Effect of dry-wet alternation on the adsorption of dissolved organic matter by soil minerals

Dry-wet alternation has an essential effect on soil minerals' adsorption of dissolved organic matter. In this study, kaolin, illite, and hematite were subjected to 0, 1, 3, and 6 dry-wet alternation incubation tests, respectively, and the changes in the characterization of the three minerals were explored by using a BET specific surface area analyzer and an X-ray diffractometer. The effects of different dry-wet alternation treatments on the adsorption of tannic acid and glucose as the representatives of dissolved organic matter were investigated by isothermal and kinetic adsorption tests as well as by different model-fitting methods. The effects of different dry-wet alternation treatments on the adsorption of tannic acid and glucose by the three minerals were investigated by isothermal and kinetic adsorption tests and different model fitting methods. The results showed that alternating dry-wet treatment could change the three minerals' specific surface area and average pore diameter to different degrees. Still, the spacing of the crystal layers did not change significantly. The dry-wet alternation did not alter the adsorption process and tannic acid and glucose adsorption mode. Still, it affected the equilibrium adsorption amount to different degrees, which was illite>hematite>kaolin, and the intensity of the effect was mainly affected by the decrease of the specific surface area of the minerals, which was not related to the change of the average pore diameter and the spacing of the crystal layers.