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1.
The effects of calcium carbonate (CaCO 3) and calcium sulfate (CaSO 4) nanoparticles on the thermal and UV-absorbing properties of polyvinyl acetate (PVAc) were analyzed in this study. Nanoparticles of CaCO 3 and CaSO 4 were synthesized by in situ deposition technique. The size and shape of nanoparticles were recognized by X-ray diffraction and scanning electron microscope (SEM) analyses which confirmed that the particle was having a diameter of 25–33 nm. In this technique, the surface modification of nanoparticles was done by non-ionic polymeric surfactant. PVAc/CaCO 3 and PVAc/CaSO 4 nanocomposites film samples with an average thickness of 30 µm and in the mass ratio of nanoparticles (0–4% (w/w)) were prepared by solution mixing technique. Chemical, structural, and elemental characterizations of nanocomposites were done by, fourier transform infrared, SEM, and energy dispersive X-ray spectroscopy analyses, respectively. Thermal properties of pure polymer and nanocomposites were characterized through differential scanning calorimetric, thermogravimetric, and differential thermogravimetry techniques. The glass transition temperature of nanocomposites increases with increase in content of nanoparticles. It may be due to the interaction between inorganic and organic components. The thermogravimetric analysis results indicate that the thermal degradation temperatures of nanocomposites were enhanced upon the addition of nanosized inorganic fillers. The thermal results show that PVAc/CaSO 4 nanocomposites were more thermally stable than PVAc/CaCO 3 nanocomposites. The addition of nanoparticles affects degradation mechanism and consequently improves thermal stability of PVAc. The reduction of polymer chain mobility and the tendency of nanoparticles to eliminate free radicals were the principal effects responsible for these enhancements. The ultraviolet–visible (UV–Vis) absorbance spectra of PVAc and its nanocomposites films show that the intensity of absorbance increases with increasing filling content, suggesting that nanocomposites films have greater UV-shielding property. 相似文献
2.
In order to improve the scale inhibition efficiency of existing polyepoxysuccinic acid (PESA) and to study the impact of their molecular structure on scale inhibition efficiency, a series of PESA with linear and hyper-branched structure have been designed and synthesized through co-polymerization reaction with glycidyl and epoxy succinate. The scale inhibition behavior of PESA with linear and hyper-branched structure against CaCO 3 and CaSO 4 scales was evaluated using static scale inhibition method, and their ability to retard deposition of CaCO 3 was also examined. The experimental results showed that, for CaCO 3 and CaSO 4, the PESA with hyper-branched structure provides a scale inhibiting efficiency as high as 95.9% and 94.3%, respectively, at an inhibitor concentration of 15?mg/L. In addition, the processes of crystal nucleation, growth and crystal morphology have been analyzed. The experimental results show that the PESA with hyper-branched structure not only prolongs the induction period of CaCO 3 crystal nucleation, but also reduces the number of crystal nuclei and changes the size and morphology of the CaCO 3 crystal. Moreover, the FTIR, SEM and XRD analyses showed that the PESA with hyper-branched structure can induce the irregularity of growing CaCO 3 crystal, destroy the formation of crystals and change the polymorphs of calcium scale crystal. This conclusion indicates that the prepared PESA with hyper-branched structure has great potential for applying in the treatment of industrial water. 相似文献
3.
Formation of precipitates containing CaSO 4 during membrane distillation, applied to the concentration of aqueous salt solutions, is discussed in this paper. It was
found that the concentration of SO 42− ions in such solutions should not exceed 600 mg L −1 when they are subjected to concentration. However, concentration of sulphates at the level of 800 mg L −1 in the feed is permissible provided that the excess of CaSO 4 is removed in a crystallizer. Crystallisation of salts, mainly CaSO 4 · 2H 2O, on the surface and inside the membrane was observed at higher feed concentrations, causing damage of the module. Precipitation
of calcium sulphate was also observed during the production of demineralised water when high values of the water recovery
coefficient (above 90 %) were used. In this case, the formed precipitate also contained CaCO 3, the co-precipitation of which significantly changed the properties of the scaling layer. The precipitate containing both
CaSO 4 and CaCO 3 was formed mainly on the membrane surface and it could easily be removed by rinsing the module with a HCl solution.
Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatransé Matliare, 26–30 May
2008. 相似文献
4.
Mixtures of CaCO 3 and varying amounts of Na 2CO 3, K 2CO 3 and NaCl were subjected separately to thermal analysis. DTG, DTA, TG analyses indicate that the presence of alkali salts in CaCO 3 influences its decomposition behaviour. A minimum DTA peak temperature of CaCO 3 decomposition is noticed at low concentrations of alkali salts (K 2CO 3 and Na 2CO 3); an increase in concentration increases the DTA peak temperature. However, in the case of NaCl no appreciable lowering of the DTA peak temperature of CaCO 3 decomposition is observed. Similarly, the minimum temperature at which decomposition completes is found to correspond to the concentration of 1 per cent salt (K 2CO 3 and Na 2CO 3) in CaCO 3. 相似文献
5.
老山汉墓土遗址中可溶-微溶盐导致遗址表面酥碱、起甲、泛白和块状脱落等病害较为严重.利用X射线荧光光谱(XRF)、X射线衍射仪(XRD)、X射线光电子能谱(XPS)以及离子色谱(IC)等方法测定了老山汉墓遗址不同取样位置及距遗址表面不同深度处可溶盐的成分及含量,并分析了盐分对遗址破坏的可能机制.结果表明,该遗址的主要有可溶盐有Na2SO4、Na2SO4·10H2O、Na Cl、Na12Mg7(SO4)13·15H2O,微溶盐有Ca SO4、Ca SO4·2H2O,此外还含有少量的Ca Cl2、KNO3、KCl、Mg Cl2、K2SO4、Mg SO4等盐分.随着取样深度增加,各盐分的种类及含量有所减少,此分布规律可能与可溶盐的赋存环境及水分运移有关.试验结果对于老山汉墓土遗址的保护措施具有一定的参考价值. 相似文献
6.
Summary The aim of the present work was to show that ion exchange resins can be used to remove sparingly and slightly soluble salts
from calcareous and gypseous soils, which may otherwise cause serious errors in the determination of cation exchange capacity.
It was shown that CaCO 3 and CaSO 4-2H 2O can be removed from a mixture with montmorillonite(Ca++) by a mixed bed resin. After resin treatment of the mixture its
C.E.C. as retained Sr ++ corresponds approximately to the C.E.C. for pure montmorillonite within certain limits. Use of an anion exchange resin alone
for removing these salts, however, gave an Sr ++ retention well below the C.E.C. for the mineral. It was assumed that this results from the blocking of exchange sites by
resin particles.
Zusammenfassung In kalkhaltigen und gipshaltigen B?den st?ren CaCO3 und CaSO4-2H2O die Bestimmung des Kationenaustauschverm?gens.
In der vorliegenden Arbeit wird gezeigt, da? Salze wie CaCO3 und CaSO4-2H2O aus Mischungen mit Ca-Montmorillonit durch Ionenaustauscher herausgel?st werden k?nnen.
Als Ionenaustauscher müssen jedoch Mischbettaustauscher verwendet werden; Anionenaustauscher allein liefern bei einer anschlie?enden
Bestimmung des Kationenaustausches mit Sr++ falsche Werte.
Die angegebene Methode erscheint vor allem für die Untersuchung von B?den wichtig zu sein.
相似文献
7.
The activity coefficients of ZnSO 4, MgSO 4, CaSO 4, and SrSO 4 are measured by means of cells with ion-exchange liquid membranes similar to those described in the previous papers of this
series. Negative deviations from the limiting law are observed in the dilute region. These deviations are, for ZnSO 4, appreciably more important than recent literature has indicated, and the corresponding activity coefficients need to be
corrected by about 12%. Pitzer’s theory best-fit coefficients have accordingly been recalculated. The osmotic coefficients
are also derived. Accessory information on the hydration state for zinc, magnesium, and sulfate ions, is presented. 相似文献
8.
Improved thermoanalytical methods have been developed that are capable of quantitative identification of various components of fly ash from a laboratory-scale fluidized bed combustion system. The thermogravimetric procedure developed can determine quantities of H 2O, Ca(OH) 2, CaCO 3, CaSO 4 and carbonaceous matter in fly ash with accuracy comparable to more time-consuming ASTM methods. This procedure is a modification of the Mikhail-Turcotte methods that can accurately analyze bed ash, with higher accuracy regarding the greater amount of carbonaceous matter in fly ash. In addition, in conjunction with FTIR and SEM/EDS analyses, the reduction mechanism of CaSO 4 as CaSO 4+4H 2 CaS + 4H 2O has been confirmed in this study. This mechanism is important in analyzing and evaluating sulfur capture in fluidized-bed combustion systems. 相似文献
9.
Summary. Calcium sulfate occurs in nature in form of three different minerals distinguished by the degree of hydration: gypsum (CaSO 4·2H 2O), hemihydrate (CaSO 4·0.5H 2O) and anhydrite (CaSO 4). On the one hand the conversion of these phases into each other takes place in nature and on the other hand it represents
the basis of gypsum-based building materials. The present paper reviews available phase diagram and crystallization kinetics
information on the formation of calcium sulfate phases, including CaSO 4-based double salts and solid solutions.
Uncertainties in the solubility diagram CaSO 4–H 2O due to slow crystallization kinetics particularly of anhydrite cause uncertainties in the stable branch of crystallization.
Despite several attempts to fix the transition temperatures of gypsum–anhydrite and gypsum–hemihydrate by especially designed
experiments or thermodynamic data analysis, they still vary within a range from 42–60°C and 80–110°C. Electrolyte solutions
decrease the transition temperatures in dependence on water activity.
Dry or wet dehydration of gypsum yields hemihydrates (α-, β-) with different thermal and re-hydration behaviour, the reason
of which is still unclear. However, crystal morphology has a strong influence.
Gypsum forms solid solutions by incorporating the ions HPO 4
2−, HAsO 4
2−, SeO 4
2−, CrO 4
2−, as well as ion combinations Na +(H 2PO 4) − and Ln 3+(PO 4) 3−. The channel structure of calcium sulfate hemihydrate allows for more flexible ion substitutions. Its ion substituted phases
and certain double salts of calcium sulfate seem to play an important role as intermediates in the conversion kinetics of
gypsum into anhydrite or other anhydrous double salts in aqueous solutions. The same is true for the opposite process of anhydrite
hydration to gypsum. Knowledge about stability ranges (temperature, composition) of double salts with alkaline and alkaline
earth sulfates (esp. Na 2SO 4, K 2SO 4, MgSO 4, SrSO 4) under anhydrous and aqueous conditions is still very incomplete, despite some progress made for the systems Na 2SO 4–CaSO 4 and K 2SO 4–CaSO 4–H 2O.
Corresponding author. E-mail: daniela.freyer@chemie.tu-freiberg.de
Received December 17, 2002; accepted January 10, 2003
Published online April 3, 2003 相似文献
10.
Polyhalite (K 2SO 4 · MgSO 4 · 2CaSO 4 · 2H 2O) and analogue triple salts, where Mg 2+ is substituted by Mn 2+, Fe 2+, Co 2+, Ni 2+, Cu 2+ and Zn 2+, have been synthesized. The salts were characterized by thermal analysis, Raman spectroscopy and X-ray powder diffraction.
Diffraction patterns and Raman spectra resemble those of natural polyhalite, except K 2SO 4 · CuSO 4 · 2CaSO 4 · 2H 2O. The latter corresponds to the mineral leightonite, which is structurally different. 相似文献
11.
The types of change in surface properties and porosity of milled materials having widely different hardness and crystal structure are reviewed. For more intensive milling, the use of vacuum balance techniques in conjunction with X-ray diffraction, optical- and electron-microscopy enables changes in microstructure and phase composition to be determined during mechanochemical reactions.Metallic or non-metallic harder materials (Mohs scale 8–9), such as transition metal nitrides or silicon nitride and boron carbide, increase their surface on milling largely due to brittle fracture, so that the surface area tends towards an upper limiting value with comparatively little development of porosity.Softer materials (Mohs scale 1–2), such as gypsum, china clay(Kaolinite) and hydrated lime and magnesia undergo plastic deformation and strain hardening on longer milling, so that the surface area passes through a maximum before decreasing to an equilibrium value. This is applicable also to materials of intermediate hardness (Mohs scale 3–5), such as calcite, magnesite and dolomite, provided that the milling is sufficiently intensive; the flow and welding processes during the plastic deformation leave the grains non-porous to nitrogen gas, but adsorption of water vapour causes development of porosity, a phenomenon also observed with lunar fines (mainly silicate minerals) which are of somewhat greater hardness but contain amorphous surface layers (cf. Beilby layer) and nuclear particle damage tracks having tubular pores with narrow constrictions forming micropores.More intensive milling can result in crystal transformation and mechanochemical reactions. Thus gypsum is converted to anhydrite, viz., CaSO 4.2H 2O → CaSO 4.2H 2O → γ—CaSO 4 → β—CaSO 4. Calcite, CaCO 3, is converted to aragonite, while calcitic CaCO 3 and magnesite, MgCO 3, form dolomite CaCO 3.MgCO 3. 相似文献
12.
The influence of various salts on the atomization signal of lead has been examined by using a transverse heated atomic absorption spectrometer. To get more information about interference mechanisms, volatilization of salts has been studied by ion chromatographic analysis of the residue left on the furnace after drying or charring. The use of a Pd/Mg chemical modifier in these model solutions has also been examined. In 0.1 M chloride medium, NaCl, MgCl 2 and CaCl 2 do not interfere significantly. However, their different behaviour in the furnace, and particularly hydrolysis of MgCl 2 influence greatly the charring curves of Pb. The use of a Pd/Mg modifier appears interesting only in the case of NaCl. Indeed, Pd stabilizes Pb sufficiently to permit the removal of NaCl by charring. In the case of MgCl 2, Pb is not sufficiently stabilized to remove chloride through hydrolysis of MgCl 2 or volatilization of MgCl 2. In the presence of CaCl 2, the Pb signal is delayed and coincides with the background absorption signal of CaCl 2; the stabilization effect is not sufficient to eliminate CaCl 2 by charring before atomization. At 0.1 M nitrate concentration, the presence of NaNO 3, Mg(NO 3) 2, and particularly Ca(NO 3) 2, greatly modifies the atomization signal shape of Pb. Pb is more stabilized in nitrate medium, but losses are observed at the decomposition step of nitrate salts. In this medium, the stabilization effect of Pd leads to a single peak signal and permits elimination of nitrate decomposition products before atomization. Interference effects are more important in the presence of 0.1 M sulphate salts and increase with the acidity of the medium. Na 2SO 4, which is reduced to Na 2S on the graphite, does not interfere significantly. However, the decomposition products of MgSO 4 and CaSO 4 induce an important interference effect on the determination of Pb which is stabilized in the furnace. In the case of Na 2SO 4, the use of the Pd/Mg modifier delays the atomization signal which coincides with the background absorption signal, leading to an important interference effect which cannot be eliminated by charring. In the presence of MgSO 4 and CaSO 4, the stabilizing effect of Pd permits the elimination of decomposition products of sulphate salts before atomization and suppresses the chemical interference effect. 相似文献
13.
在40℃时利用电导法测定了无机盐NaCl、KCl、CuCl2、ZnSO4、Fe(NO3)3及AlCl3对十二烷基磺酸钠(SDS)溶液临界胶束浓度(CMC)的影响,并推导了表示无机盐浓度和SDS溶液CMC值之间关系的线性方程.结果表明,随着各种无机盐浓度的增加,SDS溶液的CMC值降低,且不同价态的金属无机盐对SDS溶液... 相似文献
14.
Calcium sulfate whiskers can be used as the reinforcing agents in many composites, such as polymers, ceramics, cements, and papers, etc. This paper investigated the feasibility of preparing calcium sulfate whiskers using desulfurization gypsum as the raw material. The desulfurization gypsum composed mainly of CaSO 4·2H 2O (93.45 wt%) and CaCO 3 (1.76 wt%) were treated with dilute H 2SO 4 at room temperature to convert CaCO 3 to CaSO 4; the latter was then treated at 110?C150 °C to form CaSO 4·0.5H 2O whiskers. The removal of the CaCO 3 impurity from the desulfurization gypsum favored the formation of CaSO 4·0.5H 2O whiskers with high aspect ratios. 相似文献
15.
This paper aims to evaluate the influence of three kinds of sulfates from the green production of cement on its sintering and hydration. The properties of clinker and hydration were monitored by thermogravimetric and differential thermal analysis (TG–DTA), X-ray diffraction, X-ray fluorescence and isothermal conduction calorimeter. Results indicate that gypsum lowers the decomposition temperature of CaCO3 and all these Sulfates will enhance the solid-phase reaction but increase melting temperature. Sulfates reduce the content of C3S, but K2SO4 and 2CaSO4·K2SO4 is conducive to the formation of β-C2S. The hydration induction period is shortened by the sulfates. K2SO4 and 2CaSO4·K2SO4 improve the early hydration of clinker, but gypsum may lightly reduce the hydration reactivity of clinker in acceleration period. 2CaSO4·K2SO and K2SO can significantly accelerate the compressive strength development of cement clinker before 3 d; by contrast, gypsum is detrimental for that. The precipitation of hydration products (CH and C–S–H) in clinker with sulfates is more than that of clinker without sulfates at 9 h. K2SO4 can accelerate the hydration of clinker without forming ettringite. 相似文献
16.
We performed the Rupe rearrangement of 1-ethynylcyclohexan-1-ol in near-critical water to study the reaction under high temperature
conditions. The final product thus obtained was primarily 1-cyclohexen-1-ylethanone which was identified by GC-MS. The influences
of reaction time, temperature, and initial reactant-to-water ratio on the yield of 1-cyclohexen-1-ylethanone were examined.
The yield of 1-cyclohexen-1-ylethanone was 49 % in pure water at 260°C for a reaction time of 60 min. However, when additives
such as ZnSO 4, FeCl 3, and NaHSO 4, respectively, were introduced to the water to investigate the effect of salts on the Rupe rearrangement reaction, the yield
increased markedly to as much as 88 % in 5 mole % NaHSO 4 aqueous solution under the same conditions. The catalytic ability of the additives decreased in order: NaHSO 4, FeCl 3, ZnSO 4. On the basis of these results, a possible reaction mechanism of the Rupe rearrangement of 1-ethynylcyclohexan-1-ol in near-critical
water was proposed. 相似文献
17.
Ca 4[Al 6O 12]SO 4 (yeelimite) is prepared by solid state reaction of CaCO 3, Al 2O 3, and CaSO 4 (1300 °C, 4 h, slow cooling). 相似文献
18.
Literature values of the electrical conductivities of dilute aqueous solutions of alkaline metal sulfates (BeSO 4, MgSO 4, CaSO 4, SrSO 4) and of transition metal sulfates (MnSO 4, FeSO 4, CoSO 4, NiSO 4, CuSO 4, ZnSO 4, CdSO 4) were reexamined within the framework of the Quint-Viallard conductivity equations in order to obtain a uniform representation
of conductivities. It was observed that the limiting conductances of electrolytes at infinite dilution are very similar irrespective
of the applied conductivity equation, whereas the derived ion association equilibrium constants vary considerably. The ion
association equilibrium constants are therefore of doubtful physical value and should be treated rather as just fitting parameters. 相似文献
19.
Polyhalite (K 2SO 4 · MgSO 4 · 2CaSO 4 · 2H 2O) and analogue triple salts, where Mg 2+ is substituted by Mn 2+, Fe 2+, Co 2+, Ni 2+, Cu 2+ and Zn 2+, have been synthesized. The salts were characterized by thermal analysis, Raman spectroscopy and X-ray powder diffraction.
Diffraction patterns and Raman spectra resemble those of natural polyhalite, except K 2SO 4 · CuSO 4 · 2CaSO 4 · 2H 2O. The latter corresponds to the mineral leightonite, which is structurally different.
For polyhalite analogues the cell parameters of the triclinic unit cell have been determined from the powder diffraction patterns.
The length of the unit cell vectors varies regularly with the ionic radius of the substituted ion M
2+ and is explained by changes in the extension of the coordination octahedron of M
2+. Thereby increasing distances of the coordinated water molecules at M
2+ parallel with decreasing dehydration temperatures of the corresponding polyhalite.
Correspondence: Daniela Freyer, Institut für Anorganische Chemie, TU Bergakademie Freiberg, 09599 Freiberg, Germany. 相似文献
20.
Thermal decomposition of different inorganic sulphates are presented. A number of techniques, but mainly TG and DTA, are used to prove the mechanism and kinetics of CaSO 4, BaSO 4, FeSO 4·xH 2O, Al 2(SO 4) 3·xH 2O under various gas atmospheres. It is shown how the partial pressure of gas components and heating rate may effect the mechanism and kinetic parameters. There are also examples on the effects of some additives and initial treatment on the thermal processes. On the base of the results obtained some recommendations are given concerning the precautions to be taken into account in the thermal decomposition studies and the sulphur recovering. 相似文献
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