Synthesis of MgAC-Fe3O4/TiO2 hybrid nanocomposites via sol-gel chemistry for water treatment by photo-Fenton and photocatalytic reactions

Vu Khac Hoang Bui,Ju-Young Moon,Yejin An,Young-Chul Lee,Jin Seok Choi,Tuyet Nhung Pham,Hyun Uk Lee,Oh-Hyeok Kwon,Ki-Tae Kim,Duckshin Park

doi:10.1038/s41598-019-48398-5

Abstract

MgAC-Fe3O4/TiO2 hybrid nanocomposites were synthesized in different ratios of MgAC-Fe3O4 and TiO2 precursor. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray fluorescence spectrometry (XRF), electron spin resonance spectrometry (ESR), Brunauer-Emmett-Teller (BET), photoluminescence (PL), and UV photoelectron spectroscopy (UPS) were used to characterize the nanocomposites. The increase of MgAC-Fe3O4, in the hybrid nanocomposites’ core-shell structure, led to the decrease of anatase TiO2 peaks, thus reducing the photo-Fenton and photocatalytic activities. According to the obtained data, MgAC-Fe3O4 [0.05 g]/TiO2 showed the best photo-Fenton and photocatalytic activities, having removed ~93% of MB (photo-Fenton reaction) and ~80% of phenol (photocatalytic reaction) after 20 and 80 mins, respectively. On the pilot scale (30 L), MgAC-Fe3O4 [0.05 g]/TiO2 was completely removed after 27 and 30 hours by the photo-Fenton and photocatalytic activities, respectively. The synergistic effect gained from the combined photo-Fenton and photocatalytic activities of Fe3O4 and TiO2, respectively, was credited for the performances of the MgAC-Fe3O4/TiO2 hybrid nanocomposites.

Highlights

magnesium aminoclay (MgAC)-Fe3O4/TiO2 hybrid nanocomposites were synthesized in different ratios of MgAC-Fe3O4 and TiO2 precursor
One remarkable report in this research field is that of Sun et al, who found that a small number Fe3O4 NPs loaded onto TiO2 NPs (Fe/TiO2 ratio: 1/200) could enhance the degradation of organic dye (Reactive Brilliant Red X3B)
Among different MgAC-Fe3O4/TiO2 hybrid nanocomposites on the batch scale, the MgAC-Fe3O4 [0.05 g]/TiO2 sample showed the best photo-Fenton performance, more than ~93% of methylene blue (MB) having been removed after 20 min at a constant rate of ~0.1175 min−1; this was ~10 and ~100 times higher than the performances of MgAC-Fe3O4 [0.1 g]/TiO2 and MgAC-Fe3O4 [0.2 g]/TiO2, which removed ~92 and ~17% of MB from aqueous solution after 180 min of reaction, respectively (Fig. 1a and Table 1)

Summary

Introduction

MgAC-Fe3O4/TiO2 hybrid nanocomposites were synthesized in different ratios of MgAC-Fe3O4 and TiO2 precursor. Due to the small band gap of Fe3O4 NPs (0.1 eV), Fe3O4-TiO2 composites will increase the rate of electron-hole pairs recombination, with the result that photocatalysis is usually unchanged or even diminished relative to pure TiO2 NPs12 To overcome this problem, Zheng et al demonstrated that special structures such as core-shell microspheres in Fe3O4-TiO2 composites can delay the recombination of photo-induced electrons[12]; other researchers have used noble metal (Au or Ag) or rare elements (e.g. Eu) as electron traps to enhance electron-hole separation and facilitate electron excitation by creating a local hole in the electrical field[13,16,17]. Photocatalytic materials have been developed based on 2-D materials such as graphene[21]

Methods

Results

Conclusion