scholarly journals Experimental Study of Montmorillonite Structure and Transformation of its Properties under the Treatment of Inorganic Acid Solutions

2016 ◽  
Author(s):  
Victoria V. Krupskaya ◽  
Sergey V. Zakusin ◽  
Ekaterina A. Tyupina ◽  
Olga V. Dorzhieva ◽  
Anatoliy P. Zhukhlistov ◽  
...  
Keyword(s):  
Reaction Times ◽  
Thermochemical Treatment ◽  
Exchange Capacity ◽  
Acid Solutions ◽  
Inorganic Acid ◽  
Oh Groups ◽  
Different Temperatures ◽  
Bentonite Clays ◽  
Octahedral Cations

The paper discusses the mechanism of montmorillonite structure alteration and bentonites properties modification (on the example of samples from clay deposit Taganka, Kazakhstan) due to the thermochemical treatment (treatment with inorganic acid solutions at different temperatures, concentrations and reaction times). With the use of the suit of methods certain processes were distinguished: transformation of montmorillonite structure, which appears in the leaching of interlayer and octahedral cations, protonation of the interlayer and OH groups at octahedral sheets. Changes in the structure of the 2:1 layer of montmorillonite and its interlayer result in significant changes in the properties – reduction of cation exchange capacity and an increase of specific surface area. The results of the work showed that bentonite clays retain a significant portion of its adsorption properties even after the long term and intense thermochemical treatment (6M HNO3, 60°C, 108 hours)

scholarly journals Transformation of the montmorillonite structure and its adsorption properties due to the thermochemical treatment

2019 ◽  
Vol 64 (3) ◽  
pp. 300-319
Author(s):  
V. V. Krupskaya ◽  
S. V. Zakusin ◽  
E. A. Tyupina ◽  
O. V. Dorzhieva ◽  
M. S. Chernov ◽  
...  
Keyword(s):  
Organic Matter ◽  
Cation Exchange Capacity ◽  
Thermochemical Treatment ◽  
Exchange Capacity ◽  
Adsorption Properties ◽  
Structure And Properties ◽  
Oh Groups ◽  
Composition Structure ◽  
Bentonite Clays ◽  
Layer Composition

Complex studies revealed changes in the composition, structure, and properties of bentonite clays from the Taganskoye (Kazakhstan) and Dashkovskoe (Moscow region) deposits due to the thermochemical treatment. The leaching of cations from the interlayer and octahedral positions, protonation of the interlayer and OH-groups, leads to modification of the interlayer and 2:1 layer composition, which in turn contributes to significant changes in properties:-a decrease in the cation exchange capacity due to a decrease in the layer charge and increase in the specific surface due to destruction and partial amorphization. Bentonites from the Dashkovskoye deposit demonstrated higher resistance to thermochemical treatment than the bentonites from the Taganskoye deposit due to the protecting effect of the organic matter. Results of the work showed that even after quite intensive thermochemical treatment (13M HNO3, 90 °C, 5 hours), bentonite clays retain a significant part of the adsorption capacity.

Sugarcane Biochar for Agricultural Use Produced in Different Conditions of Pyrolysis

2019 ◽  
pp. 1-8
Author(s):  
Juliany Barbosa de Pinho ◽  
Aloisio Bianchini ◽  
Pedro Silvério Xavier Pereira ◽  
Letycia Cunha Nunes ◽  
Rodrigo Fernandes Daros ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Exchange Capacity ◽  
Raw Material ◽  
Physical And Chemical Properties ◽  
Oxidizing Atmosphere ◽  
Different Temperatures ◽  
Agricultural Use ◽  
Physical And Chemical ◽  
And Chemical Properties

From the pyrolysis process, biochar is a carbon rich and recalcitrant organic material with potential for long term carbon sequestration because of its aromatic structure. However, the physical and chemical properties of the biochar vary due to the diversity of raw material and the conditions of production. The present study aimed to evaluate the biochar from the sugarcane bagasse at different temperatures and under two conditions of pyrolysis. The biochar was produced at two final temperatures 200°C (1 hour); 250°C (1h) and 250°C (2h), with pyrolysis of an oxidizing and non-oxidizing atmosphere for both. PH, cation exchange capacity (CTC), carbon content (C), Nitrogen (N), hydrogen (H), H:C, C:N and ash ratios were evaluated. The contents of C, H, N and the atomic ratios H:C and C:N were higher in Biochar produced in a non-oxidizing atmosphere (BNO). However, the content of ash, pH and CTC were higher in Biochar produced in oxidizing atmospheres (BO). One can conclude the direct influence of the pyrolysis condition.

scholarly journals A Biorefinery Cascade Conversion of Hemicellulose-Free Eucalyptus Globulus Wood: Production of Concentrated Levulinic Acid Solutions for γ-Valerolactone Sustainable Preparation

Catalysts ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 169 ◽  
Author(s):  
Sandra Rivas ◽  
Anna Raspolli Galletti ◽  
Claudia Antonetti ◽  
Domenico Licursi ◽  
Valentín Santos ◽  
...  
Keyword(s):  
Formic Acid ◽  
Eucalyptus Globulus ◽  
Levulinic Acid ◽  
Reaction Times ◽  
Cross Flow ◽  
Water Soluble ◽  
Main Reaction ◽  
Acid Solutions ◽  
Different Temperatures ◽  
Single Batch

Eucalyptus globulus wood samples were subjected to preliminary aqueous processing to remove water-soluble extractives and hemicelluloses, and the resulting solid (mainly made up of cellulose and lignin) was employed as a substrate for converting the cellulosic fraction into mixtures of levulinic and formic acid through a sulfuric acid-catalyzed reaction. These runs were carried out in a microwave-heated reactor at different temperatures and reaction times, operating in single-batch or cross-flow modes, in order to identify the most favorable operational conditions. Selected liquid phases deriving from these experiments, which resulted in concentrated levulinic acid up to 408 mmol/L, were then employed for γ-valerolactone production by levulinc acid hydrogenation in the presence of the commercial 5% Ru/C catalyst. In order to assess the effects of the main reaction parameters, hydrogenation experiments were performed at different temperatures, reaction times, amounts of ruthenium catalyst and hydrogen pressure. Yields of γ-valerolactone in the range of 85–90 mol % were obtained from the hydrogenation of the wood-derived solutions containing levulinic acid, obtained by single-batch operation or by the cross-flow process. The negative effect of co-produced formic acid present in crude levulinic acid solutions was evidenced and counteracted efficiently by allowing the preliminary thermal decomposition of formic acid itself.

Chemical improvement of surfaces. Part 4: Significantly enhanced hydrophobicity of wood by covalent modification with p-silyl-functionalized benzoates

Holzforschung ◽  
2016 ◽  
Vol 70 (5) ◽  
pp. 411-419 ◽  
Author(s):  
Christian Kaldun ◽  
Sebastian Dahle ◽  
Wolfgang Maus-Friedrichs ◽  
Jan C. Namyslo ◽  
Dieter E. Kaufmann
Keyword(s):  
Photoelectron Spectroscopy ◽  
Reaction Times ◽  
Weight Percent ◽  
Contact Angles ◽  
Covalent Modification ◽  
Attenuated Total Reflection ◽  
Oh Groups ◽  
Benzoic Acid Derivatives ◽  
Covalently Bonded ◽  
Different Temperatures

Abstract One aim of this work was the chemical modification of surfaces of Scots pine (Pinus sylvestris L.) sapwood veneer chips by covalently bonded substances for improved hydrophobicity. The durable attachment of organosilyl moieties to the surface was in focus. Several benzotriazolyl-activated p-silylated benzoic acid derivatives were applied to the esterification of OH groups at different temperatures and reaction times. The reactions resulted in weight percent gains from 8% to 43% and corresponding quantities of covalently bonded organomaterials of 0.3–2.1 mmol g-1 wood. The hydrophobicity was significantly increased as indicated by contact angles from 121° to 142°. All modified wood samples were analyzed by attenuated total reflection-infrared, contact angle measurements, and X-ray photoelectron spectroscopy.

Retrieval from Memory or Procedural Strategies for Addition Problems

2011 ◽  
Vol 70 (1) ◽  
pp. 35-39 ◽  
Author(s):  
Muriel Fanget ◽  
Catherine Thevenot ◽  
Caroline Castel ◽  
Michel Fayol
Keyword(s):  
Reaction Times ◽  
Long Term Memory ◽  
Verbal Reports ◽  
Term Memory ◽  
Simple Addition ◽  
Memory Traces ◽  
Addition Problem ◽  
Retrieval From Memory ◽  
Calculation Procedures

In this study, we used a paradigm recently developed ( Thevenot, Fanget, & Fayol, 2007 ) to determine whether 10-year-old children solve simple addition problems by retrieval of the answer from long-term memory or by calculation procedures. Our paradigm is unique in that it does not rely on reaction times or verbal reports, which are known to potentially bias the results, especially in children. Rather, it takes advantage of the fact that calculation procedures degrade the memory traces of the operands, so that it is more difficult to recognize them when they have been involved in the solution of an addition problem by calculation rather than by retrieval. The present study sharpens the current conclusions in the literature and shows that, when the sum of addition problems is up to 10, children mainly use retrieval, but when it is greater than 10, they mainly use calculation procedures.

Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

1977 ◽  
Vol 16 (01) ◽  
pp. 30-35 ◽  
Author(s):  
N. Agha ◽  
R. B. R. Persson
Keyword(s):  
Complex Formation ◽  
Significant Influence ◽  
Room Temperature ◽  
Ph Value ◽  
Maximum Activity ◽  
Reduction Step ◽  
Labelling Yield ◽  
Different Temperatures ◽  
Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

Heat wave effects on biomass and vegetative growth of macrophytes after long-term adaptation to different temperatures: a mesocosm study

2015 ◽  
Vol 66 (3) ◽  
pp. 265-274 ◽  
Author(s):  
Y Cao ◽  
ÉM Neif ◽  
W Li ◽  
J Coppens ◽  
N Filiz ◽  
...  
Keyword(s):  
Heat Wave ◽  
Vegetative Growth ◽  
Wave Effects ◽  
Different Temperatures

scholarly journals UV Stimulated Manganese Dioxide for the Persulfate Catalytic Degradation of Bisphenol A

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 502
Author(s):  
Guihua Dong ◽  
Bing Chen ◽  
Bo Liu ◽  
Stanislav R. Stoyanov ◽  
Yiqi Cao ◽  
...  
Keyword(s):  
Bisphenol A ◽  
Reaction Mechanisms ◽  
Reduction Rate ◽  
Catalytic Degradation ◽  
Gas Chromatography Mass Spectrometry ◽  
Degradation Pathways ◽  
Industrial Chemicals ◽  
Oh Groups ◽  
Long Term Adverse Effects

One of the most commonly produced industrial chemicals worldwide, bisphenol A (BPA), is used as a precursor in plastics, resins, paints, and many other materials. It has been proved that BPA can cause long-term adverse effects on ecosystems and human health due to its toxicity as an endocrine disruptor. In this study, we developed an integrated MnO2/UV/persulfate (PS) process for use in BPA photocatalytic degradation from water and examined the reaction mechanisms, degradation pathways, and toxicity reduction. Comparative tests using MnO2, PS, UV, UV/MnO2, MnO2/PS, and UV/PS processes were conducted under the same conditions to investigate the mechanism of BPA catalytic degradation by the proposed MnO2/UV/PS process. The best performance was observed in the MnO2/UV/PS process in which BPA was completely removed in 30 min with a reduction rate of over 90% for total organic carbon after 2 h. This process also showed a stable removal efficiency with a large variation of pH levels (3.6 to 10.0). Kinetic analysis suggested that 1O2 and SO4•− played more critical roles than •OH for BPA degradation. Infrared spectra showed that UV irradiation could stimulate the generation of –OH groups on the MnO2 photocatalyst surface, facilitating the PS catalytic degradation of BPA in this process. The degradation pathways were further proposed in five steps, and thirteen intermediates were identified by gas chromatography-mass spectrometry. The acute toxicity was analyzed during the treatment, showing a slight increase (by 3.3%) in the first 30 min and then a decrease by four-fold over 2 h. These findings help elucidate the mechanism and pathways of BPA degradation and provide an effective PS catalytic strategy.

scholarly journals Impact of Prolonged Exposure of Eleven Years to Hot Seawater on the Degradation of a Thermoset Composite

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2154
Author(s):  
Amir Hussain Idrisi ◽  
Abdel-Hamid I. Mourad ◽  
Muhammad M. Sherif
Keyword(s):  
Exposure Time ◽  
Prolonged Exposure ◽  
Mechanical Performance ◽  
Matrix Cracking ◽  
Pull Out ◽  
Strength Based ◽  
Different Temperatures ◽  
River Line ◽  
Composite Samples

This paper presents a long-term experimental investigation of E-glass/epoxy composites’ durability exposed to seawater at different temperatures. The thermoset composite samples were exposed to 23 °C, 45 °C and 65 °C seawater for a prolonged exposure time of 11 years. The mechanical performance as a function of exposure time was evaluated and a strength-based technique was used to assess the durability of the composites. The experimental results revealed that the tensile strength of E-glass/epoxy composite was reduced by 8.2%, 29.7%, and 54.4% after immersion in seawater for 11 years at 23 °C, 45 °C, and 65 °C, respectively. The prolonged immersion in seawater resulted in the plasticization and swelling in the composite. This accelerated the rate of debonding between the fibers and matrix. The failure analysis was conducted to investigate the failure mode of the samples. SEM micrographs illustrated a correlation between the fiber/matrix debonding, potholing, fiber pull-out, river line marks and matrix cracking with deterioration in the tensile characteristics of the thermoset composite.

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