Graphene Based Copper‐Nickel Bimetal Nanocomposite: Magnetically Separable Catalyst for Reducing Hexavalent Chromium

Abstract

Graphene based copper‐nickel bimetal nanocomposite (Cu3Ni2‐rGO) was prepared via a one‐step solvothermal procedure, in which Ni(OH)2 and Cu(OH)2 were used as precursors. Structural characterization confirms that the as‐prepared Cu3Ni2‐rGO nanocomposite is composed of Cu3Ni2 nanoparticles in the size range of 20–100 nm and the reduced graphene oxide (rGO) sheets. Benefiting from the combination of Cu3Ni2 and rGO, the Cu3Ni2‐rGO nanocomposite exhibits excellent catalytic performance on reducing highly toxic Cr(VI) at room temperature. The reduction of Cr(VI) (40 mL, 100 mg L−1) can be completed within 6 min using Cu3Ni2‐rGO nanocomposite as the catalyst, which is much more efficient than using monometallic nanocomposite containing only Cu or Ni. Moreover, Cu3Ni2‐rGO nanocomposite can be magnetically separated, which enables effective recycle. Besides, Cu3Ni2‐rGO shows good cycling stability.

Inorganic nanoparticles for reduction of hexavalent chromium: Physicochemical aspects

“…Similarly Li et al (2016c) studied catalytic Cr(VI) reduction by oxalic acid at different pH values ranging from 2 to 7 under similar reaction conditions and reported pH = 2 as optimum pH for rapid conversion of Cr(VI) to Cr(III). Yao et al (2020) have recently reported effect of pH of the medium on catalytic Cr(VI) reduction to Cr(III) with formic acid using RGO supported Cu-Ni bimetallic nanoparticles as catalyst and have found exactly same trend of pH dependence of reduction of Cr(VI). They also reduced Cr(VI) with different reducing agents including methanol (neutral), citric acid (pH = 1.0) and sodium borohydride (pH = 8) but formic acid (pH = 2) was found to be the best one because of its dual role in reduction process.…”

“…Some other factors like nature of reducing agent, nature of supports used for stabilization of nano-catalysts, weight ratio of metal nanoparticles to supports, content of Cr(VI) and reducing agents may also affect the rate of reduction of Cr(VI) ( Yao et al, 2020 ) but data reported on such kind of factors is limited and has not been discussed in this report. Role of such kind of factors is not much clear and needs further studies for optimization of process parameters to carry out reduction of Cr(VI) at large scale.…”

“…Au-Pt bimetallic nanoparticles were found to be stable over the time and proved to have high activity for reduction of Cr(VI). Fabrication of RGO supported bimetallic nanoparticles for reduction of Cr(VI) has been widely reported in literature using same methodology as described above with slight modifications and can be found in recent literature ( Vellaichamy and Periakaruppan, 2016 ; Li et al, 2018 ; Yao et al, 2020 ; Lu et al, 2017 ).…”

“…Moreover, supporting materials of nanocatalysts should be able to afford harsh reaction conditions without any change in their morphology and functionality. Yao et al (2020) reported recycling of reduced graphene oxide stabilized Cu-Ni bimetallic nanoparticles from Cr(VI) catalytic reduction mixture using external magnetic field. Catalyst was found to recyclable up to eight cycles without any significant loss of activity.…”

Comparative Study of CuO, Fe3O4 and CuFe2O4/CuO over Montmorillonite Clay: Green Synthesis, Characterization and Catalytic Activity

“…[6] Nowadays, to promote the application of nanoparticles, the preparation of copper and their oxides has been investigated extensively. [7] Furthermore, copper-containing compounds with the spinel-type structure and also magnetic nanoparticles have a potential catalytic application. [8,9] Developing a simple method to assemble nanoparticles with well dispersion and stability, and their immobilization on active support is desirable methodology from the viewpoint of green synthesis and manufacturing cost.…”