Reduction of 4-Nitrophenol to 4-Aminophenol by Reusable CuFe5O8-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 (CuFe5O8) 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 degrees C to 900 degrees C. The material characterizations, including X-ray diffraction, N2 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 CuFe5O8 and copper oxide phases, where the formers are rich in Cu2+, Fe2+, and Fe3+ ions. The electron transfer between Cu2+, Fe2+, and Fe3+ led to the high efficiency of the catalytic reaction of the synthesized copper ferrites. Especially for the sample calcined at 600 degrees C, the apparent kinetic constant (k) for a reduction of 4-nitrophenol was equal to 0.25 min-1, illustrating nearly 100% conversion of 4-nitrophenol to 4-aminophenol within less than 9 min. Regarding the N2 adsorption/desorption isotherms, the samples calcined at 600 degrees C have the highest specific Brunauer-Emmett-Teller (BET) surface area (15.93 m2 g-1) 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.