Synthesis of silver nanoparticles anchored on nickel ferrite/oxidized-graphite composite for the efficient reduction of aqueous P-nitrophenol

Abstract

• Ag-NiFe 2 O 4 /O-graphite exhibits excellent catalytic activity towards reduction of P-NP. • The reduction reaction was performed using sodium borohydride as the reducing agent. • A high normalized reaction rate constant (6.04 ± 0.8 s −1 g −1 ) value was achieved with this catalyst. • The synergistic interaction between nano sized Ag and NiFe 2 O 4 improved the reaction rate. • The material displays improved water cleaning properties. The current study focuses on the synthesis of spherical shaped Ag NPs decorated onto magnetic nickel ferrite/oxidized graphite (NiFe 2 O 4 /O-graphite) support. The synthesized material is thoroughly tested to study the physicochemical properties of the material. The characterization data clearly confirms the successful incorporation of nano sized Ag and NiFe 2 O 4 NPs onto O-graphite surface. Further, the synthesized material is tested as a catalyst towards the reduction of P-nitrophenol (P-NP) with sodium borohydride (NaBH 4 ) as the reducing agent. O-graphite surface failed to reduce P-NP in the presence of NaBH 4. The material (Ag-NiFe 2 O 4 /O-graphite) exhibits excellent catalytic activity with more than 98% reduction of P-NP in less than 1 min with P-NP to NaBH 4 molar ratio of 1:10 and 10 mg of the catalyst. The normalized reaction rate constant data calculated under such reaction condition is 6.04 ± 0.8 s −1 g −1 . The high catalytic activity with an excess of NaBH 4 in the reaction medium is attributed to the synergistic interaction between nano sized Ag NPs and magnetic NiFe 2 O 4 /O-graphite support. Here, Ag NPs acts as an electron transfer medium that transfer electrons to P-NP for the reduction process. In its dual role, NiFe 2 O 4 serves as an electron transfer medium to facilitate the reduction process and separates of the catalyst efficiently from the reaction mixture post catalytic reaction owing to its magnetic nature. Further, FTIR, XRD, and TEM analysis confirms the structural stability of the spent catalyst even after three regeneration cycles. Leaching data confirms that insignificant leaching of Ag NPs from the support material in the aqueous mixture occurred during the reduction reaction. The results clearly indicate that the material may act as an efficient catalyst for the reduction of recalcitrant organic pollutants from water.