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1.
Summary The objective of this study was to investigate the reaction behavior of the photocatalytic oxidation of gaseous trichloroethylene
(TCE) using titanium dioxide at room temperature. The experiments were carried out under various humidity levels and oxygen
contents of carrier gas in an annular photoreactor. Experimental results indicated that the factors affecting the photocatalysis
of TCE by UV/TiO2 process are carrier gases and humidity. It was found that increasing the relative humidity in inlet gas flow under low humidity
could improve the decomposition of trichloroethylene and the mineralization of organic intermediates at an irradiation UV
light intensity of 2.82 W m-2 by UV/TiO2 process. The photocatalytic kinetics of gaseous trichloroethylene can be described by the Langmuir-Hinshelwood rate equation. 相似文献
2.
On adsorption of various vapours, the electrical conductivity of nitroaromatic semiconductors 9-nitroanthracene, 1,4-dinitronaphthalene
and 1,3,5-trinitrobenzene changes appreciably. This phenomenon has been used as a probe to study the adsorption and desorption
processes in these nitroaromatic polycrystals. The adsorption and desorption kinetics have been found to follow the modified
Roginsky-Zeldovich relation. Two adsorption processes have been identified. One, a two-stage process, the first of which gives
a Lennard-Jones potential energy curve and is followed by a rate-determining transition over a potential energy barrier to
the second stage of adsorption forming weakly bound complexes between the vapour molecules and the nitroaromatic crystallites.
In the second process, in addition to the two stages of the first process, a third stage with a comparatively deep potential
energy surface is reached by activation over a second potential barrier and strongly bound complexes are finally formed.
On leave from Government Arts and Science College, Durg 491 002, India 相似文献
3.
The change in semiconductive properties of β-apo-8′-carotenal, astacene and methyl bixin on adsorption of various vapours
on the crystallite surfaces has been studied at a constant sample temperature. The adsorption of vapours enhances the semiconductivity
of the polyenes appreciably. This enhancement depends on the chemical nature and also on the pressure of the adsorbed vapour.
The adsorption and desorption kinetics follow the modified Roginsky-Zeldovich relation. A two stage desorption process, the
first stage of which gives a Lennard-Jones potential energy curve and is followed by a rate-determining transition over a
potential energy barrier to the second stage of adsorption forming weakly bound complexes between the vapour molecules and
the polyene crystallites, can explain satisfactorily the experimentally observed kinetic data. 相似文献
4.
A. V. Vorontsov E. N. Savinov E. N. Kurkin O. D. Torbova V. N. Parmon 《Reaction Kinetics and Catalysis Letters》1997,62(1):83-88
The paper reports quantum efficiency dependence of the steady state gas phase photocatalytic oxidation of CO over dispersed
anatase on CO and CO2 concentrations, temperature and UV light intensity. A tentative mechanism of the process is proposed. 相似文献
5.
The photocatalytic degradation of natural organic matter (NOM) would be an attractive option in the treatment of drinking water. The performance of a submerged photocatalytic membrane reactor (PMR) was investigated with regard to the removal of NOM and the control of membrane fouling. In particular, this work focused on the adsorption and desorption of humic acids (HA) and lake water NOM at the surface of TiO2 photocatalyts and ferrihydrite (FH) adsorbents in the PMR for water treatment. The addition of FH particles with a large sorption capacity helped remove the NOM released from TiO2 particles, but FH suspended in water affected the photocatalysis of lake water NOM with a low specific UV absorbance (SUVA) value. To prevent the UV light being scattered by FH without any photocatalytic activity, FH particles were attached to a submerged microfiltration (MF) membrane, which contributed to a greater removal of NOM during long-term PMR operation. The further removal of NOM from aqueous solution was achieved due to the synergistic effect of TiO2 photocatalysis and FH adsorption in PMR while minimizing the influence of photoinduced desorption of NOM. No significant membrane fouling occurred when the submerged PMR was operated even at high flux levels (>25 L/m2 h), as long as photocatalytic decomposition took place. 相似文献
6.
Rui LiHang Li Chenyang XuXinmin Liu Rui TianHualing Zhu Laosheng Wu 《Colloids and surfaces. A, Physicochemical and engineering aspects》2011,392(1):55-66
Surface charges of particles together with the adsorbed counter ions in diffuse layer can set up a strong electrostatic field around the particles in aqueous solution. The existent kinetic models for describing cation exchange on solid/liquid interface were either empirical or semi-empirical, and in which the electrostatic field is not considered. In this paper, as considering the important effect of electrostatic field around particles on cations adsorption/desorption, for the first time the dynamic distribution equations of cations in diffuse layer for adsorption and desorption processes in both flow method and batch technique have been established. Those equations clearly show how the cation concentration changes with time in different position of diffuse layer during the cation exchange process, and the corresponding new kinetic models have been obtained upon them. The new models indicate that, in both flow method and batch technique, for the adsorption process, experimental results should appear zero order kinetic process caused by the strong force adsorption in the initial stage of adsorption, and then transform to the first order kinetic process of the weak force adsorption; and for the desorption process, however, only first order kinetic process may exist. The new models are essentially different from the classic apparent or empirical kinetic models since all the parameters have their defined physical meanings in the new models, thus the rate parameters in the new models have the potential to theoretically predict. Theoretical analyses also indicated that, the adsorption/desorption rate in flow method experiment will be much higher than that in batch technique experiment. 相似文献
7.
To describe diffusion-controlled adsorption, the diffusion equation is solved under different initial and boundary conditions
by means of a Laplace transformation. By solving this equation, it has been found that the solution, which Ward and Tordai
used, is only applicable for x>0; therefore, it is incorrect if the derivation is made at x = 0. Ward and Tordai did not notice this and the first derivation was made at x = 0 in order to get the dynamic surface adsorption, Γ(t). In this paper, an accurate solution, which is applicable for x≥ 0, is given and the expression for Γ(t) is obtained. Furthermore the relationship between the dynamic surface tension and Γ(t) is derived. As an example, the dynamic surface tensions of an aqueous octyl-β-d-glucopyranosid solution were measured by means of the maximum bubble pressure method. By using the derived theory it has
been proved that the controlling mechanism of the adsorption process of this surfactant at the long-time-adsorption limits
changes as a function of the bulk concentration; only at dilute concentration is it controlled by diffusion.
Received: 26 July 1999/Accepted in revised form: 16 September 1999 相似文献
8.
The heat, equilibrium, and kinetics of adsorption of 1-ethoxy-2-propanol vapours on granulated activated carbon were determined simultaneously by a reaction calorimeter SETARAM C80 D at T=298.15 K at various relative vapour pressures (0.1< p/ps<0.8). The adsorption isotherm was correlated by the Freundlich equation. It was observed that the enthalpies of adsorption decrease slightly with increasing of the relative vapour pressure of the adsorptive. The rate of adsorption were calculated from analysis of the heat flux signals and it was found that the mass-transfer coefficient for 1-ethoxy-2-propanol vapours in granulated activated carbon increased with increasing relative vapour pressure of the adsorptive.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
9.
Adsorption characteristics of herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) have been evaluated using bituminous shale
(BS) as a model adsorbent-containing solid organic matter in a mineral matrix. The adsorption of MCPA on BS has been studied
with varying concentration, temperature, pH and contact time, using batch technique. Adsorption ability of BS increases with
increasing temperature and decreasing pH in the studied concentration range of (0.6–4.0) × 10−4 M. Theoretical curves calculated from Freundlich, Dubinin-Radushkevich (D-R), Langmuir and Temkin isotherm equations show
a two-step isotherm shape. The results could be explained by assuming the presence of two-type sites with different affinity
on adsorbent surface. Adsorption process is endothermic and entropy controlled at the first stage, and exothermic and enthalpy
controlled at the second stage. The mechanism proposed based on surface ionization and complexation model is consistent with
the pH dependent experimental results. Kinetic data fit well to both Paterson’s and Nernst Planck model based on homogeneous
solid phase diffusion (HSPD). The values of particle diffusion coefficients (D
p
) predicted from both models are comparable each other and independent of temperature and concentration.
相似文献
10.
Dr. R. Miller 《Colloid and polymer science》1981,259(3):375-381
Summary The problem of diffusion controlled adsorption kinetics is solved by application of an implicite difference method. Thereby all forms of adsorption isotherms can be used in the calculations. Computation examples are given concerning Langmuir, Freundlich, Volmer, Frumkin, and van der Waals isotherms.
Nomenclature c concentration - c o bulk concentration - D diffusion coefficient - x distance from the surface - t time - surface concentration - 0 equilibrium surface concentration - saturation surface concentration - k o/c o - K 1,K 2 parameters of Henry and Freundlich isotherm with the dimension of a length - n parameter of Freundlich isotherm - a 1,a 2 interaction parameters - B 1,B 2,B 3,B 4 parameters of different isotherms with the dimension of a concentration - R gas law constant - T absolute temperature dimensionless parameters C c/c o - / o - X x/k - X step size ofX - Dt/k 2 - step size of - e time at - 0.95 Zentralinstitut für Organische Chemie,Bereich Grenzflhenaktive Stoffe, der Akademie der Wissenschaften der DDR, Berlin-AdlershofWith 6 figures and 1 table 相似文献
Zusammenfassung Es wird das Problem der diffusions-kontrollierten Adsorptionskinetik durch Anwendung eines impliziten Differenzenverfahrens gelöst. Dabei können bei der Berechnung alle Formen von Adsorptionsisothermen zugrunde gelegt werden. Rechenbeispiele für die Langmuir-, Freundlich-, Volmer-, Frumkin- und van-der-Waals-Isotherme werden angegeben.
Nomenclature c concentration - c o bulk concentration - D diffusion coefficient - x distance from the surface - t time - surface concentration - 0 equilibrium surface concentration - saturation surface concentration - k o/c o - K 1,K 2 parameters of Henry and Freundlich isotherm with the dimension of a length - n parameter of Freundlich isotherm - a 1,a 2 interaction parameters - B 1,B 2,B 3,B 4 parameters of different isotherms with the dimension of a concentration - R gas law constant - T absolute temperature dimensionless parameters C c/c o - / o - X x/k - X step size ofX - Dt/k 2 - step size of - e time at - 0.95 Zentralinstitut für Organische Chemie,Bereich Grenzflhenaktive Stoffe, der Akademie der Wissenschaften der DDR, Berlin-AdlershofWith 6 figures and 1 table 相似文献
11.
Experimental determination and modeling of IgG binding on a new protein A adsorbent based on a macroporous resin were performed. The new adsorbent consists of polymeric beads based on hydrophilic acrylamido and vinyl monomers with a pore structure optimized to allow favorable interactions of IgG with recombinant protein A coupled to the resin. The particles have average diameter of 57 μm and a narrow particle size distribution. The IgG adsorption equilibrium capacity is 46 mg/cm3 and the effective pore diffusivity determined from pulse response experiments for non-binding conditions is 8.0 × 10−8 cm2/s. The IgG adsorption kinetics can be described with the same effective diffusivity by taking into account a heterogeneous binding mechanism with fast binding sites, for which adsorption is completely diffusion controlled, and slow binding sites for which adsorption is controlled by the binding kinetics. As a result of this mechanism, the breakthrough curve exhibits a tailing behavior, which appears to be associated with the slow binding sites. A detailed rate model taking into account intraparticle diffusion and binding kinetics is developed and is found capable of predicting both batch adsorption and breakthrough behavior over an ample range of experimental conditions. The corresponding effective diffusivity is independent of protein concentration in solution over the range 0.2–2 mg/cm3 and of protein binding as a result of the large pore size of the support matrix. Overall, the small particle size and low diffusional hindrance allow capture of IgG with short residence times while attaining substantial dynamic binding capacities. 相似文献
12.
《中国化学快报》2020,31(10):2789-2794
In order to efficiently remove tetracycline in wastewater through the synergistic effect of adsorption and photocatalytic degradation, a series of novel composite materials (Cu doped g-C3N4) were synthesized by two-pot hydrothermal method. It was found that the composite materials with optimized ratio (Cu/CN-1) displayed outstanding adsorption and photocatalytic performance as compared with pure g-C3N4 photocatalyst. The removal efficiency of tetracycline (TC, 50 mg/L) reached almost 99% within 30 min by Cu/CN-1 through the synergy of adsorption and photocatalysis under visible-light irradiation, which was the highest removal efficiency ever reported. The adsorption kinetics and isotherms of TC on the Cu/CN-1 were well fitted with the pseudo-second-order kinetic model and Langmuir model, respectively. Moreover, it was confirmed that the main effective reactive groups were O2− and h+ in photocatalytic process. The Cu/CN-1 exhibited high stability and excellent reusability after five cycle experiments. Finally, the mechanism of synergy between Cu and g-C3N4 was proposed: on the one hand, the decoration of Cu particles significantly increased the adsorption sites of Cu/CN-1 to tetracycline, on the other hand, the modification of Cu particles effectively inhibits charge recombination and broadens the visible light absorption range of the photocatalyst.This study provided a promising photocatalyst to be used for TC removal in the actual wastewater. 相似文献
13.
《Arabian Journal of Chemistry》2020,13(8):6366-6378
In this paper, quaternary chalcogenide Cu2FeSnS4 (CFTS) thin films were synthesized by spray pyrolysis using multilayer deposition technique in which the number (N) of sequential deposition runs (DR) is N = 1, 2, 3 and 4. The delivered volume in each sample is (N × 300 ml). Correspondingly, samples are named CFTS-N. Chemical composition, morphological, structural, optical and electrical properties were characterized using dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, spectrophotometer and Hall Effect measurements. XRD and Raman spectroscopy show a purer phase and better crystalline quality of CFTS-3 than other films. Average particle size increases with DR and reaches a maximum value of about 60 nm for N = 3. Optical results show high absorption coefficient value about 105 cm−1 in visible range, with an optical band gap of about 1.47 eV. Electrical resistivity of CFTS-3 equals to 5.82 10−3 Ω cm which is the lowest value of these four samples. We have investigated the photocatalysis activity of various thin films by measuring the degradation of methylene blue (MB) and Rhodamine (RhB) as pollutant dyes. In particular we have compared the candidates: CFTS-3/SnO2:F, CFTS-3/In2S3 and CFTS-3/In2S3/SnO2:F. Under sun light irradiation, CFTS-3/In2S3/SnO2:F heterojunction exhibits the best photodegradation rate (96%) of MB dye. 相似文献
14.
Dimethylarsinic acid (DMA) is an organoarsenical compound that, along with monomethylarsonic acid, poses a health and an environmental risk, and a challenge to the energy industry. Little is known about the surface chemistry of DMA at the molecular level with materials relevant to geochemical environments and industrial sectors. We report herein the first in situ and surface-sensitive rapid kinetic studies on the adsorption and desorption of DMA to/from hematite and goethite at pH 7 and I = 0.01 M KCl using ATR-FTIR. Values for the apparent rates of adsorption and desorption were extracted from experimental data as a function of spectral components, flow rate of the aqueous phase, film thickness of hematite, and using chloride and hydrogen phosphate as desorbing agents. The adsorption kinetic data show fast and slow rates, consistent with the formation of more than one type of adsorbed DMA. Apparent adsorption and desorption rate constants were extracted from the dependency of the initial adsorption rates on [DMA(aq)]. Desorption rate constants were also extracted from desorption experiments using hydrogen phosphate and chloride solutions, and were found to be higher by 1-2 orders of magnitude than those using chloride. In light of the complex ligand exchange reaction mechanism of DMA desorption by phosphate species at pH 7, apparent desorption rate constants were found to depend on [hydrogen phosphate] with an order of 0.3. The impact of our studies on the environmental fate of DMA in geochemical environments, and the design of technologies to reduce arsenic content in fuels is discussed. 相似文献
15.
By means of a theoretical experiment it is demonstrated, that a barrier in the adsorption kinetics of a surfactant can be simulated by the presence of surface-active impurities. Hence, the application of models for the diffusion-kinetic-controlled and/or kinetic controlled adsorption presumes the proof of the surface chemical purity of the surfactant solution under investigation. 相似文献
16.
《Arabian Journal of Chemistry》2023,16(1):104436
ZnTiO3/tourmaline loaded on the nickel foam (ZnTiO3/tourmaline/Ni-foam) is prepared by a facile coating method. Morphology and structure of the photocatalyst were characterized by X-ray diffraction (XRD), scanning electrons microscopy (SEM), raman spectroscopy, UV–vis diffuse reflectance spectrum (UV–vis DRS) and photoluminescence spectroscopy (PL). The photocatalytic properties of the materials were tested by using the Rhodamine B (RhB) solution as the target pollutant. The results indicates that the ZnTiO3/tourmaline/Ni foam exhibited higher photocatalytic activity than that of ZnTiO3 and ZnTiO3/Ni foam under ultraviolet (UV) light irradiation, and its degradation rate was up to 99.2%. Moreover, the degradation rate remained at 91.3% after eight consecutive photocatalytic reaction cycles. The outstanding photocatalytic performances of ZnTiO3/tourmaline/Ni foam was mainly attributed to the existence of tourmaline, which can help to inhibit the recombination of electron-hole paris, and the proper pore structure of the carrier. Meanwhile, the trapping experiments indicated that ·O2– was the main active species in the photocatalytic degradation of RhB. 相似文献
17.
Rongliang Qiu Lin Song Yueqi Mo Dongdong Zhang Eric Brewer 《Reaction Kinetics and Catalysis Letters》2008,94(1):183-189
To investigate the influencing factors and the kinetics of photocatalytic degradation of phenol, experiments were carried
out using conjugated polymer poly(fluorene-co-thiophene) (PFT) sensitized TiO2 and ZnO under LED (light-emitting diode) lights of the wavelength of 450–475 nm. Influencing factors, such as initial phenol
concentration, photocatalyst dosage and pH value on the photocatalytic degradation of phenol were studied in detail. The reaction
kinetics was found to follow pseudo first-order law. 相似文献
18.
In this work, a high photocatalytic activity was attained by intercalating a Pt layer between SnO2 and TiO2 semiconductors, which yielded a TiO2/Pt/SnO2 - type heterostructure used in the discoloration of blue methylene (MB) solution. The porous films and platinum layer were obtained by electrophoretic deposition and DC Sputtering, respectively, and were both characterized morphologically and structurally by FE-SEM and XRD. The films with the Pt interlayer were evaluated by photocatalytic activity through exposure to UV light. An increase in efficiency of 22% was obtained for these films compared to those without platinum deposition. Studies on the reutilization of the films pointed out high efficiency and recovery of the photocatalyst, rendering the methodology favorable for the construction of fixed bed photocatalytic reactors. A proposal associated with the mechanism is discussed in this work in terms of the difference in Schottky barrier between the semiconductors and the electrons transfer and trapping cycle. These are fundamental factors for boosting photocatalytic efficiency. 相似文献
19.
D. C. Liao Y. C. Chern J. L. Han K. H. Hsieh 《Journal of Polymer Science.Polymer Physics》1997,35(11):1747-1755
The swelling equilibrium and diffusion kinetics in various solvents of the maleimide-terminated polyurethanes (UBMIs) and of the triol and tetraol-crosslinked polyurethanes (PU) were studied. The polymer volume fraction of the UBMIs at swelling equilibrium is much higher than that of the tetraol-crosslinked PU networks for the same type of polyol used in the PU. It was explained by the high functionality of the UBMIs produced in the network structure. Furthermore, the molecular weight between crosslinks (Mc) has been calculated from the swelling model and the results exhibit good agreement with the proposed network structure. The early time sorption kinetic data were obtained to investigate the diffusion mechanism of the solvent in the networks. The solubility, diffusion coefficients, and permeability of the solvent in UBMI networks were found to be lower than in the multiol-crosslinked PU networks. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1747–1755, 1997 相似文献
20.
《Journal of Saudi Chemical Society》2021,25(12):101388
A facile strategy was used for the synthesis of nickel ferrite/zinc oxide (NiFe2O4/ZnO) nanocomposite via an ultra-sonication method and observed its recyclability and photostability with enhanced visible light-driven photocatalytic performance. The photo degradation activities of as-synthesized photocatalysts were investigated using various dyes including methylene blue, crystal violet and methyl orange under solar light irradiation. Prepared material degrades 49.2% methyl orange, 44.4% methyl blue and 41.3% crystal violet in 40 min. Further, the synergistic effect of nickel ferrite and zinc oxide can reduce the probability of recombination of charge carrier and boost the charge separation which leads to remarkable photocatalytic performance. Magnetic properties of nickel ferrite reduces the agglomeration of material and increases the recyclability. The NiFe2O4/ZnO nanocomposites also exhibited better antibacterial activity for Pseudomonas aeruginosa and Staphylococcus aureus, which shows that they can be used for both environmental and biological applications. 相似文献