Sonochemically synthesized Ag/CaCO3 nanocomposites: A highly efficient reusable catalyst for reduction of 4-nitrophenol

Highlights: • Ag/CaCO₃ nanocomposite was synthesized by a two step sonochemical technique. • Ag/CaCO₃ Nanocomposite was applied for reduction of 4-nitrophenol. • In presence of Ag/CaCO₃, kinetics of reduction process increased by more than 10 times. • Catalytic activity of Ag/CaCO₃ remained nearly unchanged after three catalytic cycles. Synthesis of Ag/CaCO₃ nanocomposites was accomplished by a two step technique. CaCO₃ nanoparticles were synthesized by ultrasound assisted precipitation technique followed by deposition of silver via bio-inspired technique using a bio-reductant obtained from Andrographis paniculata and Aloe vera. X-ray diffraction pattern has confirmed the formation of CaCO₃ with Calcite phase along with few minor peaks of Vaterite and Ag with face-centered cubic structure. Electron microscopy analysis has indicated the deposition of Ag nanopaticles on CaCO₃. Resulting material was studied as catalyst for the reduction of 4-nitrophenol. The efficiency of the nanocomposites was found to be 10 fold higher than that of Ag nanoparticles and remained nearly unaltered for three consecutive cycles. Developed material is expected to be a potential catalyst candidate for environmental applications.