Effect of Strong Acids on the Spectral Characteristics of Humic Acid Extracted from Biomethane Fermentation Peat Residue.

To extend the peat utilization chain, and combine peat biomethane production with humic acid extraction, the effect of the spectral characteristics of humic acid extracted using strong acids from biomethane fermentation peat residue was investigated. The humic acid structures were characterized by Fourier transform infrared spectroscopy, fluorescence spectroscopy, and ultraviolet-visible spectroscopy (UV-vis). Fourier transform infrared results showed that the humic acid samples obtained through precipitation with different strong acids were different from the humic acid standard in terms of the functional group content. Fluorescence spectroscopy showed that the humic acid extracted by HNO₃ and H₃PO₄ had a lower fused ring and a simple molecular structure. In addition, the humic acid precipitated by HNO₃ had the lowest E₄/E₆ ratio and highest molecular weight, along with an aromatic structure. The results showed that HNO₃ is the best strong acid for the extraction of humic acid from biomethane fermentation peat residue by alkali extraction and acid precipitation. [ABSTRACT FROM AUTHOR]