Poonam Benjwal

Enhanced photocatalytic degradation of methylene blue and adsorption of arsenic(III) by reduced graphene oxide (rGO)–metal oxide (TiO2/Fe3O4) based nanocomposites

Reduced graphene oxide (rGO) and metal oxide based binary (rGO–TiO2/rGO–Fe3O4) and ternary (rGO–Fe3O4–TiO2) nanocomposites with enhanced photocatalytic and adsorption properties are successfully synthesized by a simple one-step solvothermal process. The microscopy images of the nanocomposites show that the ferric oxide (Fe3O4) and titania (TiO2) nanoparticles are firmly anchored over rGO, which enhances the surface area of the resultant nanocomposites. The as-synthesized nanocomposites are evaluated for the removal of methylene blue dye under UV and visible light irradiation as well as for the adsorption of As(III) from aqueous solution. Compared to binary, the ternary (rGO–Fe3O4–TiO2) nanocomposite exhibits the highest dye degradation efficiency (∼100% within 5 minutes). This enhancement is attributed to the synergetic interaction and increase in the surface area of rGO–Fe3O4–TiO2. For As(III) adsorption, the adsorption data are obtained by Langmuir and Freundlich adsorption isotherms. Compared to binary nanocomposites, the maximum monolayer adsorption capacity (147.05 mg g−1) is observed for rGO–Fe3O4–TiO2. These results reveal that the rGO–Fe3O4–TiO2 nanocomposite has potential application in water/wastewater treatment.

Removal of methylene blue from wastewater under a low power irradiation source by Zn, Mn co-doped TiO2 photocatalysts

In present study, a series of Zn, Mn co-doped titania (TiO2) photocatalysts with varying dopant concentrations (0.0, 1.0 and 2.0 at%) were synthesized via the sol–gel process. The co-doped photocatalysts were characterized using XRD, XPS, SEM, TEM, Raman, FTIR and UV-vis DRS techniques, where methylene blue was used as a probe environmental pollutant. The photocatalytic performances of the synthesized photocatalysts were evaluated under very low (∼2 W) UV and visible power irradiation sources. Analysis of X-ray diffraction patterns suggests the multiphase structure of the photocatalyst, while XPS results demonstrate that in co-doped TiO2, the oxidation state of doped Zn metal ions is 2 (Zn2+), while Mn is in +2 and +3 (Mn2+/Mn3+) state. The optical study results reveal a red shift in the co-doped samples, where with an increase in co-dopant concentration, the band gap is reduced. The highest photocatalytic degradation of MB is obtained with 1.0 at% Zn, Mn co-doped TiO2, which is due to enhancement of light absorbance in the UV region caused by the additional impurity energy levels introduced in the bad-gap of TiO2 by the co-dopants. The as-synthesized 1.0 at% Zn, Mn co-doped TiO2 provides a very high degradation efficiency (66.6 W−1 min−1) and thus may be practically used in the dye removal process efficiently.