BACKGROUND: Phosphate is one of the main contaminants responsible for the eutrophication of surface waters, and adsorption is a potential treatment method for this pollutant. A magnetic adsorbent manufactured from magnetite (Fe 3 O 4 ) can be recovered easily from treated water by magnetic force, without requiring further downstream treatment. In this research, the surface of magnetite modified with aluminum and silica (Al/SiO 2 /Fe 3 O 4 ) was used to adsorb phosphate in an aqueous solution in a batch system.
RESULTS:
The optimum solution pH for phosphate adsorption by Al/SiO 2 /Fe 3 O 4 was found to be 4.5. The phosphate adsorption behavior of Al/SiO 2 /Fe 3 O 4 was in good agreement with both the Langmuir and Freundlich adsorption isotherm, and the maximum adsorption capacity (q m ) and Gibbs free energy of phosphate was 25.64 mg g -1 and -21.47 kJ mol -1 , respectively. A pseudo-second-order model could best describe the adsorption kinetics, and the derived activation energy was 3.52 kJ mol -1 . The optimum condition to desorb phosphate from Al/SiO 2 /Fe 3 O 4 is provided by a solution with 0.05 mol L -1 NaOH. CONCLUSIONS: Magnetic adsorbent is a potential material for a water treatment method. The results of this study will be helpful in the development of aluminum modified silica magnetic adsorbents that can be used to remove phosphate in aqueous solution.