[Adsorption Behavior of Phosphate by CaO Remolded Sediment].

This study simulated the state of CaO loss after in situ coverage and examined the bottom 2 cm of sediment after restoration. Observations and elemental analysis of the sediment using scanning electron microscopy (SEM) and X-ray energy spectrometry (EDX) were also performed. The CaO remodeling notably changed the structure of the sediment; most of the organic matter and iron-manganese oxide attached to the sediment surface was removed, the porosity of the sediment particles increased, and the Ca content was also increased. CaO remodeling stabilized the endogenous phosphorus in the sediment; total phosphorous (TP) was reduced by approximately 20% and potential active phosphorus content was reduced by approximately 30%. Furthermore, the contents of Ca-P and Res-P were significantly increased. The amount of phosphorus released from the remodeled sediment under anaerobic conditions was significantly lower than the original sediment, indicating that the CaO remodeling greatly reduced the risk of endogenous phosphorus release. The Langmuir model was more suitable than the Freundlich and Dubinin-Radushkevich models for describing the isothermal adsorption behavior of the CaO remodeling, which significantly improved the adsorption capacity of the sediment with respect to phosphate from 1.44 mg·g to 20.91 mg·g. The mechanism of adsorption was switched from chemical adsorption to physicochemical adsorption. In addition, the adsorption kinetics of the CaO remodeled sediment with respect to phosphate could be best described using the quasi-second-order kinetic model.