Indian Journal of Chemistry

Sect. A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical

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CODEN: ICACEC; ISSN: 0376-4710 (Print), 0975-0975 (Online)

 

 

 

 

VOLUME 56A

NUMBER 3

March 2017

 

CONTENTS

 

Advances in Contemporary Research

 

 

251

 

On the current status of the mechanistic aspects of photocatalytic reduction of carbon dioxide

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Hariprasad Narayanan, M V Harindranathan Nair & Balasubramanian Viswanathan*

 

 

 

In the aqueous CO2 reduction system, the reductive photocatalytic conversion of CO2 involves all the redox reactions occurring at the interface of the semiconductor such as water splitting, hydrogen evolution, oxygen evolution, photo-oxidation reactions and reactions of radical intermediates. The overall product yield is highly dependent on the extent of these competing reactions.

 

 

 

 

Papers

 

 

270

 

Photocatalytic and DC conductivity studies of proton exchanged KAl0.33W1.67O6 and its application in
Pb2+ removal

 

 

 

 

 

 

 

 

 

 

 

 

M Srinivas, G Ravi, P Vijaya kumar,
CH Sudhakar Reddy, Sreenu K, Ravinder Guje
& M Vithal
*

 

 

 

 

 

 

 

278

 

Surfactant assisted synthesis of cobalt doped titania nanomaterial: Characterization and its applications in photocatalysis and anti-bacterial activity

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Radha Devi Chekuri & Siva Rao Tirukkovalluri*

 

 

 

Co2+-TiO2 (0.5 wt.%) was successfully prepared in the presence of sodium dodecyl sulfate through sol-gel method. The catalyst shows decreased particle size, (8.4–13.2 nm) and increased specific surface area, attributed to the influence of the surfactant during synthesis. Under the optimum conditions, the rate of degradation of methyl red solution was found to be 7.676 mg L-1min-1. The catalyst was also found effective towards the destruction of E. coli.

 

 

 

 

287

 

Combined effect of adsorbent chitosan and photosensitizer polypyrrole in ternary chitosan-polypyrrole-TiO2 photocatalyst leading to visible light activity and superior functionality

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C Murugan & E Subramanian*

 

 

 

The ternary photocatalyst, chitosan-polypyrrole-TiO2, exhibits higher visible light photodegradation efficiency towards methylene blue as compared to the individual components. Polypyrrole as a visible light sensitizer and chitosan as an adsorbent together enhance the photocatalytic efficiency of TiO2. The photocatalyst has high stability and sustainability on repeated use.

 

 

 

Graphics_cmyk.tif

 

 

 

Notes

 

297

 

Solvent activity and osmotic pressure of binary aqueous and alcoholic solutions of calcium chloride up to 368 K and high salt concentration

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

G Di Giacomo*, F Scimia & L Taglieri

 

 

 

From ambient to nearly 368 K and from very dilute solutions to nearly 50% by weight of salt, the activity of the solvent decreases significantly with the salt concentration and increases with the temperature. The molar volume of the mixtures deviates significantly from the linear behavior, and, for high salt concentration, the partial molar volume of the solvent is significantly different than that of the pure solvent. The osmotic pressure calculated in this way is of one order of magnitude higher than that predicted by the van’t Hoff equation and can reach very high values for aqueous (~400 MPa) and alcoholic (50 MPa) solutions.

 

 

 

Letter to The Editor

 

 

305

 

Comments on “Synthesis and characterization of gadolinium tungstate doped zinc oxide photocatalyst,
Indian J Chem, 56A (2017) 50-56”

 

B R Srinivasan

 

Response to the Comments (M Swaminathan)

 

 

 

 

 

 

 

Authors for correspondence are indicated by (*)

 

 

 

 

 

 

 

 

 

 

 

 

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Indian Journal of Chemistry

Vol. 56A, March 2017, pp. 251-269

 

 

Advances in Contemporary Research

 

 

 

On the current status of the mechanistic aspects of photocatalytic
reduction of carbon dioxide

Hariprasad Narayanana, b, M V Harindranathan Nairb & Balasubramanian Viswanathana, *

aNational Centre for Catalysis Research, Indian Institute of Technology Madras, Chennai 600 036, Tamil Nadu, India

Email: bviswanathan@gmail.com; bvnathan@iitm.ac.in

bSchool of Environmental Studies, Cochin University of Science and Technology, Cochin 682 022, Kerala, India

Received 21 February 2017

Photocatalytic reduction of carbon dioxide, one of the pathways involved in the carbon dioxide conversion process, has been receiving significant attention from the scientific community in the last four decades. Nevertheless, the mechanism of carbon dioxide reduction is still unclear and the information available is not sufficient for developing it into large scale applications, possibly because of the invariable hurdles associated with the reduction process. The reductive photocatalytic conversion of CO2 involves all the redox reactions occurring at the interface of the semiconductor such as water splitting, hydrogen evolution, oxygen evolution, photo-oxidation reactions and reactions of radical intermediates. The overall product yield is highly dependent on the extent of these competing reactions. Herein, we discuss our perceptions and current status of the interface reactions and their involvement in the fundamental mechanistic aspects of the photocatalytic conversion of CO2.

Keywords: Carbon dioxide activation, Carbon dioxide reduction, Carbon dioxide anion radical, Anion radicals, Reaction mechanism, Photocatalysis, Sacrificial reagents, Reactive oxygen species,
Solar energy conversion

 

Indian Journal of Chemistry

Vol. 56A, March 2017, pp. 270-277

 

 

Photocatalytic and DC conductivity studies of proton exchanged KAl0.33W1.67O6 and its application in Pb2+ removal

M Srinivas, G Ravi, P Vijaya Kumar, CH Sudhakar Reddy, Sreenu K, Ravinder Guje & M Vithal*

Department of Chemistry, Osmania University, Hyderabad 500 007, Telangana

Email: mugavithal@gmail.com

Received 28 November 2016; revised and accepted 26 February 2017

The proton exchanged metal oxide of composition HAl0.33Te1.67O6 (HAW) is synthesized by ion exchange method at room temperature and characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and UV-vis diffuse reflectance spectroscopy. Presence of water content in the HAW has been examined by thermogravimetric analysis. Conductivity and photocatalytic properties of HAW are compared with those of its parent KAl0.33W1.67O6 (KAW). HAl0.33W1.67O6 shows higher conductivity and photocatalytic activity for the degradation of methyl blue and Rhodamine B under visible light irradiation. Participation of hydroxyl radicals in the photocatalytic dye degradation has been investigated by photoluminescence studies using terephthalic acid as probe. The removal of Pb2+ from an aqueous solution of Pb(NO3)2 using pristine KAl0.33W1.67O6 is also reported.

Keywords: Photocatalytic activity, Powder X-ray diffraction, Bandgap energy, Conductivity, Lead

Indian Journal of Chemistry

Vol. 56A, March 2017, pp. 278-286

 

 

Surfactant assisted synthesis of cobalt doped titania nanomaterial: Characterization and its applications in photocatalysis and
anti-bacterial activity

Radha Devi Chekuri & Siva Rao Tirukkovalluri*

Department of Inorganic and Analytical Chemistry, School of Chemistry, Andhra University, Visakhapatnam, India

Email: Sivaraotvalluri.16@gmail.com

Received 13 December 2016; accepted 25 February 2017

The synthesis of 0.5 wt. % cobalt doped titania nanomaterial (Co2+-TiO2) assisted by sodium dodecyl sulfate anionic surfactant by sol-gel method is reported. The synthesized catalysts are characterized by XRD, UV-vis DRS, FT-IR, BET, TEM, SEM and XPS analysis. XRD results show that all the catalysts are in anatase phase. UV-vis DRS studies indicate that decrease in band gap of TiO2 is due to doping of Co2+. FT-IR studies indicate the insertion of Co2+ into TiO2 lattice as a substitutional dopant. BET analysis shows an increase in surface area of the catalyst. From SEM and TEM analysis, change in the morphology of the particles with reduced particle size is observed. XPS studies confirm the presence of Co2+ along with Ti and O. The photocatalytic efficiency of the catalyst has been evaluated by degradation of methyl red under visible light irradiation at various reaction parameters. The antibacterial activity of the catalyst against Escherichia coli has also been investigated.

Keywords: Cobalt doped titania, Titania, Nanomaterials, Surfactants, Dye degradation, Sol-gel method, Antibacterial activity, Methyl red

 

Indian Journal of Chemistry

Vol. 56A, March 2017, pp. 287-196

 

 

Combined effect of adsorbent chitosan and photosensitizer polypyrrole in ternary chitosan-polypyrrole-TiO2 photocatalyst leading to
visible light activity and superior functionality

C Murugan & E Subramanian*

Department of Chemistry, Manonmaniam Sundaranar University, Tirunelveli 627 012, Tamil Nadu, India

Email: esubram@yahoo.com

Received 25 March 2016; revised and accepted 23 February 2017

The combined effect of the components in the ternary chitosan-polypyrrole-TiO2 (Chit-Ppy-TiO2) photocatalytic system has been investigated. The role of each component in this catalyst is validated by the visible light degradation of the model dye methylene blue. The reaction parameters, viz., amount of catalyst, dye concentration, oxidant concentration and temperature are studied in detail. The ternary system exhibits greater activity when compared to both the single and binary component catalysts (chitosan-TiO2 and polypyrrole-TiO2). The superior functionality of Chit-Ppy-TiO2 (1:1:100 wt ratio) originates from the combined effect of greater dye adsorption of chitosan, visible light sensitization of polypyrrole and the catalytic functionality of TiO2. The ternary photocatalyst is recyclable even after fourth  run without appreciable loss in its activity.

Keywords: Catalysts, Ternary catalysts, Chitosan-polypyrrole-titania, Polypyrrole, Titania, Photodegradation, Dye degradation,Visible light photodegradation, Methylene blue

 

 

 

 

 

Indian Journal of Chemistry

Vol. 56A, March 2017, pp. 297-304

 

 

Solvent activity and osmotic pressure of binary aqueous and alcoholic solutions of calcium chloride up to 368 K and
high salt concentration

G Di Giacomo*, F Scimia & L Taglieri

Department of Industrial and Information Engineering and of Economics (DIIIE), University of L’Aquila, Via Giovanni Gronchi 18, 67100 L’Aquila, Italy

Email: gabriele.digiacomo@univaq.it

Received 30 June 2016; revised and accepted 28 February 2017

The solvent activity of aqueous and alcoholic liquid solutions of calcium chloride have been determined at ambient pressure, under vapor-liquid equilibrium conditions, and critically analyzed over a wide range of temperature (from ambient to ~368 K) and salt concentrations (from very dilute to nearly saturated solutions). The results are generally in good agreement with those reported or obtainable from a variety of literature data sources. In addition, for the alcoholic salted solutions, new T-concentrations regions have been explored. A solvation-dissociation based model was first parametrized and then used to establish the behavior of the activity of the solvents and to quantify the equilibrium vapor pressure lowering and the osmotic pressure of the solutions for any temperature and salt concentration. It was found that: a) activity of the solvents decreases when salt concentration increases, while it increases with temperature; b) osmotic pressure of concentrated solutions, is a function of both solvent activity and volumetric properties of the solutions, and is much higher (up to hundred-fold MPa for the aqueous solutions) of that calculated with the van’t Hoff equation; c) the behavior of the osmotic pressure with the temperature is opposite to that predicted by the van’t Hoff equation, coherently with the exothermic nature of the dilution process and the literature values of the heat of dilution.

Keywords: Solution chemistry, Solvent activity, Osmotic Pressure, Calcium Chloride

 

Indian Journal of Chemistry

Vol. 56A, March 2017, pp. 305-306

 

 

Letter to the Editor

 

 

Comments on “Synthesis and characterization of gadolinium tungstate doped zinc oxide photocatalyst, Indian J Chem, 56A (2017) 50-56”

 

Comments on “Synthesis and characterization of gadolinium tungstate doped zinc oxide photocatalyst,
Indian J Chem, 56A (2017) 50-56”

 

Dear Editor:

 

The title paper by Thirumalai et al.1 reporting on the hydrothermal synthesis of a so-called 5 wt% Gd2WO6 doped zinc oxide (1) and its photocatalytic activity attracted my attention in view of my  interest on doped crystalline materials2,3. Although the reason for the choice of the monoclinic form of Gd2WO6 for doping into the crystal structure of hexagonal zinc oxide is not clear, the synthetic methodology especially the stoichiometry of reagents employed and the methods of characterization do not provide any credible evidence whatsoever for the preparation of 1. In the following comment, it is shown that 1 is a doubtful solid and the title paper is erroneous.

 

Can monoclinic gadolinium tungstate be doped into the hexagonal zinc oxide?