Facile fabrication, characterization and enhanced heterogeneous catalytic reduction of 4-nitrophenol using undoped and doped ZrO 2 nanoparticles ARTICLE INFO (original) (raw)
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Nanochemistry Research, 2019
Here, we successfully developed the undoped, Ni2+, Cu2+, and Zn2+ doped Zirconia nanoparticles (ZrO2 NPs) by a simple co-precipitation method at room temperature and characterized by various physicochemical measurement techniques to investigate their structure, morphology, and sizes of the particles. The bandgap energy values of doped and undoped ZrO2 NPs were estimated using optical absorption spectroscopy and it was found to be in the range of 4.1-4.4 eV. The UV (304-352 nm) and visible (402-415 nm) emissions and the oxygen vacancies and band gap of the particles were investigated through PL analysis. The structure, morphology, and well-dispersed particles with the size in the range of 10-40 nm of the prepared ZrO2 NPs were deliberated by SEM and TEM analysis. The Zr–O stretching vibration and Zr–O–Zr bending vibrations were confirmed through FTIR analysis. The catalytic reduction of 4-nitrophenol (4-NP) using NaBH4 as a reducing agent was studied by the prepared doped and undoped ZrO2 NPs. The efficient catalytic activity was observed in the presence of Cu2+ doped ZrO2 NPs than the Zn2+, Ni2+ doped and undoped ZrO2 NPs due to the small size and large surface area of the particles. The results showed that 97% conversion was achieved from 4-NP to 4-aminophenol (4-AP) within 90 min and stable up to 5 consecutive recycles.
Reduction of 4-Nitrophenol as a Model Reaction for Nanocatalysis
Noble metal nanocomposites have received a great deal of attention in the field of catalysis due to their unique properties, which are directly related to their shapes and sizes. To investigate and derive a definite conclusion about the catalytic activity of various nanocatalysts with different sizes, shapes, and even porosities, a model reaction needed to be selected. The reduction of 4-nitro-phenol (4-NP) by NaBH 4 has been widely used as this model reaction, since it is easy to monitor with simple and fast analytical techniques, and there are no by-products. This reaction is also valuable in the view of green chemistry since 4-NP, one of the toxic substance in the wastewater, is converted into a commercially important substance, 4-aminophenol (4-AP). Here we present an overview of the mechanistic studies into 4-NP reduction, followed by a comprehensive overview of materials evaluated for this reaction.
Catalysis Letters, 2019
Pd 1 /Au 20 @ZrO 2 nanoreactors with the gold nuclei confined within zirconia shell and decorated with Pd were synthesized using an Au:Pd molar ratio of 20:1. The presence of even trace amounts of Pd on the gold nuclei surface, significantly enhanced catalytic activity of Pd 1 /Au 20 @ZrO 2 nanoreactors in the 4-nitrophenol to 4-aminophenol transformation by four times compared to Au@ZrO 2. In addition, the Pd 1 /Au 20 @ZrO 2 nanoreactors remained highly stable during the reaction even under harsh conditions, i.e. without nanoreactors cleaning before the subsequent catalytic run, comparable with the stability of Au@ZrO 2 nanoreactors. The presently proposed synthesis technique allowed to prepare nanoreactors of uniform structure even with relatively unstable bimetallic NPs (Pd/Au) as nuclei.
Nanocatalytic Assemblies for Catalytic Reduction of Nitrophenols: A Critical Review
Critical Reviews in Analytical Chemistry, 2019
Nitrophenol is common carcinogenic pollutant known for its adverse effects on human beings and aquatic life. During the last few decades, the chemical reduction of nitrophenol compounds has been widely reported as the advanced removal methodology for such hazardous dyes from aqueous reservoirs. Many researchers have utilized different nanocatalytic systems using sodium borohydride (NaBH 4) as the reducing agent for acquiring industrially useful reduction product of aminophenol by carrying out the chemical reduction of nitrophenols. Polymeric material supported monometallic nanoparticles are widely reported catalyst for the degradation of 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP). This review critically discusses the pros and cons of numerous supporting mediums of nanocatalytic assemblies used for the immobilization of nanomaterials. Mechanism and kinetic analysis of the reduction reaction of 2-NP and 4-NP have also been explained in this study. In addition, recent literature has also been effectively summarized in the tabular form for developing a better understanding of the reader. Pictorial representation of key nanocatalytic assemblies and catalytic reduction mechanism has also been narrated in this study.
TURKISH JOURNAL OF CHEMISTRY, 2020
A set of catalysts having gold nanoparticles deposited on γ-Al 2 O 3 (Au/ γ-Al 2 O 3) with lowest effective amount of gold content were prepared by successive impregnation and hydrogen reduction method. The structural features of prepared catalysts were analysed by X-ray diffraction (XRD), N 2 physisorption, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR). The catalytic activity was evaluated for the reduction of an organic pollutant 4-nitrophenol (4NP) to 4-aminophenol (4AP) by spectrophotometric analysis. Supported catalyst presented excellent catalytic ability to convert 4NP to 4AP in the presence of sodium borohydride (SBH) due to synergistic effect of Au NPs and mesoporous γ-Al 2 O 3 support. The reduction reaction was also performed at a range of temperatures to calculate kinetic parameters. The development of highly stable Au/ γ-Al 2 O 3 catalysts with lowest noble metal content and recyclability made the process cost effective and may promote their applications in various fields including removal of organic pollutants in industrial waste water and high-temperature gas-phase reactions.
Applied Catalysis B: Environmental, 2015
Highly catalytically active yolk-shell Au-CeO 2 @ZrO 2 nanoreactors (gold core encapsulated into porous zirconia shell and doped by ceria) for the 4-nitrophenol reduction to 4-aminophenol were synthesized. Au cores encapsulated into SiO 2 (Au@SiO 2 ) were decorated with ceria via injection of ceria precursor into a void space of silica shell (formed through surface-protected etching of silica by hot water) with its subsequent hydrolysis and thermal treatment (Au-CeO 2 @SiO 2 ). Au-CeO 2 @ZrO 2 nanoreactors were obtained using Au-CeO 2 @SiO 2 as a template and replacement of SiO 2 by ZrO 2 . The nanoreactors were characterized by STEM-EDS, in situ and ex situ UV-vis spectroscopy, and N 2 thermal adsorption. The catalytic activity for decorated Au-CeO 2 @ZrO 2 nanoreactors in the 4-nitrophenol reduction into 4-aminophenol was found to be ∼3 times higher than for non-decorated Au@ZrO 2 nanoreactors. The herein proposed route of nanoreactor core decoration may be applied for the synthesis of nanoreactors with cores modified with different materials in order to make them effective for different catalytic reactions.
IET Nanobiotechnology, 2018
The present study investigated the synthesis of gold nanoparticles (AuNPs) using mangrove plant extract from Avicennia marina as bioreductant for eco-friendly bioremediation of 4-nitrophenol (4-NP). The AuNPs synthesised were confirmed by UV spectrum, transmission electron microscopy (TEM), X-ray diffraction, Fourier transmission infrared spectroscopy (FTIR), dynamic light scattering (DLS), and zeta potential. The AuNPs were found to be spherical in shape with size ranging from 4 to 13 nm, as evident by TEM and DLS. Further, the AuNPs were encapsulated with sodium alginate in the form of gold nano beads and used as heterogeneous catalyst and degrading agent to reduce 4-NP. This reduction in 4-NP into 4-aminophenol was confirmed by UV and FTIR. The aqueous solution of 4-NP peaked its absorbance at 320 nm, and shifted to 400 nm, with an intense yellow colour, appeared due to formation of 4-nitrophenolate ion. After the addition of AuNps, the 4-NP solution became colourless and peaked at 400 nm and reduced to 290 nm corresponding to the formation of 4-aminophenol. Hence, the present work suggested the AuNPs as the potent, eco-friendly bionanocomposite catalyst for bioremediation of 4-NP.
Coatings
This work intended to enhance the unique and outstanding properties of lanthanum by synthesizing its nanocomposite. A lanthanum-based nanocomposite was prepared by a simple and cost-effective “co-precipitation” method. Lanthanum nitrate (La (NO3)3) and zinc nitrate (Zn (NO3)2) were used as precursors. The lanthanum/zinc oxide nano composite formed was then calcined at 450 °C for 4 h in order to obtain a fine powder with size in the nano range of 1–100 nm. Characterization of the prepared catalyst was done by ultraviolet/visible spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence. Crystallinity and morphology were found by X-ray diffraction and scanning electron microscopy. The synthesized nanocomposite material was also tested for heterogeneous catalytic applications of 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP). It was found to be successful in complete reduction of 4-NP with enhanced catalytic performance.
TURKISH JOURNAL OF CHEMISTRY
A set of catalysts having gold nanoparticles deposited on γ-Al 2 O 3 (Au/ γ-Al 2 O 3) with lowest effective amount of gold content were prepared by successive impregnation and hydrogen reduction method. The structural features of prepared catalysts were analysed by X-ray diffraction (XRD), N 2 physisorption, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR). The catalytic activity was evaluated for the reduction of an organic pollutant 4-nitrophenol (4NP) to 4-aminophenol (4AP) by spectrophotometric analysis. Supported catalyst presented excellent catalytic ability to convert 4NP to 4AP in the presence of sodium borohydride (SBH) due to synergistic effect of Au NPs and mesoporous γ-Al 2 O 3 support. The reduction reaction was also performed at a range of temperatures to calculate kinetic parameters. The development of highly stable Au/ γ-Al 2 O 3 catalysts with lowest noble metal content and recyclability made the process cost effective and may promote their applications in various fields including removal of organic pollutants in industrial waste water and high-temperature gas-phase reactions.