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Thermal Hydrogen Addition
Published in Cesar Ovalles, Subsurface Upgrading of Heavy Crude Oils and Bitumen, 2019
Figure 7.6 presents the logarithm of the percentage of the overall thermal conversion of the original heavy oil or bitumen vs. the inverse of temperature in the presence of steam [Hyne 1986]. In this Arrhenius plot, the slope gives the energy of activation involved in the chemical conversions during the lab experiments. The substantially greater slope of the curve at a temperature higher than 300°C demonstrates a change of the chemical reactions with much higher energy requirements than the subtler, less destructive processes that characterize the chemistry of Aquathermolysis (< 300°C). During thermal cracking of the liquid phase (> 300°C), increasing amounts of gas and coke are produced even in the presence of water. This phenomenon indicates the predominant role of thermal cracking at much higher temperatures in comparison with the Aquathermolysis “window” (200–300°C) in which little conversion of the liquid phase is observed [Hyne 1986].
The Novel Lixiviants for Maximizing Antimony Extraction from Tetrahedrite-Rich Concentrate: Mechanism and Kinetic Studies
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Sajjad Aghazadeh, Hadi Abdollahi, Mahdi Gharabaghi, Mirsaleh Mirmohammadi
Antimony and copper leaching from tetrahedrite-bearing ores are typically carried out by using conventional Na2S-NaOH solutions. Due to the low efficiency of antimony dissolution from tetrahedrite mineral, a novel attempt was made to further promote leaching efficiency and rate by combining EDTA and glycine reagents with conventional Na2S-NaOH solutions, which has never been discussed till now. As a novel result, antimony recovery was strongly improved when EDTA and glycine reagents were added into alkaline Na2S-NaOH solution. In the current research work, we studied the capability of synergistic effects of new reagents including glycine and EDTA on antimony and copper alkaline dissolution from tetrahedrite concentrate for the first time. In order to investigate the detail mechanism of leaching, the effects of important factors including lixiviants’ initial concentration and temperature were fully examined. For kinetic studies, shrinking core model was applied to explain the kinetic behavior of glycine-Na2S-NaOH and EDTA-Na2S-NaOH dissolution reactions. Subsequently, new kinetic relationships in terms of leaching variables and shrinking core parameters were established. Furthermore, activation energy and pre-exponential factors were measured using Arrhenius plot. Finally, leaching residue was analyzed and the formation of new reaction products was discussed.
Anticorrosive property of Spiraea Cantoniensisis extract as an eco-friendly inhibitor on mild steel surface in acid medium
Published in Journal of Dispersion Science and Technology, 2019
Ill-Min Chung, Kathirvel Kalaiselvi, Asokan Sasireka, Seung-Hyun Kim, Mayakrishnan Prabakaran
The activation energy Ea and Arrhenius pre-exponential factor (A) for a broad range of concentrations of the studied green inhibitor (S. cantoniensis) were calculated by linear regression between log Cr and 1000/T (Figure 2). The values are summarized in Table 3. The Arrhenius plots obtained met at straight lines and the slope (−Ea = Slope ×8.314 × 2.303) of each straight line provided its activation energy. An assessment of Table 3 data showed that the activation energy in the presence of the inhibitor was higher than that in the absence of the inhibitor. At the same time, the activation energy increased with an increase in the concentration of the inhibitor which could be interpreted as physical adsorption.[35] The Arrhenius pre-exponential factors (A) calculated for the absence and presence of the inhibitor are listed in Table 3. Analysis of these results shows that in the presence of S. cantoniensis extract the values of A are greater than those in the absence of the S. cantoniensis extract. These results confirmed the presence of a few uncovered active sites on the surface of the MS which were attacked by the 1 M HCl solution causing corrosion to some extent.
Kinetic and Mechanism Studies Using Shrinking Core Model for Copper Leaching from Chalcopyrite in Methanesulfonic Acid with Hydrogen Peroxide
Published in Mineral Processing and Extractive Metallurgy Review, 2021
Jiajia Wu, Junmo Ahn, Jaeheon Lee
The Arrhenius plot is shown in Figure 6, and the activation energy was calculated from the slope of the plot. Figure 6a shows that the activation energy was 79.8 kJ/mol from the whole temperature range, indicating the reaction is controlled by the chemical reaction. For a detailed investigation, the temperature range was divided into two regimes: 25–55°C and 55–75°C. Activation energy from 25°C to 55°C was calculated to be 22.6 kJ/mol and 148.2 kJ/mol from 55°C to 75°C, as shown in Figure 6b. The result indicates the reaction mechanism at lower temperature regime is diffusion controlled. At higher temperature regime, it became a surface chemical reaction controlled.