This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma...This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma–mass spectrometry and isotope ratio mass spectrometry was used to investigate trace and rareearth element geochemistry and hydrogen and oxygen isotopic compositions. These data were then used to infer the sediments' provenance and paleoclimatic conditions during their deposition. The sediments contained low concentrations of most trace elements, with the exceptions of Zr(651–1352 ppm), Ba(56–157 ppm), V(38–90 ppm),and Sr(15.1–59.6 ppm). Average values of Co and Ni were1.5 and 0.7 ppm, respectively. Trace and rare earth element values were lower than corresponding values for upper continental crust and Post-Archean Australian Shale, with the exception of Zr. The samples showed only slight light rare-earth enrichment and nearly flat heavy rare-earth depletion patterns, with negative Eu and Tm anomalies,typical of felsic sources. Geochemical parameters such as La/Sc, Th/Sc, and Th/Co ratios support that the kaolinitic sediments were derived from a felsic rock source, likely deposited in an oxic environment.^(18 )O values ranged from+ 15.4 to + 21.2% for the investigated samples, consistent with a residual material derived from chemicalweathering of felsic rock and redeposited in a sedimentary basin(typical values of + 19 to + 21.2%). While in the basin, the sediments experienced extended interactions with meteoric water enriched in d D and d16 O. However,the variation in d D and d16 O values for the investigated samples is attributed to the high temperature of formation(54–91 °C). The d D and d^(18 )O values suggest that the sediments, although obtained from different localities within the Lower Benue Trough, formed under similar hot,tropical climatic conditions.展开更多
In this study, Mg-Al-CO3 hydrotalcite was synthesized from a kaolinite as natural source aluminium using two simple methods. The first method uses the kaolinite in natural solid state, the second method use the filtra...In this study, Mg-Al-CO3 hydrotalcite was synthesized from a kaolinite as natural source aluminium using two simple methods. The first method uses the kaolinite in natural solid state, the second method use the filtrate of the kaolinite after dissolution by acidic solutions. The structure of the materials was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC) and Brunauer, Emmett, and Teller (BET) measurements.展开更多
Production of modified liquid glass and quartz materials from kaolinite clay of Alekseev deposit of Kazakhstan was studied. The sodium liquid glass processed by kaolinite clay, with chemical composition (g/dm3): SiO2-...Production of modified liquid glass and quartz materials from kaolinite clay of Alekseev deposit of Kazakhstan was studied. The sodium liquid glass processed by kaolinite clay, with chemical composition (g/dm3): SiO2-350;Na2O-155;Al2O3-2.1;Fe2O3- 0.3, silicate module-2.33 and density-1.49 g/cm3 has been used. The sodium liquid glass complies with the Russian Interstate standard 13078-81 for sodium liquid glass.10 samples of modified liquid glass were synthesized by introducing modifiers in an amount of 4% by weight of the solution into the liquid glass. Hard quartz material produced by using synthesized modified liquid glass was obtained. It has been established that the obtained modified liquid glass from kaolinite clay can improve the strength of the quartz material for 1.6 - 3.12 times higher than the initial liquid glass. Using liquid glass modifier to the inorganic sodium nitrate (NaNO3) increases the strength 3.12 times.展开更多
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
The paper talks about the elaboration of geopolymer with two types of kaolinite clays containing muscovite. The kaolinite materials were first calcined at different temperatures, and mixed with an activator solution, ...The paper talks about the elaboration of geopolymer with two types of kaolinite clays containing muscovite. The kaolinite materials were first calcined at different temperatures, and mixed with an activator solution, called liquid precursor, at a different solid/liquid mass ratio depending on their normal consistency to produce geopolymer binders. Results show that the geopolymer products obtained from the different clays have good physichomechanical properties: their open porosity and their water absorption rate decrease while their compressive strength and their apparent density increase with the increase in calcination temperature of the clays. The density of GABD binders varies between 2.92 and 2.47 g/cm<sup>3</sup> and that of GARD binders between 1.86 and 2.16 g/cm<sup>3</sup>. Specimens in the GABD series have the best mechanical performance, ranging from 14.43 to 31.37 MPa, while those in the GARD series oscillate between 6.18 and 11.56 MPa. These properties make kaolinite materials from this region suitable for use as construction materials for adequate waterproof structures.展开更多
Akure area in southwestern Nigeria falls within the basement complex underlain by migmatite,quartzite granite and charnockite.Geochemical features of these crystalline rocks and their overlying in-situ weathering prof...Akure area in southwestern Nigeria falls within the basement complex underlain by migmatite,quartzite granite and charnockite.Geochemical features of these crystalline rocks and their overlying in-situ weathering profiles are investigated and reported.Analytical result from ICP-MS facility at the University of Malaya reveals average SiO_(2) content in quartzite(91.1%),granite(73.8%),migmatite(67.4%)and charnockite(58.6%)categorize the rocks as siliceous.SiO_(2) contents in the weathering profiles above these rocks are 61.9%,60.2%,52.2%and 54.6%respectively.Alumina contents in the weathering profiles overlying quartzite(23.8%),granite(19.9%),migmatite(26.3%)and charnockite(24.3%)are substantially higher than the precursor rocks.In the same order,average alkali(Na_(2)O+K_(2)O)contents in the profiles are 3.38%,3.42%,3.48%and 2.68%.Chemical features of the profiles reflect that there exists some correlation between the chemistry of crystalline basement and their in-situ weathering profiles.The residual soils contain low plastic clays with kaolinitic characteristics and compare well with other clays reported from other parts of Nigeria basement complex.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
Interaction of ammonium (NH+4) and potassium (K+) is typical in field soils. However, the effects of organic matter on interaction of NH+4 and K+have not been thoroughly investigated. In this study, we examined the ch...Interaction of ammonium (NH+4) and potassium (K+) is typical in field soils. However, the effects of organic matter on interaction of NH+4 and K+have not been thoroughly investigated. In this study, we examined the changes in major physicochemical properties of three clay minerals (kaolinite, illite, and montmorillonite) after humic acid (HA) coating and evaluated the influences of these changes on the interaction of NH+4 and K+on clay minerals using batch experiments. After HA coating, the cation exchange capacity (CEC) and specific surface area (SSA) of montmorillonite decreased significantly, while little decrease in CEC and SSA occurred in illite and only a slight increase in CEC was found in kaolinite. Humic acid coating significantly increased cation adsorption and preference for NH+4, and this effect was more obvious on clay minerals with a lower CEC. Results of Fourier transform infrared spectrometry analysis showed that HA coating promoted the formation of H-bonds between the adsorbed NH+4 and the organo-mineral complexes. HA coating increased cation fixation capacity on montmorillonite and kaolinite, but the opposite occurred on illite. In addition, HA coating increased the competitiveness of NH+4 on fixation sites. These results showed that HA coating affected both the nature of clay mineral surfaces and the reactions of NH+4 and K+with clay minerals, which might influence the availability of nutrient cations to plants in field soils amended with organic matter.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
Coal slimes are mainly composed of coal and clay particles.The interaction energies among these particles were calculated using extended DLVO(DERJAGUIN-LANDAU-VERWEY-OVERBEEK)theory and the aggregation mechanisms were...Coal slimes are mainly composed of coal and clay particles.The interaction energies among these particles were calculated using extended DLVO(DERJAGUIN-LANDAU-VERWEY-OVERBEEK)theory and the aggregation mechanisms were analyzed based on the settling experiments for coal-kaolinite and coal-montmorillonite suspensions,respectively,under different conditions of water hardness.The results indicate that for coal-kaolinite suspensions,as the water hardness reaches 10.0mol/L,the coal particles aggregate with each other easily,and then,the coal particles may aggregate with kaolinite particles.However,no aggregation occurs between kaolinite particles.A clay platelet network is formed in coal-montmorillonite suspensions by montmorillonite particles and coal particles are captured into the network.Coal and montmorillonite particles settle completely.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
文摘This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma–mass spectrometry and isotope ratio mass spectrometry was used to investigate trace and rareearth element geochemistry and hydrogen and oxygen isotopic compositions. These data were then used to infer the sediments' provenance and paleoclimatic conditions during their deposition. The sediments contained low concentrations of most trace elements, with the exceptions of Zr(651–1352 ppm), Ba(56–157 ppm), V(38–90 ppm),and Sr(15.1–59.6 ppm). Average values of Co and Ni were1.5 and 0.7 ppm, respectively. Trace and rare earth element values were lower than corresponding values for upper continental crust and Post-Archean Australian Shale, with the exception of Zr. The samples showed only slight light rare-earth enrichment and nearly flat heavy rare-earth depletion patterns, with negative Eu and Tm anomalies,typical of felsic sources. Geochemical parameters such as La/Sc, Th/Sc, and Th/Co ratios support that the kaolinitic sediments were derived from a felsic rock source, likely deposited in an oxic environment.^(18 )O values ranged from+ 15.4 to + 21.2% for the investigated samples, consistent with a residual material derived from chemicalweathering of felsic rock and redeposited in a sedimentary basin(typical values of + 19 to + 21.2%). While in the basin, the sediments experienced extended interactions with meteoric water enriched in d D and d16 O. However,the variation in d D and d16 O values for the investigated samples is attributed to the high temperature of formation(54–91 °C). The d D and d^(18 )O values suggest that the sediments, although obtained from different localities within the Lower Benue Trough, formed under similar hot,tropical climatic conditions.
文摘In this study, Mg-Al-CO3 hydrotalcite was synthesized from a kaolinite as natural source aluminium using two simple methods. The first method uses the kaolinite in natural solid state, the second method use the filtrate of the kaolinite after dissolution by acidic solutions. The structure of the materials was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC) and Brunauer, Emmett, and Teller (BET) measurements.
文摘Production of modified liquid glass and quartz materials from kaolinite clay of Alekseev deposit of Kazakhstan was studied. The sodium liquid glass processed by kaolinite clay, with chemical composition (g/dm3): SiO2-350;Na2O-155;Al2O3-2.1;Fe2O3- 0.3, silicate module-2.33 and density-1.49 g/cm3 has been used. The sodium liquid glass complies with the Russian Interstate standard 13078-81 for sodium liquid glass.10 samples of modified liquid glass were synthesized by introducing modifiers in an amount of 4% by weight of the solution into the liquid glass. Hard quartz material produced by using synthesized modified liquid glass was obtained. It has been established that the obtained modified liquid glass from kaolinite clay can improve the strength of the quartz material for 1.6 - 3.12 times higher than the initial liquid glass. Using liquid glass modifier to the inorganic sodium nitrate (NaNO3) increases the strength 3.12 times.
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.
文摘The paper talks about the elaboration of geopolymer with two types of kaolinite clays containing muscovite. The kaolinite materials were first calcined at different temperatures, and mixed with an activator solution, called liquid precursor, at a different solid/liquid mass ratio depending on their normal consistency to produce geopolymer binders. Results show that the geopolymer products obtained from the different clays have good physichomechanical properties: their open porosity and their water absorption rate decrease while their compressive strength and their apparent density increase with the increase in calcination temperature of the clays. The density of GABD binders varies between 2.92 and 2.47 g/cm<sup>3</sup> and that of GARD binders between 1.86 and 2.16 g/cm<sup>3</sup>. Specimens in the GABD series have the best mechanical performance, ranging from 14.43 to 31.37 MPa, while those in the GARD series oscillate between 6.18 and 11.56 MPa. These properties make kaolinite materials from this region suitable for use as construction materials for adequate waterproof structures.
文摘Akure area in southwestern Nigeria falls within the basement complex underlain by migmatite,quartzite granite and charnockite.Geochemical features of these crystalline rocks and their overlying in-situ weathering profiles are investigated and reported.Analytical result from ICP-MS facility at the University of Malaya reveals average SiO_(2) content in quartzite(91.1%),granite(73.8%),migmatite(67.4%)and charnockite(58.6%)categorize the rocks as siliceous.SiO_(2) contents in the weathering profiles above these rocks are 61.9%,60.2%,52.2%and 54.6%respectively.Alumina contents in the weathering profiles overlying quartzite(23.8%),granite(19.9%),migmatite(26.3%)and charnockite(24.3%)are substantially higher than the precursor rocks.In the same order,average alkali(Na_(2)O+K_(2)O)contents in the profiles are 3.38%,3.42%,3.48%and 2.68%.Chemical features of the profiles reflect that there exists some correlation between the chemistry of crystalline basement and their in-situ weathering profiles.The residual soils contain low plastic clays with kaolinitic characteristics and compare well with other clays reported from other parts of Nigeria basement complex.
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Supported by the National Natural Science Foundation of China (No. 40801085)the Special Fund for Agro-Scientific Research in the Public Interest (No. 201203013)+1 种基金the Knowledge Innovation Program of the Institute of Soil Science, Chinese Academy of Sciences(No. ISSASIP0712)the International Cooperation Program of the International Plant Nutrition Institute (IPNI) (No. Nanjing-11)
文摘Interaction of ammonium (NH+4) and potassium (K+) is typical in field soils. However, the effects of organic matter on interaction of NH+4 and K+have not been thoroughly investigated. In this study, we examined the changes in major physicochemical properties of three clay minerals (kaolinite, illite, and montmorillonite) after humic acid (HA) coating and evaluated the influences of these changes on the interaction of NH+4 and K+on clay minerals using batch experiments. After HA coating, the cation exchange capacity (CEC) and specific surface area (SSA) of montmorillonite decreased significantly, while little decrease in CEC and SSA occurred in illite and only a slight increase in CEC was found in kaolinite. Humic acid coating significantly increased cation adsorption and preference for NH+4, and this effect was more obvious on clay minerals with a lower CEC. Results of Fourier transform infrared spectrometry analysis showed that HA coating promoted the formation of H-bonds between the adsorbed NH+4 and the organo-mineral complexes. HA coating increased cation fixation capacity on montmorillonite and kaolinite, but the opposite occurred on illite. In addition, HA coating increased the competitiveness of NH+4 on fixation sites. These results showed that HA coating affected both the nature of clay mineral surfaces and the reactions of NH+4 and K+with clay minerals, which might influence the availability of nutrient cations to plants in field soils amended with organic matter.
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(50425168)supported by the National Natural Science Foundation of ChinaProject (0100471413)supported by China Postdoctoral Science FoundationProject (201104547)supported by Pisdoctorcal Science Foundation of Jiangsu Province,China
文摘Coal slimes are mainly composed of coal and clay particles.The interaction energies among these particles were calculated using extended DLVO(DERJAGUIN-LANDAU-VERWEY-OVERBEEK)theory and the aggregation mechanisms were analyzed based on the settling experiments for coal-kaolinite and coal-montmorillonite suspensions,respectively,under different conditions of water hardness.The results indicate that for coal-kaolinite suspensions,as the water hardness reaches 10.0mol/L,the coal particles aggregate with each other easily,and then,the coal particles may aggregate with kaolinite particles.However,no aggregation occurs between kaolinite particles.A clay platelet network is formed in coal-montmorillonite suspensions by montmorillonite particles and coal particles are captured into the network.Coal and montmorillonite particles settle completely.
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.
