Humic Acid Extracted from Danty via Catalytic Oxidation Using H(2)O(2)/Birnessite: Characteristics and Agricultural Beneficial Effects

[Image: see text] 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 H(2)O(2) 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, H(2)O(2) 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.