Catalytic oxidation of coal waste for sustainable recovery of humic and fulvic acids

Catalytic oxidation of coal waste offers a promising route for sustainable recovery of value-added humic and fulvic acids. In this study, tetra ethylene pentamine (TEPA) was employed as a homogeneous catalyst to enhance hydrogen peroxide (H2O2)-mediated oxidation of leonardite-derived coal waste. Key process parameters, including catalyst dosage, acid concentration, temperature, and reaction time, were systematically optimized. The results showed that a TEPA dosage of 6 wt%, combined with 30 wt% mixed acid solution, 70°C reaction temperature, and 2 h reaction time, provided the maximum humic acid recovery of 77.2% and fulvic acid recovery of 17.65%, achieving a purity of 91%. Compared with conventional acid/alkali extraction methods, the catalytic approach improved yield and selectivity while maintaining structural integrity of the humic substances. These findings demonstrate the potential of TEPA-catalyzed oxidation as a sustainable and efficient method for valorizing coal waste into high-grade humic materials suitable for agricultural and environmental applications.