Hydrothermal Synthesis of Highly Effective Carbon Sorbent Based on Renewable Resources

The synthesis of new sorption materials by hydrothermal carbonization of sunflower meal (HTS) with the addition of graphene oxide (GO) and subsequent carbonization (C) was developed. To assess the morphological and phase changes during carbonization, the materials were characterized by scanning electron microscopy and IR spectroscopy. According to the results obtained, carbonization promoted the development of latent porosity, as well as a decrease in the amount of oxygen-containing and alkyl groups. Kinetic sorption studies were also carried out on the example of the Pb+2 ions and organic dye molecules – methylene blue (MB), extraction. The experiment results showed that the adsorption capacity of HTS, HTS/C, HTS/GO, and HTS/GO/C composites for the Pb+2 ions extraction was 82.9; 108.6; 168.9; 148.3 mg/g, respectively; and for MB molecules – 1481.8; 1601.1; 1920.3; 2283 mg/g, respectively. It was found that during adsorption of MB molecules, the carbonization effects significantly on the contact time. Carbonized samples show high sorption activity. The equilibrium contact time fort them was 15 min, while for non-carbonized samples it was 60 min. The equilibrium time during the Pb+2 ions adsorption was 60 min for all samples. The adsorption kinetics was described using the following models: pseudo-first order, pseudo-second order, the Elovich model, and intraparticle diffusion. It was found that the adsorption process is limited by the chemical exchange reaction and proceeds in a mixed-diffusion mode.