Modified sepiolite stabilized stearic acid as a form-stable phase change material for thermal energy storage

Sepiolite(ST) was used as a supporting matrix in compiste phase change materials(PCMs) due to its unique microstructure, good thermal stability, and other raw material advantages. In this paper, microwave acid treatment were innovatively used for the modification of sepiolite. The modified sepiolite(ST_(m)) obtained in different hydrochloric acid concentrations(0.25, 0.5, 0.75, and 1.0 mol·L^(-1)) was added to stearic acid(SA) via vacuum impregnation method. The thermophysical properties of the composites were changed by varying the hydrochloric acid concentration. The SA-ST_(m0.5)obtained by microwave acid treatment at 0.5 mol·L^(-1)hydrochloric acid concentration showed a higher loading capacity(82.63%) than other composites according to the differential scanning calorimeter(DSC) analysis. The melting and freezing enthalpies of SA-ST_(m0.5)were of 152.30 and 148.90 J·g^(-1), respectively. The thermal conductivity of SA-ST_(m0.5)was as high as 1.52 times that of pure SA. In addition, the crystal structure, surface morphology, and microporous structure of ST_(m)were studied, and the mechanism of SAST_(m0.5)performance enhancement was further revealed by Brunauere Emmett Teller(BET) analysis. Leakage experiment showed that SAST_(m0.5)had a good morphological stability. These results demostrate that SA-ST_(m0.5)has a potential application in thermal energy storage.

Internal Curing Mechanism of Sepiolite in Cement Paste

In order to explore the internal curing mechanism of sepiolite in cement-based materials,the effects of sepiolite on the water consumption of standard consistency,setting time,viscosity,strength,pore structure characteristics,micro-hardness characteristics and two-dimensional surface characteristics of cement paste were studied,respectively.The experimental results show that the water consumption of standard consistency increases linearly with the increase of sepiolite content.The setting time and viscosity are also lengthened and increased with the addition of sepiolite,respectively.When the content of sepiolite exceeds 5%,the strength of the specimen increases significantly.The BET results show that the pore structure of the interfacial transition zone(ITZ)in hardened cement paste(HCP)with sepiolite is optimized after curing for28 d and its pore volume content with below 10 nm is decreased,especially for the specimen with a lower watercement ratio.The characteristics of microhardness and strength of specimens have the same law.Backscattered electron image(BSE-IA)shows that the ITZ of the specimen with sepiolite is denser and the unhydrated cement particles are less than the reference specimen.

Ni/sepiolite催化剂的改性研究Ⅱ.载体的改性

以羟基铝改性sepiolite为载体制备了一系列Ni基催化剂。采用苯加氢为探针反应及二硫化碳中毒法系统地考察了载体改性对Ni/sepiolite催化剂活性及抗毒性能的影响。结果表明 ,载体的改性增加了催化剂的活性中心数 ,提高了Ni原子分散度 ,降低了加氢反应的活化能。动力学研究亦表明 ,羟基铝的引入既有电子效应又有几何效应 。

Y对Ru/sepiolite催化剂甲苯加氢活性的影响

以海泡石为载体,Ru为活性组分,采用浸渍法制备了Ru/sepiolite和Ru-Y/sepiolite催化剂。以甲苯加氢为探针反应,利用TPR,TPD,XRD和比表面积等测试手段对催化剂进行了表征。结果表明,Y的加入提高了Ru/sepiolite的催化活性和Ru的分散度,增加了催化剂的活性中心数和吸附性能。

Carbon Dioxide/Methane Separation by Adsorption on Sepiolite

In this work, the use of sepiolite for the removal of carbon dioxide from a carbon dioxide/methane mixture by a pressure swing adsorption （PSA） process has been researched. Adsorption equilibrium and kinetics have been measured in a fixed-bed, and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained. A model based on the LDF approximation has been employed to simulate the fixed-bed kinetics, using the Langmuir equation to describe the adsorption equilibrium isotherm. The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied. The experimental results were compared with the ones predicted by the model adapted to a PSA system. Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle. These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.

Adsorption Properties of Calcined Modified Sepiolite on SO4^2- and Cl^-

Three different kinds of sepiolite(Type A, Type B and Sepiolite fiber) were processed by calcination and analyzed by thermogravimetric analysis(TG), X-ray diffraction diffractometer(XRD), scanning electron microscopy(SEM), BET(specific surface area from N2 adsorption isotherms), mercury intrusion porosimetry(MIP), and infrared spectroscopic analysis(IR), respectively. The results show that the adsorption performance of sepiolite can be changed by calcination and environment temperatures, especially for calcination. The adsorption capacity of sepiolite fiber is bigger than that of Type A and B, and adsorption capacity of each sepiolite to sulfate is smaller than that of the chloride ions. Especially, the maximum value for adsorption of the sepiolite fibers, calcined at 600 ℃ and water bath at 60 ℃, to chlorine ion and sulfate are 5.95 and 5.71 mg/g, respectively(mg/g : the ions quantity adsorbed by a unit of sepiolite weight). The minimum adsorption of calcined sepiolite fiber to sulfate ions increased from 5.02 to 5.55 mg/g. While microstructure analysis of sepiolite by TG indicated that its structure was, for temperature not exceeding 700 ℃, was not changed significantly. Sepiolite has a porous structure, especially for sepiolite fiber, which can be observed by SEM. BET indicates that sepiolite fiber has a larger pore volume than others and this can be increased by calcination. IR shows that the adsorption of sepiolite to Cl-and SO42- belongs to physical absorption, instead of chemisorption.

Carbon Nanotubes Grown on Sepiolite as Catalyst Carrier

Multi-walled carbon nanotubes were synthesized by the catalytic decomposition of acetylene at 750oC over sepiolite powder, which was treated with aqueous cobalt nitrate. It is expected that the composite with high specific area will have high capacity of hydrogen storage.

Lanthanum-Promoted Ru/Sepiolite in Ammonia Synthesis

A new kind of Ru supported on sepiolite catalyst with La as promoter for ammonia synthesis was prepared. The effects of reaction conditions on catalytic activity were discussed. The result shows that La is an effective promoter for sepiolite-supported Ru based catalyst. When the load of Ru is 5% (mass fraction), and the molar ratio of La/Ru is 1.5, under the condition of 10 MPa 450 ℃ 20000 h-1, the ammonia synthesis rate is 38.5 mmol NH3·g-1·h-1.

Modification of Sepiolite by Treatment with Methyl Triethoxysilane

Grafting reaction of methyltriethoxysilane on sepiolite surface was studied.The structure of the silanized product before and after thermal treatment was characterized by XRD,TG-DTA,SEM and IR.It is found that the silicon monomers are grafted on the external surface of sepiolite via silicon hydroxyls.The thermal stability remains unchanged after silanization.

Effects of Promoters on a Ru/Sepiolite Catalyst for Carbon Dioxide Methanation

In this work, CO_2 methanation has been investigated over Ru-based catalysts.The effects of promoters on the activity, selectivity and reduction properties of the Ru/sepiolitecatalyst were analyzed by kinetic and thermodynamic methods. The catalysts were characterized bymeans of TPD, and the results revealed that the addition of Mo, Mn or Co improved the properties ofthe Ru/sepiolite catalyst. The effects of promoters could affect the change of enthalpy, entropy andchemical potential.

Study on Modification of Sm_2O_3 by Ni/Sepiolite Catalyst

A series of Ni Sm/sepiolite catalysts were prepared by impregnation. The modification of Sm 2O 3 for Ni/sepiolite was investigated by TPR, XPS and poisoning of CS 2, respectively. The results indicate that the addition of Sm 2O 3 improves the activity of hydrogenation and anti poisoning ability of Ni/sepiolite catalyst, and it also increases the dispersion of nickel atoms over support and the amount of active nickel atoms in catalyst. Effect of Sm 2O 3 on Ni/sepiolite catalyst includes not only electronic effect but also steric effect, whereas electronic effect seems to be principal.

Preparation and Properties of Organically Modified Sepiolite/High-performance Epoxy Nanocomposites

Fibrous organic sepiolites （OSEP） and novel epoxy/OSEP nanocomposites were prepared, and different methods were investigated to produce an intercalated/exfoliated structure of OSEP. Experimental results show that the modifier molecules can be easily adsorbed by the sepiolite, but the layer space （d001 of the sepiolite, linked by means of covalent bond, remains unchanged. A proper method to solve this problem appears to exert large shearing force on the original sepiolite followed by its organic modification （OSEP2）. The morphology observation shows that there are formed an even dispersion of nano-sized OSEP2 fibers in epoxy resin and a structure intercalated by epoxy molecules, which lead to significantly improved mechanical properties. Impact strength of the epoxy/OSEP2 nanocomposite increases from 32.1 kJ/m^2 to 44.4 kJ/m^2, 38.3% higher than that of pristine matrix with 3 wt% OSEP2 content. It is also noted that the flexural strength of the OSEP/epoxy composites has risen by about 3% higher than that of the pure epoxy resin.

Effect of Transition Metals on Catalytic Performance of Ru/Sepiolite Catalyst for Methanation of Carbon Dioxide

The effects of Mo, Mn and Zr transitional metals on the catalytic performance of Ru/sepiolite for CO2 methanation were investigated. The results indicated that addition of the transitional metals affected the activity of the Ru/sepiolite remarkably, and the activities of the catalysts were closely associated with the electronic state of the ruthenium surface. The addition of Mo increased the active surface area, the Ru dispersity, the number of active sites, and the resistance to poisoning. According to the Transition State Theory, when Mo is added into the Ru/sepiolite catalyst, the decrease in surface energy is at a cost of an increment in steric hindrance. When T≤674 K, the energy factor was dominating, and resulted in a decreasing in the ratio of S(CU4)/S(CO). Otherwise, the steric factor dominated the reaction course.

RESEARCH ON CLEANUP AND ACTIVATION OF SEPIOLITE

A simple process of purifying and activating sepiolite is introduced. Impure minerals in sepiolite can be removed by fully agitating the sepiolite suspension to which a few amount of disperser has been added. After being purified and activated, fine sepiolite particles present prior properties such as increased specific area,better dispersiveness and increased adsorptivity, moreover, the pulping ratio can be raised from original 4-5m3/2 to 20m3 /t. The process with simple technique and utilizing cheap chemical agents extends the application of low-grade sepiolite.

DEVELOPMENT OF SEPIOLITE TYPE FILTER TIPS OF CIGARETTE

Activating conditions of sepiolite are studied by determining specific surface method. Sepiolite is used in processing filter tip of cigarette of acetate silk and paper type first. Tar of cigarette with sepiolite filter tip is lowered to a lower tar level. Mechanism of the lowered tar content by sepiolite is analysed.

Study on the Adsorption Capability of Fe Modifying Sepiolite on Cr(Ⅵ)

[ Objective] The research aimed to study the adsorption capability of Fe modifying sepiolite on Cr（Vl）. [ Method] FeCl3 solution with different concentrations was used to modify sepiolite. By static adsorption experiment, the adsorption capability of Fe modifying sepiolite on Cr（VI ） was studied. [Result] Under the condition of initial Cr（VI） concentration of 90 mg/L, 10.0% IMS dosage of 5 g/L, pH of 4.5, adsorption time of 90 min, and temperature of 25 ℃ the equilibrium adsorption quantity of Fe modifying sepiolite was 6.5 mg/g. [Conclusion] The research provided an effective pathway for the application of Fe modifying sepiolite in Cr（VI）-containing wastewater treatment.

Preparation and Characterization of Sepiolite Microfibers with High Aspect Ratio

It is difficult to access exfoliated sepiolite(Sep)fibers with high aspect ratio from Sep ore.The traditional method used to purify Sep ore also reduces its aspect ratio.In this study,impurities in the Sep ore were removed by acid activation followed by a cetyltrimethylammonium chloride(C16)treatment to organically modify the purified Sep by cation exchange.Then,the organically-modified Sep(O-Sep)was stripped and processed by an ultrasonic cell crusher to obtain Sep microfibers at a specific frequency for a given period.These Sep samples had relatively high aspect ratio,compared with the Sep fibers gotten by traditional method.Scanning electron microscopy(SEM)and transmission electron microscopy(TEM)demonstrate the micro-morphology of exfoliated Sep samples in an intuitive way.Moreover,pure inorganic membrane prepared only with the exfoliated Sep fibers exhibited excellent flexibility,further demonstrating the excellent properties of Sep fibers with high aspect ratio.

Enhanced atrazine adsorption from aqueous solution using chitosan-modified sepiolite

A novel clay mineral biocomposite, chitosan-modified sepiolite(CMSEP), was prepared and used as adsorbent to remove atrazine from water. The adsorption behaviors including thermodynamic and kinetic parameters, effect factors and mechanisms of atrazine adsorption on CMSEP were studied. The results show that the adsorption capacity of atrazine on CMSEP increases with increasing temperature. Protonation of chitosan in biocomposite can improve adsorption ability of the composite to a certain extent. The parameters ΔGΘ, ΔHΘ and ΔSΘ are-1.48--2.69 k J/mol, 7.54 k J/mol and 30.28 J/mol, respectively. Langmuir isotherm is proved to describe the adsorption data better than other isotherms with a maximum adsorption capacity of 17.92 mg/g, suggesting that the adsorption process is homogeneous. Pseudo-second-order kinetic model can fit the adsorption kinetic processes well although intraparticle diffusion can not be discarded. Briefly, CMSEP has potential value in the removal of atrazine from water and wastewater.

In situ stabilization remediation of cadmium contaminated soils of wastewater irrigation region using sepiolite

The effects of immobilization remediation of Cd-contaminated soils using sepiolite on soil pH, enzyme activities and microbial communities, TCLP-Cd （toxicity characteristic leaching procedure-Cd） concentration, and spinach （Spinacia oleracea） growth and Cd uptake and accumulation were investigated. Results showed that the addition of sepiolite could increase soil pH, while the TCLP-Cd concentration in soil was decreased with increasing sepiolite. The changes of soil enzyme activities and bacteria number indicated that a certain metabolic recovery occurred after the sepiolite treatments, and spinach shoot biomass increased by 58.5%-65.5% in comparison with the control group when the concentration of sepiolite was ~ 10 g/kg. However, the Cd concentrations in the shoots and roots of spinach decreased with an increase in the rate of sepiolite, experiencing 38.4%-59.1% and 12.6%--43.6% reduction, respectively, in contrast to the control. The results indicated that sepiolite has the potential for success on a field scale in reducing Cd entry into the food chain.

Preparation and visible photocatalytic dye degradation of Mn-TiO2/sepiolite photocatalysts

The performance of Mn-TiO2/sepiolite photocatalysts prepared by the solgel method and calcinated at different temperatures was studied in the photocatalytic degradation of direct fast emerald green dye under visible light irradiation,and a series of analytical techniques such as XRD,SEM,FTIR,TG-DSC,XPS,UV-vis-DRS and Raman spectroscopy were used to characterize the morphology,structure and optical properties of the photocatalysts.It is found that the anatase TiO2 was formed in all photocatalysts.Mn4+might incorporate into the lattice structure of TiO2 and partially replace Ti4+,thus causing the defects in the crystal structure and the broadening of the spectral response range of TiO2.At the same time,TiO2 particles were dispersed on the surface of the sepiolite,which immobilized TiO2 particles with sepiolite via the bond of Ti-O-Si.Mn-TiO2/sepiolite calcined at 400°C exhibits the highest photocatalytic activity and the degradation rate of direct fast emerald green is up to 98.13%.Meanwhile,it also shows good stability and universality.