Olive leaves extract mediated zero-valent iron nanoparticles: synthesis, characterization, and assessment as adsorbent for nickel (II) ions in aqueous medium

Abstract

Zero-valent iron nanoparticles (NZVI-NPs) possess significantly high surface area and volume ratio, and this unique surface characteristic has enhanced reactivity to their adsorption potential. In this work, a bio-matter (Olive leaves extract) is deployed as a nature-inspired reducing agent for the synthesis of NZVI-NPs. The particle size of NZVI-NPs has been determined using particle sizer. The NZVI-NPs are characterized using analytical and morphological techniques such as ultraviolet − visible spectroscopy (UV − vis), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), and Fourier transform infrared (FTIR) spectroscopy. The average crystalline size of NZVI-NPs are around 30–60 nm while maximum adsorption is at 225 nm. XRD spectrum shows two distinctive diffraction peaks at 25.40° and 42.50° corresponding to lattice plane value indexed at (200) and (222) planes of faced centered cubic (FCC). At optimized experimental conditions, NZVI-NPs show 97% removal efficiency of Ni⁺² ions from aqueous solution. The equilibrium time has been found to be 55 min and the monolayer maximum adsorption capacity is 139.5 mg/g. Kinetically, Ni⁺² ions adsorption has been modelled using various physical isotherms and the data best fitted Freundlich isotherm model and pseudo-first-order kinetic; revealing a maximum adsorption capacity of 139.5 mg/g at 25 ± 3 °C and pH of 6.5. Desorption tests affirm the possibility of recovering reasonable amount of NZVI-NPs after used. The specific surface area of the NZVI-NPs sample measured by BET analysis is 21.9967 m²/g indicating a high adsorption capacity.

Graphical Abstract

Keywords:

• Application
• Characterization
• Green synthesis
• Recovery
• Zero-valent iron nanoparticles

Acknowledgments

The authors would like to thank the Head of Department of Mechanical Engineering, Faculty of Engineering, Duzce University, Turkey for granting us the permission to use some of their facilities.

Disclosure statement

The authors declare no competing interest.