Humic Acid Extracted from Danty via Catalytic Oxidation Using H₂O₂/Birnessite: Characteristics and Agricultural...

Extraction optimization is very important for the quality of humic acid (HA). In this study, actived HA (HA_b) was extracted from danty via catalytic oxidation using birnessite as a catalyst and H₂O₂ as an oxidant. Single-factor experiments and the response surface method were used to optimize the acidic functional group content of HA_b. It was found that the maximum acidic functional group content of HA_b can be achieved when danty-crushing time, H₂O₂ concentration, and birnessite dose were 105.7 min, 20, and 2%, respectively. Fourier transform infrared spectra showed that HA_b had more surface functional groups than commercial HA (HA_c) and HA extracted using the traditional method of the International Humic Substances Society (HA_I). In addition, acidic functional group titration showed that HA_b had 84.3% more acidic functional groups and 118.9% more carboxyl groups than HA_I. Additionally, HA_b had the greatest effect on promoting the dissolution of carbonate and bicarbonate, promoting the settlement of calcaline alkaline soil, and improving the germination rate of wheat seeds under saline and alkaline stress. This study provides a basis for the efficient extraction of active HA with rich functional groups and its application in agriculture and many other fields.