Photocatalytic activity of NiFe2O4 and Zn0.5Ni0.5Fe2O4 modified by Eu(III) and Tb(III) for decomposition of Malachite Green

M P Tsvetkov,M M Milanova,E P Valcheva,I R Ivanova,J Ts Zaharieva

doi:10.1515/chem-2019-0116

Abstract

AbstractThe mixed metal oxides NiFe2O4 and Zn0.5Ni0.5Fe2O4 with a spinel-like structure, pure and modified with the lanthanide ions Eu(III) and Tb(III), were prepared by a sol-gel process in which propylene oxide was used as a gelling agent and then tested as photocatalysts. The photocatalytic activity was studied under polychromic visible light irradiation (halogen lamp) for the decomposition of the water pollutant Malachite Green in model solutions which were prepared under laboratory conditions. The modified samples showed a better activity under visible light irradiation than the pure samples. The highest activity under visible light irradiation was observed for Zn0.5Ni0.5Fe2O4 that was modified with 5 wt. % Eu(III) or Tb(III), and which showed the positive effects of the doping ions. Based on the cartographic data for the smooth and equal distribution of Tb(III) on the surface of Zn0.5Ni0.5Fe2O4 particles, the surface processes may have influenced the photocatalytic activity. The energy band gap of the samples was calculated, showing somewhat lower values for the doped samples than the pure ferrites.

Highlights

The mixed metal oxides NiFe2O4 and Zn0.5Ni0.5Fe2O4 with a spinel-like structure, pure and modified with the lanthanide ions Eu(III) and Tb(III), were prepared by a sol-gel process in which propylene oxide was used as a gelling agent and tested as photocatalysts
The samples were prepared by mixing the solutions of the nitrates in 96% ethanol, and stirring the solutions for complete homogenization; propylene oxide was added in a molar ratio of 1:4 to the ethanol, the solutions were continually stirred until a sol was formed
It was found that more than 60 % of the dye was decomposed after 150 min under visible light irradiation

Summary

Introduction

Abstract: The mixed metal oxides NiFe2O4 and Zn0.5Ni0.5Fe2O4 with a spinel-like structure, pure and modified with the lanthanide ions Eu(III) and Tb(III), were prepared by a sol-gel process in which propylene oxide was used as a gelling agent and tested as photocatalysts. The photocatalytic activity was studied under polychromic visible light irradiation (halogen lamp) for the decomposition of the water pollutant Malachite Green in model solutions which were prepared under laboratory conditions. The modified samples showed a better activity under visible light irradiation than the pure samples. The highest activity under visible light irradiation was observed for Zn0.5Ni0.5Fe2O4 that was modified with 5 wt. % Eu(III) or Tb(III), and which showed the positive effects of the doping ions. The energy band gap of the samples was calculated, showing somewhat lower values for the doped samples than the pure ferrites

Methods

Results

Conclusion