Catalytic reduction of picric acid, nitrophenols and organic azo dyes via green synthesized plant supported Ag nanoparticles

A facile and single-step green synthesis of silver nanoparticles dispersed on taro (Colocasia esculenta) plant rhizome powder (TP) is reported here. In the current study, we describe for the first time, the successful adsorption-based assembly of the silver/taro power (Ag/TP) nanocomposites using the rhizome of taro as a stabilizing/supporting agent. The Ag/TP nanocomposites exhibited very high efficiency in the catalytic reduction of nitroarenes such as picric acid/trinitrophenol (TNP), 4-nitroaniline (4 -NA), 4-nitrophenol (4-NP) and 2-nitrophenol (2-NP) to the corresponding amines. The prepared catalyst also showed a high activity in the catalytic reduction of organic azo dyes such as Methyl Orange (MO), Congo Red (CR), Methyl Red (MR) and Rhoda mine B (RhB) by sodium borohydride (NaBH4). The morphology, structure and crystallite size of the prepared nanocomposites were evaluated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photo electron spectroscopy (XPS) and X-ray diffraction analysis (XRD). The calculated turnover frequency was 3.846 min(-1) for 4 -NP and 1.104 min(-1) for 2-NP. However, the pseudo-first-order constant was 527 x 10(-3) s(-1) for 4 -NP and 1.23 x 10(-3) s(-1) for 2 -NP. The prepared Ag/TP catalyst was also tested for the reduction of a mixture of nitroarenes and dyes. Ag/TP catalyst emerged as a promising, easily recoverable and reusable, with at least in 5 successive reactions and stable for 3 days. (C) 2018 Published by Elsevier B.V.