To achieve selective leaching of ion adsorption rare earth,it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements.In this study,we investigated the adsorp...To achieve selective leaching of ion adsorption rare earth,it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements.In this study,we investigated the adsorption processes of Dy and Al on the surface of K–homoionic kaolinite using batch experiments and sequential chemical extractions.The results revealed that the adsorption of Dy and Al,as well as the desorption of K,followed the Langmuir model.The maximum ion-exchangeable capacity of Dy was higher(9.39 mmol.kg^(-1))than that of Al(6.30 mmol.kg^(-1)).The ion exchange stoichiometry ratios of Dy–K and Al–K derived from the Langmuir model were2.0 and 2.6.The analysis of X-ray absorption fine structure(XAFS)and density functional theory(DFT)revealed that Dy and Al were adsorbed onto kaolinite as outer-sphere hydrated complexes via hydrogen bonds.Dy was adsorbed as[Dy(H_(2)O)_(10)]^(3+),and Al was adsorbed as[Al(OH)_(2)(H_(2)O)_(4)]^(+).In particular,the adsorption of Al resulted in protonation of the hydroxyl groups on the surface of the kaolinite.Based on the above insights,the higher ion exchange stoichiometry ratios are attributed to closer adsorption distances(6.04 A for Dy and 3.69 A for Al)and lower adsorption energies(-223.72 kJ.mol^(-1)for Dy and-268.33 kJ.mol^(-1)for Al).The maximum ionexchangeable capacity is related to the change of the surface electrical properties of kaolinite.The zeta potential was increased to-7.3 mV as the protonation resulted from aluminum adsorption,while Dy adsorption had a minor effect,maintaining a value of-17.5 m V.展开更多
In real soil environments,humus,colloids and other components significantly affect pollutant migration behavior.Investigating Tl(I)and kaolinite colloids’cotransport in quartz sand media containing sodium humate(HA-N...In real soil environments,humus,colloids and other components significantly affect pollutant migration behavior.Investigating Tl(I)and kaolinite colloids’cotransport in quartz sand media containing sodium humate(HA-Na)is vital for comprehending Tl(I)migration underground.This study examined the migration of Tl(I)and kaolinite colloids across varying pH levels(5,7),ionic strengths(ISs)(1,5,50 mmol/L),and kaolinite colloid concentra-tions.Results indicate that lower IS and pH promote Tl(I)migration when transported alone.In cotransport system,kaolinite promotes Tl(I)migration under acidic conditions but inhibits it under neutral conditions,except at high kaolinite concentrations,where the effect shifts from inhibition to promotion.This is primarily due to changes in the zeta potential of quartz sand,HA-Na,and kaolinite,as well as Tl(I)adsorption after HA-Na and kaolinite occupy binding sites.Competitive adsorption between cations and Tl(I)also plays a significant role.Conversely,in individual system,higher IS and pH inhibit kaolinite migration,while increased kaolinite concentration promotes it.In cotransport system,Tl(I)promotes kaolinite migration under acidic conditions but inhibits it under neutral conditions,except at low kaolinite concentrations.This relates to changes in the zeta potential between kaolinite and the medium,as well as the retention of HA-Na in the column and its adsorption onto kaolinite.Competitive adsorption and binding site saturation also have an impact.This study enhances understanding of Tl(I)migration by revealing the dual effect of kaolinite colloids under different environmental conditions,contributing to better knowledge of Tl(I)fate and transport in natural environments.展开更多
Cement production,while essential for global infrastructure,contributes significantly to carbon dioxide emissions,accounting for approximately 7%of total emissions.To mitigate these environmental impacts,flash calcina...Cement production,while essential for global infrastructure,contributes significantly to carbon dioxide emissions,accounting for approximately 7%of total emissions.To mitigate these environmental impacts,flash calcination of kaolinitic clays has been investigated as a sustainable alternative.This technique involves the rapid heating of clays,enabling their use as supplementary cementitious materials.The primary objective of this study was to modify the color of calcined clay in various atmospheres(oxidizing,inert,and reducing)to achieve a grayish tone similar to commercial cement while preserving its reactive properties.The experimental procedure employed a tubular reactor with precise control of gas flows(atmospheric air,nitrogen,and a carbon monoxide–nitrogen mixture).Physicochemical characterization of the raw clay was conducted before calcination,with analyses repeated on the calcined clays following experimentation.Results indicated that clay calcined in an oxidizing atmosphere acquired a reddish hue,attributed to the oxidation of iron in hematite.The Clay exhibited a pinkish tone in an inert atmosphere,while calcination in a reducing atmosphere yielded the desired grayish color.Regarding pozzolanic activity,clays calcined in oxidizing and inert atmospheres displayed robust strength,ranging from 82%to 87%.Calcination in a reducing atmosphere resulted in slightly lower strength,around 74%,likely due to the clay’s chemical composition and the calcination process,which affects compound formation and material reactivity.展开更多
Clay minerals can experience strong tensile and compressive forces in extreme environments such as the deep sea and subsurface.Moreover,the presence of water films greatly affects the mechanical properties of clay.To ...Clay minerals can experience strong tensile and compressive forces in extreme environments such as the deep sea and subsurface.Moreover,the presence of water films greatly affects the mechanical properties of clay.To explore these properties,we use a molecular dynamics(MD)simulation method to study axial mechanical behavior and failure mechanisms of hydrated kaolinite.Two types of deformation are applied to kaolinite examples with varying water film thicknesses:stretching along the transverse(x)direction,and compression along the longitudinal(z)direction.The ultimate strengths of hydrated kaolinite with different water film thicknesses range from 8.12%to 27.53%(for stretching along the x-direction)and from 15.71%to 26.02%(for compression along the z-direction)less than those of dehydrated kaolinite.Additionally,we find that hydrated kaolinite is more prone to tensile than compressive failure under high stress.When stretched along the x-direction,the diffusion of water molecules results in unstable tensile properties.When compressed along the z-direction,water films weaken the compressive strength of the system and lead to greater compressive deformation,but also delay the time at which the system fails.Furthermore,we investigated the failure mechanisms of hydrated kaolinite through analysis of interaction energies.The tensile failure along the x-direction is caused by the breaking of the covalent bonds in the clay mineral sheet.On the other hand,the compressive failure along the z-direction is due to the crushing of the internal structure of the clay mineral sheet.展开更多
The flotation and adsorption behaviors of dodecyltrimethylammonium chloride（DTAC） and cetyltrimethylammonium chloride（CTAC） on diaspore and kaolinite were studied.Solution depletion methods were used to determine ...The flotation and adsorption behaviors of dodecyltrimethylammonium chloride（DTAC） and cetyltrimethylammonium chloride（CTAC） on diaspore and kaolinite were studied.Solution depletion methods were used to determine adsorption isotherms.Fluorescence probe test along with Zeta potential measurement was also conducted for further investigation into the adsorption of quaternary amines at the mineral-water interface.The results show that the flotation recovery of kaolinite decreases with an increase in pH when DTAC and CTAC are used as collectors,while diaspore is on the contrary.As the carbon chain length of the collectors increases,the flotation recoveries of minerals increase.However,the increment rate of kaolinite is significantly lower than that of diaspore.In the low surfactant concentration range,the cationic surfactants adsorb readily on diaspore surfaces just due to electrostatic interactions.As for kaolinite surfaces,ion exchange process also exists.With a further increase in surfactant concentration,the adsorption was ascribed to the hydrophobic association of chain-chain interactions.Micro-polarity of mineral surfaces study shows that CTAC has a better hydrophobic characteristic than DTAC.Larger aggregates are formed with CTAC on diaspore than on kaolinite in the same solution concentration.The results also indicate that the chain length of cationic surfactants has a greater influence on the adsorption of diaspore than on kaolinite,which is consistent with the flotation result.展开更多
The collecting power of tertiary amines（DRN,DEN and DPN） on kaolinite follows the order of DENDPNDRN.After reacting with DRN,DEN and DPN,the surface potentials of kaolinite increase remarkably,and the recruitments c...The collecting power of tertiary amines（DRN,DEN and DPN） on kaolinite follows the order of DENDPNDRN.After reacting with DRN,DEN and DPN,the surface potentials of kaolinite increase remarkably,and the recruitments caused by collectors also follow the order of DENDPNDRN.The results of dynamics simulation show that the geometries of substituent groups bonding to N are deflected and twisted,and some of bond angles are changed when tertiary amines cations adsorb on kaolinite（001） surface.Based on the results of dynamics simulations and quantum chemistry calculations,the electrostatic forces between three tertiary amines cations and 4×4×3（001） plane of kaolinite are 1.38×10？7 N（DRN12H＋）,1.44×10-6 N（DEN12H＋）,1.383×10-6 N（DPN12H＋）,respectively.展开更多
Titanium dioxide/ kaolinite nanocomposite was prepared by the sol-gel method, with layered kaolinite as a substrate and Ti （ OC4H9 ）4 as a precursor. The effects of hydrolysis, drying and calcination on the producti...Titanium dioxide/ kaolinite nanocomposite was prepared by the sol-gel method, with layered kaolinite as a substrate and Ti （ OC4H9 ）4 as a precursor. The effects of hydrolysis, drying and calcination on the production of nanometric titanium dioxide were discussed. The optimal conditions for preparation were＂ bbtained through experiments. The 1- 10 nrn thick monolayer anatase nano TiO2 crystal was produced under the conditions as follows： hydrolyzed at 37-42 ℃ for 4 h, dried at 70-80 ℃ for 1 h, and calcined at 550-650℃ for 3 h. The rate of degradation of 40 mg/ L azo dye and 20 mg/ L acid red dye can reuch 96% and 81.45%, respectively.展开更多
This report examined electrochemical remediation of copper contaminated kaolinite by controlling electrolytes′ pH for both of anolyte and catholyte simultaneously. Results showed that electrokinetic process and remed...This report examined electrochemical remediation of copper contaminated kaolinite by controlling electrolytes′ pH for both of anolyte and catholyte simultaneously. Results showed that electrokinetic process and remediation efficiency varied obviously when different buffer systems, including citric acid (test 1), nitric acid + EDTA (test 2) and nitric acid (test 3), were used to control catholyte pH and Na_2CO_3 was used at the same time to control all anolyte one. It was found that under such pH condition soil′s pH in soil column kept at 3.0—7.0 successfully, and correspondingly no copper precipitation and decrease of soil electroconductivity appeared, which are usually observed in electrokinetic process due to OH - introduction into soil column by electrochemical reaction occurred in cathode. Electroosmosis flow rates were almost equal for these three tests, indicating that these buffers did not affect Zeta-potential of kaolinite within the examined duration. More acid and basic solution was added into electrokinetic cell when nitric acid was used as buffer than when nitric acid + EDTA and then citric acid were used. Due to introduction of large amounts of ions into soil column, significant higher current was observed for test 3 than other two. Analysis of copper speciation and total quantity in kaolinite indicated that 22.5%, 23.74% and 55.65% Cu were removed from kaolinite for test 1, test 2 and test 3 respectively after only 10 days′ electrokinetic remediation.展开更多
This paper reports the systematic investigation on the flocculation,sedimentation and consolidation characteristics of kaolinite using guar gum as a green flocculant.In-situ flocculation behavior of kaolinite at vario...This paper reports the systematic investigation on the flocculation,sedimentation and consolidation characteristics of kaolinite using guar gum as a green flocculant.In-situ flocculation behavior of kaolinite at various pH,guar gum dosages,and ionic strength were studied using a light scattering technique.The effect of these parameters on the settling rate,solid consolidation,and supernatant liquid clarity was recorded.The morphology of kaolinite and flocculated kaolinite aggregates were analyzed using FESEM.The morphology studies suggest that it is poorly crystalline with multiple steps on edge,broken edge;laminar with high aspect ratio and have rough basal surface.The complex irregularity on the basal surface and the presence of multiple steps in the edges,broken edges(hydroxyl groups)have facilitated the guar gum adsorption.The isoelectric point of kaolinite is pH 3.96.The pH,ionic strength and flocculant dosage have a significant effect on the kaolinite settling rate.The guar gum has exhibited excellent turbidity removal efficiency at pH 5.The turbidity removal is inefficient at pH 10.However,guar gum has shown high turbidity removal with 80%transmission at pH 10 in the presence of a KNO3 electrolyte.展开更多
Porous ceramics were prepared from kaolinite gangue and Al（OH）3 with double addition of MgCO3 and CaCO3 by the pore-forming in-situ technique.The characterizations of porous ceramics were investigated by X-ray diffr...Porous ceramics were prepared from kaolinite gangue and Al（OH）3 with double addition of MgCO3 and CaCO3 by the pore-forming in-situ technique.The characterizations of porous ceramics were investigated by X-ray diffractometry,scanning electron microscopy,and mercury porosimetry measurements,etc.It is found that although the decomposition of MgCO3 and CaCO3 has little contribution to the porosity,the double addition of MgCO3 and CaCO3 strongly affects the formation of liquid phase,and then changes the phase compositions,pore characterization,and strength.The appropriate mode is the sample containing 1.17wt% MgCO3 and 1.17wt% CaCO3,which has high apparent porosity（41.0%）,high crushing strength（53.5 MPa）,high mullite content（76wt%）,and small average pore size（3.24 μm）.展开更多
The composite catalytic materials based on the mineral kaolinite are considered to be a potential approach for solving global energy scarcity and environmental pollution,which have excellent catalytic performance,low ...The composite catalytic materials based on the mineral kaolinite are considered to be a potential approach for solving global energy scarcity and environmental pollution,which have excellent catalytic performance,low cost and excellent chemical stability.However,pure kaolinite does not have visible light absorption ability and cannot be used as a potential photocatalytic material.Fortunately,the unique physical and chemical properties of kaolinite can be acted as a good semiconductor carrier.Herein,this paper firstly presents the mineralogical characteristics of kaolinite.Next,kaolinite-based photocatalysts(such as TiO_(2)/kaolinite,g-C_(3)N_(4)/kaolinite,g-C_(3)N_(4)/TiO_(2)/kaolinite,Zn O)are discussed in detail from the formation of heterostructures,synthesis-modification methods,photocatalytic mechanisms,and electron transfer pathways.Furthermore,the specific role of kaolinite in photocatalytic materials is summarized and discussed.In addition,the photocatalytic applications of kaolinite-based photocatalysts in the fields of water decomposition,pollutant degradation,bacterial disinfection are reviewed.However,the modification of kaolinite is hard,the manufacture of a large number of kaolinite-based photocatalysts is difficult,the cost of doping noble metals is expensive,and the utilization rate of visible light is low,which limits its application in industrial practice.Finally,this paper presents some perspectives on the future development of kaolinite-based photocatalysts.展开更多
Experiments were conducted to study the influences of synthetic bayerite, non crystalline aluminum oxide (N AlOH), goethite, non crystalline iron oxide (N FeOH) and kaolinite on the adsorption, activity, kinetics ...Experiments were conducted to study the influences of synthetic bayerite, non crystalline aluminum oxide (N AlOH), goethite, non crystalline iron oxide (N FeOH) and kaolinite on the adsorption, activity, kinetics and thermal stability of invertase. Adsorption of invertase on iron, aluminum oxides fitted Langmuir equation. The amount of invertase held on the minerals followed the sequence kaolinite > goethite > N AlOH > bayerite > N FeOH. No correlation was found between enzyme adsorption and the specific surface area of minerals examined. The differences in the surface structure of minerals and the arrangement of enzymatic molecules on mineral surfaces led to the different capacities of minerals for enzyme adsorption. The adsorption of invertase on bayerite, N AlOH, goethite, N FeOH and kaolinite was differently affected by pH. The order for the activity of invertase adsorbed on minerals was N FeOH > N AlOH > bayerite > reak goethite > kaolinite. The inhibition effect of minerals on enzyme activity was kaolinite > crystalline oxides > non crystalline oxides. The pH optimum of iron oxide and aluminum oxide invertase complexes was similar to that of free enzyme (pH 4.0), whereas the pH optimum of kaolinite inv ertase complex was one pH unit higher than that of free enzyme. The affinity to substrate and the maximum reaction velocity as well as the thermal stability of combined invertase were lower than those of the free enzyme.展开更多
A new chemical pre-desilication process of kaolinite in diasporic bauxite in alkali solution at atmospheric pressure was proposed.The dissolution kinetics and mechanism were studied by chemical analysis,XRD and SEM.Th...A new chemical pre-desilication process of kaolinite in diasporic bauxite in alkali solution at atmospheric pressure was proposed.The dissolution kinetics and mechanism were studied by chemical analysis,XRD and SEM.The kinetic results of dissolution process show that the kaolinite is symbiotic with diaspore but without cladding.The dissolution ratio of kaolinite is close to 100%at 100℃for 90 min.The dissolution kinetic equation is 1-(1-α)^1/3=7.88×10^6 exp[-64434/(RT)]t.With the low L/S(L/S=10:1),the dissolution ratio of kaolinite decreases to 55%.This is due to the formation of lamellar hydroxyl-sodalite(OH-SOD)which is deposited on the surface of kaolinite and hinders the further dissolution of kaolinite.Under the optimum conditions,the A/S(mass ratio of Al2 O3 to SiO2)of dissolved residues is increased to 8.55,while the A/S of the bauxite is only 4.97.展开更多
How to sustainably produce bauxite by effective reverse froth flotation of kaolinite at low temperature is an urgent problem to be solved in the field of mineral processing.In this work,a novel amino-based Gemini surf...How to sustainably produce bauxite by effective reverse froth flotation of kaolinite at low temperature is an urgent problem to be solved in the field of mineral processing.In this work,a novel amino-based Gemini surfactant butadiyl-1,4-bis(dimethyl dodecylammonium bromide)(BBDB) was prepared and first utilized as a novel collector for kaolinite flotation.Its flotation performance for kaolinite was compared with that of the common monomolecular surfactant 1-dodecylamine(DDA) by micro-flotation tests.The tests results indicated that 95% kaolinite recovery was obtained using 2.0×10^(-4) mol/L BBDB at 25℃ which was half of the dosage when DDA obtained the maximum kaolinite recovery of81%.At extremely low temperature(0℃),3.0×10^(-4) mol/L BBDB could still collect 91% kaolinite,while DDA showed a frustrating ability.The contact angle tests indicated that BBDB could still significantly improve the hydrophobicity of the kaolinite surface(contact angle 71.7°) than DDA(contact angle only25.8°) at 0℃.The Krafft point comparison tests indicated that BBDB had a much lower Krafft point(below0℃) than DDA.Fourier transform infrared spectroscopy(FTIR)-spectrum analysis and zeta potential measurements showed that BBDB was physically adsorbed on the surface of kaolinite through electrostatic interaction.展开更多
For better understanding the adsorption of rare earth elements (REEs) by clay minerals and its controlling factors, the experiments on adsorption of REEs in solutions with 1 g·L-1 kaolinite were performed at diff...For better understanding the adsorption of rare earth elements (REEs) by clay minerals and its controlling factors, the experiments on adsorption of REEs in solutions with 1 g·L-1 kaolinite were performed at different conditions. The results are as follows: the REEs reach equilibrium in the adsorption-desorption process for 24; Langmuir′s adsorption curve is used for modeling the adsorption of REEs by kaolinite; a general trend is that the higher the contents of REEs are, the less obvious the fractionation is. Furthermore, there is significant effect of pH on the adsorption and fractionation of REEs by kaolinite, and the REEs distribution coefficient increases with increasing pH. When pH is nearly neutral, as reaches 7, heavy REEs are more adsorbed than light REEs.展开更多
The decomposition kinetics of Algerian Tamazarte kaolinite(TK)was investigated using thermogravimetric analysis(TG).Differential thermal analysis(DTA)and TG experiments were carried out between room temperature and140...The decomposition kinetics of Algerian Tamazarte kaolinite(TK)was investigated using thermogravimetric analysis(TG).Differential thermal analysis(DTA)and TG experiments were carried out between room temperature and1400°C,at differentheating rates from10to40°C/min.The activation energies,measured by DTG from isothermal treatments usingJohnson-Mehl-Avrami(JMA)and Ligero methods and by non-isothermal treatments using Ozawa,Boswell and Kissinger methods,were around151and144kJ/mol,respectively.The Avrami parameter of growth morphology(indicating the crystallization mode)was found to be around1.57using non-isothermal treatments;however,when using isothermal treatments it is found to be equal to1.35.The numerical factor,which depends on the dimensionality of crystal growth,is found to be1.53using Matusita equation.Thefrequency factor calculated by the isothermal treatment is equal to1.55×107s-1.The results show that the bulk nucleation is followedby three-dimensional growth of metakaolinite with polyhedron-like morphology controlled by diffusion from a constant number ofnuclei.展开更多
The surface properties of kaolinite were determined using density functional theory discrete variational method （DFT-DVM） and Gaussian 03 program. A SiO4 tetrahedral hexagonal ring with two A1 octahedra was chosen t...The surface properties of kaolinite were determined using density functional theory discrete variational method （DFT-DVM） and Gaussian 03 program. A SiO4 tetrahedral hexagonal ring with two A1 octahedra was chosen to model the kaolinite crystal. The total density of states of the kaolinite cluster are located near the Fermi level at both sides of the Fermi level. Both the highest occupied molecular orbit （HOMO） and the lowest unoccupied molecular orbit （LUMO） of kaolinite indicate that kaolinite system can not only readily interact with electron-acceptor species, but also readily interact with electron-donor species on the edge surface and the gibbsite layer surface, and thus, shows amphoteric behavior. Substitution of Al3^＋ for Si4＋ in the tetrahedral site linking the vacant Al3^＋ octahedra does not increase the surface chemical reactivity of kaolinite, while substitution of Al3^＋ for Si^4＋ in the tetrahedral site with the apex O linking Al3^＋ octahedra increase the surface chemical reactivity of the siloxane surface of kaolinite, especially acting as electron donors. Additionally, substitution of Al3^＋. for Si^4＋ in the tetrahedral site results in the re-balance of charges, leading to the increase of negative charge of the coordinated O atoms of the AlO4 tetrahedra, and therefore favoring the formation of ionic bonds between cations and the surface O atoms in the basal plane.展开更多
Understanding the interaction of CH4 with kaolinite is significant for researchers in the fields of coalbed CH4 and shale gas.The diffusion behaviors of CH4 in kaolinite with water contents ranging from 0 to 5 wt% hav...Understanding the interaction of CH4 with kaolinite is significant for researchers in the fields of coalbed CH4 and shale gas.The diffusion behaviors of CH4 in kaolinite with water contents ranging from 0 to 5 wt% have been analyzed by molecular dynamics simulations.The results of the simulations indicate that CH4 molecules can jump between adjacent holes in the kaolinite matrix.CH4 diffusion coefficient was very low (3.28 × 10-9 m2/s) and increased linearly with the increasing of water content.As the water content decreased,the value of radial distribution function first peak between CH4 and oxygen was larger,meaning that with lower water content,the interaction energy between CH4 and oxygen in kaolinite is stronger.The interaction between CH4 and water is linearly positively correlated with water content,in contrast,the interaction energy between kaolinite and water as well as between kaolinite and CH4 decreased linearly with increasing water content.On the other hand,the diffusion of CH4 molecules adsorbed on the surfaces also can be accelerated by the fast diffusion of water molecules in the middle micropore of the kaolinite.展开更多
The flotation of diaspore and kaolinite by one of a series of tertiary amines（DRN,DEN,DPN and DBN） was investigated.The tertiary amines show better floating recovery for kaolinite compared to diaspore.The maximum re...The flotation of diaspore and kaolinite by one of a series of tertiary amines（DRN,DEN,DPN and DBN） was investigated.The tertiary amines show better floating recovery for kaolinite compared to diaspore.The maximum recovery D-value is 45%over a pH range from 3 to 8.FT-IR spectra confirm the presence of hydroxyl groups on the surface of kaolinite and diaspore.Zeta potential measurements show that the mineral surfaces are negatively charged over a wide pH range.Ionization of hydroxyl groups mainly accounts for the surface charging mechanism.The adsorption of tertiary amines onto the mineral surface is due mainly to electrostatic effects and the difference in electrostatic effect between a collector and the two minerals can explain the flotation separation.Inductive electronic and steric effects from the substituent groups result in different collecting powers for the four tertiary amines.展开更多
Tertiary amine was synthesized from fatty amine and formaldehyde. And then the synthesized tertiary amine was used to react with benzyl chloride to synthesize hexadecyl dimethyl benzyl ammonium chloride (1627) at ambi...Tertiary amine was synthesized from fatty amine and formaldehyde. And then the synthesized tertiary amine was used to react with benzyl chloride to synthesize hexadecyl dimethyl benzyl ammonium chloride (1627) at ambient pressure. Using the synthesized 1627 as collector,the flotation properties of diaspore and kaolinite were investigated by single mineral and mixed mineral test. The flotation mechanism of diaspore,kaolinite and 1627 was discussed based on FTIR spectra. The results show that the mass ratio of aluminum to silicate achieves 15.02 and the recovery of alumina in concentrate is 43.07% using 1627 as a collector. The 1627 is found to be a more effective and a promising collector for reverse flotation to remove aluminum-silicate minerals from bauxite.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2021YFC2902203)the Key Research and Development Program of Guangxi Province(No.Guike-AB22080056)+2 种基金Beijing Nova Program(No.20230484379)the Science and Technology Innovation Fund of GRINM(No.2022PD0102)the Central Government Guides Local Science and Technology Development Fund Project(No.246Z4005G)。
文摘To achieve selective leaching of ion adsorption rare earth,it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements.In this study,we investigated the adsorption processes of Dy and Al on the surface of K–homoionic kaolinite using batch experiments and sequential chemical extractions.The results revealed that the adsorption of Dy and Al,as well as the desorption of K,followed the Langmuir model.The maximum ion-exchangeable capacity of Dy was higher(9.39 mmol.kg^(-1))than that of Al(6.30 mmol.kg^(-1)).The ion exchange stoichiometry ratios of Dy–K and Al–K derived from the Langmuir model were2.0 and 2.6.The analysis of X-ray absorption fine structure(XAFS)and density functional theory(DFT)revealed that Dy and Al were adsorbed onto kaolinite as outer-sphere hydrated complexes via hydrogen bonds.Dy was adsorbed as[Dy(H_(2)O)_(10)]^(3+),and Al was adsorbed as[Al(OH)_(2)(H_(2)O)_(4)]^(+).In particular,the adsorption of Al resulted in protonation of the hydroxyl groups on the surface of the kaolinite.Based on the above insights,the higher ion exchange stoichiometry ratios are attributed to closer adsorption distances(6.04 A for Dy and 3.69 A for Al)and lower adsorption energies(-223.72 kJ.mol^(-1)for Dy and-268.33 kJ.mol^(-1)for Al).The maximum ionexchangeable capacity is related to the change of the surface electrical properties of kaolinite.The zeta potential was increased to-7.3 mV as the protonation resulted from aluminum adsorption,while Dy adsorption had a minor effect,maintaining a value of-17.5 m V.
基金supported by the National Natural Science Foundation of China(Nos.52070029 and 51878092)the National Key Research and Development Program of China(No.2023YFC3904103).
文摘In real soil environments,humus,colloids and other components significantly affect pollutant migration behavior.Investigating Tl(I)and kaolinite colloids’cotransport in quartz sand media containing sodium humate(HA-Na)is vital for comprehending Tl(I)migration underground.This study examined the migration of Tl(I)and kaolinite colloids across varying pH levels(5,7),ionic strengths(ISs)(1,5,50 mmol/L),and kaolinite colloid concentra-tions.Results indicate that lower IS and pH promote Tl(I)migration when transported alone.In cotransport system,kaolinite promotes Tl(I)migration under acidic conditions but inhibits it under neutral conditions,except at high kaolinite concentrations,where the effect shifts from inhibition to promotion.This is primarily due to changes in the zeta potential of quartz sand,HA-Na,and kaolinite,as well as Tl(I)adsorption after HA-Na and kaolinite occupy binding sites.Competitive adsorption between cations and Tl(I)also plays a significant role.Conversely,in individual system,higher IS and pH inhibit kaolinite migration,while increased kaolinite concentration promotes it.In cotransport system,Tl(I)promotes kaolinite migration under acidic conditions but inhibits it under neutral conditions,except at low kaolinite concentrations.This relates to changes in the zeta potential between kaolinite and the medium,as well as the retention of HA-Na in the column and its adsorption onto kaolinite.Competitive adsorption and binding site saturation also have an impact.This study enhances understanding of Tl(I)migration by revealing the dual effect of kaolinite colloids under different environmental conditions,contributing to better knowledge of Tl(I)fate and transport in natural environments.
基金financial support for the research and for the publication costs of the articlesupported by Santa Catarina State Research Support Foundation(FAPESC)National Council for Scientific and Technological Development(CNPq no 302903/2023-2).
文摘Cement production,while essential for global infrastructure,contributes significantly to carbon dioxide emissions,accounting for approximately 7%of total emissions.To mitigate these environmental impacts,flash calcination of kaolinitic clays has been investigated as a sustainable alternative.This technique involves the rapid heating of clays,enabling their use as supplementary cementitious materials.The primary objective of this study was to modify the color of calcined clay in various atmospheres(oxidizing,inert,and reducing)to achieve a grayish tone similar to commercial cement while preserving its reactive properties.The experimental procedure employed a tubular reactor with precise control of gas flows(atmospheric air,nitrogen,and a carbon monoxide–nitrogen mixture).Physicochemical characterization of the raw clay was conducted before calcination,with analyses repeated on the calcined clays following experimentation.Results indicated that clay calcined in an oxidizing atmosphere acquired a reddish hue,attributed to the oxidation of iron in hematite.The Clay exhibited a pinkish tone in an inert atmosphere,while calcination in a reducing atmosphere yielded the desired grayish color.Regarding pozzolanic activity,clays calcined in oxidizing and inert atmospheres displayed robust strength,ranging from 82%to 87%.Calcination in a reducing atmosphere resulted in slightly lower strength,around 74%,likely due to the clay’s chemical composition and the calcination process,which affects compound formation and material reactivity.
基金supported by the National Natural Science Foundation of China(No.52009149)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515012612),China。
文摘Clay minerals can experience strong tensile and compressive forces in extreme environments such as the deep sea and subsurface.Moreover,the presence of water films greatly affects the mechanical properties of clay.To explore these properties,we use a molecular dynamics(MD)simulation method to study axial mechanical behavior and failure mechanisms of hydrated kaolinite.Two types of deformation are applied to kaolinite examples with varying water film thicknesses:stretching along the transverse(x)direction,and compression along the longitudinal(z)direction.The ultimate strengths of hydrated kaolinite with different water film thicknesses range from 8.12%to 27.53%(for stretching along the x-direction)and from 15.71%to 26.02%(for compression along the z-direction)less than those of dehydrated kaolinite.Additionally,we find that hydrated kaolinite is more prone to tensile than compressive failure under high stress.When stretched along the x-direction,the diffusion of water molecules results in unstable tensile properties.When compressed along the z-direction,water films weaken the compressive strength of the system and lead to greater compressive deformation,but also delay the time at which the system fails.Furthermore,we investigated the failure mechanisms of hydrated kaolinite through analysis of interaction energies.The tensile failure along the x-direction is caused by the breaking of the covalent bonds in the clay mineral sheet.On the other hand,the compressive failure along the z-direction is due to the crushing of the internal structure of the clay mineral sheet.
基金Projects (50974134,50804055) supported by the National Natural Science Foundation of ChinaProject (2005CB623701) supported by the National Basic Research Program of China
文摘The flotation and adsorption behaviors of dodecyltrimethylammonium chloride（DTAC） and cetyltrimethylammonium chloride（CTAC） on diaspore and kaolinite were studied.Solution depletion methods were used to determine adsorption isotherms.Fluorescence probe test along with Zeta potential measurement was also conducted for further investigation into the adsorption of quaternary amines at the mineral-water interface.The results show that the flotation recovery of kaolinite decreases with an increase in pH when DTAC and CTAC are used as collectors,while diaspore is on the contrary.As the carbon chain length of the collectors increases,the flotation recoveries of minerals increase.However,the increment rate of kaolinite is significantly lower than that of diaspore.In the low surfactant concentration range,the cationic surfactants adsorb readily on diaspore surfaces just due to electrostatic interactions.As for kaolinite surfaces,ion exchange process also exists.With a further increase in surfactant concentration,the adsorption was ascribed to the hydrophobic association of chain-chain interactions.Micro-polarity of mineral surfaces study shows that CTAC has a better hydrophobic characteristic than DTAC.Larger aggregates are formed with CTAC on diaspore than on kaolinite in the same solution concentration.The results also indicate that the chain length of cationic surfactants has a greater influence on the adsorption of diaspore than on kaolinite,which is consistent with the flotation result.
基金Project (2005CB623701) supported by the National Basic Research Program of China Project (201011031) supported by National Department Public Benefit Research Foundation from Ministry of Land and Resources of China+1 种基金 Project (2935) supported by the Foundation for the Author of Zhengzhou Institute of Multipurpose Utilization of Mineral Resources CAGS, China Project (1212011120304) supported by the Geological Surrey Program
文摘The collecting power of tertiary amines（DRN,DEN and DPN） on kaolinite follows the order of DENDPNDRN.After reacting with DRN,DEN and DPN,the surface potentials of kaolinite increase remarkably,and the recruitments caused by collectors also follow the order of DENDPNDRN.The results of dynamics simulation show that the geometries of substituent groups bonding to N are deflected and twisted,and some of bond angles are changed when tertiary amines cations adsorb on kaolinite（001） surface.Based on the results of dynamics simulations and quantum chemistry calculations,the electrostatic forces between three tertiary amines cations and 4×4×3（001） plane of kaolinite are 1.38×10？7 N（DRN12H＋）,1.44×10-6 N（DEN12H＋）,1.383×10-6 N（DPN12H＋）,respectively.
基金Funded by National "973" Plan Research Project ( No.2004CB619204) and Educational Ministry Scientific and Technologi-cal Research Key Project (No.02052)
文摘Titanium dioxide/ kaolinite nanocomposite was prepared by the sol-gel method, with layered kaolinite as a substrate and Ti （ OC4H9 ）4 as a precursor. The effects of hydrolysis, drying and calcination on the production of nanometric titanium dioxide were discussed. The optimal conditions for preparation were＂ bbtained through experiments. The 1- 10 nrn thick monolayer anatase nano TiO2 crystal was produced under the conditions as follows： hydrolyzed at 37-42 ℃ for 4 h, dried at 70-80 ℃ for 1 h, and calcined at 550-650℃ for 3 h. The rate of degradation of 40 mg/ L azo dye and 20 mg/ L acid red dye can reuch 96% and 81.45%, respectively.
文摘This report examined electrochemical remediation of copper contaminated kaolinite by controlling electrolytes′ pH for both of anolyte and catholyte simultaneously. Results showed that electrokinetic process and remediation efficiency varied obviously when different buffer systems, including citric acid (test 1), nitric acid + EDTA (test 2) and nitric acid (test 3), were used to control catholyte pH and Na_2CO_3 was used at the same time to control all anolyte one. It was found that under such pH condition soil′s pH in soil column kept at 3.0—7.0 successfully, and correspondingly no copper precipitation and decrease of soil electroconductivity appeared, which are usually observed in electrokinetic process due to OH - introduction into soil column by electrochemical reaction occurred in cathode. Electroosmosis flow rates were almost equal for these three tests, indicating that these buffers did not affect Zeta-potential of kaolinite within the examined duration. More acid and basic solution was added into electrokinetic cell when nitric acid was used as buffer than when nitric acid + EDTA and then citric acid were used. Due to introduction of large amounts of ions into soil column, significant higher current was observed for test 3 than other two. Analysis of copper speciation and total quantity in kaolinite indicated that 22.5%, 23.74% and 55.65% Cu were removed from kaolinite for test 1, test 2 and test 3 respectively after only 10 days′ electrokinetic remediation.
基金support from the Ministry of Steel,Government of India,India(GAP 214).
文摘This paper reports the systematic investigation on the flocculation,sedimentation and consolidation characteristics of kaolinite using guar gum as a green flocculant.In-situ flocculation behavior of kaolinite at various pH,guar gum dosages,and ionic strength were studied using a light scattering technique.The effect of these parameters on the settling rate,solid consolidation,and supernatant liquid clarity was recorded.The morphology of kaolinite and flocculated kaolinite aggregates were analyzed using FESEM.The morphology studies suggest that it is poorly crystalline with multiple steps on edge,broken edge;laminar with high aspect ratio and have rough basal surface.The complex irregularity on the basal surface and the presence of multiple steps in the edges,broken edges(hydroxyl groups)have facilitated the guar gum adsorption.The isoelectric point of kaolinite is pH 3.96.The pH,ionic strength and flocculant dosage have a significant effect on the kaolinite settling rate.The guar gum has exhibited excellent turbidity removal efficiency at pH 5.The turbidity removal is inefficient at pH 10.However,guar gum has shown high turbidity removal with 80%transmission at pH 10 in the presence of a KNO3 electrolyte.
基金Puyang Re-fractories Co. Ltd. for financially supporting
文摘Porous ceramics were prepared from kaolinite gangue and Al（OH）3 with double addition of MgCO3 and CaCO3 by the pore-forming in-situ technique.The characterizations of porous ceramics were investigated by X-ray diffractometry,scanning electron microscopy,and mercury porosimetry measurements,etc.It is found that although the decomposition of MgCO3 and CaCO3 has little contribution to the porosity,the double addition of MgCO3 and CaCO3 strongly affects the formation of liquid phase,and then changes the phase compositions,pore characterization,and strength.The appropriate mode is the sample containing 1.17wt% MgCO3 and 1.17wt% CaCO3,which has high apparent porosity（41.0%）,high crushing strength（53.5 MPa）,high mullite content（76wt%）,and small average pore size（3.24 μm）.
基金the financial support provided by the Science and Technology Major Projects of Shanxi Province of China(No.20181101003)Special Funds for Basic Scientific Research of Central Colleges(No.300102299306,300102299304)。
文摘The composite catalytic materials based on the mineral kaolinite are considered to be a potential approach for solving global energy scarcity and environmental pollution,which have excellent catalytic performance,low cost and excellent chemical stability.However,pure kaolinite does not have visible light absorption ability and cannot be used as a potential photocatalytic material.Fortunately,the unique physical and chemical properties of kaolinite can be acted as a good semiconductor carrier.Herein,this paper firstly presents the mineralogical characteristics of kaolinite.Next,kaolinite-based photocatalysts(such as TiO_(2)/kaolinite,g-C_(3)N_(4)/kaolinite,g-C_(3)N_(4)/TiO_(2)/kaolinite,Zn O)are discussed in detail from the formation of heterostructures,synthesis-modification methods,photocatalytic mechanisms,and electron transfer pathways.Furthermore,the specific role of kaolinite in photocatalytic materials is summarized and discussed.In addition,the photocatalytic applications of kaolinite-based photocatalysts in the fields of water decomposition,pollutant degradation,bacterial disinfection are reviewed.However,the modification of kaolinite is hard,the manufacture of a large number of kaolinite-based photocatalysts is difficult,the cost of doping noble metals is expensive,and the utilization rate of visible light is low,which limits its application in industrial practice.Finally,this paper presents some perspectives on the future development of kaolinite-based photocatalysts.
文摘Experiments were conducted to study the influences of synthetic bayerite, non crystalline aluminum oxide (N AlOH), goethite, non crystalline iron oxide (N FeOH) and kaolinite on the adsorption, activity, kinetics and thermal stability of invertase. Adsorption of invertase on iron, aluminum oxides fitted Langmuir equation. The amount of invertase held on the minerals followed the sequence kaolinite > goethite > N AlOH > bayerite > N FeOH. No correlation was found between enzyme adsorption and the specific surface area of minerals examined. The differences in the surface structure of minerals and the arrangement of enzymatic molecules on mineral surfaces led to the different capacities of minerals for enzyme adsorption. The adsorption of invertase on bayerite, N AlOH, goethite, N FeOH and kaolinite was differently affected by pH. The order for the activity of invertase adsorbed on minerals was N FeOH > N AlOH > bayerite > reak goethite > kaolinite. The inhibition effect of minerals on enzyme activity was kaolinite > crystalline oxides > non crystalline oxides. The pH optimum of iron oxide and aluminum oxide invertase complexes was similar to that of free enzyme (pH 4.0), whereas the pH optimum of kaolinite inv ertase complex was one pH unit higher than that of free enzyme. The affinity to substrate and the maximum reaction velocity as well as the thermal stability of combined invertase were lower than those of the free enzyme.
基金Project(2018YFC1901903) supported by the National Key Research and Development 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A new chemical pre-desilication process of kaolinite in diasporic bauxite in alkali solution at atmospheric pressure was proposed.The dissolution kinetics and mechanism were studied by chemical analysis,XRD and SEM.The kinetic results of dissolution process show that the kaolinite is symbiotic with diaspore but without cladding.The dissolution ratio of kaolinite is close to 100%at 100℃for 90 min.The dissolution kinetic equation is 1-(1-α)^1/3=7.88×10^6 exp[-64434/(RT)]t.With the low L/S(L/S=10:1),the dissolution ratio of kaolinite decreases to 55%.This is due to the formation of lamellar hydroxyl-sodalite(OH-SOD)which is deposited on the surface of kaolinite and hinders the further dissolution of kaolinite.Under the optimum conditions,the A/S(mass ratio of Al2 O3 to SiO2)of dissolved residues is increased to 8.55,while the A/S of the bauxite is only 4.97.
基金the support of the National Natural Science Foundation of China (No. U1607108)Natural Science Foundation of Jiangxi, China (No. 20202ACBL213008)。
文摘How to sustainably produce bauxite by effective reverse froth flotation of kaolinite at low temperature is an urgent problem to be solved in the field of mineral processing.In this work,a novel amino-based Gemini surfactant butadiyl-1,4-bis(dimethyl dodecylammonium bromide)(BBDB) was prepared and first utilized as a novel collector for kaolinite flotation.Its flotation performance for kaolinite was compared with that of the common monomolecular surfactant 1-dodecylamine(DDA) by micro-flotation tests.The tests results indicated that 95% kaolinite recovery was obtained using 2.0×10^(-4) mol/L BBDB at 25℃ which was half of the dosage when DDA obtained the maximum kaolinite recovery of81%.At extremely low temperature(0℃),3.0×10^(-4) mol/L BBDB could still collect 91% kaolinite,while DDA showed a frustrating ability.The contact angle tests indicated that BBDB could still significantly improve the hydrophobicity of the kaolinite surface(contact angle 71.7°) than DDA(contact angle only25.8°) at 0℃.The Krafft point comparison tests indicated that BBDB had a much lower Krafft point(below0℃) than DDA.Fourier transform infrared spectroscopy(FTIR)-spectrum analysis and zeta potential measurements showed that BBDB was physically adsorbed on the surface of kaolinite through electrostatic interaction.
文摘For better understanding the adsorption of rare earth elements (REEs) by clay minerals and its controlling factors, the experiments on adsorption of REEs in solutions with 1 g·L-1 kaolinite were performed at different conditions. The results are as follows: the REEs reach equilibrium in the adsorption-desorption process for 24; Langmuir′s adsorption curve is used for modeling the adsorption of REEs by kaolinite; a general trend is that the higher the contents of REEs are, the less obvious the fractionation is. Furthermore, there is significant effect of pH on the adsorption and fractionation of REEs by kaolinite, and the REEs distribution coefficient increases with increasing pH. When pH is nearly neutral, as reaches 7, heavy REEs are more adsorbed than light REEs.
文摘The decomposition kinetics of Algerian Tamazarte kaolinite(TK)was investigated using thermogravimetric analysis(TG).Differential thermal analysis(DTA)and TG experiments were carried out between room temperature and1400°C,at differentheating rates from10to40°C/min.The activation energies,measured by DTG from isothermal treatments usingJohnson-Mehl-Avrami(JMA)and Ligero methods and by non-isothermal treatments using Ozawa,Boswell and Kissinger methods,were around151and144kJ/mol,respectively.The Avrami parameter of growth morphology(indicating the crystallization mode)was found to be around1.57using non-isothermal treatments;however,when using isothermal treatments it is found to be equal to1.35.The numerical factor,which depends on the dimensionality of crystal growth,is found to be1.53using Matusita equation.Thefrequency factor calculated by the isothermal treatment is equal to1.55×107s-1.The results show that the bulk nucleation is followedby three-dimensional growth of metakaolinite with polyhedron-like morphology controlled by diffusion from a constant number ofnuclei.
基金the Key Project of Chinese Ministry of Education(No.107076)the National Natural Science Foundation of China(40172017)Calculations performed in Wuhan University of Technology(PC99691149W3733N)
文摘The surface properties of kaolinite were determined using density functional theory discrete variational method （DFT-DVM） and Gaussian 03 program. A SiO4 tetrahedral hexagonal ring with two A1 octahedra was chosen to model the kaolinite crystal. The total density of states of the kaolinite cluster are located near the Fermi level at both sides of the Fermi level. Both the highest occupied molecular orbit （HOMO） and the lowest unoccupied molecular orbit （LUMO） of kaolinite indicate that kaolinite system can not only readily interact with electron-acceptor species, but also readily interact with electron-donor species on the edge surface and the gibbsite layer surface, and thus, shows amphoteric behavior. Substitution of Al3^＋ for Si4＋ in the tetrahedral site linking the vacant Al3^＋ octahedra does not increase the surface chemical reactivity of kaolinite, while substitution of Al3^＋ for Si^4＋ in the tetrahedral site with the apex O linking Al3^＋ octahedra increase the surface chemical reactivity of the siloxane surface of kaolinite, especially acting as electron donors. Additionally, substitution of Al3^＋. for Si^4＋ in the tetrahedral site results in the re-balance of charges, leading to the increase of negative charge of the coordinated O atoms of the AlO4 tetrahedra, and therefore favoring the formation of ionic bonds between cations and the surface O atoms in the basal plane.
基金This research was financially supported by the National Natural Science Foundation of China(Nos.U1810102,51974194)The use of the Materials Studio software package,which is supported by the Key Laboratory of Coal Science and Technology of the Ministry of Education and Shanxi Province,is gratefully acknowledged.
文摘Understanding the interaction of CH4 with kaolinite is significant for researchers in the fields of coalbed CH4 and shale gas.The diffusion behaviors of CH4 in kaolinite with water contents ranging from 0 to 5 wt% have been analyzed by molecular dynamics simulations.The results of the simulations indicate that CH4 molecules can jump between adjacent holes in the kaolinite matrix.CH4 diffusion coefficient was very low (3.28 × 10-9 m2/s) and increased linearly with the increasing of water content.As the water content decreased,the value of radial distribution function first peak between CH4 and oxygen was larger,meaning that with lower water content,the interaction energy between CH4 and oxygen in kaolinite is stronger.The interaction between CH4 and water is linearly positively correlated with water content,in contrast,the interaction energy between kaolinite and water as well as between kaolinite and CH4 decreased linearly with increasing water content.On the other hand,the diffusion of CH4 molecules adsorbed on the surfaces also can be accelerated by the fast diffusion of water molecules in the middle micropore of the kaolinite.
基金supported by the National Key Fundamental Research and Development Program(No.2005CB623701)the National Department Public Benefit Research Foundation from Ministry of Land and Resources(No.201011031 )the Foundation for the Author of Zhengzhou Institute of Multipurpose Utilization of Mineral Resources CAGS(No.2935)
文摘The flotation of diaspore and kaolinite by one of a series of tertiary amines（DRN,DEN,DPN and DBN） was investigated.The tertiary amines show better floating recovery for kaolinite compared to diaspore.The maximum recovery D-value is 45%over a pH range from 3 to 8.FT-IR spectra confirm the presence of hydroxyl groups on the surface of kaolinite and diaspore.Zeta potential measurements show that the mineral surfaces are negatively charged over a wide pH range.Ionization of hydroxyl groups mainly accounts for the surface charging mechanism.The adsorption of tertiary amines onto the mineral surface is due mainly to electrostatic effects and the difference in electrostatic effect between a collector and the two minerals can explain the flotation separation.Inductive electronic and steric effects from the substituent groups result in different collecting powers for the four tertiary amines.
基金Project(2006AA06Z120) supported by the National High-Tech Research and Development Program of ChinaProject(2005CB623701) supported by the Major State Basic Research Development Program of China
文摘Tertiary amine was synthesized from fatty amine and formaldehyde. And then the synthesized tertiary amine was used to react with benzyl chloride to synthesize hexadecyl dimethyl benzyl ammonium chloride (1627) at ambient pressure. Using the synthesized 1627 as collector,the flotation properties of diaspore and kaolinite were investigated by single mineral and mixed mineral test. The flotation mechanism of diaspore,kaolinite and 1627 was discussed based on FTIR spectra. The results show that the mass ratio of aluminum to silicate achieves 15.02 and the recovery of alumina in concentrate is 43.07% using 1627 as a collector. The 1627 is found to be a more effective and a promising collector for reverse flotation to remove aluminum-silicate minerals from bauxite.
