The Enhancing Effect of Green Composite Oxidation System on the Extraction Yield and Sobering Activity of Fulvic Acids and Its Potential Mechanisms

ABSTRACT

Fulvic acids (FA), important components of natural humic substances, possess potential application value in sobering‑up effects, yet their utilization is limited by low extraction yield and insufficient bioactivity. In this study, a green hydrogen peroxide‑peracetic acid composite oxidation system was constructed to efficiently degrade lignite for preparing crude fulvic acids (CFA). Through single‑factor experiments and response‑surface optimization, the optimal conditions were determined as follows: solid‑to‑liquid ratio of 1:9.98, oxidant ratio of 1.25:1, and dilution factor of 1.25. By cleaving weak linkages within the coal matrix to facilitate depolymerization, this system raised the CFA yield from 19% to 47.3%. Structural characterization reveals that CFA2 prepared by the new process contains more abundant acidic functional groups, higher aromaticity and humification degree, as well as more concentrated low‑molecular‑weight fractions. These changes contribute to yield improvement and markedly enhance the sobering‑up bioactivity of CFA2, which may be attributed to its stronger capacities of free‑radical scavenging, metal‑ion chelation and proton donation. This study develops a new green and efficient process for CFA preparation, uncovers the intrinsic correlation among structural optimization, yield improvement and enhanced sobering‑up activity, and provides a theoretical foundation for the application of FA in pharmaceuticals and functional foods.