Chemical, Spectral and Morphological Characterization of Humic Acids Extracted and Membrane Purified from Lignite

Abstract

In this study, humic substances were extracted from lignite of Zarand coalfields, Kerman, Iran, using a stirred batch reactor. A membrane ultrafiltration system was used to purify humic acids (HAs) from lignitederived alkaline extracts obtained from the reactor. Gravimetric analysis along with several analytical methods including CHNOS, UV-Vis, FT-IR, ICP-OES and SEM were utilized to investigate the characteristics of the purified HAs. Gravimetric analysis showed that the purity of HA purified from membrane concentrated humates was higher than 95 %. CHNOS elemental analysis indicated the higher stability and condensation degree of the purified HA compared to the commercially available HAs. The ratios of E 4 /E 6 , E 2 /E 3 , and ΔlogK obtained from UV-Visible spectroscopy revealed that a purified HA had a higher molecular weight, aromaticity, and humification degree in comparison with commercial HAs. Furthermore, the peaks observed in the FT-IR analysis showed that HA had an aromatic structure. The very low concentrations of heavy metals and inorganic element contaminants observed by ICP-OES spectrometry showed a proper performance of the HA membrane purification. These results along with the results of SEM analysis showed the acceptable characteristics of purified HA from the lignite coal for agricultural and industrial applications.

Humic Acids Preparation, Characterization, and Their Potential Adsorption Capacity for Aflatoxin B1 in an In Vitro Poultry Digestive Model

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Humic acids alleviate dextran sulfate sodium-induced colitis by positively modulating gut microbiota

“…Humic acids (HAs) are macromolecular organic substances rich in hydroxyl, carboxyl, and other groups (Figure 1A), which are formed from plant and microbial residues through humification (Sarlaki et al, 2019;Xu et al, 2022). In Chinese traditional medicine, HAs have been called "WU-JIN-SAN" (乌 金 散) since 1786 (Miao et al, 2018).…”

Assessing Factors Controlling Structural Changes of Humic Acids in Soils Amended with Organic Materials to Improve Soil Functionality

“…High C/N ratios indicate high stability and humification degree of HAs [43]. Samples from S2 aside, the C/N ratios of the other samples were close to 10 (Table 3), which is considered typical for chemically stable organic compounds [26], thus suggesting relatively lower potential for mineralisation in the samples from S1, S3, and S4.…”