Abstract: Prosperity of electronic equipment in photocopying
environment not only has improved work efficiency, but also has
changed indoor air quality. Considering the number of photocopying
employed, indoor air quality might be worse than in general office
environments. Determining the contribution from any type of
equipment to indoor air pollution is a complex matter. Non-methane
hydrocarbons are known to have an important role on air quality due
to their high reactivity. The presence of hazardous pollutants in
indoor air has been detected in one photocopying shop in Novi Sad,
Serbia. Air samples were collected and analyzed for five days, during
8-hr working time in three time intervals, whereas three different
sampling points were determined. Using multiple linear regression
model and software package STATISTICA 10 the concentrations of
occupational hazards and microclimates parameters were mutually
correlated. Based on the obtained multiple coefficients of
determination (0.3751, 0.2389 and 0.1975), a weak positive
correlation between the observed variables was determined. Small
values of parameter F indicated that there was no statistically
significant difference between the concentration levels of nonmethane
hydrocarbons and microclimates parameters. The results
showed that variable could be presented by the general regression
model: y = b0 + b1xi1+ b2xi2. Obtained regression equations allow to
measure the quantitative agreement between the variables and thus
obtain more accurate knowledge of their mutual relations.
Abstract: An unconventional composite inorganic ceramic
membrane capable of enhancing carbon dioxide emission decline was
fabricated and tested at laboratory scale in conformism to various
environmental guidelines and also to mitigate the effect of global
warming. A review of the existing membrane technologies for carbon
capture including the relevant gas transport mechanisms is presented.
Single gas permeation experiments using silica modified ceramic
membrane with internal diameter 20mm, outside diameter 25mm and
length of 368mm deposited on a macro porous support was carried
out to investigate individual gas permeation behaviours at different
pressures at room temperature. Membrane fabrication was achieved
using after a dip coating method. Nitrogen, Carbon dioxide, Argon,
Oxygen and Methane pure gases were used to investigate their
individual permeation rates at various pressures. Results show that
the gas flow rate increases with pressure drop. However above a
pressure of 3bar, CO2 permeability ratio to that of the other gases
indicated control of a more selective surface adsorptive transport
mechanism.
Abstract: Catalytic combustion of methane is imperative due to
stability of methane at low temperature. Methane (CH4), therefore,
remains unconverted in vehicle exhausts thereby causing greenhouse
gas GHG emission problem. In this study, heterogeneous catalysts of
palladium with bio-char (2 wt% Pd/Bc) and Al2O3 (2wt% Pd/ Al2O3)
supports were prepared by incipient wetness impregnation and then
subsequently tested for catalytic combustion of CH4. Support-porous
heterogeneous catalytic combustion (HCC) material were selected
based on factors such as surface area, porosity, thermal stability,
thermal conductivity, reactivity with reactants or products, chemical
stability, catalytic activity, and catalyst life. Sustainable and
renewable support-material of bio-mass char derived from palm shell
waste material was compared with those from the conventional
support-porous materials. Kinetic rate of reaction was determined for
combustion of methane on Palladium (Pd) based catalyst with Al2O3
support and bio-char (Bc). Material characterization was done using
TGA, SEM, and BET surface area. The performance test was
accomplished using tubular quartz reactor with gas mixture ratio of
3% methane and 97% air. The methane porous-HCC conversion was
carried out using online gas analyzer connected to the reactor that
performed porous-HCC. BET surface area for prepared 2 wt% Pd/Bc
is smaller than prepared 2wt% Pd/ Al2O3 due to its low porosity
between particles. The order of catalyst activity based on kinetic rate
on reaction of catalysts in low temperature was 2wt%
Pd/Bc>calcined 2wt% Pd/ Al2O3> 2wt% Pd/ Al2O3>calcined 2wt%
Pd/Bc. Hence agro waste material can successfully be utilized as an
inexpensive catalyst support material for enhanced CH4 catalytic
combustion.
Abstract: Co metal supported on SiO2 and Al2O3 catalysts with
a metal loading varied from 30 of 70 wt.% were evaluated for
decomposition of methane to COx free hydrogen and carbon
nanomaterials. The catalytic runs were carried out from 550-800oC
under atmospheric pressure using fixed bed vertical flow reactor. The
fresh and spent catalysts were characterized by BET surface area
analyzer, XRD, SEM, TEM and TG analysis. The data showed that
50% Co/Al2O3 catalyst exhibited remarkable higher activity at 800oC
with respect to H2 production compared to rest of the catalysts.
However, the catalytic activity and durability was greatly declined at
higher temperature. The main reason for the catalytic inhibition of Co
containing SiO2 catalysts is the higher reduction temperature of
Co2SiO4. TEM images illustrate that the carbon materials with
various morphologies, carbon nanofibers (CNFs), helical-shaped
CNFs and branched CNFs depending on the catalyst composition and
reaction temperature were obtained.
Abstract: Kigelia africana (Lam.) Benth. (Bignoniaceae) is a
reputed traditional remedy for various human ailments such as skin
diseases, microbial infections, melanoma, stomach troubles,
metabolic disorders, malaria and general pains. In spite of the fruit
being widely used for purposes related to its antibacterial and
antifungal properties, the chemical constituents associated with the
activity have not been fully identified. To elucidate the active
principles, we evaluated the antimicrobial activity of fruit extracts
and purified fractions against Staphylococcus aureus, Enterococcus
faecalis, Moraxella catarrhalis, Escherichia coli, Candida albicans
and Candida tropicalis. Shade-dried fruits were powdered and
extracted with hydroalcoholic (1:1) mixture by soaking at room
temperature for 72 h. The crude extract was further fractionated by
column chromatography, with successive elution using hexane,
dichloromethane, ethyl acetate, acetone and methanol. The
dichloromethane and ethyl acetate fractions were combined and
subjected to column chromatography to furnish a wax and oil from
the eluates of 20% and 40% ethyl acetate in hexane, respectively. The
GC-MS and GC×GC-MS results revealed that linoleic acid, linolenic
acid, palmitic acid, arachidic acid and stearic acid were the major
constituents in both oil and wax. The crude hydroalcoholic extract
exhibited the strongest activity with MICs of 0.125-0.5 mg/mL,
followed by the ethyl acetate (MICs = 0.125-1.0 mg/mL),
dichloromethane (MICs = 0.250-2.0 mg/mL), hexane (MICs = 0.25-
2.0 mg/mL), acetone (MICs = 0.5-2.0 mg/mL) and methanol (MICs =
1.0-2.0 mg/mL), whereas the wax (MICs = 2.0-4.0 mg/mL) and oil
(MICs = 4.0-8.0 mg/mL) showed poor activity. The study concludes
that synergistic interactions of chemical constituents could be
responsible for the antimicrobial activity of K. africana fruits, which
needs a more holistic approach to understand the mechanism of its
antimicrobial activity.
Abstract: Biological conversion of biomass to methane has
received increasing attention in recent years. Grasses have been
explored for their potential anaerobic digestion to methane. In this
review, extensive literature data have been tabulated and classified.
The influences of several parameters on the potential of these
feedstocks to produce methane are presented. Lignocellulosic
biomass represents a mostly unused source for biogas and ethanol
production. Many factors, including lignin content, crystallinity of
cellulose, and particle size, limit the digestibility of the hemicellulose
and cellulose present in the lignocellulosic biomass. Pretreatments
have used to improve the digestibility of the lignocellulosic biomass.
Each pretreatment has its own effects on cellulose, hemicellulose and
lignin, the three main components of lignocellulosic biomass. Solidstate
anaerobic digestion (SS-AD) generally occurs at solid
concentrations higher than 15%. In contrast, liquid anaerobic
digestion (AD) handles feedstocks with solid concentrations between
0.5% and 15%. Animal manure, sewage sludge, and food waste are
generally treated by liquid AD, while organic fractions of municipal
solid waste (OFMSW) and lignocellulosic biomass such as crop
residues and energy crops can be processed through SS-AD. An
increase in operating temperature can improve both the biogas yield
and the production efficiency, other practices such as using AD
digestate or leachate as an inoculant or decreasing the solid content
may increase biogas yield but have negative impact on production
efficiency. Focus is placed on substrate pretreatment in anaerobic
digestion (AD) as a means of increasing biogas yields using today’s
diversified substrate sources.
Abstract: Ni-based catalysts with different amounts of Na as
promoter from 2 to 6 wt % were prepared by solution combustion
method. The catalytic activity was investigated in syngas methanation
reaction. Carbon oxides conversion and methane selectivity are greatly
influenced by sodium loading. Adding 2 wt% Na remarkably improves
catalytic activity and long-term stability, attributed to its smaller mean
NiO particle size, better distribution, and milder metal-support
interaction. However, excess addition of Na results in deactivation
distinctly due to the blockage of active sites.
Abstract: Anaerobic modeling is a useful tool to describe and
simulate the condition and behaviour of anaerobic treatment units for
better effluent quality and biogas generation. The present
investigation deals with the anaerobic treatment of brewery
wastewater with varying organic loads. The chemical oxygen demand
(COD) and total suspended solids (TSS) of the influent and effluent
of the bioreactor were determined at various retention times to
generate data for kinetic coefficients. The bio-kinetic coefficients in
the modified Stover–Kincannon kinetic and methane generation
models were determined to study the performance of anaerobic
digestion process. At steady-state, the determination of the kinetic
coefficient (K), the endogenous decay coefficient (Kd), the maximum
growth rate of microorganisms (μmax), the growth yield coefficient
(Y), ultimate methane yield (Bo), maximum utilization rate constant
Umax and the saturation constant (KB) in the model were calculated to
be 0.046 g/g COD, 0.083 (d¯¹), 0.117 (d-¹), 0.357 g/g, 0.516 (L
CH4/gCODadded), 18.51 (g/L/day) and 13.64 (g/L/day) respectively.
The outcome of this study will help in simulation of anaerobic model
to predict usable methane and good effluent quality during the
treatment of industrial wastewater. Thus, this will protect the
environment, conserve natural resources, saves time and reduce cost
incur by the industries for the discharge of untreated or partially
treated wastewater. It will also contribute to a sustainable long-term
clean development mechanism for the optimization of the methane
produced from anaerobic degradation of waste in a close system.
Abstract: Catalytic combustion is generally accepted as an environmentally preferred alternative for the generation of heat and power from fossil fuels mainly due to its advantages related to the stable combustion under very lean conditions with low emissions of NOx, CO, and UHC at temperatures lower than those occurred in conventional flame combustion. Despite these advantages, the commercial application of catalytic combustion has been delayed because of complicated reaction processes and the difficulty in developing appropriate catalysts with the required stability and durability. To develop the catalytic combustors, detailed studies on the combustion characteristics of catalytic combustion should be conducted. To the end, in current research, quantitative studies on the combustion characteristics of the catalytic combustors, with a Pd-based catalyst for MCFC power generation systems, relying on numerical simulations have been conducted. In addition, data from experimental studies of variations in outlet temperatures and fuel conversion, taken after operating conditions have been used to validate the present numerical approach. After introducing the governing equations for mass, momentum, and energy equations as well as a description of catalytic combustion kinetics, the effects of the excess air ratio, space velocity, and inlet gas temperature on the catalytic combustion characteristics are extensively investigated. Quantitative comparisons are also conducted with previous experimental data. Finally, some concluding remarks are presented.
Abstract: Steam reforming is industrially important as it is
incorporated in several major chemical processes including the
production of ammonia, methanol, hydrogen and ox alcohols. Due to
the strongly endothermic nature of the process, a large amount of heat
is supplied by fuel burning (commonly natural gas) in the furnace
chamber. Reaction conversions, tube catalyst life, energy
consumption and CO2 emission represent the principal factors
affecting the performance of this unit and are directly influenced by
the high operating temperatures and pressures.
This study presents a simulation of the performance of the
reforming of methane in a primary reformer, through a developed
empirical relation which enables to investigate the effects of
operating parameters such as the pressure, temperature, steam to
carbon ratio on the production of hydrogen, as well as the fraction of
non converted methane.
It appears from this analysis that the exit temperature Te, the
operating pressure as well the steam to carbon ratio has an important
effect on the reforming of methane.
Abstract: The intension in this work is to investigate the effect of different fuels type on engine performance for different engine speed. Brake Power, Brake Torque, and specific fuel consumption were calculated and presented to show the effect of varying fuel type on them for all cases considered. A special program used to carry out the calculations. A simulation model for one-cylinder spark ignition engine has been built and calculated.
The analysis of the results shows that for methanol the power increases about 30% at 1000 rpm and 16% at 6000 rpm comparing with methane. For the same compared fuels the increment in fuel consumption is about 100% at 1000 rpm and 115% at 6000 rpm. The increment in brake thermal efficiency for gasoline is around 11% comparing with methane at 1000 rpm and 7% for methanol comparing with methane at 4000 rpm.
Abstract: Continuous measurements of greenhouse gases (GHGs) emitted from soils are required to understand diurnal and seasonal variations in soil emissions and related mechanism. This understanding plays an important role in appropriate quantification and assessment of the overall change in soil carbon flow and budget. This study proposes to monitor GHGs emissions from soil under sugarcane cultivation in Thailand. The measurements were conducted over 379 days. The results showed that the total net amount of GHGs emitted from sugarcane plantation soil amounts to 36 Mg CO2eq ha-1. Carbon dioxide (CO2) and nitrous oxide (N2O) were found to be the main contributors to the emissions. For methane (CH4), the net emission was found to be almost zero. The measurement results also confirmed that soil moisture content and GHGs emissions are positively correlated.
Abstract: This study was focused on polymer electrolytes containing methanesulfonic acid (MSA) and p-toluene sulfonic acid (pTSA) mixed with polyacrylamide (PAAm) respectively. Impedance Spectroscopy technique has been employed to compare the ionic conductivity of these polymer electrolytes. The ionic conductivity of the PAAm hydrogel electrolytes increase upon adding the sulfonic acids. Ionic conductivity of PAAm-pTSA is higher than PAAm-MSA. The electrochemical performance evaluations were done with the tin-air cells discharge at zero current for 30minutes and at constant current density of 2.5, 5, 7.5, 10, 12.5 and 15mA/cm2. The tin-air cell of PAAm-MSA produce higher specific discharge capacity compared to PAAm-pTSA. Open-circuit voltage measurement revealed a higher voltage for tin-air cell of PAAm-MSA which is 1.27V.
Abstract: Trihalogenmethanes (THMs) are disinfection byproducts with non-carcinogenic and genotoxic effects. The contamination of 6 sites close to the water treatment plant has been monitored in second largest city of the Czech Republic. Health risk assessment including both non-carcinogenic and genotoxic risk for long term exposition was realized using the critical concentrations. Concentrations of trihalogenmethanes met national standards in all samples. Risk assessment proved that health risks from trihalogenmethanes are acceptable on each site.
Abstract: SUVA (equivalent to UV254/DOC) value in raw water is a precursor for the formation of trihalomethane during chlorination at a water treatment plant. This study collected rapidly filtered water from an advanced water treatment plant for use in experiments on raw water. The removal rate of treating the trihalomethanes formation potential (THMFP) was conducted by using a biological activated carbon. The hydraulic retention time and SUVA loading were major factors in biological degradation tests. The results showed that biological powder-activated carbon (BPAC) lowered the average concentration of UV254 and value of SUVA in raw water. A removal efficiency of THMFP was present in the treatment of the three primary organic carbon items. These results highlighted the importance of the BPAC had an excellent treatment efficiency on THMFP.
Abstract: The deposition of diamond films on a Si3N4 substrate
is an attractive technique for industrial applications because of the
excellent properties of diamond. Pretreatment of substrate is very
important prior to diamond deposition to promote nucleation and
adhesion between coating and substrate. Deposition of
nanocrystalline diamonds films on silicon nitride substrate have been
carried out by HF-CVD technique using mixture of methane and
hydrogen gases. Different pretreatment of substrate including
chemical etching consists of hot acid etching and basic etching and
mechanical etching were used to study the quality of diamond formed
on the substrate. The structure and morphology of diamond coating
have been studied using X-ray Diffraction (XRD) and Scanning
Electron Microscope (SEM) while diamond film quality has been
characterized using Raman spectroscopy. AFM was used to
investigate the effect of chemical etching and mechanical
pretreatment on the surface roughness of the substrates and the
resultant morphology of nanocrystalline diamond. It was found that
diamond film deposited on as-received, basic etched and grinded
substrate shows the morphology of cauliflower while blasted and
acidic etched substrates produce smooth, continuous diamond film.
However, the Raman investigation did not show any deviation in
quality of diamond film for any pretreatment.
Abstract: Non-premixed turbulent combustion Computational Fluid Dynamics (CFD) has been carried out in a simplified methanefuelled coaxial jet combustor employing Large Eddy Simulation (LES). The objective of this study is to evaluate the performance of LES in modelling non-premixed combustion using a commercial software, FLUENT, and investigate the effects of the grid density and chemistry models employed on the accuracy of the simulation results. A comparison has also been made between LES and Reynolds Averaged Navier-Stokes (RANS) predictions. For LES grid sensitivity test, 2.3 and 6.2 million cell grids are employed with the equilibrium model. The chemistry model sensitivity analysis is achieved by comparing the simulation results from the equilibrium chemistry and steady flamelet models. The predictions of the mixture fraction, axial velocity, species mass fraction and temperature by LES are in good agreement with the experimental data. The LES results are similar for the two chemistry models but influenced considerably by the grid resolution in the inner flame and near-wall regions.
Abstract: Proton transfer and hydrogen bonding are two aspects
of the chemistry of hydrogen that respectively govern the behaviour
and structure of many molecules, both simple and complex. All the
theoretical enol and keto conformations of 1,3-diphenyl-1,3-
propandion known as dibenzoylmethane (DBM), have been
investigated by means of atoms in molecules (AIM) theory. It was
found that the most stable conformers are those stabilized by
hydrogen bridges.The aim of the present paper is a thorough
conformational analysis of DBM (with special attention on chelated
cis-enol conformers) in order to obtain detailed information on the
geometrical parameters, relative stabilities and rotational motion of
the phenyl groups. It is also important to estimate the barrier height
for ptoton transfer and hydrogen bond strength, which are the main
factors governing conformational stability.
Abstract: In this study the enthalpies of dissociation for pure
methane and pure carbon dioxide was calculated using a hydrate
equilibrium data obtained in this study. The enthalpy of dissociation
was determined using Clausius-Clapeyron equation. The results were
compared with the values reported in literature obtained using
various techniques.
Abstract: Anxiety is a common disorder that attacks many people in society and often accompanied by physiological sensations such as tachycardia, chest pain, shortness of breath, insensitivity and etc. The purpose of this study is to characterize the putative anxiolytic-like effects of DEV (dichloromethane extracts of valerian) using the elevated plus maze (EPM) in rats. DEV was dissolved in DMSO and orally administered at different doses to adult male wistar rats, 0.5, 1.5 and 3 hours before behavioral evaluation in an EPM respectively. Control rats were treated with an equal volume of DMSO. Single treatment of DEV (at 0.1,0.2. 0.3, and 0.4 g/kg) significantly increased time-spent and arm entries into open arms of EPM versus control groups (p