Effect of Particle Size, NaOH Concentration, and S/L Ratio on the Extraction of Humic Acid from Leonardite

Abstract

Humic acids are crucial for soil quality, generating growing agricultural and environmental research interest. This study focuses on statistically evaluating the effect of particle size, solid percentage, and NaOH concentration on the extraction and production of humic acid from leonardite, employing a 2³ experimental design. ANOVA showed that all individual factors significantly impact humic acid extraction (p < 0.05). Furthermore, the factor with the greatest significance according to the F-value is the NaOH concentration. The highest humic acid yield was 875.16 g HA/kg, achieved using a particle size of 375 µm, 0.5 M NaOH, and 4% solids. The results of this study provide a foundation for improving industrial processes for humic acid extraction.