Disintegration and dissolution kinetics of wood chips in ionic liquids

Holzforschung ◽  
2011 ◽  
Vol 65 (4) ◽  
Author(s):  
Jörn Viell ◽  
Wolfgang Marquardt
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Specific Surface ◽  
Surface Area ◽  
Dissolution Kinetics ◽  
Wood Chips ◽  
Large Specific Surface Area ◽  
Microscopic Studies ◽  
Kinetics Of

Abstract Ionic liquids are able to dissolve polysaccharides and lignin, but there is only scarce knowledge about the dissolution of native wood. In the present paper, wood was dissolved by the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc). A quantitative balance of the dissolved compounds is presented and the investigations are complemented by in situ microscopy of native wood in EMIMAc. The resulting dissolution kinetics in EMIMAc reveals distinct differences between spruce and beech. While particles of 0.1–0.5 mm of spruce dissolve slowly (up to 40% after 24 h), beech is dissolved more efficiently (75% after 24 h and 90% after 72 h). Wood chips of 10 mm length show similar dissolution kinetics and lignin yields of up to 10%. Microscopic studies reveal a disintegration of wood in EMIMAc into cells with large specific surface area, and differences in dissolution between spruce and beech were observed. These findings explain the size-independent dissolution of wood in EMIMAc and may open up new opportunities for the pretreatment of wood in ionic liquids.

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.

Prediction of Uranium Adsorption by Crystalline Rocks: The Key Role of Reactive Surface Area

1990 ◽  
Vol 212 ◽  
Author(s):  
Richard B. Wanty ◽  
Cynthia A. Rice ◽  
Donald Langmuir ◽  
Paul Briggs ◽  
Errol P. Lawrence
Keyword(s):  
Specific Surface ◽  
Ground Water ◽  
Surface Area ◽  
Specific Surface Area ◽  
Dissolution Kinetics ◽  
Crystalline Rock ◽  
Thin Sections ◽  
Uranyl Carbonate ◽  
Carbonate Complexes

ABSTRACTAdsorption processes are important in controlling U concentrations in ground water. Quantifying such processes is extremely difficult in that in situ conditions cannot be directly measured. One rock characteristic that must be known to quantify adsorption is the specific surface area of reactive minerals exposed to the ground water. We evaluate here three methods for estimating specific surface area in situ. The first is based on the dissolution kinetics of sodium feldspars, the second on emanation of radon-222 and the third on adsorption of naturally-occurring U. The radon-222 method yields estimates 5 to 8 orders of magnitude greater than those obtained via the other two methods; too large probably because of effects related to fracture geometry. Estimates of specific surface area based on modelling adsorption of natural U by aquifer materials are of comparable magnitude to those from the feldspar-dissolution kinetics approach. These conclusions are based on analyses of water from 145 wells in crystalline-rock aquifers from Pennsylvania, New Jersey, Maryland, and Colorado. Computer modelling of the chemical data using PHREEQE [1] showed that uraninite or coffinite approach saturation in reducing water, limiting total U to <2 × 10−9 m. Generally, U minerals are below saturation in oxidizing ground water, where uranyl-carbonate complexes are the dominant dissolved U species. Autoradioluxographs of thin sections show areas of concentration of radioactivity in the rocks and establish that U is concentrated along fracture boundaries and on ferric oxyhydroxide grain coatings. Because U minerals generally are undersaturated, U mobility is limited by adsorption onto ferric oxyhydroxides and other mineral surfaces. Calculations of uranyl adsorption from the ground water onto goethite using the program M1NTEQ [2] show that adsorption decreases with increased carbonate concentrations due to the formation of uranyl-carbonate complexes. Results of this paper improve our understanding of the mobility of U that might be released into oxidized ground water in crystalline rock from a breached radioactive-waste repository.

The Reactivity of Different Active Forms of Sodium Carbonate with Respect to Sulfur Dioxide

1992 ◽  
Vol 57 (11) ◽  
pp. 2302-2308
Author(s):  
Karel Mocek ◽  
Erich Lippert ◽  
Emerich Erdös
Keyword(s):  
Thermal Decomposition ◽  
Liquid Phase ◽  
Sulfur Dioxide ◽  
Specific Surface ◽  
Surface Area ◽  
Sodium Carbonate ◽  
Room Temperature ◽  
Active Form ◽  
The Other ◽  
Kinetics Of

The kinetics of the reaction of solid sodium carbonate with sulfur dioxide depends on the microstructure of the solid, which in turn is affected by the way and conditions of its preparation. The active form, analogous to that obtained by thermal decomposition of NaHCO3, emerges from the dehydration of Na2CO3 . 10 H2O in a vacuum or its weathering in air at room temperature. The two active forms are porous and have approximately the same specific surface area. Partial hydration of the active Na2CO3 in air at room temperature followed by thermal dehydration does not bring about a significant decrease in reactivity. On the other hand, if the preparation of anhydrous Na2CO3 involves, partly or completely, the liquid phase, the reactivity of the product is substantially lower.

scholarly journals Controlled Nanostructuration of Cobalt Oxyhydroxide Electrode Material for Hybrid Supercapacitors

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2325
Author(s):  
Ronan Invernizzi ◽  
Liliane Guerlou-Demourgues ◽  
François Weill ◽  
Alexia Lemoine ◽  
Marie-Anne Dourges ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Energy Storage ◽  
Specific Surface ◽  
Electrode Materials ◽  
Specific Capacity ◽  
Hybrid Supercapacitors ◽  
Cobalt Oxyhydroxide ◽  
Precipitation Medium ◽  
The Impact

Nanostructuration is one of the most promising strategies to develop performant electrode materials for energy storage devices, such as hybrid supercapacitors. In this work, we studied the influence of precipitation medium and the use of a series of 1-alkyl-3-methylimidazolium bromide ionic liquids for the nanostructuration of β(III) cobalt oxyhydroxides. Then, the effect of the nanostructuration and the impact of the different ionic liquids used during synthesis were investigated in terms of energy storage performances. First, we demonstrated that forward precipitation, in a cobalt-rich medium, leads to smaller particles with higher specific surface areas (SSA) and an enhanced mesoporosity. Introduction of ionic liquids (ILs) in the precipitation medium further strongly increased the specific surface area and the mesoporosity to achieve well-nanostructured materials with a very high SSA of 265 m2/g and porosity of 0.43 cm3/g. Additionally, we showed that ILs used as surfactant and template also functionalize the nanomaterial surface, leading to a beneficial synergy between the highly ionic conductive IL and the cobalt oxyhydroxide, which lowers the resistance charge transfer and improves the specific capacity. The nature of the ionic liquid had an important influence on the final electrochemical properties and the best performances were reached with the ionic liquid containing the longest alkyl chain.

scholarly journals Nanocomposite Materials Based on Electrochemically Synthesized Graphene Polymers: Molecular Architecture Strategies for Sensor Applications

Chemosensors ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 149
Author(s):  
André Olean-Oliveira ◽  
Gilberto A. Oliveira Brito ◽  
Celso Xavier Cardoso ◽  
Marcos F. S. Teixeira
Keyword(s):  
Conducting Polymers ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Electrochemical Sensors ◽  
Structural Characteristics ◽  
Low Cost ◽  
Large Specific Surface Area ◽  
Molecular Architecture ◽  
Sensor Applications

The use of graphene and its derivatives in the development of electrochemical sensors has been growing in recent decades. Part of this success is due to the excellent characteristics of such materials, such as good electrical and mechanical properties and a large specific surface area. The formation of composites and nanocomposites with these two materials leads to better sensing performance compared to pure graphene and conductive polymers. The increased large specific surface area of the nanocomposites and the synergistic effect between graphene and conducting polymers is responsible for this interesting result. The most widely used methodologies for the synthesis of these materials are still based on chemical routes. However, electrochemical routes have emerged and are gaining space, affording advantages such as low cost and the promising possibility of modulation of the structural characteristics of composites. As a result, application in sensor devices can lead to increased sensitivity and decreased analysis cost. Thus, this review presents the main aspects for the construction of nanomaterials based on graphene oxide and conducting polymers, as well as the recent efforts made to apply this methodology in the development of sensors and biosensors.

Computational analysis of the effect of [Tea][Ms] and [Tea][H2PO4] ionic liquids on the structure and stability of Aβ(17–42) amyloid fibrils

2021 ◽  
Vol 23 (11) ◽  
pp. 6695-6709
Author(s):  
D. Gobbo ◽  
A. Cavalli ◽  
P. Ballone ◽  
A. Benedetto
Keyword(s):  
Ionic Liquid ◽  
Hydrogen Bonding ◽  
Ionic Liquids ◽  
Liquid Water ◽  
Computational Analysis ◽  
Amyloid Fibrils ◽  
Aβ Peptides ◽  
Structure And Stability ◽  
Water Solutions ◽  
Kinetics Of

Tight coordination of peptides by organic anions driven by hydrogen bonding affects the fibrillation kinetics of Aβ peptides in ionic liquid/water solutions.

Two-Dimensional Transition Metal Borides as High Activity and Selectivity Catalysts for Ammonia Synthesis

Nanoscale ◽  
2021 ◽  
Author(s):  
Haona Zhang ◽  
Shuhua Wang ◽  
Hao Wang ◽  
Baibiao Huang ◽  
Shuping Dong ◽  
...  
Keyword(s):  
Transition Metal ◽  
Specific Surface ◽  
High Activity ◽  
Surface Area ◽  
Active Site ◽  
Ammonia Synthesis ◽  
Two Dimensional ◽  
Large Specific Surface Area ◽  
Site Density ◽  
Metal Borides

In comparison to defect/doping induced activity in materials, transition metal borides with exposed metal atom, large specific surface area and high active site density show advantages as durable and efficient...

Study on the kinetics of process for obtaining cobalt nanopowder by hydrogen reduction under isothermal conditions

2021 ◽  
Vol 1 (1) ◽  
pp. 49-56
Author(s):  
Hieр Nguyen Tien
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Hydrogen Reduction ◽  
Average Particle Size ◽  
Chemical Deposition ◽  
Average Particle ◽  
Isothermal Conditions ◽  
Electron Microscopes ◽  
Kinetics Of

The kinetics of metallic cobalt nanopowder synthesizing by hydrogen reduction from Co(OH)2 nanopowder under isothermal conditions were studied. Co(OH)2 nanopowder was prepared in advance by chemical deposition from aqueous solutions of Co(NO3)2 cobalt nitrate (10 wt.%) and NaOH alkali (10 wt.%) at room temperature, pH = 9 under continuous stirring. The hydrogen reduction of Co(OH)2 nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 270 to 310 °C. The crystal structure and composition of powders was studied by X-ray phase analysis. The specific surface area of samples was measured using the BET method by low-temperature nitrogen adsorption. The average particle size of powders was determined by the measured specific surface area. Particles size characteristics and morphology were investigated by transmission and scanning electron microscopes. Kinetic parameters of Co(OH)2 hydrogen reduction under isothermal conditions were calculated using the Gray–Weddington model and Arrhenius equation. It was found that the rate constant of reduction at t = 310 °C is approximately 1.93 times higher than at 270 °C, so the process accelerates by 1.58 times for 40 min of reduction. The activation energy of cobalt nanopowder synthesizing from Co(OH)2 by hydrogen reduction is ~40 kJ/mol, which indicates a mixed reaction mode. It was shown that cobalt nanoparticles obtained by the hydrogen reduction of its hydroxide at 280 °C are aggregates of equiaxed particles up to 100 nm in size where individual particles are connected to several neighboring particles by contact isthmuses.

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