Efficient Photoreduction of Hexavalent Chromium Using the Reduced Graphene Oxide–Sm₂MoO₆–TiO₂ Catalyst under Visible Light Illumination

Abstract

In past years, the presence of toxic heavy metal ions in water and soil has caused major health problems. The ternary type semiconductor material, reduced graphene oxide (rGO)–Sm2MoO6–TiO2, has been investigated as a photocatalyst for the reduction of soluble chromium­(VI) into (III) for the first time. The as-synthesized rGO–Sm2MoO6–TiO2 catalyst was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, X-ray photoelectron spectroscopy, FT-Raman, Fourier transform infrared, and optical spectroscopy. The maximum Cr­(VI) reduction of 96% was achieved within 70 min under visible light illumination. The powder XRD analysis confirmed the formation of anatase TiO2. Field-emission SEM images depicted well-dispersed rGO sheets, and TiO2 and Sm2MoO6 particles are randomly distributed onto rGO. The reduction of Cr­(VI) by rGO–Sm2MoO6–TiO2 was considerably greater than the reduction by Sm2MoO6, TiO2, Sm2MoO6–rGO, TiO2–rGO, and Sm2MoO6–TiO2. Sm2MoO6 acts as an effective cocatalyst to TiO2 to enhance the separation of photo-generated electron–holes. Even after six consecutive cycles, the photoreduction of Cr­(VI) was more than 85%, which reveals that the excellent reusability performance of the catalyst for practical applications. The photogenerated electron plays an important role in the reduction of Cr­(VI) into nontoxic Cr­(III), and the synergistic effect of rGO greatly improved the separation of h+ and e– pairs.

One-step hydrothermal synthesis of Sb2WO6 nanoparticle towards excellent LED light driven photocatalytic dye degradation

“…For example, Chromium exists mainly in hexavalent Cr(VI) and trivalent Cr(III) forms. Among these, Cr(VI) is a type I carcinogenic causing chronic ulcers, gastrointestinal tract damage while Cr(III) is one of the essential micronutrient for human health [14,15,16]. According to World Health Organization (WHO), the maximum allowable limit for the Cr(VI) in drinking water is 0.05 ppm [14,17].…”

Sol-Gel Preparation of Tio2-Cds Composite Material for Photocatalytic Application

“…Show the photodegradation of TiO 2 and TiO 2 -CdS nanocomposite respectively. From the figure, the result it could be observed that the photo degradation of MB dye was found to be higher in the TiO 2 -CdS composite as compared with pure TiO 2 , due to the presence TiO 2 -CdS in the composite, which may be enhance the dye removal efficiency [11][12][13].…”

Efficient visible-light-driven reduction of hexavalent chromium catalyzed by conjugated organic species modified hourglass-type phosphomolybdate hybrids

“…16 Thereinto, photocatalysis with the merits of environmental friendliness, low toxicity and directly using solar energy has become a preferable and cost-effective route for the treatment of Cr(VI) in wastewater. [17][18][19] The key issue is to develop efficient heterogeneous photocatalytic materials. In this field, plentiful photocatalysts such as TiO 2 , 20 ZnO, 21 CdS, 22 etc.…”