Search results for "isotherm"
showing 10 items of 268 documents
In-situ radiotracer studies of sorption processes in solutions containing (bi)sulfite ions—II. Low carbon steel
1997
Abstract In this paper, time, potential and pH dependence of SO42− and HSO3− accumulations measured by an in-situ radiotracer method on surface oxide layers of low carbon steel are presented and discussed. This work is a continuation of a research program[1–5] and deals with the characterization of the sorption behaviour of low carbon steel in solutions containing sulfate and bisulfite ions (as a possible model of acid rain). From the experimental results it can be stated that 1. (i) the presence of bisulfite ions in the solution phase accelerates the corrosion of low carbon steel; 2. (ii) at E > 0.40 V the electrooxidation of HSO3− ions presumably proceeds to yield a steel surface covered …
Natural fluorapatite as a raw material for Portland clinker
2018
Abstract The present work focuses on the mineralogy and the reactivity of clinkers made from the integration of natural fluorapatite in the raw meals with percentages ranging from 0 up to15%. The samples were characterized by infrared spectrometry, X-ray diffraction and microscopy techniques. The distribution of phosphorous and fluorine into clinkers minerals was determined by MEB/EDS mapping. The mineralogical composition was determined by XRD/Rietveld and the samples reactivity followed by isothermal microcalorimetry. It has been found that fluorine stabilizes C3S and β-C2S which still are found with high levels of P2O5. Cements obtained from up to 8% natural fluorapatite incorporation st…
Experimental study and physical modeling of simultaneous heat and moisture transfer in bio-sourced insulating materials.
2019
The conventional heat transfer models are not sufficiently suitable for thermal characterization of bio-sourced thermal insulating materials due to their strongly hydrophilic nature. The proposed work in this PhD thesis aims to answer this problem with experimental and theoretical approaches of coupled heat-moisture transfers. In the experimental approach, a thermal insulating material based on Flax Fiber Felt (FFF) is developed and then characterized at different hygrometric conditions with an asymmetric hot plate device. The humidity diffusion characterization of the samples is done using the GAB, GDW and Park theoretical moisture adsorption isotherm models. In the theoretical approach, a…
Clay-Humic Substance Composites for Removal of Pharmaceuticals from Water
2020
Humic substances are the main component of soil organic matter and they actively interact with substances in soils, including pollutants. Humic acid-clay mineral composite materials can be considered as prospective and low-cost sorbents for contaminant removal. The aim of this study is to develop clay mineral and humic acid composite materials and to characterise their possible applications. For this research, montmorillonite, kaolinite and bentonite were saturated with three types of humic substances: technical humic acid from lignite, humic substances extracted from raised bog peat (Latvia) and technical K humate from lignite. Obtained sorbents were characterized using FTIR. The sorption …
Transport coefficients of n-butane into and through the surface of silicalite-1 from non-equilibrium molecular dynamics study
2009
We have studied coupled heat and mass transfer of n-butane through a membrane of silicalite-1. A description of the surface was given using non-equilibrium thermodynamics, and transport coefficients were determined. Three independent coefficients were found for the whole surface: the resistance to heat transfer, the coupling coefficient and the resistance to mass transfer. These coefficients were defined in stationary state. All resistances are significant, and show that the surface acts as a barrier to transport. A new scheme was devised to find the enthalpy of adsorption, from two particular coupling coefficients, namely the measurable heats of transfer. The method yields the enthalpy of …
Relations between compression and thermal contraction in 1,2,4-trichlorobenzene and melting of trichlorobenzene isomers
2015
The compression and thermal expansion of crystalline 1,2,4-trichlorobenzene, C6H3Cl3, 124TCB, investigated under isobaric and isothermal conditions, are in reverse relation, as for most of crystals, however, the isochoric strain along direction c is clearly different from those along a and b. Single crystals of 124TCB have been in situ grown under isochoric and isobaric conditions, at 270 K/0.1 MPa and 295 K/0.16 GPa, and also at 100 K/0.1 MPa and 295 K/0.64 GPa, when the unit-cell volume is similar. All crystallizations yielded the same phase, of monoclinic space group P21/n, with two symmetry-independent molecules (Z′ = 2). The structure is governed by Cl⋯Cl and Cl⋯H interactions and the …
Application of solid-state electrochemistry techniques to polyfunctional organic–inorganic hybrid materials: The Maya Blue problem
2013
Abstract The time evolution of indigo plus palygorskite powdered mixtures during isothermal heating at different temperatures between 120 and 180 °C to form Maya Blue-type materials has been monitored by means of infrared spectrometry, diffuse reflectance spectrometry in the visible region and solid state electrochemical techniques. The kinetics of the formation process of such materials can be described in terms of two consecutive reactions, the first one consisting of the loss of zeolitic water of the palygorskite coupled with clay-indigo attachment and partial indigo to denydroindigo oxidation. The palygorskite dehydration acts as a rate-determining step fitting to a 3D Avrami-Erofe’ev k…
Effect of Experimental and Sample Factors on Dehydration Kinetics of Mildronate Dihydrate: Mechanism of Dehydration and Determination of Kinetic Para…
2014
The dehydration kinetics of mildronate dihydrate [3-(1,1,1-trimethylhydrazin-1-ium-2-yl)propionate dihydrate] was analyzed in isothermal and nonisothermal modes. The particle size, sample preparation and storage, sample weight, nitrogen flow rate, relative humidity, and sample history were varied in order to evaluate the effect of these factors and to more accurately interpret the data obtained from such analysis. It was determined that comparable kinetic parameters can be obtained in both isothermal and nonisothermal mode. However, dehydration activation energy values obtained in nonisothermal mode showed variation with conversion degree because of different rate-limiting step energy at hi…
Glass capillary gas chromatography of chlorinated methyl acetates, propanoates and butanoates on Carbowax 20M and SE-30 columns
1982
The gas chromatography of all chlorinated methyl acetates, methyl propanoates and methyl mono- and dichlorobutanoates has been studied on Carbowax 20M and SE-30 glass capillary columns under various running conditions. The order of elution on a non-polar column was largely determined by the boiling point of esters, whereas on a polar column it was much influenced by the structure of compounds. Complete separation of the combined mixture of all 27 compounds could not be achieved, however, methyl 3,3-dichlorobutanoate was the only ester overlapped on both columns in spite of the various column temperatures used. The best separation of the mixture was on Carbowax 20M with a temperature program…
Gas—liquid chromatographic analyses
1984
Abstract The gas choromatographic retention behaviour of veratrole and all nine chlorinated veratroles was studied on SE-30 and OV-351 capillary columns. Temperature programming from 100°C at 6°C min−1 and isothermal operation at 140, 160, 180 and 200°C were used. The complete separation of a mixture was obtained on SE-30, the isomers being eluted in order of their degree of chlorination. On OV-351, however, the 3,4,5-trichloro and tetrachloro isomers overlap with temperature programming, being separated at 140, 160 and 200°C. Retention indices and increments of retention indices for each position of substitution are examined and the effect of increasing temperature on retention is discusse…