Effect of dilute acid on fulvic acid extracted from lignite

ABSTRACT

To explore the effect of dilute acid on the extraction of fulvic acid by lignite using an alkali-soluble acid precipitation method, lignite was acid-precipitated by H₂SO₄, HNO₃, HCl, and H₃PO₄, and the content, extraction rate, and structural characteristics of fulvic acid were analyzed. The results showed that the highest content of humic acid extracted by HNO₃ is 0.3383 mg/mL, and the lowest content of humic acid extracted by sulfuric acid is 0.0817 mg/mL. The highest extraction rate of humic acid derived from lignite extracted by hydrochloric acid is 3.84%, and the lowest extraction rate of humic acid extracted by sulfuric acid is 0.89%. Fulvic acid extracted from lignite contained functional groups such as benzyl, carbonyl, methyl, and hydroxyl, but their contents varied; the benzene ring structure in fulvic acid precipitated by HNO₃ was the most pronounced, but the aromatization degree was the lowest. By contrast, the aromatization degree of fulvic acid precipitated by H₂SO₄ was the highest. This indicates that the functional group contents in humic acid extracted from different dilute acids vary, although the types of functional groups are similar.

KEYWORDS:

• Lignite
• fulvic acid
• spectral analysis
• alkali-soluble acid precipitation method

Acknowledgements

Talent Development Fund Project of Inner Mongolia Autonomous Region (2021); Fundamental Research Funds for Inner Mongolia University of Science and Technology (2022).

Disclosure Statement

The author(s) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

The work was supported by the Talent Development Fund Project of Inner Mongolia Autonomous Region (2021); Talent Development Fund Project of Inner Mongolia Autonomous Region [2021]; Fundamental Research Funds for Inner Mongolia University of Science and Technology [2022].