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Ag–TiO2 doped photo catalytic degradation of Procion blue H-B dye in textile washwater
No full textThe photocatalytic degradation of Procion blue H-B dye in biodegraded
textile washwater has been investigated for the complete removal of color
and maximum reduction of chemical oxygen demand (COD). Pseudomonas
putida was utilized for obtaining biodegraded textile washwater. In this
process, silver-doped TiO2 photocatalyst was prepared and experiments
were carried out to study the effects of UV and mercury lamp irradiations
on COD reduction and removal of color. The thus prepared silver-doped
TiO2 catalyst was characterized by thermogravimetric and differential
thermal analysis, UV-visible spectrometer, X-ray diffraction, scanning
electron microscope, energy dispersive X-ray microanalysis, and BET
surface area techniques. Adsorption studies were also carried out to
evaluate the fitness of isotherm models. The results show that the
silver-doped TiO2 has enhanced the photodegradation of Procion blue
H-B dye under UV and mercury lamp irradiations. The enhanced activity
of silver-doped TiO2 is due to the enrichment of electron–hole separation
by electron trapping of silver particles
Carbon-Supported Palladium–Polypyrrole Nanocomposite for Oxygen Reduction and Its Tolerance to Methanol
No full textCarbon-supported palladium–polypyrrole Pd–PPy/C nanocomposite was synthesized by oxidative polymerization of pyrrole and
reduction of palladium(II) precursor salt in the presence of Vulcan XC-72R. The Pd–PPy/C composites were characterized by
X-ray diffraction (XRD), Fourier transform IR, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and
transmission electron microscopy (TEM) techniques. The XRD analysis of Pd–PPy/C shows the formation of the face-centered
cubic structure of Pd particles and the mean particle size calculated from TEM was 5.3 2.0 nm. The electrochemical stability
of Pd–PPy/C was examined by cyclic voltammetry in an acid solution. The thermal stability and Pd loading in the composite was
assessed using TGA. The introduction of Pd in the conducting PPy/C matrix gives better catalytic activity toward oxygen
reduction with resistance to methanol oxidation. This was further elucidated by the XPS analysis showing d-band vacancy that is
attributed to metal–polymer interaction. From the polarization studies, it is observed that even in the presence of methanol there
is no significant cathodic shift in the half-wave potential, revealing that Pd–PPy/C is tolerant to methanol. Rotating ring disk
electrode studies show that there is only a negligible quantity of hydrogen peroxide produced in the potential region where its
production is expected to be high. This confirms that Pd–PPy/C catalyzes reduction of oxygen directly to water through a
four-electron pathway
Facile synthesis of mesoporous N doped zirconium titanium mixed oxide nanomaterial with enhanced photocatalytic activity under visible light
No full textThe present paper deals with a hydrazine mediated synthesis of high surface area and thermally stable
N-doped zirconium titanium mixed oxide with enhanced photocatalytic activity towards reduction of
selenium (VI) to metallic Se0 under visible light. Materials were synthesized at pH ¼ 2 by varying the
hydrazine concentration and characterized by XRD, TEM, BET method, XPS, Raman spectroscopy
and UV-vis solid state spectra. Presence of low amount of zirconium oxide (10 wt%) helps in phase
stabilization and maintains the porous structure even at higher calcinations temperature in comparison
to that of pure titania. XPS spectrum justifies the presence of nitrogen and Ti3+ in the material due to
the decomposition reaction of hydrazine. Hydrazine controls the nitrogen content, surface area and the
formation of oxygen vacancy in the material. Investigation of metal oxide to hydrazine ratio on the
overall surface properties and photocatalytic activity indicates that the 1 : 6 ratio is the optimum
composition for the best result. Surface area and pore volume increases to 298 m2/g and 0.323 cm3/g.
The obtained material (TiZr-6N-400) is found to reduce selenium (VI) to selenium (0) under visible light
within only 45 min of reaction. Increased photocatalytic activity under visible light is mostly due to the
synergistic effect of substantial nitrogen doping, high surface area and presence of oxygen vacancy
Reliability of Galvanostatic Pulse Technique in Assessing the Corrosion Rate of Rebar in Concrete Structures: Laboratory vs Field Studies
No full textCorrosion of rebar in concrete structures is one among the various causes impairing its long-term durability. Precise assessment of
corrosion rate (CR) is of prime importance to evaluate the structural safety as well as for estimation of service life of concrete
structures. Among the electrochemical techniques, Galvanostatic Pulse Technique (GPT) is very promising for field mapping due to
its rapidity. The reliability of GPT in determining the CR under passive and active state of rebar has been carried out using small size
laboratory specimens and large scale aged concrete structures. The CR determined by the GPT is compared with the CR obtained by
Electrochemical Impedance Spectroscopy Technique (EIST) and weight-loss method. The study reveals that an anodic pulse of 100
μA with a pulse duration of 10 seconds is able to determine the CR from 1-663 μm/y (from negligible to higher corrosion activity) on
the rebar network more precisely even up to 65 mm of cover concrete. For instance the rebar corroding at higher rate, the CR
predicted by GPT is very close to the CR by weight-loss method whereas it is 20 times less by EIST. In the case of passive state of
rebar, the CR predicted by EIST is very close to weight-loss method whereas GPT predicts 10 times higher. In aged structures, the
change in microstructure of concrete and loss of moisture from the concrete make the potential of rebar and resistivity of concrete
more unpredictable and mislead the status of rebar embedded inside the concrete
Direct transfer of micro-molded electrodes for enhanced mass transport and water management in PEMFC
No full textSoft lithography technique is used to micropattern the electrodes on the electrolyte membrane of polymer
electrolyte fuel cell (PEMFC) in order to alleviate the issues due to poor water management and inadequate
reactant distribution in the fuel cell environment. Membrane electrode assembly with the micropatterned
electrode has shown an increase in power density at a higher temperature as well as at a higher relative
humidity when compared to a flat electrode. Consistency in cell performance is observed in the case of
micropatterned electrodes
Anodic oxidation of chlorophenols in micelles and microemulsions on glassy carbon electrode: the medium effect on electroanalysis and electrochemical detoxification
No full textThe voltammetric behavior of 2, 4-dichlorophenol
(DCP), 2, 4, 6-trichlorophenol (TCP) and pentachlorophenol
(PCP) in aqueous sodium hydroxide (NaOH),
aqueous NaOH–sodium dodecylsulphate (SDS) micellar
solution and SDS/n-hexane/n-butanol/water microemulsion
on glassy carbon electrode (GC) is reported. In aqueous
alkaline medium, the electrode fouling is significant.
Among the three media, the electrode fouling is the minimum
in aqueous microemulsion. The fouling effect also
depends on the nature of the phenolic compound. DCP
exhibits the maximum fouling effect, and PCP exhibits the
minimum fouling effect. During oxidation of the TCP in
the microemulsion, quinone–hydroquinone-like redox
couples were formed on the electrode surface. Reproducible
voltammetric responses without electrode fouling
could be obtained for all the three phenolic compounds up
to 20 mM concentrations in microemulsion. In the galvanostatic
oxidation in NaOH media, DCP and TCP led to
formation of polymeric films on the glassy carbon surface.
The Average molecular weight of the polymer obtained is
in the range of 7,500–9,500. Even 2.5% by weight of
chlorophenols could be oxidized under galvanostatic
conditions in microemulsions without significant fouling
Probing Lewis acidity and reactivity of Sn- and Ti-beta zeolite using industrially important moieties: A periodic density functional study
No full textThe Lewis acidic nature and reactivity of two industrially important catalysts, viz., Sn and Ti substituted
beta zeolite (T-BEA) are analyzed using a unique combination of structural parameters, energetics and
reactivity descriptors. To achieve this purpose, we adsorb the industrially important moieties (L) namely
NH3, H2O, CH3OH, CH3CN on the active sites of T-BEA. The calculations were performed using a periodic
density functional method where the valence electrons are described using a plane wave basis set in
conjunction with pseudo-potentials for the core electrons. The analysis of the structural properties of
these complexes reveals that TO4 shows typical characteristic splitting 120◦/90◦, close to bipyramidal
geometry as compared to tetrahedral symmetry observed in the bare T-BEA. This is associated with small
variations in the framework bond lengths (≥0.08 Å) and a substantially large variation of bond angles
(≤10◦) in all the ligand-zeolite complexes. Further in both cases of Sn and Ti substituted beta zeolite,
ligand interacts at optimum inter-atomic bond distance. Our interaction energies show that adsorption
of all ligand moieties is stronger at Sn center than that of Ti. In general, the order of stability of the different
T-BEA adducts isNH3 >H2O>CH3OH>CH3CN. The ligand interaction is associated with the corresponding
bond elongation and bond reduction of the adsorbed molecules on catalyst active site, which can be taken
as measure of red or blue shifted frequencies. Finally, the global descriptors of reactivity justify the fact
that soft acid, Sn-BEA, interacts strongly with soft bases following the Pearson’s HSAB principle. However,
hard acid, Ti-BEA interacts with soft bases to form a stable Lewis adduct. Furthermore, the HOMO–LUMO
gap of all Sn-BEA–L adducts is lower than that of Ti-BEA–L adducts indicating to its higher Lewis acidic
nature compared to Ti-BEA
Nonenzymatic Reduction of Hydrogen Peroxide Produced during the Bioelectrocatalysis of Glucose Oxidase on Urchin-like Nanofibrillar Structures of Cu on Au Substrates
No full textThis work describes the nonenzymatic reduction of hydrogen peroxide on urchin-like nanofibrillar structures
of Cu formed on gold substrates modified by a self-assembled monolayer (SAM) of p-mercaptobenzoic acid.
Because the detection is based on the electrochemical reduction, the method is less prone to interference
from easily oxidizable biologically important compounds such as dopamine, uric acid, and ascorbic acid.
This method is extended to the detection of glucose by immobilizing glucose oxidase on the nanocomposite
electrode with the help of chitosan. The linear detection range for glucose is 100 nM to 1800 nM. Sensitivity
of detection is 1.99 nA/nM. The Michaelis-Menten constant is very low (125 nM), indicating high binding
affinity of the enzyme to the substrate
Atmospheric Corrosion Performance of Engineering Materials in India
No full textIndustrial growth during the last decade
has made it necessary to evaluate
installations, equipment, and
metallic and nonmetallic structures
exposed to the atmosphere. The atmosphere
has also become more contaminated
and therefore more aggressive to
materials exposed to an enormous quantity
of gases.
India has mainly three seasons in a
year: rainy (June through September,
southwest monsoon, and October
through November, northeast monsoon),
summer (April through July), and winter
(mid-October through February). The
country has a coastline of more than
7,500 km, the reason for the high airborne
salinity in many areas. The air
quality in big cities has decreased significantly.
A variety of industrial processes,
such as the production of iron and steel,
utility factories, and crude oil processing,
pollute the atmosphere by the release of
sulfur dioxide (SO2). SO2 can also be
emitted by natural disasters or means
such as volcanoes, sea spray, plankton,
and rotting vegetation. Overall, 69.4% of
SO2 is produced by industrial combustion
and >90% of the sulfur in the atmosphere
is of human origin.1
Steel, zinc, galvanized metals, and
aluminum are found to be very sensitive
to acidic pollutants, especially SO2 and
acid rains.2 No systematic research on
atmospheric corrosion of the steel and
other metals has been done in India.
Before 1970, little quantitative atmospheric
corrosion data had been published
in India.3 More recently, results
from several studies have been reported.4-7
Ramana, et al.8 have reported the characterization
of rust phases formed on low
carbon steel exposed to a natural marine
environment.
We made a study on the kinetics of
atmospheric corrosion of mild steel (MS),
zinc, galvanized iron (GI), and aluminum
at 10 exposure stations in India9 and the results were compared with global levels.
In continuation of this work, the present
program was undertaken and the results
obtained on MS, Zn, GI, and Al corrosion
in natural atmospheres are reported.
The results are discussed as a function of
exposure time and pollution levels