Abstract
Organic acids are widespread in the environment, where they play an important role in the adsorption, desorption, and migration of Cd in soil. This study evaluated the characteristics and mechanisms of Cd adsorption and desorption in reclaimed soil from the Panyi Mine, in the Huainan mining area (China), under the influence of humic acid (HA). The addition of HA inhibited the adsorption of Cd but enhanced its desorption in reclaimed soil. With an increasing concentration of added HA, the adsorption capacity of Cd in the reclaimed soil gradually decreased, while the desorption capacity gradually increased. That is, the adsorption inhibition/desorption promotion effect was stronger under higher concentrations of organic acid. Cd adsorption and desorption dynamics could be described as a logarithmic function of organic acid concentration. Kinetic curves for Cd adsorption and desorption in reclaimed soil under the influence of organic acid showed that both adsorption and desorption involved two stages: a fast reaction stage, followed by a slow reaction stage. The factors influencing the capacity of Cd adsorption and desorption in soil were analyzed by gray correlation analysis, and their resulting rank order was as follows: Cd concentration > HA concentration > pH > temperature. Using linear regression analysis, a multi-factor coupling functional model of soil Cd adsorption and desorption under the influence of DOC was established, in the form of Y = a + bXHA + cXT + dXPH + eXCd.
Adsorption and desorption characteristics and mechanism of Cd in reclaimed soil under the influence of dissolved organic carbon