Synthesis of Rice-Husk-Carbon-Supported Nickel Ferrite Catalyst for Reduction of Nitrophenols.

In this paper, magnetic NiFe₂O₄-RHC (rice husk carbon) catalysts with different NiFe₂O₄ contents are prepared through a one-step hydrothermal method and employed as a catalyst for the reduction of nitrophenols. The resulting catalysts are characterized using various techniques. It is indicated that the NiFe₂O₄ nanoparticles are well dispersed on the RHC with the average size of 9.97 nm and 224.13 m²·g-1 BET surface area. NiFe₂O₄-RHC (0.75) has the highest activity for the reduction of nitrophenols (k = 0°8872 min-1). The combination of NiFe₂O₄ nanoparticles with RHC results in a dramatic conversion of the inert NiFe₂O₄ into a highly active catalyst for the reduction of nitrophenols at 25 °C employing NaBH4 as the reducing agent in aqueous medium. The excellent catalytic performance of NiFe₂O₄-RHC (0.75) may be attributed to the specific characteristics of the nanostructure and the synergistic effect between NiFe₂O₄ and RHC. The effect of the substituent and temperature are also investigated. The activation energy was reduced to 15.342 kJ mol-1, facilitating the reaction at lower temperature. Furthermore, the catalyst NiFe₂O₄-RHC (0.75) is very cheap when RHC is introduced as the support compared to other carbon materials. The catalyst also exhibits magnetic performance and good stability; it can be used for 10 successive experiments with a conversion of 96%.