The reaction between carbonic acid and montmorillonite minerals was studied in order to provide a theoretical basis for analyzing changes in the physical properties of coal seams after CO_(2)injection and for optimizi...The reaction between carbonic acid and montmorillonite minerals was studied in order to provide a theoretical basis for analyzing changes in the physical properties of coal seams after CO_(2)injection and for optimizing CO_(2) pumping parameters.A single montmorillonite mineral of purity[90%was selected and subjected to reactions at 25,35,and 45℃in carbonic acid solutions of varying acidity.The Si and Al concentrations in the solutions and the structure and elemental compositions of the montmorillonite before and after the reactions were analyzed using a spectrophotometer,an X-ray diffractometer,and an energy-dispersive X-ray spectrometer;kinetic reaction models were established for the dissolution of Si and Al in carbonic acid solutions in order to estimate the apparent activation energy of Si dissolution under different acidity conditions.The results indicate that Al dissolved rapidly and soon reached solubility equilibrium.On the other hand,Si concentration in the solutions increased rapidly and then gradually declined with vibrations,with maximum values at 25,35,and 45℃,which were observed at approximately 96,72,and 48 h,respectively.In addition,Si dissolution fitted the diffusion-controlled reaction model well;as the pH value decreased,the apparent activation energy of Si dissolution decreased,and Si became easier to dissolve.Furthermore,it was concluded that as a weak acid,carbonic acid causes little damage to the mineral structure of montmorillonite.展开更多
Hydrogen-enriched ironmaking presents a promising approach to mitigate coke consumption and carbon emission in blast furnace(BF)operations.This work investigated the relationship between the structural features of cok...Hydrogen-enriched ironmaking presents a promising approach to mitigate coke consumption and carbon emission in blast furnace(BF)operations.This work investigated the relationship between the structural features of cokes and their reactivity towards solution loss(SL),especially under hydrogen-enriched atmospheres.Six cokes were characterized,and their SL behaviors were examined under varying atmospheres to elucidate the effects of hydrogen enrichment.The results indicate that an increase in fixed carbon content leads to a decrease in the coke reactivity index(CRI)and an increase in coke strength after reaction(CSR),in the CO_(2) atmosphere,the CSR of coke increases from 35.76%−62.83%,while in the 90CO_(2)/10H_(2) atmosphere,the CSR of coke increases from 65.67%−84.09%.There is a good linear relationship between CRI and microcrystalline structure parameters of coke.Cokes with larger crystalline size,lower amorphous content,and smaller optical texture index(OTI)values show enhanced resistance to degradation and maintain structural integrity in BF.Kinetic analysis performed with the shifted-modified-random pore model(S-MRPM)reveals that alterations in pore structure and intrinsic mineral composition significantly influence the reaction rate.The introduction of a small amount of water vapor raises SL rates,whereas a minor addition of hydrogen(<10%)decelerates SL due to its incomplete conversion to water vapor and the reduced partial pressure of the gasifying agent.Thermodynamic calculations also indicate that the introduced hydrogen does not convert into the same fraction of water vapor.The shift from chemical reaction control to gas diffusion control as the rate-determining step with rising temperatures during SL process was confirmed,and the introduction of hydrogen does not notably alter SL behavior.This result demonstrated that introducing a small amount of hydrogen(<10%)can mitigate SL rates,thereby enhancing coke strength and reducing coke consumption and carbon emissions.展开更多
To understand the mechanism of fluoride removal from the simulated zinc sulfate solution by the La(III)-modified zeolite,the adsorbent was characterized by XRD,SEM and EDS.The effects of absorbent dose and contact tim...To understand the mechanism of fluoride removal from the simulated zinc sulfate solution by the La(III)-modified zeolite,the adsorbent was characterized by XRD,SEM and EDS.The effects of absorbent dose and contact time,the adsorption isotherms and the sorption kinetics were investigated.The experimental results were compatible with the Langmuir isotherm model.The theoretical maximum adsorption capacities are 20.83 and 23.04 mg/g at 303 and 313 K,respectively.And the physisorption is revealed using the Temkin isotherm model and the D-R isotherm model.The sorption process is more suitable by the pseudo-second-order kinetic models.Thermodynamic parameters such as standard free energy change(ΔGΘ<0 kJ/mol),standard enthalpy change(ΔHΘ=8.28 kJ/mol)and standard entropy change(ΔSΘ=0.030 kJ/(mol?K))indicate the spontaneity of adsorption and endothermic physical sorption.Furthermore,the fluoride concentration in the industrial zinc sulfate solution decreases from 98.05 to 44.09 mg/L with the adsorbent dosage of 15 g/L.展开更多
The formation kinetics and mechanism of tricalcium aluminate hydrate and calcium oxalate in dilute sodium aluminate solution and sodium oxalate solution were studied respectively based on the lime causticization, and ...The formation kinetics and mechanism of tricalcium aluminate hydrate and calcium oxalate in dilute sodium aluminate solution and sodium oxalate solution were studied respectively based on the lime causticization, and the optimal conditions for removing the oxalate in dilute sodium aluminate solution as well as the mechanism were finally obtained.The formation processes of tricalcium aluminate hydrate and calcium oxalate are mainly controlled by the chemical reaction and the inner diffusion respectively,and the corresponding reaction rate equations as well as the apparent activation energy were calculated. The hydrocalumite with a spatially interleaved structure will form in dilute sodium aluminate solution with sodium oxalate, greatly removing the oxalate impurity by absorption. Calcium oxalate can be converted to tricalcium aluminate hydrate with the increasing reaction time. The oxalate causticization efficiency and the alumina loss rate can be over 90% and below 31% respectively when reacted at 50℃ with a stirring rate of 200 r/min.展开更多
In order to carry out decolorization, sludge protein solution, a dark brown close to black solution from activated sludge, was subjected to ^(60)Co γ-ray irradiation in the presence of hydrogen peroxide. UV/Vis spect...In order to carry out decolorization, sludge protein solution, a dark brown close to black solution from activated sludge, was subjected to ^(60)Co γ-ray irradiation in the presence of hydrogen peroxide. UV/Vis spectrophotometric method was used to investigate the effect of H2O2 on the coloration apparent kinetics and rate constants of sludge protein solution under γ-ray irradiation. In addition, the effects of irradiation dose, initial sludge protein solution concentration, and pH value on the decolorization efficiency of sludge protein solution were studied. Results showed that the decolorization apparent kinetics of sludge protein solution was a first-order reaction. The solution decolorization percentage increased with the increase of irradiation dose or the decrease of initial sludge protein solution concentration. The examination results of pH value showed that the sludge protein solution could be more efficiently decolorized in alkaline media than in acid media. Moreover, sensory evaluation and foamability analysis indicated that irradiated samples under H2O2 oxidation showed better sensory score and foamability.展开更多
Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was de...Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was deve- loped. The simulation results indicate that the rate of apparent crystal growth during seeded precipitation exhibits a manifest dependence on the crystal size. In general, there is an obvious increase in the apparent crystal growth rate with the augment in crystal size. The apparent activation energy increases with the increase of characteristic crystal size, which indicates that the growth of small crystals is controlled by surface chemical reaction; it is gradually controlled by both the surface reaction and diffusion with the augment in crystal size.展开更多
A new device was designed,which can effectively avoid the undesired nucleation and agglomeration of fine particles on the experimental results during the sead ed precipitation of sodium aluminate solution,and moreover...A new device was designed,which can effectively avoid the undesired nucleation and agglomeration of fine particles on the experimental results during the sead ed precipitation of sodium aluminate solution,and moreover,the experimental co nditions are nearly kept constant during the experiment. With the new device,it is proven that a good result can be obtained on the kinetics study of the cryst al growth in seeded precipitation of sodium aluminate solution.Experiments were carried out with the concentration of Na2O （Nk）170 g/L,the mole ratio of Na2O to Al2O3 （αk） all between 1.52 to 2.01,at 65,70,75 ℃,respectively. And the kinetics equation of crystal growth of gibbsite was deduc ed.展开更多
The leaching kinetics of copper from low-grade copper ore was investigated in ammonia-ammonium sulfate solution with sodium persulfate. The effect parameters of stirring speed, temperature, particle size, concentratio...The leaching kinetics of copper from low-grade copper ore was investigated in ammonia-ammonium sulfate solution with sodium persulfate. The effect parameters of stirring speed, temperature, particle size, concentrations of ammonia, ammonium sulfate and sodium persulfate were determined. The results show that the leaching rate is nearly independent of agitation above 300 r/min and increases with the increase of temperature, concentrations of ammonia, ammonium sulfate and sodium persulfate. The EDS analysis and phase quantitative analysis of the residues indicate that bornite can be dissolved by persulfate oxidization. The leaching kinetics with activation energy of 22.91 kJ/mol was analyzed by using a new shrinking core model （SCM） in which both the interfacial transfer and diffusion across the product layer affect the leaching rate. A semi-empirical rate equation was obtained to describe the leaching process and the empirical reaction orders with respect to the concentrations of ammonia, ammonium sulfate and sodium persulfate are 0.5, 1.2 and 0.5, respectively.展开更多
The dissolving processes,thermochemical properties and thermokinetic parameters of manganese carbohydrazide styph-nate([Mn2(CHZ)2(TNR)2(H2O)4]),nickel carbohydrazide styphnate([Ni(CHZ),(TNR)],)and lead carbohydrazide ...The dissolving processes,thermochemical properties and thermokinetic parameters of manganese carbohydrazide styph-nate([Mn2(CHZ)2(TNR)2(H2O)4]),nickel carbohydrazide styphnate([Ni(CHZ),(TNR)],)and lead carbohydrazide styphnate([Pb_(2)(CHZ)_(2)(TNR)_(2)(H_(2)O)_(2)])in N,N-dimethylformamide(DMF)at 298,15 K were studied by a SETARAM C80 calorime-ter.The results show that the dissolving process of them in DMF are exothermic,however the exothermic peaks are different.The results are associated with the different molecular structure and polarity of solutes.The empirical formulas for the enthalpies of dis-solution(△mH),the relative apparent molar enthalpies(ΦL;),the relative partial molar enthalpies(L,),and the enthalpies of di-lution(△aHt.:)are respectively deduced by polynomial fitting of experimental data.The standard enthalpies of dissolution(Aai H)are calculated respectively as-17.75kJ·mol^(-1),-29.76kJ·mol^(-1)and-15.35 kJ·mol^(-1).The rate constant of dissolution reaction(k),and the reaction order(n)are obtained from the kinetic formulas.展开更多
In order to control the grain size during hot forming,grain growth behavior of a pre-extruded Mg-6Zn magnesium alloy and its correlation with solute and second phase distribution were investigated.Isothermal annealing...In order to control the grain size during hot forming,grain growth behavior of a pre-extruded Mg-6Zn magnesium alloy and its correlation with solute and second phase distribution were investigated.Isothermal annealing was conducted on a Gleeble-1500 thermo-mechanical simulator.The mean grain size Dg of each annealed specimen was measured by the quantitative metallography technique.The grain growth kinetics of the Mg-6Zn alloy annealed at 473-623 K was obtained as Dg^4- Dg0^4=2.25 ×10^11 exp（-95450）by the least square linear regression method.The deviation of grain growth exponent n = 4 from the theoretical value of 2 may be attributed to the presence of solute zinc and second phases which will retard the boundary migration.Microscopic observations show that the non-uniform distribution of grain size for samples pre-extruded or annealed at low temperatures is closely related to the non-uniform distribution of fine and dispersed second phases but not to the non-uniform distribution of solute zinc.This indicates that second phase pinning effect plays an important role in microstructure refinement.展开更多
Morphology and growth rate of carbon dioxide hydrate on the interface between liquid carbon dioxide and humic acid solutions were studied in this work.It was found that after the growth of the hydrate film at the inte...Morphology and growth rate of carbon dioxide hydrate on the interface between liquid carbon dioxide and humic acid solutions were studied in this work.It was found that after the growth of the hydrate film at the interface,further growth of hydrate due to the suction of water in the capillary system formed between the wall of the cuvette and the end boundary of the hydrate layer occurs.Most probably,substantial effects on the formation of this capillary system may be caused by variations in reactor wall properties,for example,hydrophobic-hydrophilic balance,roughness,etc.We found,that the rate of CO_(2) hydrate film growth on the surface of the humic acid aqueous solution is 4-fold to lower in comparison with the growth rate on the surface of pure water.We suppose that this is caused by the adsorption of humic acid associates on the surface of hydrate particles and,as a consequence,by the deceleration of the diffusion of dissolved carbon dioxide to the growing hydrate particle.展开更多
The leaching kinetics of low-grade copper ore with high-alkality gangues was studied in ammonia-ammonium sulphate solution.The main parameters,such as ammonia and ammonium sulphate concentrations,particle size,solid-t...The leaching kinetics of low-grade copper ore with high-alkality gangues was studied in ammonia-ammonium sulphate solution.The main parameters,such as ammonia and ammonium sulphate concentrations,particle size,solid-to-liquid ratio and reaction temperature,were chosen in the experiments.The results show that the increase of temperature,concentrations of ammonia and ammonium sulphate is propitious to the leaching rate of copper ore.The leaching rate increases with the decrease of particle size and solid-to-liquid ratio.The leaching rate is controlled by the diffusion through the ash layer and the activation energy is determined to be 25.54 kJ/mol.A semi-empirical equation was proposed to describe the leaching kinetics.展开更多
The effects of temperature (1650-2250°C), time (20-180 min), particle size of WC (1-13 μm) and that of TiO2 (1-7 μm) on the formation process of solid solution Ti0.5W0.5C have been investigated by X-ray diffrac...The effects of temperature (1650-2250°C), time (20-180 min), particle size of WC (1-13 μm) and that of TiO2 (1-7 μm) on the formation process of solid solution Ti0.5W0.5C have been investigated by X-ray diffraction, optical microscopy, SEM and EPMA methods. It is found that the formation of (Ti, W)C is controlled by diffusion process between WC and disequilibrium (Ti, W)C. According to Jander and Arrhenius equation, the apparent activation energy was calculated to be 318-380 kJ/mol (for T<1850°C) and 100-117 kJ/mol (for T≥1850°C). The diffusion model for different temperature interval was proposed. An X-ray diffraction calculating index H was also developed to examine the micro-inhomogeneity of (Ti, W)C. The H value variation agrees well with the experimental results.展开更多
The corundum(α-alumina) core has been considered as a suitable candidate for investment casting of hollow, high pressure turbine engine airfoils due to its excellent properties. However, the efficiency of removing al...The corundum(α-alumina) core has been considered as a suitable candidate for investment casting of hollow, high pressure turbine engine airfoils due to its excellent properties. However, the efficiency of removing alumina cores in concentrated caustic solution cannot meet the needs of industrial production. In this paper, the effects of temperature and initial solution concentration on dissolution of α-alumina were studied by the classical weight-loss method. The fractal kinetic model was developed in order to describe α-alumina dissolution, assuming that the nonporous particles shrank during reaction process. The results show that the dissolution rate increases with increasing reaction temperature and initial solution concentration. Especially, the initial solution concentration has a significant influence on α-alumina dissolution rate at a higher reaction temperature. The activation energies decrease with increasing initial solution concentration, and the chemical reaction is the rate-controlling step.展开更多
The solution diffusion coefficient is a great important intrinsical parameter in crystal growth.On earth,it is impossible to accurately determine the diffusion coefficient since there is nature convection.One of the m...The solution diffusion coefficient is a great important intrinsical parameter in crystal growth.On earth,it is impossible to accurately determine the diffusion coefficient since there is nature convection.One of the marked charateristics of space-crystal growth is to eleminate nature convection,so that purely diffusion-controlled condition of crystal growth could be realized and precise measurement of the diffusion coefficient should be approved.展开更多
Alpha radiolysis of nitric acid aqueous solution by a ^(238)Pu source is investigated experimentally and theoretically.The time dependence of the nitrous acid yield on dose rate,nitric acid concentration,and nitrate i...Alpha radiolysis of nitric acid aqueous solution by a ^(238)Pu source is investigated experimentally and theoretically.The time dependence of the nitrous acid yield on dose rate,nitric acid concentration,and nitrate ion concentration is studied.A novel kinetic model for the α-radiolysis of nitric acid aqueous solution is established,by considering the direct and indirect effects.The simulation results agree well with the experimental data,indicating the validity of our model to treat the reaction paths for generation and consumption of nitrous acid.It is shown that the redox reactions involving Pu cannot be neglected in theα-radiolysis of the solution.The results provide a better understanding of the α-ray radiolysis of aqueous nitric acid.展开更多
The adsorption behavior of ion exchange resin D301 in the extraction of hexavalent molybdenum from high acidic leach solution was investigated. SEM, EDS and Raman spectra analyses were applied to studying the adsorpti...The adsorption behavior of ion exchange resin D301 in the extraction of hexavalent molybdenum from high acidic leach solution was investigated. SEM, EDS and Raman spectra analyses were applied to studying the adsorption capacity, reaction kinetics and possible adsorption mechanism in detail. Results showed that the adsorption capacity of D301 resin for molybdenum from high acidic leach solution was up to 463.63 mg/g. Results of the kinetic analysis indicated that the adsorption process was controlled by the particle diffusion with the activation energy 25.47 k J/mol（0.9-1.2 mm） and 20.38 k J/mol（0.6-0.9 mm）. Furthermore, the molybdenum loaded on the resin could be eluted by using 2 mol/L ammonia hydroxide solution. Besides, dynamic continuous column experiments verified direct extraction of molybdenum from acidic leach solutions by ion exchange resin D301 and the upstream flow improved dynamic continuous absorption.展开更多
The precipitation performance and kinetics of gibbsite from sodium aluminate solution with different sodium oxalate concentrations as well as the corresponding influence mechanism of oxalate during the seed precipitat...The precipitation performance and kinetics of gibbsite from sodium aluminate solution with different sodium oxalate concentrations as well as the corresponding influence mechanism of oxalate during the seed precipitation process were systematically investigated by physicochemical properties test,using SEM and Raman spectra.As the concentration of sodium oxalate increases,both the precipitation rate and particle size of gibbsite decrease.The presence of sodium oxalate not only increases the viscosity of sodium aluminate solution,but also promotes the transformation of Al(OH)4^? to Al2O(OH)6^2?.The overall reaction rate constant decreases and the apparent activation energy of gibbsite increases with the increasing sodium oxalate concentration,the rate controlling step of which is chemical reaction.The needle-like sodium oxalate precipitates on the gibbsite crystals and covers the active Al(OH)3 seed sites,which leads to the lower precipitation rate and the finer particle size of gibbsite during the seed precipitation process.展开更多
In the present study,we selected solutes to be added to the Cr Co Ni medium-entropy alloy(MEA)based on the mismatch of self-diffusion activation energy(SDQ)between the alloying elements and constituent elements of the...In the present study,we selected solutes to be added to the Cr Co Ni medium-entropy alloy(MEA)based on the mismatch of self-diffusion activation energy(SDQ)between the alloying elements and constituent elements of the matrix,and then investigated their grain growth behavior and mechanical properties.Mo and Al were selected as the solutes for investigation primarily because they have higher and lower SDQ,respectively,than those of the matrix elements;a secondary factor was their higher and lower shear modulus.Their concentrations were fixed at 3 at.%each because previous work had shown these compositions to be single-phase solid solutions with the face-centered cubic structure.Three alloys were produced by arc melting,casting,homogenizing,cold rolling and annealing at various temperatures and times to produce samples with different grain sizes.They were(a)the base alloy Cr Co Ni,(b)the base alloy plus 3 at.%Mo,and(c)the base alloy plus 3 at.%Al.The activation energies for grain growth of the Cr Co Ni,Cr Co Ni-3Mo and CrCo Ni-3Al MEAs were found to be^251,~368 and^219 k J/mol,respectively,consistent with the notion that elements with higher SDQ(in this study Mo)retard grain growth(likely by a solute-drag effect),whereas those with lower values(Al)accelerate grain growth.The roomtemperature tensile properties show that Mo increases the yield strength by^40%but Al addition has a smaller strengthening effect consistent with their relative shear moduli.The yield strength as a function of grain size for the three single-phase MEAs follows the classical Hall-Petch relationship with much higher slopes(>600 MPaμm-0.5)than traditional solid solutions.This work shows that the grain growth kinetics and solid solution strengthening of the Cr Co Ni MEA can be tuned by selecting solute elements that have appropriate diffusion and physical properties.展开更多
The transfer kinetics of phenol between aqueous phase and N,N di(methyl heptyl) acetaminde (N503) in kerosene has been studied using Lewis cell technique. The effects of the factors including the concentrations of p...The transfer kinetics of phenol between aqueous phase and N,N di(methyl heptyl) acetaminde (N503) in kerosene has been studied using Lewis cell technique. The effects of the factors including the concentrations of phenol in aqueous phase and organic phase, the concentration of N503 in organic phase, the acidity of aqueous phase, the stirring speed and the temperature on the rates of forward and backward extraction of phenol have been examined. The regularity of extraction rate has been obtained. According to experimental results, the rates of both forward and backward extraction of phenol might be controlled by diffusion process. The diffusion step of phenol from aqueous phase to interface for forward extraction and from interface to aqueous phase for backward extraction might be the rate controlling steps.展开更多
基金This research was supported by the National Science and Technology Special Foundation for Major Large Oil and Gas Fields and Coal Bed Methane Development(2011ZX05042-003)the Provincial Ministry of State Key Laboratory Breeding Base of Open Projects Henan Gas Geology and Gas Control Laboratory(WS2013B06).
文摘The reaction between carbonic acid and montmorillonite minerals was studied in order to provide a theoretical basis for analyzing changes in the physical properties of coal seams after CO_(2)injection and for optimizing CO_(2) pumping parameters.A single montmorillonite mineral of purity[90%was selected and subjected to reactions at 25,35,and 45℃in carbonic acid solutions of varying acidity.The Si and Al concentrations in the solutions and the structure and elemental compositions of the montmorillonite before and after the reactions were analyzed using a spectrophotometer,an X-ray diffractometer,and an energy-dispersive X-ray spectrometer;kinetic reaction models were established for the dissolution of Si and Al in carbonic acid solutions in order to estimate the apparent activation energy of Si dissolution under different acidity conditions.The results indicate that Al dissolved rapidly and soon reached solubility equilibrium.On the other hand,Si concentration in the solutions increased rapidly and then gradually declined with vibrations,with maximum values at 25,35,and 45℃,which were observed at approximately 96,72,and 48 h,respectively.In addition,Si dissolution fitted the diffusion-controlled reaction model well;as the pH value decreased,the apparent activation energy of Si dissolution decreased,and Si became easier to dissolve.Furthermore,it was concluded that as a weak acid,carbonic acid causes little damage to the mineral structure of montmorillonite.
基金supported by National Natural Science Foundation of China(22178002,22178001)Natural Science Foundation of Anhui Province(2308085Y19)Excellent Youth Research Project of Anhui Provincial Department of Education(2022AH030045).
文摘Hydrogen-enriched ironmaking presents a promising approach to mitigate coke consumption and carbon emission in blast furnace(BF)operations.This work investigated the relationship between the structural features of cokes and their reactivity towards solution loss(SL),especially under hydrogen-enriched atmospheres.Six cokes were characterized,and their SL behaviors were examined under varying atmospheres to elucidate the effects of hydrogen enrichment.The results indicate that an increase in fixed carbon content leads to a decrease in the coke reactivity index(CRI)and an increase in coke strength after reaction(CSR),in the CO_(2) atmosphere,the CSR of coke increases from 35.76%−62.83%,while in the 90CO_(2)/10H_(2) atmosphere,the CSR of coke increases from 65.67%−84.09%.There is a good linear relationship between CRI and microcrystalline structure parameters of coke.Cokes with larger crystalline size,lower amorphous content,and smaller optical texture index(OTI)values show enhanced resistance to degradation and maintain structural integrity in BF.Kinetic analysis performed with the shifted-modified-random pore model(S-MRPM)reveals that alterations in pore structure and intrinsic mineral composition significantly influence the reaction rate.The introduction of a small amount of water vapor raises SL rates,whereas a minor addition of hydrogen(<10%)decelerates SL due to its incomplete conversion to water vapor and the reduced partial pressure of the gasifying agent.Thermodynamic calculations also indicate that the introduced hydrogen does not convert into the same fraction of water vapor.The shift from chemical reaction control to gas diffusion control as the rate-determining step with rising temperatures during SL process was confirmed,and the introduction of hydrogen does not notably alter SL behavior.This result demonstrated that introducing a small amount of hydrogen(<10%)can mitigate SL rates,thereby enhancing coke strength and reducing coke consumption and carbon emissions.
基金Projects(51474238,51674301)supported by the National Natural Science Foundation of China
文摘To understand the mechanism of fluoride removal from the simulated zinc sulfate solution by the La(III)-modified zeolite,the adsorbent was characterized by XRD,SEM and EDS.The effects of absorbent dose and contact time,the adsorption isotherms and the sorption kinetics were investigated.The experimental results were compatible with the Langmuir isotherm model.The theoretical maximum adsorption capacities are 20.83 and 23.04 mg/g at 303 and 313 K,respectively.And the physisorption is revealed using the Temkin isotherm model and the D-R isotherm model.The sorption process is more suitable by the pseudo-second-order kinetic models.Thermodynamic parameters such as standard free energy change(ΔGΘ<0 kJ/mol),standard enthalpy change(ΔHΘ=8.28 kJ/mol)and standard entropy change(ΔSΘ=0.030 kJ/(mol?K))indicate the spontaneity of adsorption and endothermic physical sorption.Furthermore,the fluoride concentration in the industrial zinc sulfate solution decreases from 98.05 to 44.09 mg/L with the adsorbent dosage of 15 g/L.
基金Project(2018YFC1901903)supported by the National Key R&D Program of ChinaProjects(51774079,51674075)supported by the National Natural Science Foundation of ChinaProject(N182508026)supported by the Fundamental Research Funds for the Central Universities,China
文摘The formation kinetics and mechanism of tricalcium aluminate hydrate and calcium oxalate in dilute sodium aluminate solution and sodium oxalate solution were studied respectively based on the lime causticization, and the optimal conditions for removing the oxalate in dilute sodium aluminate solution as well as the mechanism were finally obtained.The formation processes of tricalcium aluminate hydrate and calcium oxalate are mainly controlled by the chemical reaction and the inner diffusion respectively,and the corresponding reaction rate equations as well as the apparent activation energy were calculated. The hydrocalumite with a spatially interleaved structure will form in dilute sodium aluminate solution with sodium oxalate, greatly removing the oxalate impurity by absorption. Calcium oxalate can be converted to tricalcium aluminate hydrate with the increasing reaction time. The oxalate causticization efficiency and the alumina loss rate can be over 90% and below 31% respectively when reacted at 50℃ with a stirring rate of 200 r/min.
基金Supported by Foundation of Universities Double-Five Science and Technology Program of Tianjin(No.W20080003)
文摘In order to carry out decolorization, sludge protein solution, a dark brown close to black solution from activated sludge, was subjected to ^(60)Co γ-ray irradiation in the presence of hydrogen peroxide. UV/Vis spectrophotometric method was used to investigate the effect of H2O2 on the coloration apparent kinetics and rate constants of sludge protein solution under γ-ray irradiation. In addition, the effects of irradiation dose, initial sludge protein solution concentration, and pH value on the decolorization efficiency of sludge protein solution were studied. Results showed that the decolorization apparent kinetics of sludge protein solution was a first-order reaction. The solution decolorization percentage increased with the increase of irradiation dose or the decrease of initial sludge protein solution concentration. The examination results of pH value showed that the sludge protein solution could be more efficiently decolorized in alkaline media than in acid media. Moreover, sensory evaluation and foamability analysis indicated that irradiated samples under H2O2 oxidation showed better sensory score and foamability.
文摘Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was deve- loped. The simulation results indicate that the rate of apparent crystal growth during seeded precipitation exhibits a manifest dependence on the crystal size. In general, there is an obvious increase in the apparent crystal growth rate with the augment in crystal size. The apparent activation energy increases with the increase of characteristic crystal size, which indicates that the growth of small crystals is controlled by surface chemical reaction; it is gradually controlled by both the surface reaction and diffusion with the augment in crystal size.
文摘A new device was designed,which can effectively avoid the undesired nucleation and agglomeration of fine particles on the experimental results during the sead ed precipitation of sodium aluminate solution,and moreover,the experimental co nditions are nearly kept constant during the experiment. With the new device,it is proven that a good result can be obtained on the kinetics study of the cryst al growth in seeded precipitation of sodium aluminate solution.Experiments were carried out with the concentration of Na2O （Nk）170 g/L,the mole ratio of Na2O to Al2O3 （αk） all between 1.52 to 2.01,at 65,70,75 ℃,respectively. And the kinetics equation of crystal growth of gibbsite was deduc ed.
基金Project(2007CB613601)supported by the National Basic Research Program of ChinaProject(10C1095)supported by the Foundation of Hunan Educational Committee,China
文摘The leaching kinetics of copper from low-grade copper ore was investigated in ammonia-ammonium sulfate solution with sodium persulfate. The effect parameters of stirring speed, temperature, particle size, concentrations of ammonia, ammonium sulfate and sodium persulfate were determined. The results show that the leaching rate is nearly independent of agitation above 300 r/min and increases with the increase of temperature, concentrations of ammonia, ammonium sulfate and sodium persulfate. The EDS analysis and phase quantitative analysis of the residues indicate that bornite can be dissolved by persulfate oxidization. The leaching kinetics with activation energy of 22.91 kJ/mol was analyzed by using a new shrinking core model （SCM） in which both the interfacial transfer and diffusion across the product layer affect the leaching rate. A semi-empirical rate equation was obtained to describe the leaching process and the empirical reaction orders with respect to the concentrations of ammonia, ammonium sulfate and sodium persulfate are 0.5, 1.2 and 0.5, respectively.
基金Technology fund on Applied Physical Chemistry Laboratory(9140C3703051105 and 9140C370303120C37142)State Key Laboratory of Explosion Science and Technology(QNKT12-02)
文摘The dissolving processes,thermochemical properties and thermokinetic parameters of manganese carbohydrazide styph-nate([Mn2(CHZ)2(TNR)2(H2O)4]),nickel carbohydrazide styphnate([Ni(CHZ),(TNR)],)and lead carbohydrazide styphnate([Pb_(2)(CHZ)_(2)(TNR)_(2)(H_(2)O)_(2)])in N,N-dimethylformamide(DMF)at 298,15 K were studied by a SETARAM C80 calorime-ter.The results show that the dissolving process of them in DMF are exothermic,however the exothermic peaks are different.The results are associated with the different molecular structure and polarity of solutes.The empirical formulas for the enthalpies of dis-solution(△mH),the relative apparent molar enthalpies(ΦL;),the relative partial molar enthalpies(L,),and the enthalpies of di-lution(△aHt.:)are respectively deduced by polynomial fitting of experimental data.The standard enthalpies of dissolution(Aai H)are calculated respectively as-17.75kJ·mol^(-1),-29.76kJ·mol^(-1)and-15.35 kJ·mol^(-1).The rate constant of dissolution reaction(k),and the reaction order(n)are obtained from the kinetic formulas.
基金the financial support from the National Natural Science Foundation of China(Grant No.51105328)the Natural Science Foundation of Jiangsu Province of China(No.BK20130447)the Colleges and Universities in Jiangsu Province Natural Science Foundation of China(Grant No.13KJB430026)
文摘In order to control the grain size during hot forming,grain growth behavior of a pre-extruded Mg-6Zn magnesium alloy and its correlation with solute and second phase distribution were investigated.Isothermal annealing was conducted on a Gleeble-1500 thermo-mechanical simulator.The mean grain size Dg of each annealed specimen was measured by the quantitative metallography technique.The grain growth kinetics of the Mg-6Zn alloy annealed at 473-623 K was obtained as Dg^4- Dg0^4=2.25 ×10^11 exp（-95450）by the least square linear regression method.The deviation of grain growth exponent n = 4 from the theoretical value of 2 may be attributed to the presence of solute zinc and second phases which will retard the boundary migration.Microscopic observations show that the non-uniform distribution of grain size for samples pre-extruded or annealed at low temperatures is closely related to the non-uniform distribution of fine and dispersed second phases but not to the non-uniform distribution of solute zinc.This indicates that second phase pinning effect plays an important role in microstructure refinement.
基金supported by the Russian Science Foundation(23-29-00830).
文摘Morphology and growth rate of carbon dioxide hydrate on the interface between liquid carbon dioxide and humic acid solutions were studied in this work.It was found that after the growth of the hydrate film at the interface,further growth of hydrate due to the suction of water in the capillary system formed between the wall of the cuvette and the end boundary of the hydrate layer occurs.Most probably,substantial effects on the formation of this capillary system may be caused by variations in reactor wall properties,for example,hydrophobic-hydrophilic balance,roughness,etc.We found,that the rate of CO_(2) hydrate film growth on the surface of the humic acid aqueous solution is 4-fold to lower in comparison with the growth rate on the surface of pure water.We suppose that this is caused by the adsorption of humic acid associates on the surface of hydrate particles and,as a consequence,by the deceleration of the diffusion of dissolved carbon dioxide to the growing hydrate particle.
基金Project(2007CB613601) supported by the National Basic Research Program of ChinaProject(10C1095) supported by the Foundation of Hunan Educational Committee,China
文摘The leaching kinetics of low-grade copper ore with high-alkality gangues was studied in ammonia-ammonium sulphate solution.The main parameters,such as ammonia and ammonium sulphate concentrations,particle size,solid-to-liquid ratio and reaction temperature,were chosen in the experiments.The results show that the increase of temperature,concentrations of ammonia and ammonium sulphate is propitious to the leaching rate of copper ore.The leaching rate increases with the decrease of particle size and solid-to-liquid ratio.The leaching rate is controlled by the diffusion through the ash layer and the activation energy is determined to be 25.54 kJ/mol.A semi-empirical equation was proposed to describe the leaching kinetics.
文摘The effects of temperature (1650-2250°C), time (20-180 min), particle size of WC (1-13 μm) and that of TiO2 (1-7 μm) on the formation process of solid solution Ti0.5W0.5C have been investigated by X-ray diffraction, optical microscopy, SEM and EPMA methods. It is found that the formation of (Ti, W)C is controlled by diffusion process between WC and disequilibrium (Ti, W)C. According to Jander and Arrhenius equation, the apparent activation energy was calculated to be 318-380 kJ/mol (for T<1850°C) and 100-117 kJ/mol (for T≥1850°C). The diffusion model for different temperature interval was proposed. An X-ray diffraction calculating index H was also developed to examine the micro-inhomogeneity of (Ti, W)C. The H value variation agrees well with the experimental results.
基金financially supported by Special Project for High-end CNC Machine Tools and Basic Manufacturing Equipment of China(2012ZX04007-021)Liaoning Excellent Talents in University,China(LR2014004)
文摘The corundum(α-alumina) core has been considered as a suitable candidate for investment casting of hollow, high pressure turbine engine airfoils due to its excellent properties. However, the efficiency of removing alumina cores in concentrated caustic solution cannot meet the needs of industrial production. In this paper, the effects of temperature and initial solution concentration on dissolution of α-alumina were studied by the classical weight-loss method. The fractal kinetic model was developed in order to describe α-alumina dissolution, assuming that the nonporous particles shrank during reaction process. The results show that the dissolution rate increases with increasing reaction temperature and initial solution concentration. Especially, the initial solution concentration has a significant influence on α-alumina dissolution rate at a higher reaction temperature. The activation energies decrease with increasing initial solution concentration, and the chemical reaction is the rate-controlling step.
文摘The solution diffusion coefficient is a great important intrinsical parameter in crystal growth.On earth,it is impossible to accurately determine the diffusion coefficient since there is nature convection.One of the marked charateristics of space-crystal growth is to eleminate nature convection,so that purely diffusion-controlled condition of crystal growth could be realized and precise measurement of the diffusion coefficient should be approved.
基金partly supported by the National Natural Science Foundation of China(No.21377122)
文摘Alpha radiolysis of nitric acid aqueous solution by a ^(238)Pu source is investigated experimentally and theoretically.The time dependence of the nitrous acid yield on dose rate,nitric acid concentration,and nitrate ion concentration is studied.A novel kinetic model for the α-radiolysis of nitric acid aqueous solution is established,by considering the direct and indirect effects.The simulation results agree well with the experimental data,indicating the validity of our model to treat the reaction paths for generation and consumption of nitrous acid.It is shown that the redox reactions involving Pu cannot be neglected in theα-radiolysis of the solution.The results provide a better understanding of the α-ray radiolysis of aqueous nitric acid.
基金Projects(21376251,21406233) supported by the National Natural Science Foundation of China
文摘The adsorption behavior of ion exchange resin D301 in the extraction of hexavalent molybdenum from high acidic leach solution was investigated. SEM, EDS and Raman spectra analyses were applied to studying the adsorption capacity, reaction kinetics and possible adsorption mechanism in detail. Results showed that the adsorption capacity of D301 resin for molybdenum from high acidic leach solution was up to 463.63 mg/g. Results of the kinetic analysis indicated that the adsorption process was controlled by the particle diffusion with the activation energy 25.47 k J/mol（0.9-1.2 mm） and 20.38 k J/mol（0.6-0.9 mm）. Furthermore, the molybdenum loaded on the resin could be eluted by using 2 mol/L ammonia hydroxide solution. Besides, dynamic continuous column experiments verified direct extraction of molybdenum from acidic leach solutions by ion exchange resin D301 and the upstream flow improved dynamic continuous absorption.
基金Projects(51774079,51674075)supported by the National Natural Science Foundation of ChinaProject(N182508026)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The precipitation performance and kinetics of gibbsite from sodium aluminate solution with different sodium oxalate concentrations as well as the corresponding influence mechanism of oxalate during the seed precipitation process were systematically investigated by physicochemical properties test,using SEM and Raman spectra.As the concentration of sodium oxalate increases,both the precipitation rate and particle size of gibbsite decrease.The presence of sodium oxalate not only increases the viscosity of sodium aluminate solution,but also promotes the transformation of Al(OH)4^? to Al2O(OH)6^2?.The overall reaction rate constant decreases and the apparent activation energy of gibbsite increases with the increasing sodium oxalate concentration,the rate controlling step of which is chemical reaction.The needle-like sodium oxalate precipitates on the gibbsite crystals and covers the active Al(OH)3 seed sites,which leads to the lower precipitation rate and the finer particle size of gibbsite during the seed precipitation process.
基金the U.S.Department of Energy,Office of Science,Basic Energy Sciences,Materials Sciences and Engineering Division,E.P.Georgethe National Nature Science Foundation of China(No.51971099)+3 种基金the open fund of State Key Laboratory for Advanced Metals and Materials(No.2018-ZD03),X.W.Liuthe National Nature Science Foundation of China(No.51975425),L.C.Zengthe open fund of State Key Laboratory of Materials Processing and Die&Mould Technology(P2019-005),H.Duthe Research and Development Program of Jiangxi Academy of Sciences(No.2020-YZD-23),Q.Hu。
文摘In the present study,we selected solutes to be added to the Cr Co Ni medium-entropy alloy(MEA)based on the mismatch of self-diffusion activation energy(SDQ)between the alloying elements and constituent elements of the matrix,and then investigated their grain growth behavior and mechanical properties.Mo and Al were selected as the solutes for investigation primarily because they have higher and lower SDQ,respectively,than those of the matrix elements;a secondary factor was their higher and lower shear modulus.Their concentrations were fixed at 3 at.%each because previous work had shown these compositions to be single-phase solid solutions with the face-centered cubic structure.Three alloys were produced by arc melting,casting,homogenizing,cold rolling and annealing at various temperatures and times to produce samples with different grain sizes.They were(a)the base alloy Cr Co Ni,(b)the base alloy plus 3 at.%Mo,and(c)the base alloy plus 3 at.%Al.The activation energies for grain growth of the Cr Co Ni,Cr Co Ni-3Mo and CrCo Ni-3Al MEAs were found to be^251,~368 and^219 k J/mol,respectively,consistent with the notion that elements with higher SDQ(in this study Mo)retard grain growth(likely by a solute-drag effect),whereas those with lower values(Al)accelerate grain growth.The roomtemperature tensile properties show that Mo increases the yield strength by^40%but Al addition has a smaller strengthening effect consistent with their relative shear moduli.The yield strength as a function of grain size for the three single-phase MEAs follows the classical Hall-Petch relationship with much higher slopes(>600 MPaμm-0.5)than traditional solid solutions.This work shows that the grain growth kinetics and solid solution strengthening of the Cr Co Ni MEA can be tuned by selecting solute elements that have appropriate diffusion and physical properties.
文摘The transfer kinetics of phenol between aqueous phase and N,N di(methyl heptyl) acetaminde (N503) in kerosene has been studied using Lewis cell technique. The effects of the factors including the concentrations of phenol in aqueous phase and organic phase, the concentration of N503 in organic phase, the acidity of aqueous phase, the stirring speed and the temperature on the rates of forward and backward extraction of phenol have been examined. The regularity of extraction rate has been obtained. According to experimental results, the rates of both forward and backward extraction of phenol might be controlled by diffusion process. The diffusion step of phenol from aqueous phase to interface for forward extraction and from interface to aqueous phase for backward extraction might be the rate controlling steps.
