Study on leaching kinetics of hexavalent chromium from aged calcium-free chromium slag

2021 ◽  
pp. 1-13
Author(s):  
Quan Qi ◽  
Liang Li ◽  
Liangyu Wei ◽  
Baoming Hu ◽  
Zheng Liu ◽  
...  
Keyword(s):  
Hexavalent Chromium ◽  
Resource Utilization ◽  
Scientific Basis ◽  
Diffusion Reaction ◽  
Leaching Kinetics ◽  
Leaching Rate ◽  
Chromium Slag ◽  
Leaching Solution ◽  
Main Components ◽  
Kinetics Of

To provide a scientific basis for the resource utilization of chromium slag, this article studies the release law of hexavalent chromium in the aged calcium-free chromium slag. XRD (X-ray diffractometer) and MLA (Mineral Liberation Analyzer) were used to analyze the composition of the chromium slag; using sulfuric acid-nitric acid as the leaching solution, the release law of hexavalent chromium in chromium slag and the leaching kinetics were studied. The results show that main components of the chromium slag are magnesioferrite, chromite, hematite, hydrargillite, and spinel; chromium is mainly present in chromite and magnesioferrite; the leaching rate of hexavalent chromium increases with the increase of temperature or the decrease of pH. The analysis of leaching kinetics shows the leaching rate is controlled by the internal diffusion reaction, and the apparent activation energy is 11.93 kJ·mol–1. The chromium slag is aged in high temperature seasons, which is conducive to the precipitation of hexavalent chromium in the chromium slag, can increase the yield of chromate in the roasting kiln, and is conducive to resource utilization; chromium slag should be stored in order to prevent acid rain erosion which leads to environmental pollution risk (e.g. drinking water).

scholarly journals Kinetics of solute leachate from imbibing Caesalpinia echinata Lam. (Brazilwood) seeds

Revista CERES ◽  
2014 ◽  
Vol 61 (1) ◽  
pp. 90-97 ◽  
Author(s):  
Nestor Martini Neto ◽  
Edmir Vicente Lamarca ◽  
Claudio José Barbedo
Keyword(s):  
Seed Coat ◽  
Room Temperature ◽  
Initial Moisture Content ◽  
Leaching Kinetics ◽  
Leaching Rate ◽  
Different Temperatures ◽  
Physiological Quality ◽  
Rapid Tests ◽  
Caesalpinia Echinata ◽  
Kinetics Of

The electrical conductivity of leachates from imbibing seeds has been used as a vigor test for several species. The adaptation of this methodology to different species requires knowledge on the leaching kinetics of electrolytes. For Brazilwood seeds, the classic method was not satisfactory and rapid tests are essential because they have low storage capacity at room temperature. Leaching kinetics during seed imbibition is a function of physiological quality, presence or absence of seed coat, imbibing temperature and the initial moisture content of seed. In this study, the electrolyte leaching rate of six different categories of seeds, from two regions, was evaluated in seeds with and without seed coat and incubated with different moisture contents and at different temperatures. The results showed that the electrolyte leaching rate in Brazilwood seeds is independent of the physiological quality, the presence or absence of seed coat and imbibition temperature, but these factors changed the total amount of electrolytes leached. The leaching rate increased in the first few minutes of imbibition, suggesting that the adjustment of the methodology must consider the reduction in imbibition time, reduction in temperature, use of a controlled and slower pre-imbibition, and replacement of the imbibition solution after the first few minutes.

Leaching Kinetics of MnO2 from Electrolytic Manganese Anode Slimes in the Presence of SO2

2011 ◽  
Vol 233-235 ◽  
pp. 532-536 ◽  
Author(s):  
Ying Fen Li ◽  
Hua Ye ◽  
Can Cao ◽  
Li Na He
Keyword(s):  
Activation Energy ◽  
Kinetic Equation ◽  
Apparent Activation Energy ◽  
Diffusion Control ◽  
Leaching Kinetics ◽  
Leaching Rate ◽  
Electrolytic Manganese ◽  
Activation Energy For Diffusion ◽  
Partical Size ◽  
Kinetics Of

Thepaper describes the kinetics of MnO2from electrolytic manganese (EM) anode slimesleached by SO2.The effects of stirring speed,SO2concentration,temperature, and partical size on the leaching rate of manganese are discussed. Experimental results indicated that the leaching of MnO2by SO2is 0.86 order with respect to SO2concentration. The apparent activation energy values for re-action is 25.7KJ/mol,which is consist with the values of activation energy for diffusion control. The kinetic equation can be expressed as: 1-(2/3)x-(1-x)^2/3=(k1/ρr){[SO2]0.86exp(-25700/RT)}t. Meanw-hile, comparative experiments were operated, using analytical class MnO2and pyrolusite, the differ-ence among the three MnO2simples reaction with SO2was identified.

Leaching Kinetics of Gold Involved in the System S2O32--EDTA-Cu2+

2020 ◽  
Vol 1001 ◽  
pp. 212-218
Author(s):  
Peng Zhi Xiang ◽  
Chao Deng ◽  
Huang Yao ◽  
Long Jiang Liu ◽  
S. Mogdal
Keyword(s):  
Ethylenediaminetetraacetic Acid ◽  
Reaction Order ◽  
Effect Of Temperature ◽  
Leaching Kinetics ◽  
Leaching Rate ◽  
Gold Ores ◽  
Remarkable Effect ◽  
Copper Addition ◽  
A Value ◽  
Kinetics Of

Thiosulphate gold leaching is an alternative technology to the cyanidation of gold ores. Ethylenediaminetetraacetic acid is referred to as EDTA.A study on the leaching kinetics of gold involved in the system S2O32--EDTA-Cu2+ for the gold in this paper. The effect of temperature and of the addition of copper has been also analyzed, temperature has a remarkable effect over the overall reaction rate in the range from 293 to 323k, the result shows that the leaching process conforms to the chemical control model. The concentration of [S2O32-] considerably affects the leaching rate obtaining a value of for the order of reaction in the range of concentrations from 0.05 to 0.3 mol/L of S2O32- which obtaining a reaction order of 1.029. Copper addition favored the leaching rate of gold which obtaining a reaction order of 0.441,Thiosulphater addition also favored the leaching rate of gold .kinetics model was established which is 1−(1−x)1/3=4950.8c (S2O32-)1.029c (Cu2+)0.441exp (-9911/8.314T).

Leaching Kinetics and Seperation of Antimony and Arsenic from Arsenic Alkali Residue

2011 ◽  
Vol 402 ◽  
pp. 57-60 ◽  
Author(s):  
Gui Sheng Zeng ◽  
Hui Li ◽  
Su Hua Chen ◽  
Xin Man Tu ◽  
Wen Bin Wang
Keyword(s):  
Shrinking Core Model ◽  
Leaching Kinetics ◽  
Surface Chemical ◽  
Leaching Rate ◽  
Kinetics Equation ◽  
Surface Chemical Reaction ◽  
Liquid Ratio ◽  
Shrinking Core ◽  
Solid Liquid ◽  
Kinetics Of

The separation of antimony and arsenic and leaching kinetics of arsenic from arsenic alkali residue were investigated. The influencing factors such as solid/liquid ratio, stir speed, temperature and time on leaching of arsenic were studied. The results show that the leaching rate reaches 87.75% at the condition of solid/liquid ratio of 1:4 , stir speed of 600r/min ,temperature of 90°C and time of 60min. The leaching process was controlled by the surface chemical reaction and the kinetics of leaching arsenic followed the model of shrinking core. The activation energy was found to be 666.57kJ/mol. The kinetics equation was expressed as shrinking core model.

Polarographic studies on renaturation of urea-denatured human serum albumin

1989 ◽  
Vol 54 (2) ◽  
pp. 536-543 ◽  
Author(s):  
Josef Chmelík ◽  
Pavel Anzenbacher ◽  
Vítěz Kalous
Keyword(s):  
Human Serum Albumin ◽  
Serum Albumin ◽  
Human Serum ◽  
Irreversible Process ◽  
State Model ◽  
Native Protein ◽  
Main Components ◽  
Two State Model ◽  
Kinetics Of

The renaturation of the two main components of human serum albumin, i.e. of mercaptalbumin and nonmercaptalbumin, was studied polarographically. It has been demonstrated that renaturation of both proteins after 1-min denaturation in 8M urea is reversible. By contrast, renaturation after 200 min denaturation in 8M urea is an irreversible process; the characteristics of renatured mercaptalbumin differ more from the properties of the native protein than the characteristics of nonmercaptalbumin. The studies of the kinetics of renaturation of both proteins have shown that the renaturation can be represented by a two-state model. This means that the existence of stable intermediary products during the renaturation process was not determined polarographically.

scholarly journals Fluoride Leaching of Titanium from Ti-Bearing Electric Furnace Slag in [NH4+]-[F−] Solution

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1176
Author(s):  
Fuqiang Zheng ◽  
Yufeng Guo ◽  
Feng Chen ◽  
Shuai Wang ◽  
Jinlai Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electric Furnace ◽  
Kinetic Equations ◽  
Surface Chemical ◽  
Leaching Rate ◽  
Surface Chemical Reaction ◽  
Mechanism And Kinetics ◽  
Semi Empirical ◽  
Kinetics Of ◽  
Furnace Slag

The effects of F− concentration, leaching temperature, and time on the Ti leaching from Ti-bearing electric furnace slag (TEFS) by [NH4+]-[F−] solution leaching process was investigated to reveal the leaching mechanism and kinetics of titanium. The results indicated that the Ti leaching rate obviously increased with the increase of leaching temperature and F− concentration. The kinetic equation of Ti leaching was obtained, and the activation energy was 52.30 kJ/mol. The fitting results of kinetic equations and calculated values of activation energy both indicated that the leaching rate of TEFS was controlled by surface chemical reaction. The semi-empirical kinetics equation was consistent with the real experimental results, with a correlation coefficient (R2) of 0.996. The Ti leaching rate reached 92.83% after leaching at 90 °C for 20 min with F− concentration of 14 mol/L and [NH4+]/[F−] ratio of 0.4. The leaching rates of Si, Fe, V, Mn, and Cr were 94.03%, 7.24%, 5.36%, 4.54%, and 1.73%, respectively. The Ca, Mg, and Al elements were converted to (NH4)3AlF6 and CaMg2Al2F12 in the residue, which can transform into stable oxides and fluorides after pyro-hydrolyzing and calcinating.

scholarly journals Investigation of cultivated lavender (Lavandula officinalis L.) extraction and its extracts

2014 ◽  
Vol 20 (1) ◽  
pp. 71-86 ◽  
Author(s):  
Vesna Nadjalin ◽  
Zika Lepojevic ◽  
Mihailo Ristic ◽  
Jelena Vladic ◽  
Branislava Nikolovski ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Essential Oil ◽  
Experimental Results ◽  
Flame Ionisation Detector ◽  
Main Components ◽  
Lavandula Officinalis ◽  
Physical And Chemical ◽  
Kinetics Of ◽  
Flame Ionisation ◽  
Ionisation Detector

In this study essential oil content was determined in lavender flowers and leaves by hydrodistillation. Physical and chemical characteristics of the isolated oils were determined. By using CO2 in supercritical state the extraction of lavender flowers was performed with a selected solvent flow under isothermal and isobaric conditions. By the usage of gas chromatography in combination with mass spectrometry (GC/MS) and gas chromatography with flame ionisation detector (GC/FID) the qualitative and quantitative analysis of the obtained essential oil and supercritical extracts (SFE) was carried out. Also, the analysis of individual SFE extracts obtained during different extraction times was performed. It turned out that the main components of the analysed samples were linalool, linalool acetate, lavandulol, caryophyllene oxide, lavandulyl acetate, terpinen-4-ol and others. Two proposed models were used for modelling the extraction system lavender flower - supercritical CO2 on the basis of experimental results obtained by examining the extraction kinetics of this system. The applied models fitted well with the experimental results.

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