Zeolite catalysts have found extensive applications in the synthesis of various fine chemicals.However,the micropores of zeolites impose diffusion limitations on bulky molecules,greatly reducing the catalytic efficien...Zeolite catalysts have found extensive applications in the synthesis of various fine chemicals.However,the micropores of zeolites impose diffusion limitations on bulky molecules,greatly reducing the catalytic efficiency.Herein,we explore an economic and environmentally friendly method for synthesizing hierarchical NaX zeolite that exhibits improved catalytic performance in the Knoevenagel condensation reaction for producing the useful fine chemical 2-cyano-3-phenylacrylate.The synthesis was achieved via a low-temperature activation of kaolinite and subsequent in-situ transformation strategy without any template or seed.Systematic characterizations reveal that the synthesized NaX zeolite has both intercrystalline and intra-crystalline mesopores,smaller crystal size,and larger external specific surface area compared to commercial NaX zeolite.Detailed mechanism investigations show that the inter-crystalline mesopores are generated by stacking smaller crystals formed from in-situ crystallization of the depolymerized kaolinite,and the intra-crystalline mesopores are inherited from the pores in the depolymerized kaolinite.This synthesis strategy provides an energy-saving and effective way to construct hierarchical zeolites,which may gain wide applications in fine chemical manufacturing.展开更多
This study delves into the intricate relationship between iron(Fe)content in kaolinite and its impact on the adsorption behavior of sodium oleate.The effects of different iron concentrations on adsorption energy,hydro...This study delves into the intricate relationship between iron(Fe)content in kaolinite and its impact on the adsorption behavior of sodium oleate.The effects of different iron concentrations on adsorption energy,hydrogen bond kinetics and adsorption efficiency were studied through simulation and experimental verification.The results show that the presence of iron in the kaolinite structure significantly improves the adsorption capacity of sodium oleate.Kaolinite samples with high iron content have better adsorption properties,lower adsorption energy levels and shorter and stronger hydrogen bonds than pure kaolinite.The optimal concentration of oleic acid ions for achieving maximum adsorption efficiency was identified as 1.2 mmol/L across different kaolinite samples.At this concentration,the adsorption rates and capacities reach their peak,with Fe-enriched kaolinite samples exhibiting notably higher flotation recovery rates.This optimal concentration represents a balance between sufficient oleic acid ion availability for surface interactions and the prevention of self-aggregation phenomena that could hinder adsorption.This study offers promising avenues for optimizing the flotation process in mineral processing applications.展开更多
This study focuses on the adsorption at temperatures below 70℃, of carotenoids from carrots on clay materials such as kaolinite in the raw state, activated with a 0.5 M HCl solution or treated with a sodium solution ...This study focuses on the adsorption at temperatures below 70℃, of carotenoids from carrots on clay materials such as kaolinite in the raw state, activated with a 0.5 M HCl solution or treated with a sodium solution of Al<sup>+</sup>. The kinetic study of carotenoid adsorption shows that equilibrium is reached after 30 minutes and the temperature has little influence on carotenoid adsorption. On the other hand, the quantities adsorbed at equilibrium increase with the initial concentration of carotenoids. The kinetic model that best describes the experimental data is that of the pseudo-second order, adsorption is made in two time. For the carotenoid adsorption isotherms, the best correlation is obtained with the Freundlich model. The low values of the Freundlich constants indicate that the adsorption is probably of a physical type. This conclusion is confirmed by the effective desorption of carotenoids observed during desorption experiments.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 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
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
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
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
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
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
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
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
The flocculation behavior of ultrafine kaolinite suspension was investigated through settlement tests and FTIR method was employed to probe the adsorption mechanism of flocculant on kaolinite. The results show that th...The flocculation behavior of ultrafine kaolinite suspension was investigated through settlement tests and FTIR method was employed to probe the adsorption mechanism of flocculant on kaolinite. The results show that the maximum settling rate of kaolinite occurs at pH value of 3.33,which is close to the point of zero charge(PZC) of kaolinite (3.5). This result is in good agreement with the double electric layer theory. Kaolinite suspension reaches the largest settling rate at a low concentration of 39 g/t for poly diallyl-dimethyl-ammonium chloride(PDADMA) flocculant,whereas for polyacrylamides(PAM) the dosage is required to be 500 g/t. When macromolecule polymer is adsorbed on surface,kaolinite particles may be flocculant due to the bridging effect. There are cation flocculant characteristic bands on the spectrum of kaolinite but no obvious shifting. Thus,the adsorption of poly diallyl-dimethyl-ammonium chloride on kaolinite surface is physical adsorption.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
基金The financial supports from the National Natural Science Foundation of China (22178059, 22208054 and 22072019)Natural Science Foundation of Fujian Province, China (2020J01513)+1 种基金Sinochem Quanzhou Energy Technology Co., Ltd. (ZHQZKJ-19-F-ZS0076)Qingyuan Innovation Laboratory (00121002)
文摘Zeolite catalysts have found extensive applications in the synthesis of various fine chemicals.However,the micropores of zeolites impose diffusion limitations on bulky molecules,greatly reducing the catalytic efficiency.Herein,we explore an economic and environmentally friendly method for synthesizing hierarchical NaX zeolite that exhibits improved catalytic performance in the Knoevenagel condensation reaction for producing the useful fine chemical 2-cyano-3-phenylacrylate.The synthesis was achieved via a low-temperature activation of kaolinite and subsequent in-situ transformation strategy without any template or seed.Systematic characterizations reveal that the synthesized NaX zeolite has both intercrystalline and intra-crystalline mesopores,smaller crystal size,and larger external specific surface area compared to commercial NaX zeolite.Detailed mechanism investigations show that the inter-crystalline mesopores are generated by stacking smaller crystals formed from in-situ crystallization of the depolymerized kaolinite,and the intra-crystalline mesopores are inherited from the pores in the depolymerized kaolinite.This synthesis strategy provides an energy-saving and effective way to construct hierarchical zeolites,which may gain wide applications in fine chemical manufacturing.
基金supported by the Natural Science Foundation of China(No.52174232)the Project was supported by Open Research Grant of Joint National-Local Engineering Research Centre for Safe and Precise Coal Mining(Nos.EC2022003 and EC2023005)+1 种基金Anhui University of Science and Technology 2023 Graduate Student Innovation Fund(No.2023cx2106)Open Research Grant of Anhui Engineering Research Center for Coal Clean Processing and Carbon Emission Reduction(No.CCCE-2023003).
文摘This study delves into the intricate relationship between iron(Fe)content in kaolinite and its impact on the adsorption behavior of sodium oleate.The effects of different iron concentrations on adsorption energy,hydrogen bond kinetics and adsorption efficiency were studied through simulation and experimental verification.The results show that the presence of iron in the kaolinite structure significantly improves the adsorption capacity of sodium oleate.Kaolinite samples with high iron content have better adsorption properties,lower adsorption energy levels and shorter and stronger hydrogen bonds than pure kaolinite.The optimal concentration of oleic acid ions for achieving maximum adsorption efficiency was identified as 1.2 mmol/L across different kaolinite samples.At this concentration,the adsorption rates and capacities reach their peak,with Fe-enriched kaolinite samples exhibiting notably higher flotation recovery rates.This optimal concentration represents a balance between sufficient oleic acid ion availability for surface interactions and the prevention of self-aggregation phenomena that could hinder adsorption.This study offers promising avenues for optimizing the flotation process in mineral processing applications.
文摘This study focuses on the adsorption at temperatures below 70℃, of carotenoids from carrots on clay materials such as kaolinite in the raw state, activated with a 0.5 M HCl solution or treated with a sodium solution of Al<sup>+</sup>. The kinetic study of carotenoid adsorption shows that equilibrium is reached after 30 minutes and the temperature has little influence on carotenoid adsorption. On the other hand, the quantities adsorbed at equilibrium increase with the initial concentration of carotenoids. The kinetic model that best describes the experimental data is that of the pseudo-second order, adsorption is made in two time. For the carotenoid adsorption isotherms, the best correlation is obtained with the Freundlich model. The low values of the Freundlich constants indicate that the adsorption is probably of a physical type. This conclusion is confirmed by the effective desorption of carotenoids observed during desorption experiments.
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.
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.
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).
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.
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.
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.
基金Project(2005CB623701) supported by the Major State Basic Research Development Program of China
文摘The flocculation behavior of ultrafine kaolinite suspension was investigated through settlement tests and FTIR method was employed to probe the adsorption mechanism of flocculant on kaolinite. The results show that the maximum settling rate of kaolinite occurs at pH value of 3.33,which is close to the point of zero charge(PZC) of kaolinite (3.5). This result is in good agreement with the double electric layer theory. Kaolinite suspension reaches the largest settling rate at a low concentration of 39 g/t for poly diallyl-dimethyl-ammonium chloride(PDADMA) flocculant,whereas for polyacrylamides(PAM) the dosage is required to be 500 g/t. When macromolecule polymer is adsorbed on surface,kaolinite particles may be flocculant due to the bridging effect. There are cation flocculant characteristic bands on the spectrum of kaolinite but no obvious shifting. Thus,the adsorption of poly diallyl-dimethyl-ammonium chloride on kaolinite surface is physical adsorption.
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.