[Phosphate Adsorption from Water on CaO₂-loaded Magnetic Diatomite]

In this study,magnetic diatomite was used as a carrier to load calcium peroxide(CaO₂) nanoparticles,fabricating a high efficiency phosphate adsorption and recovery composite material(MDCP).The micromorphology, inner structure,crystalline constituents and element composition of MDCP were characterized by SEM,EDX-mapping,XRD, XDS, and VSM,respectively.The adsorption isotherm data of MDCP exhibited good agreement with the Langmuir isotherm model. According to the Langmuir model,when T=20℃,the maximum monolayer phosphate adsorption capacities can reach 191.84mg·g^-1 for MDCP. The isotherm and kinetics studies showed that MDCP has a regulating effect on the pH of the solution,which can maintain the pH of the solution at the level where adsorption of phosphate occurs on MDCP as a chemisorption process. pH plays a important role on the adsorption of phosphate by MDCP,the pH of effective adsorption ranges from 4 to 10,and the pH of the adsorbed solution can still be maintained in the range of 7 to 9.The MDCP exhibited a high selective adsorption for phosphate in the presence of anions,including Cl^-, SO₄^2-, CO₃^2-, HCO₃^2-, F^-, and NO₃^-.The recovered MDCP could be desorbed by HCl solution,and after desorption, the phosphate removal rate of MDCP after re-loading CaO₂ could still reach 70% of the initial adsorption.