: Core/shell magnetic nanoparticles of Fe3O4/Mn0.75Zn0.25Fe2O4 were synthesized using co-precipitation method; and characterized by inductively coupled plasma spectroscopy, Fourier-transform infrared spectroscopy, surface area and porosity analyzer, and transmission electron microscopy techniques. Fe3O4/Mn0.75Zn0.25Fe2O4 nanoparticles were used as adsorbent to remove phosphate from water. The response surface methodology, central composite design, and Design Expert software version 10 were applied to model the process. The model was used to study the effects of the operating conditions such as pH, adsorbent dose, and phosphate initial concentration. The significance of the model was confirmed by large F-value, and low p-value. The results indicated that adsorbent dose had the largest effect on the response. The phosphate adsorption decreased with increasing pH. The adsorption isotherm followed Langmuir model. The thermodynamic studies showed the endothermic nature of the process. The kinetics of the adsorption was studied, and the experimental data were better fitted to the pseudo second order model.
