Chemical and Spectroscopic Characterization of Humic Acid Isolated from Ilgin Lignite, Turkey

Abstract

To isolate humic acid (HA) from Ilgin Lignite (IL), alkali extraction method was used. Extracted samples were analyzed for elemental composition (C, H, N and O) by Elemental Analyzer. Spectroscopic techniques such as Fourier-transformed infrared (FTIR), ultraviolet–visible (UV), and fluorescence spectroscopy in emission and excitation modes were also used for characterization of IL-HA.  Results obtained were compared with standard HA proposed from International Humic Substance Society (IHSS). Sulfur contents and C/N ratio of IL-HA (1.44) were found to be higher than that of standard IHSS-HA (0.76). The FTIR evidence suggested that IL-HA has an aromatic structure due to the presence of intense band at 1609.3 cm^-1. E₄/E₆ values of IL-HA and IHSS-HA were found to be comparable but, E₄/E₆ value of IL-HA (3.9) is slightly lower than that of the IHSS-HA (4.9).  Results of present study might be useful for practical and commercial applications of IL-HA on basis of their humification parameters.

Keywords: humic acid, isolation, lignite, elemental composition, spectroscopic characterization