Ammonium adsorption by green synthesized iron oxide nanoparticles with Eucalyptus globulus extracts from aqueous solutions

Improper use of ammonium fertilizer could cause this type of pollutant to enter the aquatic ecosystem and enriches water resources. In this research, ammonium adsorption by green synthesized iron oxide nanoparticles with Eucalyptus globulus (EL-Fe NPs) as innovative, inexpensive, and eco-friendly method, was investigated. Characterization of nanoparticles was determined by transmission electron microscopy (TEM), X-Ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The effect of time (0-120), pH (3-11), and KCl salt as ionic strengths on ammonium adsorption by EL-Fe NPS was investigated. Also, kinetics models were fitted with ammonium adsorption data. The results showed iron oxide nanoparticles encapsulated by polyphenols from Eucalyptus globulus extract and have an irregular nanoparticulate structure with a size range between 50-100 nanometers. Ammonium adsorption by EL-Fe NPS was equilibrated at pH≈3.7 after 30 min and 11/86% ammonium was removed from 10 mg/L of initial concentration. Based on the results, this reaction is affected by pH and ionic strength (KCl). By increasing pH, Ammonium removal increased and at pH=7.8 maximum amount of pollutant (76.9%) was removed. Moreover, ionic strength had a contrary effect on ammonium adsorption. In the ionic strengths 0, 0.001, 0.01, and 0.1 ammonium adsorption 76.9, 64.2, 28.2, and 5% was decreased, respectively. These results depict ammonium and potassium compete for adsorption sites of EL-Fe NPs. The pseudo-second-order kinetic model provided a good description for ammonium adsorption (r2=0.998). Considering the effect of increasing the ionic strength in reducing the absorption rate and also the dependence of ammonium absorption on pH, it is expected that the reaction between ammonium and EL-Feb NPs is most likely through electrostatics. In general, it seems that Ammonium adsorption by EL-Fe NPs is influenced by solution chemistry.