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Wyszukujesz frazę "dissolution kinetics" wg kryterium: Temat

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    Wyświetlanie 1-7 z 7
    Tytuł:
    Dissolution kinetics of secondary covellite resulted fromdigenitedissolutionin ferric/acid/chloride media
    Autorzy:
    Aracena, Alvaro
    Espinoza, Camila
    Jerez, Oscar
    Carvajal, Danilo
    Jaques, Aldonza
    Powiązania:
    https://bibliotekanauki.pl/articles/110306.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dissolution kinetics
    digenite
    covellite
    diffusion
    Opis:
    Dissolution kinetics of digenite (Cu9S5) was studied in Fe3+-H2SO4-NaCl media. The temperature range for the study was between 297 and 373 K (24 and 100°C), with a ferric concentration between 0.0100 and 0.0806 mol/dm3, a sulfuric acid concentration of 0.05 to 1.5 mol/dm3 and a NaCl concentration of 1.5 to 5 mol/dm3. Agitation speed and particle size were also studied. Results indicate that the dissolution mechanisms of digenite occurs in two stages: i) generation of covellite (CuS) with the formation of cupric ion (Cu2+) and ii) dissolution of covellite (CuS) with copper production in the system, as well as amorphous sulfur (S°). The second stage occurred very slowly compared to the first stage, the above variables studied directly affected the second stage. Temperature, Fe3+ and H2SO4 concentration positively affected dissolution of covellite formed (second stage), while the presence of NaCl did not increase dissolution of Cu9S5 or CuS. Results showed that stirring speed had an important role in the dissolution rate of CuS. Dissolution kinetics was analyzed using the model of diffusion through the porous layer. Covellite dissolution reaction order was 2.3 and 0.2 with respect to the concentration of ferric and sulfuric acid, respectively, and the rate was inversely proportional to particle size. The calculated activation energy was 36.1 kJ/mol, which is a typical value for a reaction controlled by diffusion in the porous layer at temperature between 297 and 373 K (24 and 100°C).
    Źródło:
    Physicochemical Problems of Mineral Processing; 2019, 55, 4; 840-851
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Process improvement and kinetic study on copper leaching from low-grade cuprite ores
    Autorzy:
    Bai, S.
    Fu, X.
    Li, C.
    Wen, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/109660.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    cuprite
    dissolution kinetics
    sulfuric acid leaching
    SCM
    Opis:
    Process improvement and kinetic study on copper leaching from low-grade cuprite ores in sulfuric acid solution are presented in this paper. Effects of major leaching parameters on copper leaching efficiency are determined. The results indicate that copper minerals in the raw ores are mainly cuprites. The reaction rate of this ore increases with an increase in temperature, reaction time, sulfuric acid concentrations and decrease in the particle size of ore. Leaching of about 92.5% of copper is achieved using 0.125-0.074 mm ore particle size at a reaction temperature of 353 K for 180 min reaction time with 150 g/dm3 sulfuric acid. The solid/liquid ratio was maintained constant at 1:15. Leaching kinetic indicates experimental data complies with shrinking core mode (SCM). It is found in the study that agitation rate is not an influential factor on leaching rate and that the dissolution rate is controlled by surface chemical reaction. The average activation energy of the process is determined to be 45.28 kJ mol-1, and the reaction order of H2SO4 is 0.8093.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2018, 54, 2; 300-310
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The effect of co-processed dry binder with microcrystalline cellulose on release of verapamil hydrochloride from hydrophilic matrix tablets
    Autorzy:
    Komersová, Alena
    Lochař, Václav
    Myslíková, Kateřina
    Mužíková, Jitka
    Bartoš, Martin
    Powiązania:
    https://bibliotekanauki.pl/articles/895631.pdf
    Data publikacji:
    2018-10-31
    Wydawca:
    Polskie Towarzystwo Farmaceutyczne
    Tematy:
    matrix tablets
    Dissolution kinetics
    Verapamil hydrochloride
    hypromellose
    Comprecel® 102
    MicroceLac®100
    Opis:
    The aim of this study was to evaluate the use of co-processed dry binder MicroceLac®100 (lactose and microcrystalline cellulose in ratio 3:1) and Comprecel® 102 (pure microcrystalline cellulose) in formulations for the extended release of verapamil hydrochloride. Hydrophilic matrix tablets containing verapamil hydrochloride, hypromellose and dry binder were prepared by the direct compression method. Hypromelloses MethocelTM K4M Premium CR or MethocelTM K100M Premium CR were used as controlled release agents. Using scanning electron microscopy regular distribution of the active substance in the prepared tablets was confirmed. Release of verapamil hydrochloride from the prepared formulations was studied by the dissolution test method. The dissolution profiles were fitted to the first-order kinetic model, Higuchi diffusion model, Korsmeyer-Peppas and Weibull model and kinetic parameters as the first order release rate constant (k1), release exponent (n) from Korsmeyer-Peppas model, Higuchi constant (KH) and parameters of Weibull model (b, λ) were determined. Based on results of non-linear regression analysis, the higher release rate constants were found for formulations containing co-processed dry binder MicroceLac®100 in comparison with formulations containing pure microcrystalline cellulose (Comprecel® 102). In addition, tablets swelling, erosion and disintegration during the dissolution test were monitored photographically.
    Źródło:
    Acta Poloniae Pharmaceutica - Drug Research; 2018, 75, 5; 1223-1231
    0001-6837
    2353-5288
    Pojawia się w:
    Acta Poloniae Pharmaceutica - Drug Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A study on the dissolution kinetics of iron oxide leaching from clays by oxalic acid
    Autorzy:
    Arslan, Volkan
    Powiązania:
    https://bibliotekanauki.pl/articles/1447278.pdf
    Data publikacji:
    2021
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    clay
    physico-chemical characterization
    chemical leaching
    oxalic acid
    dissolution kinetics
    activation energy
    Opis:
    Clay is widely used in a number of industries due to its special properties like fine particle size, brightness and whiteness, chemical inertness, platy structure, etc. In this study, the general characteristics of clays have been investigated by XRF, XRD, FT-IR, TG-DTA and SEM. The presence of iron as an impurity decreases its commercial value due to giving unwanted colors to clay mineral. Therefore, the dissolution capacity of clay ore was investigated by oxalic acid leaching. Under optimized leaching conditions (0.8 M oxalic acid concentration, 85°C reaction temperature, 1.75 ambient pH, 106+75 µm particle size, 15% w/v solids concentration and 150 min. leaching time) with 250 rpm stirring, 83.90% of $Fe_2O_3$ was removed. The amount of iron oxide, the main impurity in the clay, has been reduced from 2.70 to 0.40%. The iron dissolution kinetics was mainly controlled by internal diffusion control of shrinking core model and activation energy, $E_a$, of 26.29 kJ/mol was obtained for the process. The results also showed that the studied clays have adequate characteristics for ceramics industry, earthenware and porcelain production.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2021, 57, 3; 97-111
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dissolution kinetics of hemimorphite in methane sulfonic acid
    Autorzy:
    Zhang, Qian
    Wen, Shuming
    Feng, Qicheng
    Nie, Wenlin
    Wu, Dandan
    Powiązania:
    https://bibliotekanauki.pl/articles/110482.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    hemimorphite
    methane sulfonic acid
    dissolution
    kinetics
    Opis:
    Hemimorphite has a large content of zinc, but its recovery using flotation alone is low. Nowadays, hydrometallurgical and pyrometallurgical methods are used to treat zinc ores. In this work, the leaching and dissolution kinetics of hemimorphite by using methane sulfonic acid (MSA) as an alternative leaching reagent was investigated. The effects of several experimental parameters including reaction temperature, MSA concentration, particle size, and stirring speed were also analyzed. Results showed that zinc leaching increased with increased reaction temperature, MSA concentration, and stirring speed, as well as decreased particle size. The mechanism of hemimorphite dissolution in MSA solutions may be a new variant of the shrinking-core model. Based on experimental data and kinetics, the apparent activation energy was determined to be 49.50 kJ/mol. The rate of reaction equation was also obtained to describe the process and found that the MSA concentration largely influenced the leaching of hemimorphite.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2019, 55, 1; 1-9
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study of the reaction between dolomite and nitric acid
    Autorzy:
    Pultar, Martin
    Vidensky, Jan
    Sedlarova, Ivona
    Powiązania:
    https://bibliotekanauki.pl/articles/109398.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dolomite
    nitric acid
    kinetics
    dissolution
    shrinking core model
    Opis:
    This paper is focused on the kinetics of the reaction between natural dolomite and diluted solutions of nitric acid at various temperatures. All experiments were carried out in a semi-batch reactor with an approximately constant nitric acid concentration using the pH-stat titration method. The reaction was studied in the temperature range from 293 to 353 K and the nitric acid concentration in the range from 0.001 to 0.200 mol dm-3. The strong effects of both temperature and nitric acid concentration were observed. The determined fractional values of the apparent reaction order (0.39 to 0.75) indicate a very complex reaction mechanism. In the studied concentration range, the values of the apparent activation energy increase from 30 to 58 kJ mol-1. Based on these data it can be assumed that the reaction takes place in the transitional regime with the stronger influence of chemical reaction. This assumption was verified by calculation of the nitric acid concentration on the surface of the dolomite grain using Sherwood criterion equation. The change in the role of the rate-controlling step was found for highly diluted solutions (< 0.010 mol dm-3 HNO3).
    Źródło:
    Physicochemical Problems of Mineral Processing; 2019, 55, 2; 370-379
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dissolution kinetics of smithsonite in boric acid solutions
    Autorzy:
    Abali, Y.
    Bayca, S. U.
    Gumus, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/109836.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dissolution
    leaching
    kinetics
    reaction engineering
    smithsonite
    zinc borate
    Opis:
    The dissolution of smithsonite in boric acid solutions was investigated. The influence of the reaction temperature, acid concentration, solid-to-liquid ratio, particle size and stirring speed on the zinc extraction were determined in the experiments. The results show that the dissolution rate increases with increasing acid concentration and reaction temperature, and with decreasing particle size and solid-to-liquid ratio. The dissolution results were analyzed by reaction control models. The activation energy of smithsonite in boric acid solution was also calculated.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2017, 53, 1; 161-172
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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