Production of biochar with pyrolysis of hazelnut shell and walnut shell and investigation of their adsorption characteristics in removal of heavy metal ions from aqueous solutions

Removal of heavy metals, which have many physiological and toxic effects on living things, from the aquatic environment using appropriate treatment techniques is of great importance. In this study, it was aimed to investigate the adsorption properties of the biochar obtained by pyrolysis of hazelnut shell and walnut shell from agricultural wastes which are abundant in our country for removal of lead and copper ions from aqueous solutions. The characterization of raw biomass and also biochars produced by pyrolysis were performed using FT-IR, TGA-DTG, BET, SEM, partial and elemental analysis techniques. The optimum conditions were determined by investigating the effect of adsorption parameters (initial heavy metal concentration, temperature, adsorbent amount, pH, contact time and mixing speed) for efficient removal of heavy metals from aqueous solution by batch adsorption experiments carried out under different conditions and the experimental results were investigated in terms of Langmuir, Freundlich and Temkin isotherm models. Together with the calculated thermodynamic parameters, the adsorption mechanism was tried to be explained. In order to determine the kinetic model of the adsorption process, the experimental data were applied to the pseudo first-order kinetic model, the pseudo second-order kinetic model and the intra-particle diffusion model, and the model constants and correlation coefficients were investigated. As a result, it has been demonstrated that biochar is an effective adsorbent for the removal of Cu2+ and Pb2+ ions from aqueous solutions and that it is possible to evaluate in removal of environmental pollutants from water sources in an economical way.