Preparation of B4C/AgFe2O4 heterostructures for photoreduction of Cr (VI)

Title : Preparation of B4C/AgFe2O4 heterostructures for photoreduction of Cr (VI)

Abstract:

It was aimed to couple boron carbide (B₄C) and silver ferrite (AgFe₂O₄) nanoparticles in the composite heterojunction structure for the Cr(VI) photoreduction application. For this purpose, a polymer precursor, polyvinyl borate (PVB) was synthesized from polyvinyl alcohol and boric acid using the crosslinking reaction. A heat treatment was applied to the as-prepared polymer precursor to convert I to B₄C nanoparticles using the carbothermal reduction process. Then, B₄C/AgFe₂O₄ composites were prepared though the synthesis of magnetic AgFe₂O₄ nanoparticles in the presence of the as-prepared B₄C nanoparticles using an auto-combustion process. B₄C and B₄C/AgFe₂O₄ composite nanoparticles were synthesized successfully, which was proved by Fourier-transform infrared spectroscopy and X-ray powder diffraction analyses. According to field emission scanning electron microscopy and N₂ adsorption-desorption studies, all the samples had a mesoporous surface area and the specific surface area of the prepared samples was close to each other. According to UV-Vis absorption spectroscopy, the composite samples exhibited high light absorption both in the UV light and in the visible light regions. When compared with B₄C, there was an increase in light absorption within the UV-Vis light region. Combining B₄C with magnetic AgFe₂O₄ in the composite heterojunction structure provided improvement in the Cr(VI) photoreduction efficiency. The Cr(VI) photoreduction efficiency increased from 65.1% to 98.0% after 120 min of visible light irradiation. According to photoluminescence spectroscopy, combining B₄C with magnetic AgFe₂O₄ in the composite structure suppressed the recombination of the photoexcited charge carriers on both semiconductors, which might be the reason for the enhancement in the Cr(VI) removal efficiency. Different experiment conditions, like the initial solution pH, the initial solution concentration and the initial catalyst concentration, were investigated for their effects on the Cr(VI) ratio. Under acidic conditions, the Cr(VI) removal rate in the presence of B₄C/AgFe₂O₄ increased to almost 99%. The Cr(VI) photoreduction efficiency decreased to 89.9% when real wastewater spiked with Cr(VI) ions was used instead of the simulated Cr(VI) solution. Based on the reusability experiments and the magnetic property analysis, the prepared composites were reusable for the consecutive Cr(VI) photoreduction processes and could be easily separated from the Cr(VI) solution through the magnetic separation technique.

Audience Take Away: 

• B₄C/AgFe₂O₄ is a new example for photocatalyst. The application potential for Cr(VI) removal from the aquatic environment was explored in this study and will be presented at the conference.
• Highly toxic Cr(VI) can be converted to less toxic Cr(III) through the photoreduction process.
• Combining B₄C with magnetic AgFe₂O₄ enhanced the separation of the photoinduced electron-hole pairs on the photocatalyst, leading to an improvement in the Cr(VI) removal rate.
• Magnetic AgFe₂O₄ enhanced the reusability of the prepared composite photocatalyst.
• Application of the Cr(VI) photoreduction in the wastewater treatment is also new topic. The audience could inform about different photocatalyst for the wastewater treatment purpose.

Biography:

Dr. Ozcan Koysuren received his B.S. degree from Middle East Technical University (Ankara, Turkey) in 2002 and Ph.D. degree from the same University in 2008. Dr. Koysuren started his academic career as a research assistant in the Chemical Engineering department of Middle East Technical University in 2002. He is currently Associated Professor in the Energy Engineering department of Ankara University (Ankara, Turkey). Dr. Koysuren has published 30 research articles in SCI(E) journals.