Surface deposition of magnesium ferrite
nanoparticles
(MgFe2O4 NPs) with bimetallic gold/silver (Au/Ag)
nanoparticles
was conducted using the seed-mediated growth method to obtain magnetic–metallic
composite catalysts for use in the catalytic reduction of nitroaromatics.
Two types of amine-functionalized MgFe2O4 and
MgFe2O4@SiO2 NPs were used as magnetic
supports for the surface deposition process. The combination of several
characterization analyses (i.e., XRD, XPS, TEM, SEM, EDS, and VSM)
confirmed the successful syntheses of the MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag NPs.
The catalytic reduction of 4-nitrophenol using sodium borohydride
as a reducing agent revealed that the reaction was completed within
2 min by using MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag NPs as catalysts. The appearance
rate constant of the MgFe2O4/Au/Ag NPs was slightly
higher than that of the MgFe2O4@SiO2/Au/Ag NPs. In terms of reusability, high conversion (>80%) of
the
reduction of 4-nitrophenol was still obtained after 7 and 10 consecutive
cycles for the MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag catalysts, respectively. Interestingly,
these two catalysts exhibited the highly catalytic conversion of the
chosen nitroaromatic derivatives (i.e., 4-nitrobenzaldehyde and 4-nitroaniline).
On the whole, the MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag NPs could be utilized
as suitable and sustainable catalysts for the catalytic reduction
of nitroaromatics due to several desirable features (i.e., high activity,
facile and rapid separation by a magnet, and good reusability).