Calcium peroxide, with the chemical formula CaO2, has a relatively high oxygen and calcium content. Its high oxygen and alkaline properties effectively adsorb and purify various phosphates in water, especially orthophosphates. Under normal circumstances, organic phosphorus and polyphosphates hydrolyze into orthophosphates under acidic conditions. Its effectiveness is significantly affected by pH, dosage, and coexisting substances, and may be accompanied by the oxidative decomposition of organic phosphorus.

1. In the presence of high concentrations of coexisting anions, the phosphorus removal capacity of calcium peroxide(CaO2) may decrease by 15%. Therefore, the presence of coexisting anions should be minimized during CaO2 phosphorus removal. This may be because coexisting anions compete with phosphate ions for adsorption sites. Since the number of adsorption sites on the adsorbent is limited, coexisting anions occupy a portion of these sites, reducing the number of available phosphate ion adsorption sites, inhibiting Ca-P formation, and thus reducing the phosphorus removal efficiency of CaO2. 1. The H₂O₂ and reactive oxygen species produced by the decomposition of calcium peroxide can oxidize and decompose organic phosphorus compounds in water, converting them into inorganic orthophosphates. This process alters the form of phosphorus, potentially affecting the overall removal efficiency and pathway.

2. CaO2 gradually decomposes upon contact with water, generating Ca(OH)₂ and H₂O₂. The resulting Ca²⁺ can react with phosphate ions (PO₄³⁻) in water to form Ca₅(PO₄)₃OH, which is sparingly soluble in water, or other forms of calcium phosphate precipitate. This is the most important and effective pathway for phosphate removal.

3. The CaO2 adsorption rate increases with increasing phosphate concentration in the solution, reaching adsorption equilibrium in approximately 240 seconds. Higher solution concentrations allow for more phosphorus adsorption by the substrate. Furthermore, the concentration difference between the solution and the liquid film on the substrate surface increases with increasing solution concentration, leading to a greater driving force for phosphorus migration to the substrate surface. Therefore, increasing solution concentration is beneficial for increasing the amount of phosphorus adsorbed by the substrate.

Calcium peroxide(CaO2) purifies phosphates primarily through precipitation, adsorption, oxidation, and controlled release. It is suitable for deep purification of low-concentration phosphorus, reshaping sediment structure, reducing total phosphorus (TP) by approximately 20% and potential reactive phosphorus by approximately 30%, while simultaneously releasing oxygen, adjusting pH, and removing organic matter. It is well-suited for treating black and odorous water bodies, landscape water, and aquaculture wastewater.