Effect of Fe(III) Modification on the Phosphorus Removal Behavior of Ce(III) Carbonate Adsorbents

Excessive phosphorus (P) in water is the main reason for eutrophication, which has been a global problem for many years. For the adsorption treatment of phosphorus-containing wastewater, adsorbents are key research topics. In this study, we develop the synthesis of a series of Ce/Fe adsorbents by modifying the commercial cerium carbonate with Fe₂(SO₄)₃. By conducting comprehensive analysis with XRD, FTIR, and SEM, we find that the amorphous granular structure and large chunky structure created by the high and low Fe content, respectively, both had a negative effect on the adsorption capacity of phosphate. Among different adsorbents, Ce/Fe-15/3, with Ce loading of 28.33 wt % and Fe loading of 5.66 wt %, exhibits high P adsorption capacity of 58 mg P/g (in pH = 7, 30 mg P/L solution). It also demonstrates excellent selectivity toward phosphate adsorption in Cl^–, SO₄^2–, and NO₃^– solution (up to 20 times of the phosphate molarity) and good adsorption stability in acidic environments (pH = 3–6). The adsorption behavior of Ce/Fe-15/3 can be modeled well by the Langmuir model and pseudo-second-order (PSO) model. By conducting the XPS analysis, we conclude that the adsorption mechanism is a combination effect of Ce/PO₄^3– and Fe/PO₄^3– chemical interactions.