Preparation of iron nanoparticles-loaded Spondias purpurea seed waste as an excellent adsorbent for removal of phosphate from synthetic and natural waters.

The synthesis and characterization of nanoscale zerovalent iron particles (NZVI) supported on Spondias purpurea seed waste (S-NaOH-NZVI) was performed for the adsorption of phosphate (P) ions from waste waters. The effects of various parameters, such as contact time, pH, concentration, reusability and temperature were studied. The adsorption of phosphate ions has been studied in terms of pseudo-first- and -second-order kinetics, and the Freundlich, and Langmuir isotherms models have also been used to the equilibrium adsorption data. The adsorption kinetics followed the mechanism of the pseudo-second-order equation. The thermodynamic parameters (ΔG, ΔH and ΔS) indicated that the adsorption of phosphate ions were feasible, spontaneous and endothermic at 25-80 °C. No significant loss of activity was observed; confirming that the S-NaOH-NZVI has high stability during the adsorption process even after 12th runs. The suggested adsorbent in this paper was also implemented to remove P from the Persian Gulf water. XRD, FTIR and EDX analysis indicated the presence of Fe3 (PO4)2⋅8H2O (vivianite) on the S-NaOH-NZVI@P surface.