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    Wyświetlanie 1-11 z 11
    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
    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:
    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:
    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:
    Kinetics study and reaction mechanism for titanium dissolution from rutile ores and concentrates using sulfuric acid solutions
    Autorzy:
    Ismael, Mohamed H.
    Mohammed, Hesham S.
    El Hussaini, Omneya M.
    El-Shahat, Mohamed F.
    Powiązania:
    https://bibliotekanauki.pl/articles/2146851.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    leaching kinetics
    leaching mechanism
    titanium
    rutile concentrate
    leaching design
    shrinking
    core model
    Opis:
    Recent developments of acid leaching of titanium concentrates and ores have produced renewed industrial and commercial interest. However, the leaching kinetics and mechanism of these concentrates and ores had received little attention. This work, therefore, addresses the leaching kinetics and mechanism of Ti from a rutile concentrate in sulfuric acid solution. The leaching reaction was controlled by diverse parameters like temperature, particle size, acid concentration, liquid/solid (L/S) ratio, and stirring speed. The leaching kinetics was investigated using the Shrinking Core Model in order to determine the optimum criteria which control the reaction. The kinetics analysis showed that the rate of dissolution of Ti increased by increasing reaction temperature, L/S ratio, and stirring speed, while it decreased upon increasing particle size. The kinetics analysis revealed that the dissolution reaction is controlled by the chemical reaction at the rutile particle surface. Applying the Arrhenius relation, the apparent energy of activation Ea for the leaching reaction was calculated to be 23.4kJ/mol. A semi-empirical overall rate equation was introduced to describe the combined effects of the process variables upon the rate of the dissolution reaction: 〖1-(1-x)〗^(1/3)=k_0 〖 C〗_([H2SO4])^0.803 〖 (dp)〗^(-0.518) 〖(L/S)〗^0.793 〖(w)〗^0.668 e^((-23400/RT)) t
    Źródło:
    Physicochemical Problems of Mineral Processing; 2022, 58, 1; 138--148
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mechanism and Kinetics of Precipitation and Dissolution of GP Zone and Metastable Phase in Al-3wt% Cu Alloy
    Autorzy:
    Khamel, B.
    Sahnoune, F.
    Fatmi, M.
    Brihi, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/1033403.pdf
    Data publikacji:
    2017-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.30.Mh
    81.70.Pg
    81.30.Bx
    Opis:
    Thermal analysis techniques remain important tools amongst the large variety of methods used for analysis of the precipitation and dissolution of the Guinier-Preston zone and metastable phase θ' in Al-3wt% Cu. In the present study, the kinetics of precipitation and dissolution of the Guinier-Preston zone and metastable phase θ' in Al-3wt% Cu was investigated using differential scanning calorimetry carried out between room temperature and 430°C at heating rates of 20, 25, and 30°C min¯¹. The activation energies evaluated through isothermal differential scanning calorimetry treatment using the Johnson-Mehl-Avrami theory were 25, 100, and 80 kJ mol¯¹ for the Guinier-Preston zone precipitation, formation of θ'/θ and dissolution of θ', respectively. The Avrami constant n obtained by the Ligero method was about 1.5 for the formation of θ'/θ indicating that bulk nucleation is dominant in θ'/θ formation controlled by diffusion from a constant number of nuclei.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 1; 133-135
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    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:
    Effect of particle size on chalcocite dissolution kinetics in column leaching under controlled Eh and its implications
    Autorzy:
    Phyo, Htet Aung
    Jia, Yan
    Tan, Qiaoyi
    Zhao, Shenggui
    Liang, Xinxing
    Ruan, Renman
    Niu, Xiaopeng
    Powiązania:
    https://bibliotekanauki.pl/articles/1449094.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    particle size
    column leaching
    chalcocite
    shrinking core model
    X-ray CT
    Opis:
    Natural high grade chalcocite samples were leached in column under controlled Eh, constant temperature and solution pH to investigate the effect of particle size on dissolution kinetics. Moreover, low grade ores of larger size fractions were leached in column using raffinate from the industrial heap as an irrigation solution to simulate the real heap conditions. The leaching rate of large particle sizes (31-200 mm) were very slow without inflection point which are normally present in the leaching of small particle sizes (0.054-31 mm). The effect of particle size was more remarkable in the dissolution of large particles than that of small particles during the first stage (<45% dissolution). However, the dissolution rate of the second stages (>45% dissolution) were not noticeably affected by the particle size. Results of kinetics analysis of leaching of small particles using shrinking core model indicated that the first stage was controlled by fluid diffusion and confirmed by the low activation energies (20.98 kJ/mol). The kinetics of second stage was controlled by chemical reaction and product layer diffusion and the later control became prominent with increasing particle size. Similarly, product layer diffusion was the rate-controlling step for the first and second stages of leaching of large particles. X-ray CT and SEMEDS studies observed the increasing numbers of cracks and porosity and the formation of sulfur layer on the surface of the residue samples. The findings in this study provided some useful implications to optimize the heap performance and understand the leaching behavior of large particles.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2020, 56, 4; 676-692
    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 malachite in ethylene diamine phosphate solutions
    Autorzy:
    Shen, Peilun
    Liu, Ruizeng
    Liu, Dianwen
    Zhan, Xiaolin
    Jia, Xiaodong
    Song, Kaiwei
    Powiązania:
    https://bibliotekanauki.pl/articles/110214.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    malachite
    organic amine
    ethylene diamine phosphate
    dissolution
    kinetic
    Opis:
    Ethylene diamine phosphate (EDP), as a synthetic organic reagent, was used for the first time to leach malachite, and a new method of using organic amine to leach copper oxide ore was developed. The effects of stirring speed, particle size, reagent concentration, and reaction temperature on EDP-dissolution malachite were investigated. Results showed that malachite rapidly dissolved in EDP solution. The malachite-dissolving rate also increased with increased reagent concentration, increased reaction temperature, and decreased particle size. Stirring speed exhibited nearly no effect on EDP-induced malachite dissolution. The leaching kinetics was found to follow the shrinking-core model, and dissolution was controlled by surface chemical reaction with an activation energy of 52.63kJ×mol−1. A semiempirical rate equation was obtained to describe the dissolution process expressed as 1-(1-XCu)1/3=0.0149(CEDP)0.7814 × (Pmalachite)−0.7982×exp(−6.3308/T) ×t.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2019, 55, 4; 1039-1048
    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
      Wyświetlanie 1-11 z 11

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