Anodic polarization behavior of gold, silver, copper, nickel and iron in potentiostatic condition has been examined in an alkaline aqueous thiourea solution, where gold is hardly dissoluble normally. The addition of N...Anodic polarization behavior of gold, silver, copper, nickel and iron in potentiostatic condition has been examined in an alkaline aqueous thiourea solution, where gold is hardly dissoluble normally. The addition of Na2SO3 into the solution can accelerate anodic dissolution of gold. The factors affecting selective dissolution of gold in the alkaline thiourea solution by electrolysis have been studied, and the optimum condition was obtained. In 0.1 mol/L thiourea solution of pH 12. 5 containing 0. 5 mol/L Na2SO3 and 2. 5% acetone, at the potential of 0. 34 V vs NHE, at the temperature of 323 K, the dissolved mass of gold anode with the exposed area of 1. 0 cm2 reached more than 300 mg·dm-3 within 30 min, and other metals such as silver, copper, nickel and iron could hardly dissolve.展开更多
Aiming to the low-grade rhodium-containing waste materials, a new process was proposed to enrich and activate rhodium by smelting using iron oxide as a trapping agent and activator. A rhodium concentrate was obtained ...Aiming to the low-grade rhodium-containing waste materials, a new process was proposed to enrich and activate rhodium by smelting using iron oxide as a trapping agent and activator. A rhodium concentrate was obtained by the separation of base metals and precious metals. The concentrate was reacted with dilute aqua regia to obtain rhodium solution. The factors influencing the enrichment and activation effects were discussed in this paper. The results showed that the dissolution rate is greater than 99% under the optimum conditions. In this process, the activation of rhodium was finished in the enrichment process. The iron oxide is both a trapping agent and activator, which simplifies the process and reduce the cost.展开更多
In order to simulate the instability phenomenon of a nonaqueous phase liquid(NAPL) dissolution front in a computational model, the intrinsic characteristic length is commonly used to determine the length scale at whic...In order to simulate the instability phenomenon of a nonaqueous phase liquid(NAPL) dissolution front in a computational model, the intrinsic characteristic length is commonly used to determine the length scale at which the instability of the NAPL dissolution front can be initiated. This will require a huge number of finite elements if a whole NAPL dissolution system is simulated in the computational model. Even though modern supercomputers might be used to tackle this kind of NAPL dissolution problem, it can become prohibitive for commonly-used personal computers to do so. The main purpose of this work is to investigate whether or not the whole NAPL dissolution system of an annular domain can be replaced by a trapezoidal domain, so as to greatly reduce the requirements for computer efforts. The related simulation results have demonstrated that when the NAPL dissolution system under consideration is in a subcritical state, if the dissolution pattern around the entrance of an annulus domain is of interest, then a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system.However, if the dissolution pattern away from the vicinity of the entrance of an annulus domain is of interest, then a trapezoidal domain can be used to replace an annular domain in the computational simulation of the NAPL dissolution system. When the NAPL dissolution system under consideration is in a supercritical state, a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system.展开更多
Homogeneity and heterogeneity are two totally different concepts in nature.At the particle length scale,rocks exhibit strong heterogeneity in their constituents and porosities.When the heterogeneity of porosity obeys ...Homogeneity and heterogeneity are two totally different concepts in nature.At the particle length scale,rocks exhibit strong heterogeneity in their constituents and porosities.When the heterogeneity of porosity obeys the random uniform distribution,both the mean value and the variance of porosities in the heterogeneous porosity field can be used to reflect the overall heterogeneous characteristics of the porosity field.The main purpose of this work is to investigate the effects of porosity heterogeneity on chemical dissolution front instability in fluid-saturated rocks by the computational simulation method.The related computational simulation results have demonstrated that:1) since the propagation speed of a chemical dissolution front is inversely proportional to the difference between the final porosity and the mean value of porosities in the initial porosity field,an increase in the extent of the porosity heterogeneity can cause an increase in the mean value of porosities in the initial porosity field and an increase in the propagation speed of the chemical dissolution front.2) An increase in the variance of porosities in the initial porosity field can cause an increase in the instability probability of the chemical dissolution front in the fluid-saturated rock.3) The greater the mean value of porosities in the initial porosity field,the quicker the irregular morphology of the chemical dissolution front changes in the supercritical chemical dissolution systems.This means that the irregular morphology of a chemical dissolution front grows quicker in a porosity field of heterogeneity than it does in that of homogeneity when the chemical dissolution system is at a supercritical stage.展开更多
Many scientific and engineering problems need to use numerical methods and algorithms to obtain computational simulation results because analytical solutions are seldom available for them.The chemical dissolution-fron...Many scientific and engineering problems need to use numerical methods and algorithms to obtain computational simulation results because analytical solutions are seldom available for them.The chemical dissolution-front instability problem in fluid-saturated porous rocks is no exception.Since this kind of instability problem has both the conventional(i.e.trivial)and the unconventional(i.e.nontrivial)solutions,it is necessary to examine the effects of different numerical algorithms,which are used to solve chemical dissolution-front instability problems in fluid-saturated porous rocks.Toward this goal,two different numerical algorithms associated with the commonly-used finite element method are considered in this paper.In the first numerical algorithm,the porosity,pore-fluid pressure and acid/solute concentration are selected as basic variables,while in the second numerical algorithm,the porosity,velocity of pore-fluid flow and acid/solute concentration are selected as basic variables.The particular attention is paid to the effects of these two numerical algorithms on the computational simulation results of unstable chemical dissolution-front propagation in fluid-saturated porous rocks.The related computational simulation results have demonstrated that:1)the first numerical algorithm associated with the porosity-pressure-concentration approach can realistically simulate the evolution processes of unstable chemical dissolution-front propagation in chemical dissolution systems.2)The second numerical algorithm associated with the porosity-velocity-concentration approach fails to simulate the evolution processes of unstable chemical dissolution-front propagation.3)The extra differential operation is the main source to result in the failure of the second numerical algorithm.展开更多
Determination of dissolution rate of alumina is one of the classical problems in aluminum electrolysis. A novel method which can measure the dissolution rate of alumina was presented. Effect of factors on dissolution ...Determination of dissolution rate of alumina is one of the classical problems in aluminum electrolysis. A novel method which can measure the dissolution rate of alumina was presented. Effect of factors on dissolution rate of alumina was studied intuitively and roundly using transparent quartz electrobath and image analysis techniques. Images about dissolution process of alumina were taken at an interval of fixed time from transparent quartz electrobath of double rooms. Gabor wavelet transforms were used for extracting and describing the texture features of each image. After subsampling several times, the dissolution rate of alumina was computed using these texture features in local neighborhood of samples. Regression equation of the dissolution rate of alumina was obtained using these dissolution rates. Experiments show that the regression equation of the dissolution rate of alumina is y=-0.000 5x^3＋0.024 0x^2-0.287 3x＋ 1.276 7 for Na3AIF6-AIF3-Al2O3-CaF2-LiF- MgF2 system at 920 ℃.展开更多
The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 ...The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 °C were systematically investigated.The dissolution property of high-ferrite gibbsitic bauxite is increased by increasing the dissolution temperature and the Na OH concentration or decreasing the particle size of bauxite,which is easy to dissolve under atmospheric pressure.The kinetic equations of gibbsitic bauxites with different ferrite contents during the dissolution process at different temperatures for different times were established,and the corresponding activation energies were calculated.The ferrite in the gibbsitic bauxite reduces the dissolution speed and increases the activation energy of dissolution,the diffusion process of which is the rate-controlling step.展开更多
In the feeding process of aluminum electrolytic, feeding quantity of alumina affects eventually dissolved quantity at the end of a feeding cycle. Based on the OpenFOAM platform, dissolution model coupled with heat and...In the feeding process of aluminum electrolytic, feeding quantity of alumina affects eventually dissolved quantity at the end of a feeding cycle. Based on the OpenFOAM platform, dissolution model coupled with heat and mass transfer was established. Applying the Rosin-Rammler function, alumina particle size distribution under different feeding quantities was obtained. The temperature response of electrolyte after feeding was included and calculated, and the dissolution processes of alumina with different feeding quantities (0.6, 0.8, 1.0, 1.2, 1.4, 1.6 kg) after feeding were simulated in 300 kA aluminum reduction cell. The results show that with the increase of feeding quantity, accumulated mass fraction of dissolved alumina decreases, and the time required for the rapid dissolution stage extends. When the feeding quantity is 0.6 kg and 1.2 kg, it takes the shortest time for the electrolyte temperature dropping before rebounding back. With the increase of feeding quantity, the dissolution rate in the rapid dissolution stage increases at first and then decreases gradually. The most suitable feeding quantity is 1.2 kg. The fitting equation of alumina dissolution curve under different feeding quantities is obtained, which can be used to evaluate the alumina dissolution and guide the feeding quantity and feeding cycle.展开更多
The dissolution behavior of CaO-MgO-SiO2 glass fiber was investigated by scanning electron microscopy （SEM）, Fourier-transform infrared spectrometer （FTIR） and inductively coupled plasma atomic emission spectrosco...The dissolution behavior of CaO-MgO-SiO2 glass fiber was investigated by scanning electron microscopy （SEM）, Fourier-transform infrared spectrometer （FTIR） and inductively coupled plasma atomic emission spectroscopy （ICP-AES） using in-vitro tests. The results show that the soaked fiber is surrounded by an outer calcium-magnesium silicate hydrated layer, and there exists a balancing fimction between the formation and abscission of the hydrated layer during the dissolution process. The concentrations of leached ions increase constantly, and the mass loss of the fibers and pH changes of the solution are found to rise rapidly during the initial dissolution process, then their increasing rates are controlled by the balancing function of the hydrated layer at the subsequent dissolution stages. The dissolution rate constant and time for complete dissolution are estimated to be 274 ng/（cm2.h） and 15.2 d, respectively, presenting preferable biosolubilities.展开更多
Acid mine drainage(AMD)has become a widespread environmental issue and its toxicity can cause permanent damage to the ecosystem.However,there are few studies focusing on the formation of AMD under moderately thermophi...Acid mine drainage(AMD)has become a widespread environmental issue and its toxicity can cause permanent damage to the ecosystem.However,there are few studies focusing on the formation of AMD under moderately thermophilic conditions,hence we employed X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and 16S rRNA sequencing to study the dissolution of pyrite and bornite by a moderate thermophilic consortium,and explored the role of free and attached microorganisms in the formation of AMD.The consortium mainly comprised Acidithiobacillus caldus,Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans.The results indicated that total iron in pyrite solution system reached 33.45 g/L on the 12th day,and the copper dissolution rate of bornite dissolution reached 91.8%on the 24th day.SEM results indicated that the surfaces of pyrite and bornite were significantly corroded by microorganisms.XRD and XPS results showed that ore residues contained jarosite,and the dissolving residue of bornite contained elemental sulfur.The dominant bacterial genus in pyrite dissolution was A.caldus,and L.ferriphilum in bornite dissolution.To sum up,microbes significantly accelerated the mineral dissolution process and promoted the formation of AMD.展开更多
In this paper, the dissolution characteristics of Xining dustfall in citric acid solution was studied to evaluate the physical chemical change in acid conditions. pH along with conductivity was tested with time. FTIR,...In this paper, the dissolution characteristics of Xining dustfall in citric acid solution was studied to evaluate the physical chemical change in acid conditions. pH along with conductivity was tested with time. FTIR, SEM and ICP analysis were applied to analyze the residuum and filtrate after 2 days’ dissolution experiment. It was shown in the pH/conductivity variation, solution’s pH rise sharply in the front 4 hours, then decrease slowly. After 4 hours, both the pH and conductivity become stable. Based on combined analysis of XRD and FTIR spectrum of dustfall before and after dissolution, that calcite and dolomite in dustfall are dissolved completely in the 0.05M citric acid solution in two days. Besides, amount of metal cations were extracted from the dustfall during the dissolution, including Ca2+,K+,Mg2+,Fe3+,Al3+,Si. In general, after the dissolution of dustall in citric acid, some minerals are dissolved and amount of metal elements are extracted. Carbonate minerals almost dissolved completely, also the structure of silicate minerals changed as the extraction of elements.展开更多
In order to study the control factors and mechanism of oolitic limestone reservoir being corroded by organic acid produced in burial stage,the reactions of acetic acid(pH=3) with oolitic limestone were investigated us...In order to study the control factors and mechanism of oolitic limestone reservoir being corroded by organic acid produced in burial stage,the reactions of acetic acid(pH=3) with oolitic limestone were investigated using the rotating-disk Corrosion Reactor System(CRS).The effects of disk rotational speed, temperature and system pressure were examined. Scanning Electron Microscope attached with Energy Dispersive X-Ray Analyzer(SEM-EDX) was展开更多
This article describes the characteristics of natural dusts, artificial dusts and industrial dusts, such as mineral phases, chemical components, morphological observation and size. Quartz and calcite are the main phas...This article describes the characteristics of natural dusts, artificial dusts and industrial dusts, such as mineral phases, chemical components, morphological observation and size. Quartz and calcite are the main phases of natural dusts and industrial dusts with high SiO2, CaO and low K2O, Na2O on the chemical composition. Natural dusts are mainly irregular shaped and some particle aggregation made of small dusts on the surface of large dust. Industrial dusts are globular and blob-like, but artificial dusts are columnar and fibrous. The fine particles are mainly in the range of 0.3-5 μm,of which the dusts of less than 5 μm are over 99%.The dissolution and electrochemical action of dusts in glutamic acid liquor at the simulated human body temperature (37 ℃) in 32 hours were investigated. The changes of pH values and electric conductivity of those dusts were similar, increased slowly in first 8 hours, and then the pH values increased rapidly. The total amount of dissolved ions of K, Ca, Na, Mg was 35.4-429 mg/L, particularly Ca was maximal of 20-334 mg/L. The total amount of dissolved ions of Fe, Zn, Mn, Pb, Ba was 0.18-5.59 ppm and the Al, Si was 3.0-21.7 mg/L. Each element dissolved rapidly relatively in first 16 hours. The relative solubility order of dusts in glutamic acid are: wollastonite > serpentine > sepiolite, the cement plant industrial dusts > power plant industrial dusts, and natural dusts have similar solubility. The wollastonite and power plant industrial dusts have highest solubility, which have high content of CaO; this shows there are a poorer corrosion-resisting ability and lower bio-resistibility. Sepiolite and cement plant industrial dusts have lowest solubility, which have high content of SiO2; this shows there are a higher corrosion-resisting ability and stronger bio-resistibility.展开更多
The dissolution kinetics of calcined ulexite in ammonium chloride solutions at high solid-to-liquid ratios were investigated. In the experiments, calcination temperature, solution concentration, reaction temperature, ...The dissolution kinetics of calcined ulexite in ammonium chloride solutions at high solid-to-liquid ratios were investigated. In the experiments, calcination temperature, solution concentration, reaction temperature, and pre-hydration were chosen as parameters. It was observed that the dissolution rate increased with increasing calcination temperature, solution concentration, and reaction temperature, whereas it was not affected by pre-hydration. Employing graphical and statistic methods, the dissolution rate, based on homogeneous reaction model, can be given as: (1-X(B2O3))-1-1= k(c(NH4Cl))1.982t. The activation energy for the dissolution of the ulexite sample calcined at 160 ℃ was found to be 84.04 kJ·mol-1.展开更多
Gold dissolves easily in an alkaline thiourea solution with Na2SO3 and Na2S2O8, where the accompanied elements of Au, such as Ag, Cu, Ni and Fe can hardly dissolve. It was considered that electrochemical reduction and...Gold dissolves easily in an alkaline thiourea solution with Na2SO3 and Na2S2O8, where the accompanied elements of Au, such as Ag, Cu, Ni and Fe can hardly dissolve. It was considered that electrochemical reduction and catalytic action of SO32- prevent thiourea from decomposing irreversibly and accelerates dissolution of gold.The S2O82- as an oxidant can control the potential so that formamidine disulfide may form efficiently. The dissolution of gold is mainly through oxidation of Au by formamidine disulfide and complexation of thiourea with An+,and not direct oxidation of S2O82-. Thus,sufficient formamidine disulfide is necessary to accelerate the dissolution of gold. The reason for Ag, Cu hardly being dissoluble is that the black layers of Ag2S and Cu1.92S form on the surface of Ag and Cu. The metal Ni and Fe do not dissolve in the alkaline media due to their sulfide films passivation samely.展开更多
The gold dissolution in anoxic cyanide solution in the presence of chalcopyrite was studied with a rotating disc electrode.It was found that the presence of chalcopyrite reduced and enhanced the dissolution activity o...The gold dissolution in anoxic cyanide solution in the presence of chalcopyrite was studied with a rotating disc electrode.It was found that the presence of chalcopyrite reduced and enhanced the dissolution activity of pure gold in the low and high potential regions,respectively.The dissolution of gold was diffusion-controlled at low potentials(≤177 mV)and low cyanide concentrations(≤980 mg/L);however,above the cyanide concentration of 980 mg/L,the current density of gold decreased and the dissolution of gold changed from diffusion-control to electrochemical reaction-control.At high potentials(>177 mV),gold dissolution was always controlled by diffusion.In cyanide solution containing chalcopyrite,appropriate increase of pH value and temperature could accelerate the dissolution of gold,but high pH value would promote the generation of passivation,which was harmful for the dissolution of gold in cyanide solution.展开更多
The dissolution mechanism of hemimorphite in NH3-（NH4）2SO4-H2O system at 298.15 K was investigated by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy ...The dissolution mechanism of hemimorphite in NH3-（NH4）2SO4-H2O system at 298.15 K was investigated by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS） analysis. The results show that hemimorphite is soluble in NH3-（NH4）2SO4-H2O system and its residue exists in the form of an amorphous SiO2 layer on the hemimorphite surface. The XPS data also indicate that the Si 2p3/2 and O ls spectra of the hemimorphite are broadened and shift to higher binding energies and their binding energies are closer to silica with an increase of total ammonia and time. Solubility of hemimorphite in NH3-（NH4）2SO4-H2O system was measured by means of isothermal solution method at 298.15 K based on the study of the dissolution mechanism of hemimorphite. The results show that the solubility of zinc in solution increases firstly and then decreases with the increase of cr（NH3） （total ammonia concentration） at different NH3/NH4^＋ ratios. The solubility of silicon in solution decreases from 0.0334 mol/kg in ct（NH3）-4.1245 mol/kg NH3-（NH4）2SO4-H2O solution to 0.0046 mol/kg in cT（NH3）=7.6035 mol/kg NH3-（NH4）2SO4-H2O solution.展开更多
INTRODUCTION Dissolution and precipitation of carbonates plays an important role in nature, such as in the chemistry of seawater, the sedimentation of carbonate at the seafloor, the geochemical evolution of freshwater...INTRODUCTION Dissolution and precipitation of carbonates plays an important role in nature, such as in the chemistry of seawater, the sedimentation of carbonate at the seafloor, the geochemical evolution of freshwater aquifers and last but not least, most spectacular, the evolution of karst landscapes. To provide a deeper understanding to all these processes knowledge is required展开更多
文摘Anodic polarization behavior of gold, silver, copper, nickel and iron in potentiostatic condition has been examined in an alkaline aqueous thiourea solution, where gold is hardly dissoluble normally. The addition of Na2SO3 into the solution can accelerate anodic dissolution of gold. The factors affecting selective dissolution of gold in the alkaline thiourea solution by electrolysis have been studied, and the optimum condition was obtained. In 0.1 mol/L thiourea solution of pH 12. 5 containing 0. 5 mol/L Na2SO3 and 2. 5% acetone, at the potential of 0. 34 V vs NHE, at the temperature of 323 K, the dissolved mass of gold anode with the exposed area of 1. 0 cm2 reached more than 300 mg·dm-3 within 30 min, and other metals such as silver, copper, nickel and iron could hardly dissolve.
基金The Nationa lBasic Research Program(973Plan)of China(2010CB735501)
文摘Aiming to the low-grade rhodium-containing waste materials, a new process was proposed to enrich and activate rhodium by smelting using iron oxide as a trapping agent and activator. A rhodium concentrate was obtained by the separation of base metals and precious metals. The concentrate was reacted with dilute aqua regia to obtain rhodium solution. The factors influencing the enrichment and activation effects were discussed in this paper. The results showed that the dissolution rate is greater than 99% under the optimum conditions. In this process, the activation of rhodium was finished in the enrichment process. The iron oxide is both a trapping agent and activator, which simplifies the process and reduce the cost.
基金Project(11272359)supported by the National Natural Science Foundation of China
文摘In order to simulate the instability phenomenon of a nonaqueous phase liquid(NAPL) dissolution front in a computational model, the intrinsic characteristic length is commonly used to determine the length scale at which the instability of the NAPL dissolution front can be initiated. This will require a huge number of finite elements if a whole NAPL dissolution system is simulated in the computational model. Even though modern supercomputers might be used to tackle this kind of NAPL dissolution problem, it can become prohibitive for commonly-used personal computers to do so. The main purpose of this work is to investigate whether or not the whole NAPL dissolution system of an annular domain can be replaced by a trapezoidal domain, so as to greatly reduce the requirements for computer efforts. The related simulation results have demonstrated that when the NAPL dissolution system under consideration is in a subcritical state, if the dissolution pattern around the entrance of an annulus domain is of interest, then a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system.However, if the dissolution pattern away from the vicinity of the entrance of an annulus domain is of interest, then a trapezoidal domain can be used to replace an annular domain in the computational simulation of the NAPL dissolution system. When the NAPL dissolution system under consideration is in a supercritical state, a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system.
基金Project(11272359)supported by the National Natural Science Foundation of China
文摘Homogeneity and heterogeneity are two totally different concepts in nature.At the particle length scale,rocks exhibit strong heterogeneity in their constituents and porosities.When the heterogeneity of porosity obeys the random uniform distribution,both the mean value and the variance of porosities in the heterogeneous porosity field can be used to reflect the overall heterogeneous characteristics of the porosity field.The main purpose of this work is to investigate the effects of porosity heterogeneity on chemical dissolution front instability in fluid-saturated rocks by the computational simulation method.The related computational simulation results have demonstrated that:1) since the propagation speed of a chemical dissolution front is inversely proportional to the difference between the final porosity and the mean value of porosities in the initial porosity field,an increase in the extent of the porosity heterogeneity can cause an increase in the mean value of porosities in the initial porosity field and an increase in the propagation speed of the chemical dissolution front.2) An increase in the variance of porosities in the initial porosity field can cause an increase in the instability probability of the chemical dissolution front in the fluid-saturated rock.3) The greater the mean value of porosities in the initial porosity field,the quicker the irregular morphology of the chemical dissolution front changes in the supercritical chemical dissolution systems.This means that the irregular morphology of a chemical dissolution front grows quicker in a porosity field of heterogeneity than it does in that of homogeneity when the chemical dissolution system is at a supercritical stage.
基金Project(11272359)supported by the National Natural Science Foundation of China
文摘Many scientific and engineering problems need to use numerical methods and algorithms to obtain computational simulation results because analytical solutions are seldom available for them.The chemical dissolution-front instability problem in fluid-saturated porous rocks is no exception.Since this kind of instability problem has both the conventional(i.e.trivial)and the unconventional(i.e.nontrivial)solutions,it is necessary to examine the effects of different numerical algorithms,which are used to solve chemical dissolution-front instability problems in fluid-saturated porous rocks.Toward this goal,two different numerical algorithms associated with the commonly-used finite element method are considered in this paper.In the first numerical algorithm,the porosity,pore-fluid pressure and acid/solute concentration are selected as basic variables,while in the second numerical algorithm,the porosity,velocity of pore-fluid flow and acid/solute concentration are selected as basic variables.The particular attention is paid to the effects of these two numerical algorithms on the computational simulation results of unstable chemical dissolution-front propagation in fluid-saturated porous rocks.The related computational simulation results have demonstrated that:1)the first numerical algorithm associated with the porosity-pressure-concentration approach can realistically simulate the evolution processes of unstable chemical dissolution-front propagation in chemical dissolution systems.2)The second numerical algorithm associated with the porosity-velocity-concentration approach fails to simulate the evolution processes of unstable chemical dissolution-front propagation.3)The extra differential operation is the main source to result in the failure of the second numerical algorithm.
基金Projects(51101104,51072121) supported by the National Natural Science Foundation of ChinaProject(LS2010109) supported by the Key Laboratory Foundation of Liaoning Province,China
文摘Determination of dissolution rate of alumina is one of the classical problems in aluminum electrolysis. A novel method which can measure the dissolution rate of alumina was presented. Effect of factors on dissolution rate of alumina was studied intuitively and roundly using transparent quartz electrobath and image analysis techniques. Images about dissolution process of alumina were taken at an interval of fixed time from transparent quartz electrobath of double rooms. Gabor wavelet transforms were used for extracting and describing the texture features of each image. After subsampling several times, the dissolution rate of alumina was computed using these texture features in local neighborhood of samples. Regression equation of the dissolution rate of alumina was obtained using these dissolution rates. Experiments show that the regression equation of the dissolution rate of alumina is y=-0.000 5x^3＋0.024 0x^2-0.287 3x＋ 1.276 7 for Na3AIF6-AIF3-Al2O3-CaF2-LiF- MgF2 system at 920 ℃.
基金Projects(51104041,51174054,51374065)supported by the National Natural Science Foundation of ChinaProject(N130402010)supported by the Fundamental Research Funds for the Central Universities of China
文摘The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 °C were systematically investigated.The dissolution property of high-ferrite gibbsitic bauxite is increased by increasing the dissolution temperature and the Na OH concentration or decreasing the particle size of bauxite,which is easy to dissolve under atmospheric pressure.The kinetic equations of gibbsitic bauxites with different ferrite contents during the dissolution process at different temperatures for different times were established,and the corresponding activation energies were calculated.The ferrite in the gibbsitic bauxite reduces the dissolution speed and increases the activation energy of dissolution,the diffusion process of which is the rate-controlling step.
基金Project(2010AA065201) supported by the High-Tech Research and Development Program of ChinaProject(2018zzts157) supported by the Fundamental Research Funds for the Central Universities,China
文摘In the feeding process of aluminum electrolytic, feeding quantity of alumina affects eventually dissolved quantity at the end of a feeding cycle. Based on the OpenFOAM platform, dissolution model coupled with heat and mass transfer was established. Applying the Rosin-Rammler function, alumina particle size distribution under different feeding quantities was obtained. The temperature response of electrolyte after feeding was included and calculated, and the dissolution processes of alumina with different feeding quantities (0.6, 0.8, 1.0, 1.2, 1.4, 1.6 kg) after feeding were simulated in 300 kA aluminum reduction cell. The results show that with the increase of feeding quantity, accumulated mass fraction of dissolved alumina decreases, and the time required for the rapid dissolution stage extends. When the feeding quantity is 0.6 kg and 1.2 kg, it takes the shortest time for the electrolyte temperature dropping before rebounding back. With the increase of feeding quantity, the dissolution rate in the rapid dissolution stage increases at first and then decreases gradually. The most suitable feeding quantity is 1.2 kg. The fitting equation of alumina dissolution curve under different feeding quantities is obtained, which can be used to evaluate the alumina dissolution and guide the feeding quantity and feeding cycle.
基金Projects(50872098, 51004080) supported by the National Natural Science Foundation of ChinaProject(B0903) supported by the Opening Fund of Research Center of Green Manufacturing and Energy-saving & Emission Reduction Technology of Wuhan University of Science and Technology, China
文摘The dissolution behavior of CaO-MgO-SiO2 glass fiber was investigated by scanning electron microscopy （SEM）, Fourier-transform infrared spectrometer （FTIR） and inductively coupled plasma atomic emission spectroscopy （ICP-AES） using in-vitro tests. The results show that the soaked fiber is surrounded by an outer calcium-magnesium silicate hydrated layer, and there exists a balancing fimction between the formation and abscission of the hydrated layer during the dissolution process. The concentrations of leached ions increase constantly, and the mass loss of the fibers and pH changes of the solution are found to rise rapidly during the initial dissolution process, then their increasing rates are controlled by the balancing function of the hydrated layer at the subsequent dissolution stages. The dissolution rate constant and time for complete dissolution are estimated to be 274 ng/（cm2.h） and 15.2 d, respectively, presenting preferable biosolubilities.
基金Projects(51934009,52074353)supported by the National Natural Science Foundation of ChinaProject(2019YFC1803600)supported by the National Key Research and Development Program of ChinaProject(2021JJ30855)supported by the Natural Science Foundation of Hunan Province,China。
文摘Acid mine drainage(AMD)has become a widespread environmental issue and its toxicity can cause permanent damage to the ecosystem.However,there are few studies focusing on the formation of AMD under moderately thermophilic conditions,hence we employed X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and 16S rRNA sequencing to study the dissolution of pyrite and bornite by a moderate thermophilic consortium,and explored the role of free and attached microorganisms in the formation of AMD.The consortium mainly comprised Acidithiobacillus caldus,Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans.The results indicated that total iron in pyrite solution system reached 33.45 g/L on the 12th day,and the copper dissolution rate of bornite dissolution reached 91.8%on the 24th day.SEM results indicated that the surfaces of pyrite and bornite were significantly corroded by microorganisms.XRD and XPS results showed that ore residues contained jarosite,and the dissolving residue of bornite contained elemental sulfur.The dominant bacterial genus in pyrite dissolution was A.caldus,and L.ferriphilum in bornite dissolution.To sum up,microbes significantly accelerated the mineral dissolution process and promoted the formation of AMD.
基金Supported by the National Natural Science Foundation of China (No. 41130746)
文摘In this paper, the dissolution characteristics of Xining dustfall in citric acid solution was studied to evaluate the physical chemical change in acid conditions. pH along with conductivity was tested with time. FTIR, SEM and ICP analysis were applied to analyze the residuum and filtrate after 2 days’ dissolution experiment. It was shown in the pH/conductivity variation, solution’s pH rise sharply in the front 4 hours, then decrease slowly. After 4 hours, both the pH and conductivity become stable. Based on combined analysis of XRD and FTIR spectrum of dustfall before and after dissolution, that calcite and dolomite in dustfall are dissolved completely in the 0.05M citric acid solution in two days. Besides, amount of metal cations were extracted from the dustfall during the dissolution, including Ca2+,K+,Mg2+,Fe3+,Al3+,Si. In general, after the dissolution of dustall in citric acid, some minerals are dissolved and amount of metal elements are extracted. Carbonate minerals almost dissolved completely, also the structure of silicate minerals changed as the extraction of elements.
文摘In order to study the control factors and mechanism of oolitic limestone reservoir being corroded by organic acid produced in burial stage,the reactions of acetic acid(pH=3) with oolitic limestone were investigated using the rotating-disk Corrosion Reactor System(CRS).The effects of disk rotational speed, temperature and system pressure were examined. Scanning Electron Microscope attached with Energy Dispersive X-Ray Analyzer(SEM-EDX) was
基金Project supported by National Natural Science Fundation of China (No. 41130746).
文摘This article describes the characteristics of natural dusts, artificial dusts and industrial dusts, such as mineral phases, chemical components, morphological observation and size. Quartz and calcite are the main phases of natural dusts and industrial dusts with high SiO2, CaO and low K2O, Na2O on the chemical composition. Natural dusts are mainly irregular shaped and some particle aggregation made of small dusts on the surface of large dust. Industrial dusts are globular and blob-like, but artificial dusts are columnar and fibrous. The fine particles are mainly in the range of 0.3-5 μm,of which the dusts of less than 5 μm are over 99%.The dissolution and electrochemical action of dusts in glutamic acid liquor at the simulated human body temperature (37 ℃) in 32 hours were investigated. The changes of pH values and electric conductivity of those dusts were similar, increased slowly in first 8 hours, and then the pH values increased rapidly. The total amount of dissolved ions of K, Ca, Na, Mg was 35.4-429 mg/L, particularly Ca was maximal of 20-334 mg/L. The total amount of dissolved ions of Fe, Zn, Mn, Pb, Ba was 0.18-5.59 ppm and the Al, Si was 3.0-21.7 mg/L. Each element dissolved rapidly relatively in first 16 hours. The relative solubility order of dusts in glutamic acid are: wollastonite > serpentine > sepiolite, the cement plant industrial dusts > power plant industrial dusts, and natural dusts have similar solubility. The wollastonite and power plant industrial dusts have highest solubility, which have high content of CaO; this shows there are a poorer corrosion-resisting ability and lower bio-resistibility. Sepiolite and cement plant industrial dusts have lowest solubility, which have high content of SiO2; this shows there are a higher corrosion-resisting ability and stronger bio-resistibility.
文摘The dissolution kinetics of calcined ulexite in ammonium chloride solutions at high solid-to-liquid ratios were investigated. In the experiments, calcination temperature, solution concentration, reaction temperature, and pre-hydration were chosen as parameters. It was observed that the dissolution rate increased with increasing calcination temperature, solution concentration, and reaction temperature, whereas it was not affected by pre-hydration. Employing graphical and statistic methods, the dissolution rate, based on homogeneous reaction model, can be given as: (1-X(B2O3))-1-1= k(c(NH4Cl))1.982t. The activation energy for the dissolution of the ulexite sample calcined at 160 ℃ was found to be 84.04 kJ·mol-1.
文摘Gold dissolves easily in an alkaline thiourea solution with Na2SO3 and Na2S2O8, where the accompanied elements of Au, such as Ag, Cu, Ni and Fe can hardly dissolve. It was considered that electrochemical reduction and catalytic action of SO32- prevent thiourea from decomposing irreversibly and accelerates dissolution of gold.The S2O82- as an oxidant can control the potential so that formamidine disulfide may form efficiently. The dissolution of gold is mainly through oxidation of Au by formamidine disulfide and complexation of thiourea with An+,and not direct oxidation of S2O82-. Thus,sufficient formamidine disulfide is necessary to accelerate the dissolution of gold. The reason for Ag, Cu hardly being dissoluble is that the black layers of Ag2S and Cu1.92S form on the surface of Ag and Cu. The metal Ni and Fe do not dissolve in the alkaline media due to their sulfide films passivation samely.
基金Project(51474169)supported by the National Natural Science Foundation of ChinaProject(18JS061)supported by the Key Laboratory Research Project of Education Department in Shaanxi Province,China。
文摘The gold dissolution in anoxic cyanide solution in the presence of chalcopyrite was studied with a rotating disc electrode.It was found that the presence of chalcopyrite reduced and enhanced the dissolution activity of pure gold in the low and high potential regions,respectively.The dissolution of gold was diffusion-controlled at low potentials(≤177 mV)and low cyanide concentrations(≤980 mg/L);however,above the cyanide concentration of 980 mg/L,the current density of gold decreased and the dissolution of gold changed from diffusion-control to electrochemical reaction-control.At high potentials(>177 mV),gold dissolution was always controlled by diffusion.In cyanide solution containing chalcopyrite,appropriate increase of pH value and temperature could accelerate the dissolution of gold,but high pH value would promote the generation of passivation,which was harmful for the dissolution of gold in cyanide solution.
基金Projects(511340071) supported by the National Natural Science Foundation of China
文摘The dissolution mechanism of hemimorphite in NH3-（NH4）2SO4-H2O system at 298.15 K was investigated by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS） analysis. The results show that hemimorphite is soluble in NH3-（NH4）2SO4-H2O system and its residue exists in the form of an amorphous SiO2 layer on the hemimorphite surface. The XPS data also indicate that the Si 2p3/2 and O ls spectra of the hemimorphite are broadened and shift to higher binding energies and their binding energies are closer to silica with an increase of total ammonia and time. Solubility of hemimorphite in NH3-（NH4）2SO4-H2O system was measured by means of isothermal solution method at 298.15 K based on the study of the dissolution mechanism of hemimorphite. The results show that the solubility of zinc in solution increases firstly and then decreases with the increase of cr（NH3） （total ammonia concentration） at different NH3/NH4^＋ ratios. The solubility of silicon in solution decreases from 0.0334 mol/kg in ct（NH3）-4.1245 mol/kg NH3-（NH4）2SO4-H2O solution to 0.0046 mol/kg in cT（NH3）=7.6035 mol/kg NH3-（NH4）2SO4-H2O solution.
基金Foundation ttem Project C. B. 10.00. GL. 03 at Idaho National LaboratoryAcknowledgements This work is supported by the laboratory directed research and development （LDRD） project C. B. 10.00. GL. 03 at Idaho National Laboratory （INL）, which is operated by the Battelle Energy Alliance for the U. S. Department of Energy.
文摘INTRODUCTION Dissolution and precipitation of carbonates plays an important role in nature, such as in the chemistry of seawater, the sedimentation of carbonate at the seafloor, the geochemical evolution of freshwater aquifers and last but not least, most spectacular, the evolution of karst landscapes. To provide a deeper understanding to all these processes knowledge is required
