scholarly journals Drying Characteristics of Dracocephalum moldavica Leaves: Drying Kinetics and Physicochemical Properties

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 509 ◽  
Author(s):  
Stanisław Rudy ◽  
Dariusz Dziki ◽  
Beata Biernacka ◽  
Andrzej Krzykowski ◽  
Mariusz Rudy ◽  
...  
Keyword(s):  
Phenolic Compounds ◽  
Essential Oils ◽  
Chemical Properties ◽  
Total Content ◽  
Convective Drying ◽  
Vacuum Drying ◽  
Drying Process ◽  
Total Flavonoids Content ◽  
Physical And Chemical ◽  
Kinetics Of

The aim of the study was to determine the effect of the method and temperature of the sublimation, vacuum and convective drying process on the kinetics of dehydration of the Moldovan dragonhead leaves, as well as on the physical and chemical properties, such as color coordinates, total content of phenolic compounds, antioxidant capacity, total monomeric anthocyanins content, total flavonoids content and content of essential oils. It was shown that the kinetics of the sublimation and vacuum drying process are best described by the logarithmic and Page models. Sublimation and vacuum drying were characterized by comparable process times. An increase in drying temperature caused a decrease in the content of phenolic compounds and antioxidant activity of the dried material and a significant change in the composition of essential oils. The lowest brightness of the dried material and the lowest color saturation was found after sublimation drying at 20 °C. The highest dried material quality was found in case of convective and sublimation drying at 20 °C.

Di-imide: Some Physical and Chemical Properties, and the Kinetics and Stoichiometry of the Gas-phase Decomposition

1973 ◽  
Vol 51 (21) ◽  
pp. 3605-3619 ◽  
Author(s):  
C. Willis ◽  
R. A. Back
Keyword(s):  
Gas Phase ◽  
Room Temperature ◽  
Chemical Properties ◽  
Phase Decomposition ◽  
Important Intermediate ◽  
Long Lifetime ◽  
Physical And Chemical ◽  
Text Formation ◽  
Kinetics Of

Preparation of di-imide by passing hydrazine vapor through a microwave discharge yields mixtures with NH3 containing typically about 15% N2H2, estimated from the gases evolved on decomposition. The behavior of the mixture (which melts at −65 °C) on warming from −196 to −30 °C suggests a strong interaction between the components. Measurements of magnetic susceptibility and e.p.r. experiments showed that N2H2 is not strongly paramagnetic, which with other observations points to a singlet rather than a triplet ground-state.Di-imide can be vaporized efficiently, together with NH3, by rapid warming, and the vapor is surprisingly long-lived, with a typical half-life of several minutes at room temperature. The near-u.v. (3200–4400 Å) absorption spectrum of the vapor was photographed; it shows well-defined but diffuse bands, with εmax = 6(± 3) at 3450 Å.Di-imide decomposes at room temperature in two ways:[Formula: see text][Formula: see text]Formation of NH3 was not observed but cannot be ruled out. The decomposition of the vapor is complicated by a sizeable and variable decomposition that occurs rapidly during the vaporization. The stoichiometry of this and the vapor-phase decomposition depends on total pressure and di-imide concentration. The kinetics of the decomposition of the vapor were studied from 22 to 200 °C by following the disappearance of N2H2 by absorption of light at 3450 Å, or the formation of N2H4 by absorption at 2400 Å, and by mass spectrometry. The kinetics are complex and can be either first- or second-order, or mixed, depending on surface conditions. The effect of olefin additives on the decomposition was studied, and is also complex.Mechanisms for the decomposition are discussed, including the possible role of trans-cis isomerization. The relatively long lifetime found for di-imide in the gas phase suggests that it may be an important intermediate in many reactions of hydronitrogen systems.

scholarly journals Adsorption of Copper in Soil and its Dependence on Physical and Chemical Properties

2018 ◽  
Vol 66 (1) ◽  
pp. 219-224 ◽  
Author(s):  
Vítězslav Vlček ◽  
Miroslav Pohanka
Keyword(s):  
Soil Properties ◽  
Solid Phase ◽  
Chemical Properties ◽  
Total Content ◽  
Exchange Capacity ◽  
Soil Reaction ◽  
Available Phosphorus ◽  
Copper Adsorption ◽  
Phosphorus And Potassium ◽  
Physical And Chemical

Soil samples (n = 11) were collected in the chernozem areas of the Czech Republic (the Central Europe) from the topsoil and used as representative samples. All sampling areas have been used for agricultural purposes (arable soil) and they were selected as typical representatives of agricultural soil. These samples represented the soil with same genesis (to reduction differencies between soil types) but with different soil properties (physical and chemical). Complete chemical and physical analyses were made for confirmation of copper adsorption on solid phase: we analysed the particle size distribution, content of oxidizable carbon (Cox), the cation exchange capacity (CEC), supply of exchange calcium, magnesium, sodium, phosphorus and potassium, soil reaction and the total supply of Fe, Al, Mn, Ca, Mg, K, P and N. The strongest simple correlation between analysed soil properties and copper concentration had content of available magnesium (r = 0.44) and available phosphorus (r = −0.51). In the case of multiple correlations (i. e. collective influence of multiple soil properties) had the strongest influence combination of clay, soil reaction, total content of phosphorus, available magnesium and available phosphorus. The main influence of phosphorus and magnesium is evident. We suppose that copper and phosphorus enter into specific complex. Influence of these five soil properties can explain 92.7 % (r = 0.927) changes in the content of copper changes in the experiment.

scholarly journals The prediction model of moisture content’s stabilization during tobacco strip drying process

2018 ◽  
Author(s):  
Mingjian Zhang ◽  
Feng Huang ◽  
Qing Chen ◽  
Le Wang ◽  
Haisheng Wang ◽  
...  
Keyword(s):  
Moisture Content ◽  
Probability Distributions ◽  
Chemical Properties ◽  
Mean Value ◽  
Drying Process ◽  
Variance Model ◽  
Initial Stage ◽  
The Mean ◽  
Agriculture Products ◽  
Physical And Chemical

A mathematical model was established to predict the mean value and variance of tobacco strip during drying processing, based that the physical and chemical properties of tobacco strip as agriculture products show probability distributions. The results show that the model can predict the mean value of moisture content at different times, and there is a certain deviation in predicting the variance of moisture content at initial stage of drying process. However, the prediction value of the variance of tobacco strip is much more accurate while the moisture content is between 8% and 10%, which is the interval of quality requirements.Keywords: tobacco strip; drying; mean value;variance model.  

Changes of phenolic compounds in black currant during vacuum drying process

2011 ◽  
Vol 40 (Supplement 1) ◽  
pp. 120-129 ◽  
Author(s):  
B. Nótin ◽  
M. Stéger-Máté ◽  
R. Juhász ◽  
D. Jakab ◽  
J. Monspart-Sényi ◽  
...  
Keyword(s):  
Phenolic Compounds ◽  
Vacuum Drying ◽  
Drying Process ◽  
Black Currant

Effects of Preparation of Cement Raw Meal with Carbide Slag on the Environment and Equipments

2014 ◽  
Vol 787 ◽  
pp. 123-127 ◽  
Author(s):  
Ya Li Wang ◽  
Su Ping Cui ◽  
Hui Wang ◽  
Shi Jie Dong ◽  
Yan Yao
Keyword(s):  
Heavy Metal Ions ◽  
Raw Materials ◽  
Chemical Properties ◽  
Exhaust Gas ◽  
Physical And Chemical Properties ◽  
Drying Process ◽  
Calcination Process ◽  
Carbide Slag ◽  
Physical And Chemical ◽  
And Chemical Properties

Based on the physical and chemical properties of carbide slag, the contents of heavy metals in effluent came from carbide slag drying process were studied, and then the composition of exhaust gas emitted from the carbide slag drying process and calcinations process of raw materials prepared with carbide slag was detected, in order to know whether there are harmful or corrosive gases released and the effect of the emissions on the environment and related equipments. The results indicate that the exhaust gases emitted from the calcination process of raw meal prepared with carbide slag is mainly composed of CO2 and water vapor, and is free from harmful gases. However, a lot of water in carbide slag during the pre-heat and decomposition process under high temperature would accelerate the corrosion of equipments. Simultaneously, a small number of heavy metal ions contained in the carbide slag can cause environmental pollution and sulfides would be adverse to the cement calcination process resulting in the crust blockage of kiln.

Radiation damage in polyethylene as studied by electron spin resonance

1961 ◽  
Vol 262 (1309) ◽  
pp. 207-218 ◽  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Alkyl Radical ◽  
Room Temperature ◽  
Chemical Properties ◽  
Resonance Method ◽  
Alkyl Radicals ◽  
Spin Resonance ◽  
Physical And Chemical ◽  
Kinetics Of

The electron spin resonance method was employed to study the nature, concentration and kinetics of the disappearance under varying conditions of radicals produced in polyethylene by fast electron irradiation at 77°K. The predominant radical species at 77°K is the alkyl radical —CH 2 —ĊH—CH 2 —. On being warmed to room temperature it disappears rapidly, revealing a more stable un­identified radical. The kinetics of the decay at room temperature of both radicals was observed. Their stabilities were found to vary in polyethylene samples of differing physical and chemical properties. G values for these radicals are given. Comparison was made with spectra obtained under similar conditions with two pure paraffins and a pure olefin to evaluate the effect of crystallinity branching, molecular weight and unsaturation. In the olefin there is evidence for a build-up of allyl radicals due to the encounter of an alkyl radical with main chain unsaturation. This supports the view that alkyl radicals are mobile, and cross-linking occurs when two such radicals meet.

scholarly journals Kinetics Of Fruit Crops Drying With Instant Pressure Release

2020 ◽  
Vol 02 (10) ◽  
pp. 45-54
Author(s):  
Rustamov E.S. ◽  
◽  
Djuraev Kh.F. ◽  
Gafurov K.Kh. ◽  
◽  
...  
Keyword(s):  
Energy Supply ◽  
Infrared Heating ◽  
Convective Drying ◽  
Drying Process ◽  
Fruit Crops ◽  
Technological Parameters ◽  
Pressure Impact ◽  
Instantaneous Pressure ◽  
Kinetics Of

The article covers results of research of drying process of apricot fruits by the method of three-stage energy supply. The main stages of drying have been defined, including: pulsed infrared heating, instantaneous pressure impact, convective drying. Optimal technological parameters of energy supply in the process of drying apricot fruits at each stage have been developed. The choice of the method for the experimental determination of the drying speed by the parameters of the drying agent for the capillary-porous material is substantiated. The sequence of changes in moisture content in a given material under the influence of a three-stage energy supply is described. The conditions for drying fruits are established and the values of the drying speed in the first period for various methods of energy supply have been selected.

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