Thermally induced oxygen related defects in eco-friendly ZnFe2O4 nanoparticles for enhanced wastewater treatment efficiencies

Basma Al-Najar; Adnan Younis; Layla Hazeem; Shama Sehar; Suad Rashdan; M Nasiruzzaman Shaikh; Hanan Albuflasa; Nicholas P Hankins

doi:10.1016/j.chemosphere.2021.132525

Thermally induced oxygen related defects in eco-friendly ZnFe₂O₄ nanoparticles for enhanced wastewater treatment efficiencies

Chemosphere. 2022 Feb;288(Pt 2):132525. doi: 10.1016/j.chemosphere.2021.132525. Epub 2021 Oct 12.

Authors

Basma Al-Najar¹, Adnan Younis², Layla Hazeem³, Shama Sehar³, Suad Rashdan⁴, M Nasiruzzaman Shaikh⁵, Hanan Albuflasa², Nicholas P Hankins⁶

Affiliations

¹ Department of Physics, College of Science, University of Bahrain, P.O. Box 32038, Sakhir Campus, Bahrain. Electronic address: balnajar@uob.edu.bh.
² Department of Physics, College of Science, University of Bahrain, P.O. Box 32038, Sakhir Campus, Bahrain.
³ Department of Biology, College of Science, University of Bahrain, P.O. Box 32038, Sakhir Campus, Bahrain.
⁴ Department of Chemistry, College of Science, University of Bahrain, P.O. Box 32038, Sakhir Campus, Bahrain.
⁵ Interdisciplinary Research Center for Hydrogen and Energy Storage (IRC-HES), King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia.
⁶ Department of Engineering Science, The University of Oxford, Parks Road, OX3 1PJ, Oxford, UK.

PMID: 34653481
DOI: 10.1016/j.chemosphere.2021.132525

Abstract

Herein, a simple but highly effective strategy of thermal annealing to modulate oxygen vacancies related defects in ZnFe₂O₄ (ZFO) nanoparticles for obtaining enhanced wastewater treatment efficiencies is reported. The as-prepared nanoparticles were thermally annealed at three different temperatures (500 °C, 600 °C and 700 °C) and their phase purity was confirmed by X-ray diffraction (XRD). All samples were found to exhibit pure phases of ZFO with different crystallite sizes ranging from 10 nm to 25 nm. The transmission electron microscope (TEM) images showed well dispersed nanoparticles and a strong correlation of grain size growth with annealing temperature was established. The optical absorption and emission characteristics were estimated through UV-visible and Photoluminescence (PL) spectroscopy. Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) confirmed the variation of oxygen vacancies in the synthesized samples' lattice. The photocatalytic activities of all samples were investigated and the highest efficiencies were recorded for the ZFO samples annealed at 500 °C. Under high salinity condition, the organic dye degradation efficiency of the same sample remained the highest among all. The excellent dye degradation abilities in ZFO samples can be attributed to the abundance of oxygen vacancies in the crystal lattice that slow down the recombination rate during the photocatalysis process. Moreover, cytotoxicity tests revealed that all prepared ZFO samples showed insignificant cell structure effects on Picochlorum sp microalgae, as verified by Fourier-transform infrared (FTIR) spectroscopy. On the other hand, no significant changes were detected on the viable cell concentration and Chlorophyll a content. This work presents a systematic way to finely tune the crystal sizes and to modulate oxygen related defects in ZFO through a highly effective annealing approach to signify their potential in industrial wastewater and seawater treatment processes.

Keywords: Crystal size; Cytotoxicity; Dye mineralisation; Oxygen vacancies; Photocatalysis; Picochlorum sp,.

MeSH terms

Chlorophyll A
Nanoparticles*
Oxygen
Spectroscopy, Fourier Transform Infrared
Water Purification*

Substances

Oxygen
Chlorophyll A