Production of hydrochar from hazelnut waste and its use in the removal of heavy metal ions from wastewater

The spread of heavy metals throughout the ecosystem is quite dangerous for human health, animals, plants and natural resources. Therefore, it is important to remove heavy metal ions from wastewater in the most effective way. Numerous studies have been conducted and continue to be conducted to eliminate or reduce such pollutants. Hydrochar has emerged as a promising adsorbent for the removal of heavy metals from water and wastewater. Hydrochar, obtained from hydrothermal carbonization of biomass, has unique physical and chemical properties that are highly effective in capturing heavy metals through surface complexation, electrostatic interactions and ion exchange mechanisms. In this study, hydrochar was produced from hazelnut waste, and Pb and Cr ion removal research was conducted with this adsorbent. In this way, both the evaluation of hazelnut waste was provided and the removal of heavy metals, which are very harmful for the environment. The structural and morphological properties of the produced hydrochars were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR), and EDX analyses. The effects of many parameters, such as initial concentration, temperature, adsorbent dosages, contact time, and pH on adsorption were discussed. In the studies executed in different parameter environments, it was determined that hydrochar removed 76% and 67% of Pb and Cr ions, respectively. Also, Langmuir and Freundlich isotherm models, pseudo-first-order and pseudo-second-order kinetic models, and thermodynamic parameters like Gibbs free energy were investigated in order to gain a better understanding of the adsorption system of the generated hydrochar. Furthermore, the hydrochar' s reusability as an adsorbent was investigated, and it was demonstrated that the material continued to function effectively even after four cycles.