The catalytic activities of first row transition metal oxides in the conversion of p-nitrophenol to p-aminophenol were investigated. The conversion was carried out at room temperature (30°&nbsp;C) using aqueous sodium borohydride. The reduction process was accelerated by CuO, Co3O4, Fe2O3 and NiO. The oxides such as TiO2, V2O5, Cr2O3, MnO2 and ZnO were found to be inactive towards the conversion of the nitrophenol. The active catalysts were analyzed before and after the reaction by XRD and the reduction reaction was monitored and confirmed by UV–vis, HPLC, 1H NMR and FT-IR techniques.

Buvaneswari G

Department of Chemistry

School of Advanced Sciences

Vellore Campus

Mandlimath T.R

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

&nbsp;

&nbsp;

VIT University

Journal of Molecular Catalysis A: Chemical

The present study reports on CuO-assisted reduction of Cr(VI) under ambient conditions using sodium borohydride and its complete removal. The confirmation of the reductive removal of Cr(VI) was assisted by powder X-ray diffraction, Fourier transform infrared, scanning electron microscopy, mic absorption spectro, UV–vis, and UV–vis–diffuse reflectance spectroscopy techniques. The analysis revealed that the process involved adsorption of dichromate ion on the surface of copper oxide, reduction of Cr(VI), and precipitation of Cr(III) as its hydroxide. Cr(VI) reduction capacity of CuO was found to be around 27.2 mmol/(g h). The residue collected showed promising reusability for 3 to 4 cycles, and the exhausted residue was finally converted into a black composite, CuO/CuCr2O4. The composite showed positive response for the photodegradation of methyl orange. Thus, the current protocol proposed a complete package of cost-effective reduction of Cr(VI) to Cr(III), precipitation into its hydroxide, and the conversion of the residue into a photoactive composite.

Fulltext

ACS Omega

Integrated Approach for Hazardous Cr(VI) Removal: Reduction, Extraction, and Conversion into a Photoactive Composite, CuO/CuCr2O4

Strontium hydroxyapatite was modified by two ways: (i) by chemical replacement of ‘Sr’ by copper (ii) by in-situ generation of copper on the surface of the apatite. Current synthetic route resulted in the formation of nanorods of the parent phase and the copper substituted phases of the formula Sr5−xCux(PO4)3OH (x&nbsp;=&nbsp;0, 0.01, 0.03 and 0.05). The copper modified phases exhibited high catalytic activity for the selective reduction of p-nitrophenol to p-aminophenol at room temperature. The rate of the reaction was found to be faster (3.63&nbsp;×&nbsp;10−3&nbsp;s−1 and 1.27&nbsp;×&nbsp;10−3&nbsp;s−1 for copper substituted and dispersed systems respectively) and comparable with other noble metal based catalyst systems studied for such conversion.

Applied Catalysis A: General

Investigation of catalytic activity of copper modified Sr5(PO4)3OH in electron transfer reaction

Microbial synthesis of gold nanoparticles (GNPs) has attracted considerable attention in recent times due to their exceptional capability for the bioremediation of industrial wastes and also for the treatment of wastewater. A bacterial strain Staphylococcus warneri, isolated from the estuarine mangroves of Sundarbans region produced highly stable GNPs by reducing hydrogen auric chloride (HAucl4) salt using intracellular protein extract. The nanoparticles were characterized utilizing ultraviolet-visible spectrophotometry, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, and surface enhanced Raman scattering. Highly dispersed, spherically shaped GNPs varied around 15–25 nm in size and were highly crystalline with face-centered cubic structures. Recyclable catalytic activity of as-synthesized GNPs was evidenced by complete degradation of nitro aromatic pollutants like 2-nitroaniline, 4-nitroaniline, 2-nitrophenol and 4-nitrophenol. Our GNPs show excellent and efficient catalytic activity with significantly high rate constant (10−1 order) and high turnover frequency (103 order) in recyclable manner up to three times. To our knowledge, this is the first report of Staphylococcus warneri in the production of gold nanoparticles. This green technology for bioremediation of toxic nitro aromatic pollutants is safe and economically beneficial to challenge the development and sustainability issue. © 2017, Springer-Verlag GmbH Germany.

Environmental Science and Pollution Research

Green-fabrication of gold nanomaterials using Staphylococcus warneri from Sundarbans estuary: an effective recyclable nanocatalyst for degrading nitro aromatic pollutants

Manganese substituted cobalt ferrite nanoparticles with composition;CoMnxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized using;sol-gel technology and characterized using the Fourier transform;infrared spectroscopy, high resolution transmission electron microscopy;and X-ray diffraction techniques to confirm their formation. The;prepared ferrite samples were explored as catalysts for the reduction of;nitrophenols in the presence of NaBH4 as reducing agent. Pure cobalt;ferrite was found to be inactive. However, catalytic efficiency enhanced;dramatically with the introduction of Mn ions into the catalytically;active surface sites (octahedral sites) of the cobalt ferrite lattice.;This could be due to the presence of synergistic effect between the;Co3+, Mn3+ and Fe3+ ions present in the octahedral sites. CoMn02Fe1.8O4;ferrite was observed to have the best catalytic activity for the;reduction of nitrophenols because of the highest Fe3+/Mn3+ and Co3+/Mn3+;ionic ratio at the catalytically active octahedral sites. The kinetics;of reduction was studied and the reduction reaction followed pseudo;first order kinetics. The rates of reduction of the three isomers of;nitrophenols followed the order - 2-nitrophenol > 4-nitrophenol >;3-nitrophenol.

Applied Surface Science

Mn substituted cobalt ferrites (CoMnxFe2-xO4 (x=0.0, 0.2, 0.4, 0.6, 0.8,;1.0)): As magnetically separable heterogeneous nanocatalyst for the;reduction of nitrophenols

Materials Letters

Application of NiCo2O4 as a catalyst in the conversion of p-nitrophenol to p-aminophenol

Perovskite-type LaFeO3 nanoparticles prepared by thermal decomposition of the La[Fe(CN)6]·5H2O complex: A new reusable catalyst for rapid and efficient reduction of aromatic nitro compounds to arylamines with propan-2-ol under microwave irradiation

Quantum clusters (QCs) of silver such as Ag7(H2MSA)7, Ag8(H2MSA)8 (H2MSA, mercaptosuccinic acid) were synthesized by the interfacial etching of Ag nanoparticle precursors and were loaded on metal oxide supports to prepare active catalysts. The supported clusters were characterized using high resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and laser desorption ionization mass spectrometry. We used the conversion of nitro group to amino group as a model reaction to study the catalytic reduction activity of the QCs. Various aromatic nitro compounds, namely, 3-nitrophenol (3-np), 4-nitrophenol (4-np), 3-nitroaniline (3-na), and 4-nitroaniline (4-na) were used as substrates. Products were confirmed using UV-visible spectroscopy and electrospray ionization mass spectrometry. The supported QCs remained active and were reused several times after separation. The rate constant suggested that the reaction followed pseudo-first-order kinetics. The turn-over frequency was 1.87 s-1 per cluster for the reduction of 4-np at 35°C. Among the substrates investigated, the kinetics followed the order, SiO2 &gt; TiO2 &gt; Fe2O3 &gt; Al2O3. © 2011 Leelavathi et al.

Journal	Data powered by TypesetJournal of Molecular Catalysis A: Chemical
Publisher	Data powered by TypesetElsevier BV
ISSN	1381-1169
Open Access	0