for 580 °C it was 4.83 and 8.92 °C·min−1. Determining these properties is important due to the use of biochar, e.g., in the processes of sorption of pollutants from the water and soil environment. The technical parameters of the pyrolysis process used allowed us to obtain hydrophilic materials with porosity in the range of 10.11% to 15.43% and a specific surface area of 0.93 m2·g−1 to 2.91 m2·g−1. The hydrophilic nature of biochar makes it possible to use them in the processes of removing inorganic pollutants and polar organic pollutants. The presence of macropores in biochar may contribute to the improvement of water management in the soil and affect the assimilation of microelements by plants. The low content of heavy metals in biochar does not pose a threat to the environment.