scholarly journals Metal Foams as Novel Catalyst Support in Environmental Processes

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 587 ◽  
Author(s):  
Anna Gancarczyk ◽  
Katarzyna Sindera ◽  
Marzena Iwaniszyn ◽  
Marcin Piątek ◽  
Wojciech Macek ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mechanical Stability ◽  
Packed Bed ◽  
Metal Foams ◽  
High Porosity ◽  
Slow Kinetics

Metal foams are considered as promising catalyst carriers due to their high porosity, large specific surface area, and satisfactory thermal and mechanical stability. The study presents heat transfer and pressure drop experiments performed for seven foams of different pore densities made from diverse metals. Mass transfer characteristics are derived using the Chilton–Colburn analogy. It was found that the foams display much more intense heat/mass transfer than a monolith, comparable to packed bed. Next, the foams’ efficiencies have been compared, using 1D reactor modeling, in catalytic reactions displaying either slower (selective catalytic reduction of NOx) or faster kinetics (catalytic methane combustion). For the slow kinetics, the influence of carrier specific surface area at which catalyst can be deposited (i.e., catalyst amount) was decisive to achieve high process conversion and short reactor. For this case, monolith appears as the best choice assuming it’s the lowest pressure drop. For the fast reaction, the mass transfer becomes the limiting parameter, thus solid foams are the best solution.

Initial aggregate formation: Disentangling the effects of soil texture, OM properties and microbial community using artificial model soils

2021 ◽  
Author(s):  
Franziska B. Bucka ◽  
Vincent J.M.N.L. Felde ◽  
Stephan Peth ◽  
Ingrid Kögel-Knabner
Keyword(s):  
Microbial Community ◽  
Specific Surface ◽  
Structure Formation ◽  
Surface Area ◽  
Specific Surface Area ◽  
Soil Structure ◽  
Mechanical Stability ◽  
Aggregate Formation ◽  
Water Stable Aggregates ◽  
Mineral Particles

<p>The interaction between mineral particles and organic matter (OM) is an important and complex process in the course of soil structure formation. For a better understanding it is necessary to disentangle the texture-dependent interplay of individual OM types and mineral particles. We developed an experimental set-up to study early aggregate formation within a controlled lab environment. Artificial soil microcosms with a mineral mixture resembling arable soils of three different textures (clay loam, loam and sandy loam) were used in a short-term, 30-day incubation experiment under constant water-tension. OM was added individually either as plant litter (POM) of two different sizes (0.63-2 mm and < 63 µm, respectively) or bacterial necromass (Bacillus subtilis). The mechanisms of soil structure formation were investigated by isolating water-stable aggregates after the incubation, analyzing their mechanical stability and organic carbon allocation, and measuring the specific surface area and OM covers of the mineral surface, microbial activity, and community structure.</p><p>The dry mixing process and incubation of the mineral mixtures led to particle-particle interactions and fine particle coatings of the sand grains as shown by a reduction of the specific surface area. The OM input of all types caused between 3 to 17% of the mineral surfaces to be covered by OM, with larger covered areas in the clay-rich mixtures. The added OM was quickly accessed and degraded by microbes, as shown by the peak in CO<sub>2</sub>-release within the first 10 days of the incubation. The POM of both sizes induced the predominant formation of water-stable macroaggregates (0.63-30 mm) with a mass contribution of 72 to 91% (irrespective of texture) and fostered the development of a microbial community with a high relative abundance of fungi. The bacterial necromass induced the formation of macroaggregates, but also microaggregates (63-200 µm), while the microbial community was dominated by bacteria. The mechanical stability analysis showed that very small forces < 4 N were sufficient for aggregate failure and breakdown to 80% of the original aggregate size.</p><p>We propose that the microbial degradation of all OM types leads to small, distinct OM clusters consisting of OM substrate, microbes, and extracellular polymeric substances. These interact with mineral particles, resulting in the cross-linking of particles and formation of water-stable aggregates in all textures. The OM can thereby act both as microbial substrate and as structural building block. The initially formed aggregates are a loosely connected scaffold with a very low mechanical stability. Differences in the developed microbial community may lead to additional stabilization mechanisms, like fungal hyphae enmeshing and stabilizing larger aggregates also in sandy texture.</p>

In-situ controlled synthesis of NiFe MOF materials with excellent electrocatalytic performances for water splitting

2021 ◽  
Vol 14 (02) ◽  
pp. 2151011
Author(s):  
Jingwen Jia ◽  
Longfu Wei ◽  
Ziting Guo ◽  
Fang Li ◽  
Changlin Yu ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Water Splitting ◽  
Specific Surface Area ◽  
High Performance ◽  
Alkaline Condition ◽  
High Porosity ◽  
Large Specific Surface Area ◽  
Electrocatalytic Performance

Metal–organic frameworks (MOFs) are the electrocatalytic materials with large specific surface area, high porosity, controllable structure and monodisperse active center, which is a promising candidate for the application of electrochemical energy conversion. However, the electrocatalytic performance of pure MOFs is seriously limited its poor conductivity and stability. In this work, high-performance electrocatalyst was fabricated through combining NiFe/MOF on nickel foam (NF) via in-situ growth strategy. Through rational control of the time and ratio in reaction precursors, we realized the effective manipulation of the growth behavior, and further investigated the electrocatalytic performance in water splitting. The catalyst presented excellent electrocatalytic performance for water splitting, with low overpotential of 260 mV in alkaline condition at a current density of 50 mA[Formula: see text], which is benefited from the large specific surface area and active sites. This study demonstrates that the rational design of NiFe MOF/NF plays a significant role in high-performance electrocatalyst.

Direct molecular hydrogen sulphide scrubbing with hollow fibre membranes

2001 ◽  
Vol 44 (9) ◽  
pp. 135-142 ◽  
Author(s):  
N. Boucil ◽  
B. Jefferson ◽  
S.A. Parsons ◽  
S.J. Judd ◽  
R.M. Stuetz
Keyword(s):  
Mass Transfer ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Flow Rate ◽  
Hydrogen Sulphide ◽  
Gas Flow ◽  
Hollow Fibre ◽  
The Other ◽  
Gas Flow Rate

The emission of hydrogen sulphide is a major problem associated with anaerobic treatment of sulphate and sulphite containing wastewaters. Conventional absorbing processes, such as packed towers, spray towers or bubble columns, are all constrained by factors such as flooding and foaming. Membrane systems, on the other hand, enable independent control of the liquid and gas flow rate and a step change order of magnitude increase in the specific surface area of the contact process. The membrane acts as a gas absorber with a design similar to a shell and tube heat exchanger. On the other hand, they are limited by facets of the membrane such as its resistance to mass transfer and permselectivity, as well as its cost. The work presented in this paper refers to an absorption process based on a non-wetted hollow fibre membrane for the scrubbing of hydrogen sulphide from air, with water as the contact solvent. Results presented describe the performance of the unit in terms of overall transfer and outlet liquid concentration as a function of circulation regime, gas flow rate, liquid flow rate and specific surface area. In particular, results are presented using traditional plots of Sherwood number (Sh) against Graetz (Gr) number for the liquid flowing in the lumens, such that experimental and available empirical descriptions of the process performance are directly compared. Results suggest that, as expected, very efficient mass transfer is obtained. However, the mass transfer was found to reach a maximum value against Gr, contrary to available empirical models.

Using Activated Diatomite as Adsorbent for Treatment of Arsenic Contaminated Water

2020 ◽  
Vol 850 ◽  
pp. 16-21
Author(s):  
Hoc Thang Nguyen ◽  
Phong Thanh Dang
Keyword(s):  
Specific Surface ◽  
Adsorption Capacity ◽  
Surface Area ◽  
Specific Surface Area ◽  
Contaminated Water ◽  
Viet Nam ◽  
High Porosity ◽  
Room Condition ◽  
Main Chemical Composition ◽  
Adsorbent Capacity

Diatomite or diatomaceous earth (DE) is one of materials which can be used as an adsorbent to treat heavy metal ions from waste water, even there are many factories used it to clean the water for drinking. However, natural DE (raw DE) has very low adsorption capacity because of low specific surface area. In this work, natural DE from Lam Dong province, Viet Nam was demagnetized to remove iron and activated by HCl solution for 90 minutes with concentration of 10% at room condition. Adsorbent capacity was evaluated using As solution and the results show that the activated diatomite has adsorption capacity three times higher than that of raw DE, and the specific surface area of activated diatomite was increased 47.5% with the main chemical composition of 90.8% SiO2 and high porosity

scholarly journals Manufacture of Fine-Pored Ceramics by the Gelcasting Method

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Bronisław Psiuk ◽  
Anna Gerle ◽  
Małgorzata Osadnik ◽  
Andrzej Śliwa
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Design Theory ◽  
Nanoporous Materials ◽  
Silica Sol ◽  
High Porosity ◽  
Simple Method ◽  
Fine Grained ◽  
Wide Range

The fine-pored materials represent a wide range of applications and searches are being continued to develop methods of their manufacturing. In the article, based on measurements on fine-grained powders of Al2O3, TiO2, and SiO2, it has been demonstrated that gelcasting can be relatively simple method of obtaining of nanoporous materials with high values of both specific surface area and open porosity. The powders were dispersed in silica sol, and the gelling initiator was NH4Cl. The usefulness of experiment design theory for developing of fine-pored materials with high porosity and specific surface area was also shown.

Mathematical Modeling of Biodiesel Production under Intense Agitation

2016 ◽  
Vol 14 (1) ◽  
pp. 445-451
Author(s):  
Aliakbar Roosta ◽  
Jafar Javanmardi ◽  
Elham Sadat Behineh
Keyword(s):  
Mass Transfer ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Rapeseed Oil ◽  
Catalyst Concentration ◽  
Biodiesel Production ◽  
Transfer Coefficients ◽  
Increasing Temperature ◽  
Intense Agitation

AbstractIn this study, a new approach is proposed to investigate the kinetics of sunflower oil and rapeseed oil transesterification in the presence of potassium hydroxide. Transesterification is a heterogeneous process which affected by a number of parameters, that are not readily available in the literature, such as mass transfer coefficients, partition coefficients, and specific surface area of the dispersed phase. However, under intense agitation condition, mass transfer restrictions may be neglected, and the two phases are supposed to remain in thermodynamic equilibrium, during the process. Therefore, a model was developed independent of the mass transfer coefficient and specific surface area, which is reliable for the intense agitation condition. According to the results, the model is valid at least for mixing rates over 500 rpm. The results of the model were used to study the effects of temperature, methanol-to-oil ratio, and catalyst concentration on the biodiesel conversion. Biodiesel production rate increases with increasing temperature, although rapeseed oil transesterification is more temperature dependent. The results show that the maximum amount of catalyst concentration is less than 1% (by weight); however, the optimum value depends on the operating temperature. The optimum value of the methanol-to-oil-ratio decreases with increasing temperature. Thus, at higher temperatures, less amount of methanol and catalyst are required, which leads to easier purification of biodiesel.

Effect of the specific surface area and operating mode on biological phenol removal using packed bed reactors

Desalination ◽  
2007 ◽  
Vol 211 (1-3) ◽  
pp. 128-137 ◽  
Author(s):  
G Tziotzios ◽  
Ch.N. Economou ◽  
G. Lyberatos ◽  
D.V. Vayenas
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Operating Mode ◽  
Packed Bed ◽  
Phenol Removal ◽  
Packed Bed Reactors

scholarly journals Preparation of Electrospun Active Molecular Membrane and Atmospheric Free Radicals Capture

Molecules ◽  
2019 ◽  
Vol 24 (17) ◽  
pp. 3037 ◽  
Author(s):  
Wang ◽  
Su ◽  
Yu ◽  
Li ◽  
Ma ◽  
...  
Keyword(s):  
Free Radicals ◽  
Impact Strength ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
High Porosity ◽  
Large Specific Surface Area ◽  
Optimal Parameters ◽  
Electrospun Membranes ◽  
Reaction Capacity

We load the natural active molecules onto the spin film in an array using electrospinning techniques. The electrospun active molecular membranes we obtain in optimal parameters exhibit excellent capacity for scavenging radical. The reaction capacity of three different membranes for free radicals are shown as follow, glycyrrhizin acid membrane > quercetin membrane > α-mangostin membrane. The prepared active molecular electrospun membranes with a large specific surface area and high porosity could increase the interaction area between active molecules and free radicals. Additionally, it also has improved anti-airflow impact strength, anti-contaminant air molecular interference ability, and the ability to capture free radicals.

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