Phosphorus (P) removal from aqueous solutions was investigated using TiO2, Al2 O3, and Fe3O4 nanoparticles (NPs). Adsorption study was performed to determine the optimum operation conditions such as adsorption time, temperature, pH, and adsorbent dosage. Sorption isotherms were well described by linear, Freundlich and Langmuir models. The maximum adsorption capacity of P was 28.3, 24.4, and 21.5 mg g21 for TiO2, Fe3O4 and Al2O3, respectively. Desorption analysis showed that the desorption capacities were in an order of Al2O3>Fe3O4>TiO2. Kinetic data were best fitted with pseudo-second-order and intra-particle diffusion kinetic models. Scanning electron microscopy (SEM), energy dispersive X-ray (XRD), and NPs solution saturation indices (SI) before and after P sorption showed that the main mechanism of P sorption by TiO2 was adsorption, whereas P sorption by Al2O3 and Fe3O4 were due to adsorption and precipitation. Results showed that double layer model (DLM) could be modeled P adsorption onto adsorbents over a wide range of pH. Thermodynamic parameters confirmed the endothermic and not spontaneity nature of the P adsorption. These NPs have potential for use as efficient sorbents for the removal of P from aqueous solutions and TiO2 NPs were identified as the most promising sorbent due to their high metal uptake.
