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Taylor Dispersion with Adsorption and Desorption  [PDF]
Maximilien Levesque,Olivier Bénichou,Rapha?l Voituriez,Benjamin Rotenberg
Physics , 2012, DOI: 10.1103/PhysRevE.86.036316
Abstract: We use a stochastic approach to show how Taylor dispersion is affected by kinetic processes of adsorption and desorption onto surfaces. A general theory is developed, from which we derive explicitly the dispersion coefficients of canonical examples like Poiseuille flows in planar and cylindrical geometries, both in constant and sinusoidal velocity fields. These results open the way for the measurement of adsorption and desorption rate constants using stationary flows and molecular sorting using the stochastic resonance of the adsorption and desorption processes with the oscillatory velocity field.
Synthesis, Characterization and Adsorption Capability of MOF-5  [PDF]
N. Iswarya,M.G. Kumar,K.S. Rajan,R.J.B. Balaguru
Asian Journal of Scientific Research , 2012,
Abstract: Metal Organic Frameworks (MOF) are three dimensional organic-inorganic hybrid crystalline materials where a metal containing inorganic cluster is coordinated to a polydentate organic ligand. MOF-5 consists of Zn4O inorganic moiety, that acts as secondary building unit, coordinating to benzene 1,4-dicarboxylate, a bidentate ligand that acts as spacers, to form a three dimensional structure. We report the synthesis of MOF-5 using zinc nitrate and terephthalic acid as precursors dissolved in dimethyl formamide. The synthesized MOF-5 has been characterized using Fourier Transform Infrared Spectroscopy, X-ray diffractometry, Thermal analysis, Scanning Electron Microscopy and Transmission Electron Microscopy. Surface morphology reveals well-ordered structures with large number of pores in meso-scale. Adsorption capability towards vapours and gases has been studied using ethanol and CO2 as the model vapours using a chemi-resistive approach. Present results indicate that MOF-5 is a promising candidate for CO2 sequestration and gas storage.
Effect of the freezing-thawing on kinetics of adsorption-desorption of the soil cadmium
冻融作用对土壤镉动力学吸附解吸的影响

WANG Zhan,ZHANG Liang,DANG Xiuli,ZHANG Yulong,
王展
,张良,党秀丽,张玉龙

环境科学学报 , 2012,
Abstract: In order to investigate the effect of freezing-thawing on the adsorption-desorption of cadmium,kinetics adsorption isotherms of soil contained with cadmium and the quantity, ratio and speed of adsorption-desorption under freezing-thawing conditions were carried out. The results showed that freezing-thawing promoted cadmium adsorption of the soil. The quantity, ratio and speed of cadmium adsorption increased with the increase of freezing-thawing frequency. Freezing-thawing retarded soil cadmium desorption. With the increasing freezing-thawing cycles, the speed and ratio of soil cadmium desorption decreased and the decrement of the soil cadmium desorption speed increased.
NMR study of small molecule adsorption in MOF-74-Mg  [PDF]
M. G. Lopez,Pieremanuele Canepa,T. Thonhauser
Physics , 2013, DOI: 10.1063/1.4800952
Abstract: We calculate the carbon nuclear magnetic resonance (NMR) shielding for CO_2 and the hydrogen shieldings for both H_2 and H_2O inside the metal organic framework MOF-74-Mg. Our ab initio calculations are at the density functional theory level using the van der Waals including density functional vdW-DF. The shieldings are obtained while placing the small molecules throughout the structure, including the calculated adsorption site for various loading scenarios. We then explore relationships between loading, rotational and positional characteristics, and the NMR shieldings for each adsorbate. Our NMR calculations show a change in the shielding depending on adsorbate, position, and loading in a range that is experimentally observable. We further provide a simple model for the energy and the NMR shieldings throughout the cavity of the MOF. By providing this mapping of shielding to position and loading for these adsorbates, we argue that NMR probes could be used to provide additional information about the position at which these small molecules bind within the MOF, as well as the loading of the adsorbed molecule.
Behavior and mechanism of the adsorption/desorption of tectonically deformed coals
YiWen Ju,Bo Jiang,QuanLin Hou,YongJie Tan,GuiLiang Wang,WenJiao Xiao
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-008-0412-4
Abstract: The physical and chemical texture of tectonically deformed coals produced by various formational mechanisms are different from those of primary coals, thus resulting in major differences among the physical properties of the reservoirs of these coals. We have studied the adsorption/desorption behavior of tectonically deformed coals by the use of isothermal adsorption/desorption experiments under equilibrium moisture condition. Experiments of isothermal adsorption/desorption of methane or multi-component gases have indicated that, the adsorption curves of coals with a low degree of tectonic deformation conform to the type of isothermal adsorption curve described by the Langmuir equation; the methane adsorption curves of coals with strong tectonic deformation cannot be described by the Langmuir equation. The adsorption/desorption process of methane and multi-component gases in the deformed coals is not consistent with primary coals, which form an effect of hysteresis in different kinds of tectonically deformed coals. With the change of pore structure of tectonically deformed coals at reservoir condition, the added adsorbed CH4 in the experiments is desorbed on the pore surface of coals during the pressure reduction process. Thus, the result shows that the adsorption volume in the process of desorbing is greater than that in adsorbing. Because of the deformation, structural change, and transformation of the adsorption potential field of coals, it is essential to form a new kind of isothermal adsorption curve and the hysteresis effect of the desorption process.
Adsorption and Desorption Mechanisms of Methylene Blue Removal with Iron-Oxide Coated Porous Ceramic Filter  [PDF]
Fangwen LI, Xiaoai WU, Songjiang MA, Zhongjian XU, Wenhua LIU, Fen LIU
Journal of Water Resource and Protection (JWARP) , 2009, DOI: 10.4236/jwarp.2009.11006
Abstract: Adsorption and desorption mechanisms of methylene blue (MB) removal with iron-oxide coated porous ce-ramics filter (IOCPCF) were investigated in batch and column mode. The results revealed that MB removal mechanisms included physical adsorption and chemical adsorption, of which chemical adsorption by surface ligand complex reaction played a dominant role after infrared spectrum analysis. Recycling agents were se-lected from dilute nitric acid (pH=3), sodium hydroxide solution (pH=12) and distilled water. Among three agents, dilute metric acid (pH=3) was the best recycling agent. Regeneration rate of IOCPCF arrived at 82.56% at batch adsorption and regeneration was finished in 75min at column adsorption. Adsorp-tion-desorption cycles of IOCPCF after batch and column adsorption were four and three times, respectively. Further, compared with fresh IOCPCF, MB removal rate with these desorbed IOCPCF adsorption only slightly decreased, which suggested that IOCPCF should be used repeatedly.
High-throughput screening of small-molecule adsorption in MOF  [PDF]
Pieremanuele Canepa,Calvin A. Arter,Eliot M. Conwill,Daniel H. Johnson,Brian A. Shoemaker,Karim Z. Soliman,T. Thonhauser
Physics , 2013, DOI: 10.1039/C3TA12395B
Abstract: Using high-throughput screening coupled with state-of-the-art van der Waals density functional theory, we investigate the adsorption properties of four important molecules, H_2, CO_2, CH_4, and H_2O in MOF-74-M with M = Be, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Zr, Nb, Ru, Rh, Pd, La, W, Os, Ir, and Pt. We show that high-throughput techniques can aid in speeding up the development and refinement of effective materials for hydrogen storage, carbon capture, and gas separation. The exploration of the configurational adsorption space allows us to extract crucial information concerning, for example, the competition of water with CO_2 for the adsorption "pockets." We find that only a few noble metals---Rh, Pd, Os, Ir, and Pt---favor the adsorption of CO_2 and hence are potential candidates for effective carbon-capture materials. Our findings further reveal significant differences in the binding characteristics of H_2, CO_2, CH_4, and H_2O within the MOF structure, indicating that molecular blends can be successfully separated by these nano-porous materials.
Monomer Adsorption-Desorption Processes

KE Jian-Hong,LIN Zhen-Quan,CHEN Xiao-Shuang,

中国物理快报 , 2009,
Abstract: We propose an adsorption-desorption model for a deposit growth system, in which the adsorption and desorption of particles coexist. By means of the generalized rate equation we investigate the cluster (island) size distribution in the dynamic equilibrium state. The results show that the evolution behaviour of the system depends crucially on the details of the rate kernels. The cluster size distribution can take the scale-free power-law form in some cases, while it grows exponentially with size in other cases.
Collectiive Properties of Adsorption-Desorption Processes  [PDF]
P. L. Krapivsky,E. Ben-Naim
Physics , 1993, DOI: 10.1063/1.467037
Abstract: A reversible adsorption-desorption parking process in one dimension is studied. An exact solution for the equilibrium properties is obtained. The coverage near saturation depends logarithmically on the ratio between the adsorption rate, $\k_+$, and the desorption rate, $\k_-$, \hbox{$\req\cong 1-1/\log(k_+/k_-)$}, when $\k_+\gg\k_-$. A time dependent version of the reversible problem with immediate adsorption ($k_+=\infty$) is also considered. Both heuristic arguments and numerical simulations reveal a logarithmically slow approach to the completely covered state, \hbox{$1-\rho(t)\sim 1/\log(t)$}.
Enhanced Saturation Coverages in Adsorption-Desorption Processes  [PDF]
Paul R. Van Tassel,Pascal Viot,Gilles Tarjus,Jeremy J. Ramsden,Julian Talbot
Physics , 1999, DOI: 10.1063/1.480715
Abstract: Many experimental studies of protein deposition on solid surfaces involve alternating adsorption/desorption steps. In this paper, we investigate the effect of a desorption step (separating two adsorption steps) on the kinetics, the adsorbed-layer structure, and the saturation density. Our theoretical approach involves a density expansion of the pair distribution function and an application of an interpolation formula to estimate the saturation density as a function of the density at which the desorption process commences, $\rho_1$, and the density of the depleted configuration, $\rho_2$. The theory predicts an enhancement of the saturation density compared with that of a simple, uninterrupted RSA process and a maximum in the saturation density when $\rho_2={2/3}\rho_1$. The theoretical results are in qualitative and in semi-quantitative agreement with the results of numerical simulations.
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