Adsorption and desorption characteristics and mechanism of Cd in reclaimed soil under the influence of dissolved organic carbon

Organic acids are widespread in the environment and play an important role in the adsorption, desorption, and migration of soil Cd. This study evaluated the characteristics and mechanism of Cd adsorption and desorption in reclaimed soil from Panyi Mine in the Huainan mining area under the influence of humic acid (HA) and citric acid (CA). The addition of HA and CA inhibited the adsorption and enhanced the desorption of Cd in reclaimed soil, with HA having a stronger effect than CA. As the concentration of added HA or CA increased, 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 for higher concentrations of organic acid. Cd adsorption and desorption could be described as a logarithmic function of organic acid concentration. The kinetic curves of Cd adsorption and desorption in reclaimed soil under the influence of organic acids show that both adsorption and desorption involved two stages: a fast reaction stage followed by a slow reaction stage.