Systematic study of catalytic degradation of nitrobenzene derivatives using core@shell composite micro particles as catalyst

Abstract

Polystyrene-poly(N-isopropylmethacrylamide-acrylic acid) [Pst@pnIPM-Ac] core@shell micro particles were synthesized by two step method and used as template for the fabrication of silver nanoparticles (silver-NPs). Silver-NPs were loaded in shell of core@shell micro particles from in-situ reduction of AgNO3 salt using NaBH4 as reductant. Pure Pst@pnIPM-Ac core@shell micro particles and silver-NPs endowed silver-Pst@pnIPM-Ac core@shell composite micro particles were characterized by Fourier transform infrared spectroscopy (FT-Ir), UV visible spectroscopy (UV vis), transmission electron microscopy (TEM) and dynamic light scattering (DLS). Morphological analysis revealed that micro particles showed core@shell morphology while the diameter of Pst core and pnIPM-Ac shell was found in range of 0.12 to 0.14 μm and 0.081 to 0.083 μm, respectively. Pst@pnIPM-Ac micro particles showed response to change in pH of the medium due to presence of acrylic acid (Ac) unit in polymer network. Catalytic properties of silver-Pst@pnIPM-Ac core@shell hybrid micro particles were checked by reducing the nitrobenzene derivatives (NbD) possessing different substitute at para position of aromatic ring [p-nitro toluene (p-NT) and p-chloro nitrobenzene (p-CNB)] using NaBH4 as reductant. Values of apparent rate constant (kapp) were found to be 0.1532 and 0.103 min−1 for the reduction of p-NT and p-CNB, respectively. Effect of concentration of NaBH4 and catalyst dose on the value of kapp for reduction of p-NT was also investigated. Kinetic analysis illustrated that NbD reduction followed Langmuir-Hinshelwood mechanism. Prepared silver-Pst@pnIPM-Ac composite micro particles catalyst was found to be efficient for reduction of NbD. Recyclability and reusability of reported catalyst was also checked for the reduction of p-NT. It was observed that silver-Pst@pnIPM-Ac core@shell composite micro particles maintained the percentage activity in the range of 97–100 % for three successive cycles for the reduction of p-NT. The protocol adopted for the catalytic reduction of p-NT was proved to be effective.