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EN
The research study investigated the biosorption behavior of Pb(II) ions by treated and untreated biomass of B. subtilis. At initial biosorption conditions, the biosorption efficiency was found to be 36.75%. At the optimized experimental conditions, control biomass showed maximum biosorption efficiency of 58.04% where the biomass was treated with different chemicals. The biomass treated with formaldehyde showed the highest efficiency of 80.9% which was further optimized and attained maximum efficiency of 89.8% for Pb(II) ions. SEM (Scanning Electron Microscope) and EDX (Energy dispersive X- ray) analysis evaluates the structural and elemental changes that occurred as a result of biosorption. Functional groups that are involved in biosorption were revealed by FTIR (Fourier Transform Infrared spectroscopy). Kinetic data showed the best fit with the pseudo second-order model. Effective removal of lead ions from industrial contaminated water sources by pretreatment biomass of B. subtilis elucidates its potential use as biosorbent for metal remediation.
EN
Agricultural residues rich in lignocellulosic biomass are low-cost and sustainable adsorbents widely used in water treatment. In the present research, thermodynamics, kinetics, and equilibrium of nickel(II) and lead(II) ion biosorption were studied using a corncob (Zea mays). The experiments were performed in a batch system evaluating the effect of temperature and dose of adsorbent. Langmuir and Freundlich isotherms were used to study the equilibrium. Thermodynamic and kinetic parameters were determined using kinetic models (pseudo-first order, pseudo-second order, Elovich). Biosorbent characteristics were studied by Fourier-transform infrared spectroscopy, Scanning Electron Microscopy and Energy-dispersive X-ray spectroscopy. It was found that the hydroxyl, carboxyl, and phenolic groups are the major contributors to the removal process. Besides, Pb(II) ions form micro-complexes on the surface of the biomaterial while Ni(II) ions form bonds with active centers. It was found that the highest Ni(II) removal yields were achieved at 0.02 g of adsorbent and 70°C, while the highest Pb(II) removal yields were achieved at 0.003 g and 55°C. A maximum Ni(II) adsorption capacity of 3.52 mg∙g–1 (86%) and 13.32 mg∙g–1 (94.3%) for Pb(II) was obtained in 250 and 330 min, respectively. Pseudo-first order and pseudo-second order models best fit experimental data, and Langmuir and Freundlich models well describe the isotherm of the process. Thermodynamic parameters (ΔH0, ΔG0, ΔS0) suggest that the adsorption process of both cations is exothermic, irreversible, and not spontaneous.
EN
The study has investigated the technical characteristics of a number of sorption materials (natural mineral) and the possibility of their use for the purification of surface and wastewater from oil and oil products. At the first step, regularities of the process of purification of oily waters have been established taking into account the processes of filtration and sorption. After that, the sorption capacity of the sorbents has been estimated, and the factors influencing it analysed. As a final step, the optimal conditions for the sorption process have been selected depending on the conditions and nature of purification. Results indicated that the maximum purification degree has been reached at the concentration of 500 mg∙dm–3 and temperature of 20°С.
PL
Jednym z głównych czynników mających wpływ na efektywność zabiegów kwasowania matrycowego, jak i szczelinowania kwasem jest szybkość reakcji płynu kwasującego ze skałą węglanową. Często zabiegi wykonywane przy użyciu cieczy kwasujących opartych na roztworach HCl kończą się niepowodzeniem ze względu na bardzo szybką reakcję tych cieczy z węglanami w wysokich temperaturach złożowych. Ciecz kwasująca nie penetruje wtedy odpowiednio głęboko w formację z utworzeniem otworów robaczkowych, a rozpuszcza tylko jej czoło, co skutkuje słabą efektywnością zabiegów. Celem niniejszej pracy było określenie wpływu rodzaju cieczy kwasującej na przebieg reakcji ze skałą pochodzącą z poziomu cechsztyńskiego dolomitu głównego (Ca2). Założono również, że dzięki nowym żelowanym i emulgowanym cieczom kwasującym możliwe będzie zmniejszenie szybkości reakcji roztworów kwasu solnego z wymienioną wcześniej skałą złożową. W ramach realizacji pracy wykonano badania stabilności emulsji typu kwas w ropie, a następnie testy reologiczne żelowanych i emulgowanych cieczy kwasujących. Badania kinetyki reakcji przeprowadzono na korkach rdzeniowych wyciętych ze skały pochodzącej z dolomitu głównego (Ca2), charakteryzujących się małymi wartościami współczynników przepuszczalności (0,03–0,14 mD) i porowatości (7,69–12,90%). Do wyznaczenia kinetyki reakcji trzech rodzajów cieczy kwasujących ze skałą złożową użyto aparatu wirujący dysk. Badania przeprowadzone na tym urządzeniu pozwoliły na określenie trzech następujących wielkości: współczynnika dyfuzji efektywnej (De), stałej szybkości reakcji (k) i rzędu reakcji (n). W części teoretycznej niniejszej publikacji opisano sposoby opóźniania szybkości reakcji cieczy kwasujących ze skałami węglanowymi. Omówiono również wpływ parametrów na szybkość reakcji cieczy kwasujących ze skałami złożowymi oraz metody wyznaczania współczynnika dyfuzji oraz szybkości reakcji. Szczegółowo opisano zastosowanie aparatu wirujący dysk do wyznaczania tych wielkości. Badania wykazały, że wartości współczynnika dyfuzji efektywnej (De) rosną wraz z temperaturą i stężeniem kwasu solnego w zakresie od 5% do 15% oraz zależą również od rodzaju cieczy kwasującej. Największy wzrost jego wartości w analizowanym zakresie stężeń odnotowano dla roztworu HCl w temperaturze pomiarowej 30°C i wynosił on 7,10·10−8 cm2/s, natomiast najmniejszy – dla emulgowanych cieczy kwasujących w 40°C i był równy 9,20·10−10 cm2/s. Wartości tego współczynnika w przypadku żelowanych cieczy kwasujących w temperaturze 120°C są od 9- do 13-krotnie mniejsze, natomiast w przypadku emulgowanych cieczy kwasujących od 396- do 938-krotnie mniejsze w porównaniu do roztworów HCl. Z kolei wartości stałej szybkości reakcji dla emulsji kwasowych były o około rząd wielkości mniejsze niż dla żelowanych cieczy kwasujących i dwa rzędy wielkości mniejsze w porównaniu do roztworów HCl. Wszystkie wartości wyznaczonych rzędów reakcji zawierają się w zakresie pomiędzy 0 a 1, a więc typowym dla reakcji heterogenicznych. Emulgowane ciecze kwasujące – spośród cieczy poddanych badaniom – najbardziej efektywnie obniżają szybkość reakcji ze skałą dolomitową. Odbywa się to poprzez zmniejszenie szybkości transportu masy, jak i samej reakcji na powierzchni skały złożowej. Ciecze te zostały z powodzeniem zastosowane w zabiegach kwasowania matrycowego w odwiertach zlokalizowanych w utworach dolomitu głównego. Zarówno w otworach ropnych, jak i gazowych osiągnięto wzrost produkcji z jednoczesnym spadkiem ciśnienia różnicowego, przy którym to wydobycie jest prowadzone.
EN
One of the main factors affecting the effectiveness of matrix acidizing treatment and acid fracturing is the reaction rate of acidizing fluid with carbonate rock. Often, treatments performed using acidizing liquids based on HCl solutions fail due to their very fast reaction with carbonates at high reservoir temperatures. The acidizing liquid does not penetrate deeply into the formation so as to create wormholes, but only dissolves its face, which results in poor treatment effectiveness. The aim of this study was to determine the effect of the type of acidizing liquid on the rate of reaction with the rock of the Zechstein Main Dolomite (Ca2). It was also assumed that thanks to new gelled and emulsified acidizing liquids it would be possible to reduce the reaction rate of hydrochloric acid solutions with the reservoir rock mentioned earlier. As part of the study, stability tests of acid-in-oil emulsions were performed, followed by rheological tests of gelled and emulsified acidizing liquids. Reaction kinetics studies were performed on core plugs cut from the Main Dolomite (Ca2) rock, characterized by low values of permeability coefficients (0.03 - 0.14 mD) and porosity (7.69 - 12.90%). A rotating disk apparatus was used to determine the kinetics of the reaction of reservoir rock with three types of acidizing liquids. Tests carried out on this device allowed the determination of the following three quantities: effective diffusion coefficient (De), reaction rate constant (k) and reaction order (n). Methods of reaction rate retardation of acidizing liquids with carbonate rocks were described in the theoretical part of this publication. Factors that affect reaction rate of acidizing liquids with reservoir rocks and the methods for determining the diffusion coefficient and reaction rate were also discussed. The use of a rotating disk apparatus for determining these quantities has been described in detail. Studies have shown that the values of effective diffusion coefficient (De) increase with the temperature and concentration of hydrochloric acid in the range from 5% to 15%. Moreover, this effect depends on the type of acidizing liquid. The biggest increase in its value in the analyzed concentration range was noted for the HCl solution at the measuring temperature of 30°C, this being 7.10·10-8 cm2/s, while the smallest for emulsified acidizing liquids at 40°C was equal to 9.20·10-10 cm2/s. The values of this coefficient for gelled acidizing liquids at 120°C are from 9 to 13 times lower, while for emulsified acidizing liquids – from 396 to 938 times lower compared to HCl solutions. In turn, the reaction rate constant values for acidic emulsions were about an order of magnitude smaller than for gelled acidizing liquids and two orders of magnitude smaller compared to HCl solutions. All values of the determined orders of reaction are between 0 and 1, which is typical for heterogeneous reactions. Emulsified acidizing liquids, among all tested liquids, most effectively decrease the rate of reaction with dolomite rock. This came about due to reducing the rate of mass transport, as well as the effect of the reaction itself on the surface of the reservoir rock. These liquids have been successfully used in matrix acidizing treatment in wells located in the Main Dolomite strata. Both in oil and gas wells, the application of these liquids have simultaneously enabled increased production and reduction of the differential pressure at which extraction is carried out.
EN
In this paper the adsorption and photodegradation of caffeine (CAF) using modified photocatalysts were studied. The laboratory synthesis method of commercial titanium(IV) oxide, activated carbon and ultrasound was proposed. The adsorption effect of caffeine was described by the Langmuir and Freundlich isotherms. The effectiveness of CAF photocatalytic decomposition was evaluated as well as the parameters of the pseudo-first-order and pseudo-second-order reaction kinetics were estimated. It was determined that the caffeine adsorption fit both the Langmuir and Freundlich isotherms. The value of the experimental maximum adsorption capacity (qe) was the highest for TiO2 modified with activated carbon and ultrasounds (TiO2/AC/Us). The highest removal degree (over 99.0%) of CAF was observed for titanium(IV) oxide modified with activated carbon. Both photodegradation kinetics models show good or very good fit; however, the pseudo-first-order model shows better fit to the experimental data (R2 = 97–99%). After 20 minutes of the photodegradation process, the following efficiency order was determined: TiO2 < TiO2/AC < TiO2/AC/US. The results indicate that the combination of TiO2, activated carbon and ultrasound is an interesting alternative for the efficient degradation of caffeine, comparing to commercial TiO2.
EN
The degradation of 4-bromochlorobenzene (4-BCB) containing both chlorine and bromine by mechanochemical destruction (MCD) using CaO powder was investigated. The degradation efficiency of 4-BCB almost achieved 100% after 2 h milling. The debromination rate (0.41 h–1) was higher than the dechlorination rate (0.31 h−1) which can be ascribed to the lower dissociation energy of C–Br bond than that of C–Cl bond in 4-BCB. The kinetic analysis demonstrates that nucleation growth was the control step of dehalogenation reactions. Additionally, the dehalogenation efficiency increased with increasing rotate speed and milling ball weight. The XRD and FT-IR spectra analysis manifests that the CaO powder was transformed to CaCl2, CaBr2, Ca(OH)2, and CaCO3. The identification of intermediates and analysis of Raman spectra indicates that the 4-BCB degradation by MCD treatment using CaO powder may occur through three pathways: (a) breakup of the benzene ring to form small molecular halogenated hydrocarbons and mineralization to form CO2 and H2O in sequence, (b) dehalogenation reaction to form benzene and monohalogenobenzene and addition reaction of halogen radicals to form dihalogenobenzenes in sequence; (c) polymerization reaction to form biphenyl, halogenated biphenyl, and graphite.
EN
The study of the kinetics of extraction of phenolic compounds and flavonoids from crushed roots of Carlina acaulis using 40% and 70% of water-ethanol mixture by infusion method is described in the article. The total value of the mass transfer coefficient and the value of the transfer coefficient through the cell wall, in the intercellular space and the volume of the extractant were determined. Particles of Carlina acaulis roots of different sizes (0.2, 0.3, 0.5 mm) were studied; different concentrations of ethyl alcohol were used - 40% and 70%; the ratio of raw materials: extractant was 1:10. The analytical dependence of the mass transfer coefficient k and the leaching coefficient A on the solid particle size d and the concentration of the extractant was obtained, which allows to predict the extraction process and to design equipment for the technological process in production. Kinetic equations of the process of extraction of phenolic compounds and flavonoids from Carlina acaulis roots by infusion method are derived. The obtained equations allow to determine the concentrations of phenolic compounds and flavonoids in the extracts at a given point in time with a particle size of the solid phase from 1 to 10 mm, as well as to determine the optimal diameter of the solid phase particles for maximum extraction of the target substance.
EN
This paper presents an experimental study on Cochineal Red A dye adsorptive removal by yeast. Batchequilibrium and kinetic tests were conducted in constant temperature of 30◦C for the dye’s initialconcentration range of 0.02–0.50 g/L (pH=3and 10) and 0.02–0.35 g/L (pH=7:6). The equilibriumwas reached after 105–120 min. Yeast demonstrated the adsorption capacity of 10.16 mg/g for acidicenvironment (pH=3) and slightly lower values (8.13 mg/g and 8.38 mg/g respectively) for neutral(pH=7:6) and alkaline environment (pH=10). The experimental equilibrium results were fitted withLangmuir, Freundlich, Sips and Toth isotherm models. Most of them (Freundlich model being theexception) were proven sufficient for the experimental data correlation. The adsorption kinetic studiesshowed that the pseudo-second order model fits better the experimental data than the pseudo-first-order model. Results achieved from intra-particle diffusion model indicate that powdered yeast are anonporous adsorbent. The percentage of solution discoloration reached a maximum value of 75% atpH=3for an initial dye concentration of 0.02 g/L.
EN
In this work, the spectrophotometric studies on the kinetics of redox reaction between gold(III) bromide complexes and sodium nitrite, were carried out. From the kinetic curves collected under different conditions of reactants concentration, addition of bromide ions, temperature, pH and ionic strength, corresponding rate constants have been determined. The obtained results suggest the complex path of the [AuBr4]- reduction consisting of two parallel, bimolecular reactions where different reductant species (HNO2 and NO2-) take place and consecutive step with the metallic gold production. The second-order rate constants at 20°C are equal to 2.948 and 0.191 M-1·s-1, respectively. The values of activation enthalpy and activation entropy for the first and the second parallel step of the reaction were found to be ΔH‡ = 29.18 kJ·mol-1 and ΔS‡ = –13.95 J·mol-1·K, and ΔH‡ = 40.75 kJ·mol-1 and ΔS‡ = –31.06 J·mol-1·K, respectively. It was found that the reaction accelerates significantly with the increase of pH and is inhibited with the increase of Br- concentration. The substitutive, inner-sphere mechanism of electron transfer in the studied system was also suggested.
10
Content available remote Silne efekty entropowe orientacji molekularnej w kinetyce krystalizacji polimerów
PL
Obliczono i przedyskutowano wpływ orientacji molekularnej oraz temperatury na szybkość nukleacji i wzrostu kryształów ze wskazaniem na rolę entropii w kinetyce krystalizacji polimerów. W celu określenia efektów entropowych w całym zakresie orientacji molekularnej wywołanej naprężeniami rozciągającymi zastosowano dwa przybliżenia statystyki molekularnej. Badania doświadczalne kinetyki krystalizacji orientowanej przeprowadzono dla orientowanej włókniny z polilaktydu (PLLA) oraz nieorientowanego granulatu PLLA jako przykładowego polimeru, z wykorzystaniem różnicowego kalorymetru skaningowego DSC. Przedstawiono znaczny wpływ orientacji molekularnej na szybkość nukleacji, wzrostu kryształów i szybkość krystalizacji, wynikający ze spadku entropii fazy amorficznej w warunkach orientacji. Ujęte jest to w rozszerzonych modelach Hoffmana i Lauritzena oraz Avramiego i Evansa dla orientowanej krystalizacji i w eksperymentalnych wynikach badań kalorymetrycznych DSC.
EN
Effect of mol. orientation and temp. on the nucleation and crystal growth rates of polymers were calcd. and discussed to indicate the role of entropy in the kinetics of its crystn. Two approximations of mol. statistics were used to det. the entropic effects in the entire range of mol. orientation produced by tensile stresses. The exp. investigations on the oriented crystn. kinetics of polylactide nonwoven fibres and unoriented pellets were carried out by differential scanning calorimetry. High effects of the mol. orientation in the entropy strongly affecting the nucleation and crystal growth rates, as well as the crystn. rate were shown based on the Hoffman-Lauritzen and Avrami-Evans models.
PL
Przedstawiono wyniki badań kinetycznych procesu estryfikacji kwasu laurynowego n-heksanolem, n-oktanolem oraz n-dekanolem. Syntezę laurynianów alkoholi prowadzono w obecności 0,39% mas. kwasu molibdenowofosforowego (H3PMo12O40) jako katalizatora, w warunkach izotermicznych w doświadczalnym reaktorze półokresowym z ciągłym odprowadzaniem wody. Stwierdzono, że reakcje są drugiego rzędu (pierwszego rzędu względem kwasu i pierwszego rzędu względem alkoholu). Określono parametry równania kinetycznego, wartości energii aktywacji malały z 69 do 59 kJ/mol w szeregu n-heksanol > n-oktanol > n-dekanol.
EN
Lauric acid was esterified with n-hexanol, n-octanol and n-decanol at 393-413 K and molar (alc.:acid) ratios between 3:1 and 10:1 in presence of the H3PMo12O40 catalyst (0.39% by mass) to study the reaction kinetics. The reactions were of 2nd order and their activation energy decreased from 69 down to 59 kJ/mol in the alc. series: n-hexanol > n-octanol > n-decanol.
EN
The aim of this study was to analyse the steam gasification process of ‘Janina’ coal with and without Na-, K- and Ca-catalysts. The catalysts were physically mixed with the coal due to the simplicity of this method, short time of execution and certainty that the amount of catalyst is exactly as the adopted one. The isothermal measurements were performed at 800, 900 and 950°C and a pressure of 1 MPa using thermovolumetric method. The obtained results enabled assessment of the effect of analysed catalysts on the process at various temperatures by determination of: i) carbon conversion degree; ii) yield and composition of the resulting gas; and iii) kinetics of formation reactions of main gas components – CO and H2. The addition of catalysts, as well as an increase in operating temperature, had a positive effect on the coal gasification process – reactions rates increased, and the process time was reduced.
EN
Fly ash and slag were examined for the removal processes of Pb(II) ions from water in batch experiments under different conditions of adsorbent dosage, initial concentration, pH and contact time. The materials are industrial waste generated from the high temperature treatment of sewage sludge by the circulating fluidized bed combustion (CFBC) technology. Physical and chemical properties, as well as adsorption efficiency and calculated maximum adsorption capacity of Pb(II) ions were determined using a variety of methods. The kinetic analysis revealed that the adsorption process is better described by the pseudo-second order equation and it is well fitted to the Freundlich model.
14
EN
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).
EN
Sulphuric acid leach solution of waste printed circuit boards (PCBs) contains predominantly copper and iron with later remain problematic during electrowinning of the formal. In this study, performance of Dowex M 4195 resin for recovery of copper and nickel from polymetallic sulphate leach solution of waste PCBs was investigated by batch experiments. It was observed that at pH 0.5, about 45.2 and 3.6 % Cu2+ and Ni2+ was selectively recovered respectively. Recovery efficiency of Ni2+ increased with increase in pH from 0.5 -5.0 while pH2 was optimum for the recovery of Cu2+. Sharp increase in co-recovery of Fe3+/Fe2+ was observed at pH above 2 with that of Zn2+ and Co2+ became low due to hindrance from binding site by high concentration of Cu2+. Adsorption data obtained for Cu2+ and Ni2+ were tested with adsorption isotherms as well as kinetics. It is shown that adsorption of Cu2+ and Ni2+was well fitted to both Langmuir and Freundlich isotherm. Kinetics of Cu2+ and Ni2+ fitted into Pseudo-first and well fitted to second order. Reuse studies shows that the resin strong affinities for Cu2+ and Ni2+ remain unchanged.
EN
In this study, the feasibility of lead dissolution from lead concentrate using fluoroboric acid by hydrometallurgical method was investigated in order to aviod the disadvantages of the pyrometallurgical processes. The effects of important operating parameters such as leaching time, liquid/solid ratio, stirring speed, temperature and fluoroboric acid concentration on the lead recovery were investigated using response surface methodology (RSM) based on the central composite design (CCD) model. The results show that the optimum conditions for the high lead recovery were: leaching time= 30 min, liquid/solid ratio= 10, stirring rate= 500 rpm, temperature= 80oC and fluoroboric acid concentration= 3.35 mol/L. More than 94% of lead was recovered in the optimum conditions. The results indicated that the liquid/solid ratio, fluoroboric acid concentration, temperature and leaching time were the most effective parameters on the process efficiency, respectively. Dissolution kinetics studies of lead in the fluoroboric acid were also evaluated. The chemical reaction was determined as the controlling mechanism of reaction at the shrinking core model. The activation energy was determined using Arrhenius model as 5.99 kJ/mol.
EN
The mechanism and leaching kinetics of a molybdenite concentrate in a H2O2-H2SO4 system were studied. The experimental work was performed in a batch reactor equipped with a condenser, a mechanical agitator and a temperature control system. The effects of the temperature, H2O2 and H2SO4 concentrations, particle size, liquid/solid ratio and agitation speed on the Mo recovery were investigated. The thermodynamic results showed that the leaching mechanism it was governed by several intermediate reactions; however, the influences of sulfuric acid and passivation were not observed in the reaction. The most predominant experimental result was the maximum Mo recovery of 81.3% by leaching 64 μm particles at 333 K (60 °C) for 5400 s (90 min). The molybdenum recovery was generally enhanced by increasing the H2O2 and H2SO4 concentrations. However, at H2SO4 concentrations higher than 1.0 mol/dm3, the Mo recovery decreased. Although the agitation speed affected the Mo recovery considerably, high recoveries could be still obtained without mixing. The experimental results and XRD analysis confirmed the reaction mechanisms. The leaching kinetics were analyzed using a shrinking core model in which the rate was controlled by diffusion through a porous layer with radius ro. The reaction rate orders were 1.0 and 0.2 for the H2O2 and H2SO4 concentrations, respectively, and the rate was inversely proportional to the square of the initial particle radius. The calculated activation energy was 75.2 kJ/mol in the temperature range of 278-333 K (5-60 °C).
EN
Anatase, as an important titanium resource, is attracting more and more attention in research and application. In this study, an efficient process of comprehensively extracting the titanium and other valuable elements from the anatase mineral was proposed. The effect of particle size, stirring speed, initial sulphuric acid concentration, solid-to-liquid ratio, and reaction temperature on the leaching rate of titanium from anatase was investigated. Under appropriate two-stage countercurrent leaching conditions, with the first stage of the liquid-to-solid ratio of 1/3 g/cm3, reaction temperature of 120 °C, initial acid concentration of 11 mol/dm3, residence time of 30 min, stirring speed of 200 rpm, and the second stage of the liquid-to-solid ratio of 1/3 g/cm3, reaction temperature of 200 °C, initial acid concentration of 13 mol/dm3, residence time of 30 min, and stirring speed of 200 rpm, over 99% TiO2, 99% Al2O3, and 97% Sc2O3 were extracted respectively with quartz still remained in the residue. X-ray diffraction, X-ray fluorescence spectrometer, and scanning electron microscopy/energy-dispersive spectroscopy were used to characterize the anatase samples before and after the leaching. Additionally, the leaching kinetics analysis indicated that both acid concentration and temperature were the most significant parameters for the leaching process. And, the titanium leaching reaction rate was controlled by the diffusion of reactants through the residual layer.
EN
In this study, the leaching process of a lead-bearing ore, consisting mainly of cerussite, in an ammonium citrate tribasic medium was investigated. The parameters including temperature, reagent concentration, particle size, and stirring speed were examined. During leaching process, the lead conversion rate increased with an increase in reagent concentration, reaction temperature, and stirring speed, and a decrease in particle size. The results show that about 95% of lead content was extracted from the samples with particle size range of +75-96 μm after 21 min leaching in 1.25 mol/L ammonium citrate tribasic solution at 800 r/min and 40°C. It was found that the leaching reaction followed the shrinking core model. The results indicated that ammonium citrate tribasic could be used as an effective leaching reagent for extracting lead from lead oxide ore.
EN
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.
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