Catalytic reduction of toxic dyes in the presence of silver nanoparticles impregnated core-shell composite microgels

Novel polystyrene-poly(N-isopropylmethacrylamide-acrylic acid) [PSTY-PNIPMA-ACC] core-shell micro particles were prepared by seed induced emulsion polymerization. Nano-Ag-PSTY-PNIPMA-ACC composite particles were synthesized by reduction of AgNO3 salt with reductant NaBH4 in the presence of water as medium and micro particles as template. The pure and composite micro particles were characterized by various techniques such as UV-visible spectroscopy (UV-vis) and Fourier transform infrared spectroscopy (FTiR) to illustrate their optical properties and structural hierarchies, respectively. Dynamic light scattering (DLS) analysis was performed to study the particles size distribution. TEM analysis shows that Ag NPs were monodispersed and equally distributed in spherical shaped shell of PSTY-PNIPMA-ACC micro particles. The prepared nano-Ag-PSTY-PNIPMA-ACC particles were used as catalyst in reduction of Rhodamine B (Rh-B) using NaBH4 as reductant. For comparative analysis, reduction of Rh-B was also performed in absence of nano-Ag-PSTY-PNIPMA-ACC catalyst and in the absence of NaBH4, respectively. Rh-B was only reduced in short time at feasible rate in presence of both composite micro particles and NaBH4. Degradation of Rh-B followed the pseudo first order kinetics and values of apparent rate constant (kapp) were come out to be 1.127 and 0.004min(-1) with percentage degradation of 99.03 and 4.37%, respectively. Results showed that our prepared nano-Ag-PSTY-PNIPMA-ACC particles are promising catalysts. High catalytic activity of composite micro particles may be attributed to their core-shell type morphology, sieved shell, small sized Ag NPs restricted in shell region. Langmuir Hinshelwood mechanism was followed by degradation of dye. Optimum concentration for maximum degradation of Rh-B in small time interval was found 4.95 mM. Various other toxic dyes such as brilliant blue (Bb) and methylene blue (MB) were also reduced individually and simultaneously under same reaction conditions. (C) 2018 Elsevier Ltd. All rights reserved.