Cu/ZnO/Al2O3 catalysts with different compositions
were prepared from Cu–Zn–Al layered double hydroxides
(LDHs) and tested for the water–gas shift reaction. LDHs were
synthesized by the coprecipitation method, and Cu–Zn–Al
LDHs or Cu–Al LDHs could be formed depending on the (Cu + Zn)/Al
atomic ratio. Upon calcination, LDHs decomposed to form mixed metal
oxides consisting of CuO, ZnO, ZnAl2O4, CuAl2O4, and/or amorphous Al2O3. After reduction, well dispersed Cu metal particles with 18–48%
dispersion and 2–6 nm size were formed. It was observed that
the initial activity of Cu/ZnO/Al2O3 catalysts
was proportional to the number of surface Cu0 atoms and
the 30%Cu/Zn1Al catalyst showed the highest activity. Moreover,
this optimum catalyst exhibited better activity, thermal stability,
and long-term stability than a commercial Cu/ZnO/Al2O3 catalyst. It was considered that a synergetic effect between
Cu metal and ZnAl2O4 spinel might exist and
play a key role for the high catalytic performance.
An innovative method of combustion–calcination of a nitrate–ethanol solution to produce magnetic Co0.5Ni0.5Fe2O4 nanoparticles was developed. The calcination temperature and the volume of ethanol were two pivotal elements that determine the properties of the Co0.5Ni0.5Fe2O4 nanoparticles in this study. When the volume of ethanol used was increased from 20 ml to 40 ml, the crystallinity of the Co0.5Ni0.5Fe2O4 nanoparticles increased; further increase of the volume of ethanol decreased the crystallinity. The smallest nanoparticle was obtained using 20 ml ethanol. As the calcination temperature increased from 400 °C to 700 °C, the saturation magnetization of the Co0.5Ni0.5Fe2O4 nanoparticles increased from 12.8 emu g−1 to 30.8 emu g−1. Co0.5Ni0.5Fe2O4 nanoparticles fabricated using 20 ml ethanol at 400 °C were used to study the removal of methyl blue (MB) by adsorption. Experimental data revealed that the adsorption was best described by pseudo-second kinetics. The adsorption isotherm applied the Temkin model, which indicated the presence of a single and multilayer associative mechanism in the adsorption of MB on the Co0.5Ni0.5Fe2O4 nanoparticles. The effect of pH and recycling on the adsorption was measured. At pH values ≥5, the adsorption was high. After eight cycles of use and recycling, the relative removal rate of MB by the Co0.5Ni0.5Fe2O4 nanoparticles was 75% of the initial adsorption value.
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