Reduction of 4-Nitrophenol to 4-Aminophenol by Reusable CuFeO-Based Catalysts Synthesized by Co-Precipitation Method.

The reduction of unfriendly 4-nitrophenol to make it unimpactful with the environment (4-aminophenol) was carried out using the metastable form of copper ferrite (CuFeO) synthesized by the co-precipitation of metal nitrate salts, an efficient method with inexpensive and abundant starting materials. The samples were obtained by calcination at various temperatures ranging from 600 °C to 900 °C. The material characterizations, including X-ray diffraction, N adsorption/desorption, scanning electron microscope, X-ray absorption spectroscopy, and ultraviolet-visible spectrometry, were employed to identify the detailed structures and describe their correlations with catalytic activities. The X-ray diffraction and X-ray absorption spectroscopy analyses revealed the presence of mixed CuFeO and copper oxide phases, where the formers are rich in Cu, Fe, and Fe ions. The electron transfer between Cu, Fe, and Fe led to the high efficiency of the catalytic reaction of the synthesized copper ferrites. Especially for the sample calcined at 600 °C, the apparent kinetic constant (k) for a reduction of 4-nitrophenol was equal to 0.25 min, illustrating nearly 100% conversion of 4-nitrophenol to 4-aminophenol within less than 9 min. Regarding the N adsorption/desorption isotherms, the samples calcined at 600 °C have the highest specific Brunauer-Emmett-Teller (BET) surface area (15.93 m g) among the others in the series, which may imply the most effective catalytic performance investigated herein. The post-catalytic X-ray diffraction investigation indicated the stability of the prepared catalysts. Furthermore, the chemical stability of the prepared catalysts was confirmed by its reusability in five consecutive cycles.