Removal of phosphate using iron oxide nanoparticles synthesized by eucalyptus leaf extract in the presence of CTAB surfactant

• Iron oxide nanoparticles (IONP) were synthesized using Eucalyptus leaf extract.
• Fast adsorption of phosphate was achieved only 45 min by IONP.
• Phosphate adsorption onto the IONP was observed in a wide pH range (1–11).
• The removal mechanism of phosphate using IONO was proposed.

This study investigated the use of cetyltrimethylammonium bromide (CTAB) as a stabilizer in green synthesis to improve the reactivity of iron oxide nanoparticles (IONP). Results show that efficiency in removing phosphate increased from 71.0% to 97.3%. To understand how to improve the reactivity of IONP by CTAB: firstly, characterizations of IONP before and after phosphate removal by SEM, EDS, FTIR, XPS show the adsorption of P onto the IONP; secondly, batch experiments indicate that the adsorption capacity of phosphate increased when temperature or initial phosphate concentration increased and decreased with an increase in both adsorbent dose and pH. Adsorption followed the pseudo-second-order kinetics model and the equilibrium data fitted well to the Langmuir isotherm. Thermodynamic data confirmed the spontaneous and endothermic nature of the adsorption process. Finally, it was proposed that the adsorption of phosphate using CTAB-modified IONP was mainly associated with inner-sphere complexing mechanism and electrostatic attraction.