Impacts of calcium peroxide on phosphorus and tungsten releases from sediments.

In this study, CaO was used as a capping material to control the release of Phosphate (P) and tungsten (W) from the sediment due to its oxygen-releasing and oxidative properties. The results revealed significant decreases in SRP and soluble W concentrations after the addition of CaO. The mechanisms of P and W adsorption by CaO were mainly chemisorption and ligand exchange mechanisms. In addition, the results showed significant increases in HCl-P and amorphous and poorly crystalline(oxyhydr)oxides bound W after the addition of CaO. The highest reduction rates of sediment SRP and soluble W release were 37 and 43%, respectively. Furthermore, CaO can promote the redox of iron (Fe) and manganese (Mn). On the other hand, a significant positive correlation was observed between SRP/soluble W and soluble Fe (II) and between SRP/soluble W and soluble Mn, indicating that the effects of CaO on Fe and Mn redox play a crucial role in controlling P and W releases from sediments. However, the redox of Fe plays a key role in controlling sediment P and W release. Therefore, CaO addition can simultaneously inhibit sediment internal P and W release.