14 research outputs found
Dechlorination of Environmental Contaminants Using a Hybrid Nanocatalyst: Palladium Nanoparticles Supported on Hierarchical Carbon Nanostructures
This paper demonstrates the effectiveness of a new type of hybrid nanocatalyst material that combines the high surface area of nanoparticles and nanotubes with the structural robustness and ease of handling larger supports. The hybrid material is made by fabricating palladium nanoparticles on two types of carbon supports: as-received microcellular foam (Foam) and foam with carbon nanotubes anchored on the pore walls (CNT/Foam). Catalytic reductive dechlorination of carbon tetrachloride with these materials has been investigated using gas chromatography. It is seen that while both palladium-functionalized carbon supports are highly effective in the degradation of carbon tetrachloride, the rate of degradation is significantly increased with palladium on CNT/Foam. However, there is scope to increase this rate further if the wettability of these structures can be enhanced in the future. Microstructural and spectroscopic analyses of the fresh and used catalysts have been compared which indicates that there is no change in density or surface chemical states of the catalyst after prolonged use in dechlorination test. This implies that these materials can be used repeatedly and hence provide a simple, powerful, and cost-effective approach for dechlorination of water
Simulation and Experiments on One Phase and Three Phase Shunt Active Power Filters
Based on synchronous detection method a shunt active power filter for a single phase has been developed. Harmonic pollution is increasing day-to-day by the use of non-linearity devices such as power electronics rectifier, inverters and many other device. Improvement in the quality of power has become the big task for the present electrical society. So we modelled a 1-phase SAPF(shunt power filter active in nature) using the synchronous detection method under which the hysteresis and triangular current controller technique was shown and total harmonics distortion was shown for both the cases. Results based on simulation were highlighted to depict the working of 1-phase SAPF due to non-linearity in the load. To prove the simulation results an experimental setup was also developed using various components in the project work.Also an instantaneous reactive power technique was developed for the compensation of reactive power and reduction in harmonics, and the results of the total harmonic distortion was compared for every cas
Upward Flow Constructed Wetland For Treatment Of Water Contaminated With Chlorinated Aliphatics
An improved upward flow constructed wetland cell for treatment of water contaminated with chlorinated aliphatics is disclosed. The improvements include adding ammonia-oxidizing microorganisms to the methane-oxidizing microorganisms already present in an oxygenated root zone and adding improved pore-water sample chambers for measuring the performance of the constructed wetland cell
Dechlorination of Environmental Contaminants Using a Hybrid Nanocatalyst: Palladium Nanoparticles Supported on Hierarchical Carbon Nanostructures
This paper demonstrates the effectiveness of a new type of hybrid nanocatalyst material that combines the high surface area of nanoparticles and nanotubes with the structural robustness and ease of handling larger supports. The hybrid material is made by fabricating palladium nanoparticles on two types of carbon supports: as-received microcellular foam (Foam) and foam with carbon nanotubes anchored on the pore walls (CNT/Foam). Catalytic reductive dechlorination of carbon tetrachloride with these materials has been investigated using gas chromatography. It is seen that while both palladium-functionalized carbon supports are highly effective in the degradation of carbon tetrachloride, the rate of degradation is significantly increased with palladium on CNT/Foam. However, there is scope to increase this rate further if the wettability of these structures can be enhanced in the future. Microstructural and spectroscopic analyses of the fresh and used catalysts have been compared which indicates that there is no change in density or surface chemical states of the catalyst after prolonged use in dechlorination test. This implies that these materials can be used repeatedly and hence provide a simple, powerful, and cost-effective approach for dechlorination of water
Dechlorination of Environmental Contaminants Using a Hybrid Nanocatalyst: Palladium Nanoparticles Supported on Hierarchical Carbon Nanostructures
This paper demonstrates the effectiveness of a new type of hybrid nanocatalyst material that combines the high surface area of nanoparticles and nanotubes with the structural robustness and ease of handling larger supports. The hybrid material is made by fabricating palladium nanoparticles on two types of carbon supports: as-received microcellular foam (Foam) and foam with carbon nanotubes anchored on the pore walls (CNT/Foam). Catalytic reductive dechlorination of carbon tetrachloride with these materials has been investigated using gas chromatography. It is seen that while both palladium-functionalized carbon supports are highly effective in the degradation of carbon tetrachloride, the rate of degradation is significantly increased with palladium on CNT/Foam. However, there is scope to increase this rate further if the wettability of these structures can be enhanced in the future. Microstructural and spectroscopic analyses of the fresh and used catalysts have been compared which indicates that there is no change in density or surface chemical states of the catalyst after prolonged use in dechlorination test. This implies that these materials can be used repeatedly and hence provide a simple, powerful, and cost-effective approach for dechlorination of water
Biological Redox Cycling of Iron in Nontronite and Its Potential Application in Nitrate Removal
Biological redox cycling of structural
Fe in phyllosilicates is
an important but poorly understood process. The objective of this
research was to study microbially mediated redox cycles of Fe in nontronite
(NAu-2). During the reduction phase, structural Fe(III) in NAu-2 served
as electron acceptor, lactate as electron donor, AQDS as electron
shuttle, and dissimilatory Fe(III)-reducing bacterium <i>Shewanella
putrefaciens</i> CN32 as mediator in bicarbonate- and PIPES-buffered
media. During the oxidation phase, biogenic Fe(II) served as electron
donor and nitrate as electron acceptor. Nitrate-dependent Fe(II)-oxidizing
bacterium <i>Pseudogulbenkiania</i> sp. strain 2002 was
added as mediator in the same media. For all three cycles, structural
Fe in NAu-2 was able to reversibly undergo three redox cycles without
significant dissolution. Fe(II) in bioreduced samples occurred in
two distinct environments, at edges and in the interior of the NAu-2
structure. Nitrate reduction to nitrogen gas was coupled with oxidation
of edge-Fe(II) and part of interior-Fe(II) under both buffer conditions,
and its extent and rate did not change with Fe redox cycles. These
results suggest that biological redox cycling of structural Fe in
phyllosilicates is a reversible process and has important implications
for biogeochemical cycles of carbon, nitrogen, and other nutrients
in natural environments
Sulfidation of Iron-Based Materials: A Review of Processes and Implications for Water Treatment and Remediation
Iron-based
materials used in water treatment and groundwater remediationespecially
micro- and nanosized zerovalent iron (nZVI)can be more effective
when modified with lower-valent forms of sulfur (i.e., “sulfidated”).
Controlled sulfidation for this purpose (using sulfide, dithionite,
etc.) is the main topic of this review, but insights are derived by
comparison with related and comparatively well-characterized processes
such as corrosion of iron in sulfidic waters and abiotic natural attenuation
by iron sulfide minerals. Material characterization shows that varying
sulfidation protocols (e.g., concerted or sequential) and key operational
variables (e.g., S/Fe ratio and sulfidation duration) result in materials
with structures and morphologies ranging from core–shell to
multiphase. A meta-analysis of available kinetic data for dechlorination
under anoxic conditions, shows that sulfidation usually increases
dechlorination rates, and simultaneously hydrogen production is suppressed.
Therefore, sulfidation can greatly improve the efficiency of utilization
of reducing equivalents for contaminant removal. This benefit is most
likely due to inhibited corrosion as a result of sulfidation. Sulfidation
may also favor desirable pathways of contaminant removal, such as
(i) dechlorination by reductive elimination rather than hydrogenolysis
and (ii) sequestration of metals as sulfides that could be resistant
to reoxidation. Under oxic conditions, sulfidation is shown to enhance
heterogeneous catalytic oxidation of contaminants. These net effects
of sulfidation on contaminant removal by iron-based materials may
substantially improve their practical utility for water treatment
and remediation of contaminated groundwater