Humic Substances Extracted from a Bio-stabilized Waste Applying Different Operating Conditions

Humic substances are the major constituents of the organic matter of soils and sediments and were adopted in different industrial applications for their high content of functional groups. Recently, the research interest is focused on the possibility of extract these substances also from organic wastes, such as biowastes. However, an interesting option could be to extract humic substances from other organic stabilized wastes that differently from compost has no further use. Namely, in this study the possibility of extract Humic Acids (HA) from the bio-stabilized waste produced from a Mechanical Biological Treatment plant adopting different maturation durations was evaluated. Furthermore, the effect of the main operating conditions applied during the alkaline extraction of the humic acids was also investigated (i.e. material particle size, liquid–solid ratio, NaOH concentration and extraction time), analysing the elemental composition, the main functional groups content and the optical properties of the extracted HA. The operating conditions that showed to improve the extraction extent were the NaOH concentration and the extraction time. Furthermore, the HA obtained in these specific conditions showed higher functional groups content and aromaticity, in agreement with the characteristics of the commercial HA, allowing to consider these substances for various industrial applications. Graphic Abstract