Removal of phosphate using calcium and magnesium-modified iron-based adsorbents

- Magnetic Ca and Mg-modified iron oxide adsorbents were synthesized.
- PVA imparted magnetism to the adsorbents for easy separation.
- Batch adsorption experiments were carried out to gain insights on the adsorption kinetics and equilibrium.
- The adsorbents effectively removed phosphates from water at a capacity of nearly 17 mg g−1.

Magnetic calcium (Ca) and magnesium (Mg)-modified iron oxide adsorbents were synthesized using CaCl2, CaCO3, MgCl2, or MgCO3 by a simple combustion method for the remediation of phosphate. Modification with Ca and Mg significantly improved the phosphate adsorption capacity of the magnetic iron oxide adsorbents. Additionally, polyvinyl alcohol (PVA) was incorporated during synthesis to aid in the magnetism of the samples, making the adsorbents easy to separate from solutions. Physicochemical properties of the adsorbents were determined by characterization with X-ray diffraction (XRD), particle analyzer, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high resolution TEM (HR-TEM). Batch adsorption experiments were carried out to gain insight on the materials' ability to remove phosphate from water supplies. Samples without the addition of PVA had higher phosphate capacities (ranging from 16.92 to 16.97 mg g−1) compared to PVA-containing samples (ranging from 12.39 to 16.74 mg g−1), yet the PVA-containing samples were magnetic and thus, easily separable.

New Ca- and Mg-modified iron oxides were successfully synthesized to enhance the adsorption capacity of phosphate of iron oxides.438