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1.
The dependences of the differential molar isosteric heat of adsorption and entropy of adsorption of CO2 on zeolite NaX were determined in wide temperature (196–423 K) and pressure (0.1 Pa to 5.4 MPa) intervals. In the initial region of adsorption (a < 1 mmol g–1), the differential molar heat of adsorption increases from 40 to 43 kJ mol–1 and then decreases to 33 kJ mol–1. The heat of adsorption remains virtually unchanged at 3 mmol g–1< a < 6.5 mmol g–1 and decreases sharply at high fillings of zeolite micropores (a > 7 mmol g–1). The heat of adsorption was found to be temperature-dependent. The region with the constant heats shrinks with the temperature increase, and the heats begin to decrease at lower fillings of micro pores. The dependences of the change in the differential entropy of the adsorption system on the amount adsorbed were calculated at different temperatures. The specific features of the behavior of the thermodynamic functions of this adsorption system in the initial and medium region of fillings kre associated with interactions of adsorbate molecules with Na+ cations and walls of large cavities. For high fillings, an increase in repulsion forces between adsorbed molecules results in a sharp expansion of the adsorbent and a decrease in the heat of adsorption.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1570–1573, August, 2004. 相似文献
2.
Boleslav Taraba 《Journal of Thermal Analysis and Calorimetry》2012,107(3):923-926
Simple adaptation of the technique of immersion calorimetry enables determining both integral and differential adsorption
heats as well as the course of the adsorption isotherm of phenol on activated carbon. The innovative aspect of the applied
procedure consists in bringing the phenol aqueous solution to contact with the suspension of carbon with water. Thus, the “interfering” heat effect of carbon interaction with water is eliminated, and only the net
adsorption heat of phenol is monitored. The value of −52.5 kJ mol−1 was ascertained as the molar differential adsorption heat at the low surface coverage (cca 0.2 mmol g−1) of the sample of microporous carbon. As the adsorption process continues, for adsorption uptakes exceeding the value of
about 1 mmol g−1, molar differential adsorption heats appear to be established at a level of about −20 + 5 kJ mol−1. 相似文献
3.
Kharitonov A. B. Fomkin A. A. Pribylov A. A. Sinitsyn V. A. 《Russian Chemical Bulletin》2001,50(4):591-594
Carbon dioxide adsorption on the microporous carbon adsorbent PAU-10 within the 177.8—423 K temperature and 0.1—5.13·106 Pa pressure intervals was studied. The isosteres of absolute adsorption are well approximated by straight lines, which do not change their slope on going to temperatures higher than the critical temperature of CO2. An increase in the differential molar isosteric heat of adsorption (q
st) at 0 < a < 1 mmol g–1 is explained by the influence of the endothermic effect of adsorption expansion of the adsorbent. In the region of high pressures and nonideal gas phase, q
st is temperature-dependent. 相似文献
4.
Isotherms of carbon dioxide adsorption and adsorption-induced deformation of pelletized crystalline NaX zeolite at pressures of 0.2--5.4 MPa and temperatures of 195--423 K are measured. The adsorption deformation is positive at low zeolite micropore filling (a < 1 mmol g-1) at all temperatures, i.e., the zeolite suffers expansion. Further, as the amount of the adsorbed substance increases, the adsorption deformation curves pass first through a maximum and then through a minimum. In the range of high fillings (a > 7 mmol g-1) the NaX zeolite shows dramatic expansion. 相似文献
5.
Jiankun Xie Qinyan Yue Hui Yu Wenwen Yue Renbo Li Shengxiao Zhang Xiaona Wang 《Frontiers of Chemistry in China》2008,3(1):33-40
Activated carbon was prepared from the sewage sludge of municipal wastewater treatment plant by chemical activation (activation
reagent is ZnCl2) and was used for the adsorption of dye (reactive brilliant red K-2BP). The impact of adsorbent amount, adsorption time and
pH value on adsorption effect, the adsorption kinetics, and the adsorption thermodynamics were discussed according to batch
adsorption tests. The results indicated that the activated carbon developed from sewage sludge (ACSS), which was mesoporous,
possessed opened porous structures. The iodine number of the ACSS was 326 mg·g−1. The rate of achievement was 51.31%. The BET surface area was 298 m2·g−1 and the contents of heavy metals in the leachate didn’t exceed the contents limit. The adsorption kinetics of reactive brilliant
red K-2BP on the ACSS was accorded with the two-step kinetics rate equation and pseudo-second-order kinetics equation. Compared
to the Freundlich isotherm equation, the Langmuir isotherm equation showed better applicability for the adsorption. The adsorption
which was favorable was an endothermic (enthalpy ΔH > 0) and spontaneous (free energy ΔG < 0) process and was accompanied by an increase in entropy (ΔS > 0).
__________
Translated from Journal of Shandong University (Natural Science), 2007, 42(3): 64–70 [译自: 山东大学学报(理学版)] 相似文献
6.
Summary A new graphitized carbon black (Carbograph 5) with a specific surface area (560 m2 g−1) greater than those of commerically available graphitized carbons was studied by gas chromatography to determine the enthalpy,
entropy, and free energy of adsorption of a series of alkanes (C2−C6). The adsorption properties were also investigated by considering changes in the isosteric heats and entropies of adsorption
when a nonpolar stationary phase (squalane) was added to the adsorbent. The data obtained are discussed and compared with
literature values for other graphitized carbon blacks. 相似文献
7.
Yakovlev V. Yu. Fomkin A. A. Tvardovski A. V. Sinitsyn V. A. Pulin A. L. 《Russian Chemical Bulletin》2003,52(2):354-358
Deformation of the ACC microporous carbon adsorbent during adsorption of carbon dioxide, nitrogen, and argon in the temperature interval from 243 to 393 K and at pressures of 1—5·106 Pa was studied. The effect of adsorbent contraction was found in the initial temperature interval at relatively low pressures. However, the negative value of relative linear deformation L/L smoothly transforms into positive values with the pressure increase. Only the effect of adsorbent expansion is observed at high temperatures in the whole pressure interval. The dependence of the deformation effects for different systems on the adsorbent nature was revealed. 相似文献
8.
Fomkin A. A. Nikiforov Yu. V. Sinitsyn V. A. Savel"ev E. G. 《Russian Chemical Bulletin》2002,51(12):2161-2164
The adsorption of perfluoropropane (N3F8) on the PAC microporous carbon adsorbent, which is close in properties to monoporous adsorbents, was studied at temperatures of 216, 243, 295, 318, and 343 K in the pressure interval from 1 to 1·105 Pa. The adsorption isosters are well approximated by straight lines in the studied interval of temperatures and pressures. The dependence of the isosteric heats of adsorption on filling is described by a curve with a maximum in the region of high fillings. Such a curve is characteristic of adsorbents with a narrow pore size distribution. 相似文献
9.
Adsorption of vanadium(V) from aqueous solution onto ZnCl2 activated carbon developed from coconut coir pith was investigated to assess the possible use of this adsorbent. The influence
of various parameters such as agitation time, vanadium concentration, adsorbent dose, pH and temperature has been studied.
First, second order, Elovich and Bangham’s models were used to study the adsorption kinetics. The adsorption system follows
second order and Bangham’s kinetic models. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherms have been employed
to analyze the adsorption equilibrium data. Equilibrium adsorption data followed all the four isotherms—Langmuir, Freundlich,
D-R and Temkin. The Langmuir adsorption capacity (Q
0) was found to be 24.9 mg g− 1 of the adsorbent. The per cent adsorption was maximum in the pH range 4.0–9.0. The pH effect and desorption studies showed
that ion exchange mechanism might be involved in the adsorption process. Thermodynamic parameters such as ΔG
0, ΔH
0 and ΔS
0 for the adsorption were evaluated. Effect of competitive anions in the aqueous solution such as PO4
3 −, SO4
2−, ClO4
−, MoO4
2−, SeO3
2−, NO3
− and Cl− was examined. SEM and FTIR were used to study the surface of vanadium(V) loaded ZnCl2 activated carbon. Removal of vanadium(V) from synthetic ground water was also tested. Results show that ZnCl2 activated coir pith carbon is effective for the removal of vanadium(V) from water. 相似文献
10.
R. Naumann d’Alnoncourt B. Graf X. Xia M. Muhler 《Journal of Thermal Analysis and Calorimetry》2008,91(1):173-179
The back-titration of atomic oxygen chemisorbed on metallic copper using carbon monoxide is investigated by microcalorimetry.
Results from simulations based on a microkinetic model of the back-titration are used for processing of microcalorimetric
data. In addition, surface oxidation of copper by nitrous oxide is investigated by microcalorimetry. The results are compared
with results obtained by nitrous oxide reactive frontal chromatography and by static oxygen adsorption studied by microcalorimetry.
The heat of adsorption of nitrous oxide on copper amounts to 304 kJ mol−1, and the heat of adsorption of carbon monoxide on surfaceoxidized copper is in the range from 120 to 70 kJ mol−1. 相似文献
11.
Biosorption of metal ions with Penicillium chrysogenum 总被引:1,自引:0,他引:1
Biosorption of metal ions with Penicillium chrysogenum mycelium is described in this article. Alkaline pretreatment was used to remove proteins and nucleic acids from cells, and
this treatment increased the adsorption capacities, for Cr3+ from 18.6 mg g−1 to 27.2 mg g−1, for Ni2+ from 13.2 mg g−1 to 19.2 mg g−1, for Zn2+ from 6.8 mg g−1 to 24.5 mg g−1. The adsorption of metal ions was strongly pH dependent. The mycelium could beused for large-scale removal of Cr3+ from tannery wastewater. The results show that this inexpensive mycelium adsorbent has potential in industry because of its
high adsorption capacity. The main chelating sites are amino groups (−NH2) of chitosan in the mycelium. A new model is established, which describes the relation of adsorption of metal ions on pH
according to amino group chelating with metal ions and H+. The relative errors of simulation for Cu2+, Ni2+, Zn2+, and Cr3+ are 4.66%, 5.45%, 11.55%, and 1.69%, respectively. 相似文献
12.
M. Mufazzal Saeed Abdul Ghaffar 《Journal of Radioanalytical and Nuclear Chemistry》1998,232(1-2):171-177
The nature of adsorption behavior of Au(III) on polyurethane (PUR) foam was studied in 0.2M HCl aqueous solution. The effect
of shaking time and amount of adsorbent were optimized for 3.16·10−5M solution of Au(III) in 0.2M HCl. The classical Freundlich and Langmuir adsorption isotherms have been employed successfully.
The Freundlich parameters 1/n and adsorption capacityK are 0.488±0.016 and (1.40±0.22)·10−2 mol·g−1, respectively. The Langmuir constants of saturation capacityM and binding energyb are (1.66±0.08)·10−4mol·g−1 and 40294±2947 l·g−1, respectively, indicating the monolayer chemical sorption. The mean free energy (E) of adsorption of Au(III) on PUR foam has been evaluated using D-R isotherm and found to be 11.5±0.16 kJ·mol−1 reflecting the ion exchange type of chemical adsorption. The effect of temperature on the adsorption has also been studied.
the isosteric heat of adsorption was found to be 44.03±1.66 kJ·mol−1. The thermodynamic parameters of ΔG, ΔH, ΔS and equilibrium constantK
c
have been calculated. The negative values of ΔG, ΔH and ΔS support that the adsorption of Au(III) on PUR foam is spontaneous, exothermic and of ion exchange chemisorption. The nature
of the Au(III) species sorbed on PUR foam have been discussed. 相似文献
13.
Adsorption of cetyltrimethylammonium bromide (CTAB) onto bituminous coal (BC) and a clay mineral, montmorillonite (MMT), was
studied. Simultaneous measurements of the CTAB adsorption and zeta potential determination of the adsorption suspensions were
carried out. The adsorption isotherms were found to be of the typical Langmuir type; values of the CTAB adsorption capacities
were calculated (a
m = 0.65 mmol g−1 for coal and a
m = 3.24 mmol g−1 for MMT). The shape of the adsorption isotherms was correlated with zeta potential values at the adsorption equilibrium.
The adsorption properties of both sorbents were studied by voltammetry on carbon paste electrodes (CPE) modified with coal-CTAB
and MMT-CTAB system, respectively. Open circuit sorption with differential pulse voltammetry was performed in order to compare
the sorption properties of the systems with the unmodified sorbents. The Cu2+ adsorption on BC and MMT decreased to approximately 50 % and 40 %, respectively. The surface adsorption mechanism of CTAB
on coal based on hydrophilic interactions was proposed. In the case of montmorillonite, the CTAB intercalation is expected
via ion exchange into the inter-layer space forming a double- or triple-layer arrangement. 相似文献
14.
In this work, a kinetic study on the thermal degradation of carbon fibre reinforced epoxy is presented. The degradation is
investigated by means of dynamic thermogravimetric analysis (TG) in air and inert atmosphere at heating rates from 0.5 to
20°C min−1 . Curves obtained by TG in air are quite different from those obtained in nitrogen. A three-step loss is observed during
dynamic TG in air while mass loss proceeded as a two step process in nitrogen at fast heating rate. To elucidate this difference,
a kinetic analysis is carried on. A kinetic model described by the Kissinger method or by the Ozawa method gives the kinetic
parameters of the composite decomposition. Apparent activation energy calculated by Kissinger method in oxidative atmosphere
for each step is between 40–50 kJ mol−1 upper than E
a calculated in inert atmosphere.
The thermo-oxidative degradation illustrated by Ozawa method shows a stable apparent activation energy (E
a ≈130 kJ mol−1 ) even though the thermal degradation in nitrogen flow presents a maximum E
a for 15% mass loss (E
a ≈60 kJ mol−1 ).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
The adsorption behavior and the differential heat of adsorption of chloroform were measured on various types of zeolite (faujasite,
ZSM-5 and mordenite) with different Si/Al ratios. The results reveal that saturated adsorption is almost proportional to the
micropore volume and is independent of the micropore structure or the Si/Al ratio. However, initial heat of adsorption was
the highest (90 kJ mol−1) on the mordenite with low Si/Al ratio, while low on the faujasite with high Si/Al ratio or ZSM-5 (50 kJ mol−1). Change in initial heat of adsorption with Si/Al ratio is small for faujasite or mordenite and large for ZSM-5. For the
comparison, trichloroethylene adsorption behavior of zeolite was also investigated. Saturated adsorption of trichloroethylene
was almost constant for all types of zeolite, while the faujasite with high Si/Al ratio exhibited an adsorption isotherm of
type V in BDDT (Brunauer, Deming, Deming and Teller) classification. The tendencies of heat of immersion are similar to the
results of the initial heat of adsorption. 相似文献
16.
Garth R. Parker Jr. 《Adsorption》1995,1(2):113-132
Aqueous 1,1,2-trichloroethene (TCE) adsorption isotherms were obtained on Ambersorb1® 563 and 572 adsorbents and Filtrasorb2® 400 granular activated carbon (GAC). The data for Ambersorb 563 adsorbent covers TCE concentrations from 0.0009 to 600 mg/L. The data for each adsorbent was fit to 15 isotherm equations to determine an optimum equation.The best equation for the TCE adsorption isotherms is the Dubinin-Astakov (DA) isotherm. The DA isotherm coefficients were used to estimate the TCE micropore volume and the adsorption potential distribution. For each adsorbent, the TCE micropore volume is equivalent to the N2 porosimetry micropore volume. The mean adsorption potential is 18.8, 13.0, and 8.9 kJ/mol, with coefficients of variation of 0.37, 0.53, and 0.67, for Ambersorb 563 and 572 adsorbents and Filtrasorb 400 GAC, respectively. Thus, Ambersorb 563 adsorbent has the most energetic and most homogeneous adsorption volume, while Filtrasorb 400 GAC has the least energetic and most heterogeneous adsorption volume. For these reasons, Ambersorb 563 adsorbent has the highest TCE capacity at low concentrations, whereas Filtrasorb 400 GAC has the highest TCE capacity at high concentrations. The performance of Ambersorb 572 adsorbent is generally intermediate to the other two adsorbents. 相似文献
17.
Modified Sorrel’s cement was prepared by the addition of ferric chloride. The modified cement (MF5) was analyzed and characterized
by different methods. Adsorption of Gd(III) and U(VI) ions in carbonate solution has been studied separately as a function
of pH, contact time, adsorbent weight, carbonate concentration, concentration of Gd(III) and U(VI) and temperature. From equilibrium
data obtained, the values of Δ H, Δ S and Δ G were found to equal −30.9 kJ ⋅ mol−1, −85.4 J ⋅ mol−1 ⋅,K−1, and −5.4 KJ ⋅ mol−1, respectively, for Gd(III) and 18.9 kJ ⋅ mol−1, 67.8 J ⋅ mol−1 K−1 and −1.3 KJ ⋅ mol−1, respectively, for U(VI). The equilibrium data obtained have been found to fit both Langmuir and Freundlich adsorption isotherms.
The batch kinetic of Gd(III) and U(VI) on modified Sorrel’s cement (MF5) with the thermodynamic parameters from carbonate
solution were studied to explain the mechanistic aspects of the adsorption process. Several kinetic models were used to test
the experimental rate data and to examine the controlling mechanism of the adsorption process. Various parameters such as
effective diffusion coefficient and activation energy of activation were evaluated. The adsorption of Gd(III) and U(VI) on
the MF5 adsorbent follows first-order reversible kinetics. The forward and backward constants for adsorption, k
1and k
2 have been calculated at different temperatures between 10 and 60∘C. Form kinetic study, the values of Δ H
* and Δ S
* were calculated for Gd(III) and U(VI) at 25∘C. It is found that Δ H
* equals −14.8 kJmol−1 and 7.2 kJmol−1 for Gd(III) and U(VI), respectively, while Δ S
* were found equal −95.7 Jmol−1K−1 and −70.5 Jmol−1K−1 for Gd(III) and U(VI), respectively. The study showed that the pore diffusion is the rate limiting for Gd(III) and (VI). 相似文献
18.
Summary A new graphitized carbon black, Carbograph 4, with a specific surface area of 240 m2 g−1 was studied in terms of enthalpy, entropy and free energy of adsorption, determined by gas chromatographic method on a series
of alkanes (C2−C6) and on benzene. The changes in the isosteric heat and entropy of adsorption when a non-polar stationary phase (squalane)
was added to the adsorbent were also investigated. The data obtained are discussed and compared to those present in the literature
for other graphitized carbon blacks. Some examples of separations obtained with Carbograph 4 are reported. 相似文献
19.
Lei Zhang Hongmei Li Xueyan Liu Pingli Kang 《Russian Journal of Inorganic Chemistry》2012,57(4):622-628
Titanium dioxide nanoparticles were employed for the sorption of Ge(IV) ions from aqueous solution. The process was studied
in detail by varying the sorption time, pH, and temperature. The sorption process was found to be fast, equilibrium was reached
within 3 min. A maximum sorption could be achieved from solution when the pH ranges between 4.0 and 11.0. Sorbed Ge(IV) ions
can be completely desorbed with 2 mL of 0.3 mol L−1 K3PO4-1.0 mol L−1 H2SO4 mixture solution. The kinetic experimental data properly correlate with the second-order kinetic model (k
2 = 0.88 g mg−1 min−1 (25°C)), Reichenberg equation and Morris-Weber model. The estimated E
a
for Ge(IV) adsorption on nano-TiO2 was 19.66 kJ mol−1. The overall rate process appears to be influenced by intra-particle diffusion. The sorption data could be well interpreted
with the Langmuir and Dubinin-Radushkevich (D-R) type sorption isotherms. The D-R parameters were calculated to be K = −0.00321 mol2 kJ−2, q
m
= 0.59 mmol g−1 and E = 12.48 kJ mol−1 at room temperature. Furthermore, the thermodynamic parameters were also determined, and the ΔH
0 and ΔG
0 values indicated a spontaneous exothermic behavior. 相似文献
20.
Sayed Z. Mohammadi Mohammad A. Karimi Daryoush Afzali Fatemeh Mansouri 《Central European Journal of Chemistry》2010,8(6):1273-1280
Two series of activated carbon have been prepared by chemical activation of Amygdalus Scoparia shell with phosphoric acid or zinc chloride for the removal of Pb(II) ions from aqueous solutions. Several methods were employed
to characterize the active carbon produced. The surface area was calculated using the standard Brunauer-Emmet-Teller method.
The microstructures of the resultant activated carbon were observed by scanning electron microscopy. The chemical composition
of the surface resultant activated carbon was determined by Fourier transform infrared spectroscopy. In the batch tests, the
effect of pH, initial concentration, and contact time on the adsorption were studied. The data were fitted with Langmuir and
Freundlich equations to describe the equilibrium isotherms. The maximum adsorption capacity of Pb(II) on the resultant activated
carbon was 36.63 mg g−1 with H3PO4 and 28.74 mg g−1 with ZnCl2. To regenerate the spent adsorbents, desorption experiments were performed using 0.25 mol L−1 HCl. Here we propose that the activated carbon produced from Amygdalus Scoparia shell is an alternative low-cost adsorbent for Pb(II) adsorption. 相似文献