In this research, novel chemically Expanded Graphite (EG) modified by magnesium oxide (MgO) nanoparticles were synthesized and applied to remove phosphate from aqueous solutions. The seawater was also used instead of magnesium Chloride (MgCl2) as a source of magnesium ions which indicated similar promising results. Different analyses investigated the characteristics of the adsorbent. The Field-Emission Scanning Electron Microscopy (FESEM) images, Energy-Dispersive Spectroscopy (EDS), and the X-ray Diffraction (XRD) analysis indicated that MgO nanoparticles were immobilized on EG surface crystalline structures; furthermore, Raman and Fourier Transform Infrared (FTIR) spectra displayed the surface functional groups of the adsorbent. The Brunauer-Emmett-Teller (BET) analysis indicated the surface areas of 10.99 to 26.92 m(2)/g for EG and composite, respectively. The maximum adsorption capacity of the composite was observed at the MgO/EG mass ratio of 0.52. The interfering effects of co-existing (SO42- Cl-, NO3-) ions were also studied, and the results showed that commonly co-existing ions have no significant impact on the adsorption process. Kinetics experiments were conducted to understand the adsorption mechanism of the study. The experimental data were well fitted with pseudo-second-order and intraparticle diffusion models. The experimental equilibrium data were fitted into the Langmuir model, demonstrating a remarkable adsorption capacity of 491.6 mg/g for the phosphate at the initial pH of 7, the adsorbent dosage of 1 g/L, and contact time of 90 min. The feasibility of the EG-MgO application for the post-treatment of real municipal effluent was also examined, confirming excellent phosphate removal.
