Introduction Humic substances are one of the most important components of soil. They form a large part of the organic matter in the soil and play an effective role in its producibility. Humic substances have a macromolecular and complex structure. They consist of the chemical and biological degradation of animal and plant residues in soil, water, and sediments, so they can be obtained from any source of organic matter [1,2]. Many studies have been performed to attain humic substances from biological wastes [3-7]. They can exist in different ambients; for example soils, natural waters, rivers, lakes, sea sediment plants, and composts, but it has been observed that the chemical properties, quantities, and proportions of humic substances obtained from wastes can vary according to their sources [8-10]. There is no consensus on the structural and chemical properties of the final product to be obtained from humic substances [11]. Apart from agricultural fields, there are many different uses for humic substances, such as a dispersant in ceramic suspensions, wastewater treatment as an adsorbent, drilling fluids, medicine and creams for the treatment of various diseases, lead acid batteries as surfactant material, etc. [12]. However, they do not have certain or identified structures and features, depending on their sources and extraction conditions. Although they are chemically heterogeneous compounds with different proportions and configurations of functional groups, they comprise elements, especially C, H, N, O, and S, and the carboxyl (-COOH), amine (-NH 2), hydroxyl (-OH), and phenol (Ar-OH) functional groups [13]. Alkali humates are obtained from extraction processes with alkaline solutions (NaOH, KOH solutions, etc.) of humic substance sources. They are known as water-soluble salts of humic acid and have many benefits, such as expediting plant growth/development and enhancing plant resistance against unsuitable ambient situations. Moreover, it has been stated that the preoxidation step increases the extraction efficiency of humic acid [14,15]. Thermal analysis [TG analysis-differential thermogravimetry/differential scanning calorimetry (TG/DTG-DSC)] is often utilized to describe the thermal stability or behavior of humic substances under various conditions and to investigate Abstract: A humic substance was obtained from hazelnut husk using an alkali extraction. The chemical and morphological structure of the humic matter was characterized via elemental analysis, Fourier transform infrared spectrometry (FTIR), nuclear magnetic resonance, Brunauer-Emmet-Teller (BET) analysis, scanning electron microscopy (SEM), and thermogravimetric-FTIR (TG-FTIR). In addition, thermal analysis measurements TG analysis-differential thermogravimetry/differential scanning calorimetry (TGA-DTG/ DSC) were performed under dynamic air conditions to better determine the origin, physical and chemical structure, and decomposition process of the humic matter. The Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were used to cal...
