Preparation and characterization of magnetic photocatalyst from the banded iron formation for effective photodegradation of methylene blue under UV and visible illumination

Abstract

The present study devoted to the production of an efficient and low-cost magnetic photocatalyst (γ-Fe2O3/ Fe3O4/ SiO2) from the banded iron formation (BIF) via a single-stage heat-treatment process. The X-ray diffraction (XRD) analysis of Argon modified BIF ore showed complete phase transformation of hematite phase into maghemite. The hematite conversion into the maghemite phase was confirmed from the Fe2p and O1s XPS spectra of the Ar-modified BIF ore. SEM-EDX results revealed the existence of carbon sheets around the iron oxide grains due to polyvinyl alcohol (PVA) decomposition. Optical characterization revealed that Ar-modified BIF has the lowest band gap energy of about 4.2 eV and the lowest photoluminescence emission peak suggesting the highest hole-electron recombination rate among all BIF samples. Various affecting parameters on the photocatalytic performance of both original and modified BIF ore samples were consistently optimized for decolorization of methylene blue (MB) as the model reaction under ultraviolet (UV) light including reaction time, pH and photocatalyst dose. The kinetics of MB photocatalysis on the BIF samples showed an excellent fitting to the pseudo-first-order reaction. The Ar-modified BIF samples exhibited the maximum photocatalytic efficiency of about 87.5% under UV and 76.9% under visible light because of the combined effects of structure defects, oxygen vacancies, and carbon sheets. This research opens the way for the significant and multiple uses of natural raw materials as fast collective photocatalyst under magnetic field for wastewater treatment on a large scale.