Statics and Kinetics of Interaction of Acids and Alkalis with VION AN-1 Fibrous Pyridine-Containing Chemisorbent

The acid—base and kinetic properties of VION AN-1 fibrous pyridine-containing sorbent were studied by the potentiometric, calorimetric, and sorption methods. The ionization of VION AN-1 was completely characterized thermodynamically. It was shown that the interaction of acids and bases with the chemisorbent was controlled by the inside diffusion mechanism. The inside diffusion coefficients were determined. VION AN-1 offers promise for conditioning gas—air and aqueous media.     

The Kinetics of Sorption of Lead Ions on Clinoptilolite in the H-Form

The kinetics of ion exchange of lead ions on clinoptilolite in the H-form was studied experimentally. The kinetic parameters of sorption of lead ions by the natural zeolite were calculated as depending on zeolite dispersity and solution concentration.     

Sorption Preconcentration of Platinum-Group Metals with Filled Fibrous POLYORGS Sorbents

The sorption of platinum, palladium, and rhodium with fibrous filled POLYORGS sorbents was studied depending on the concentration of hydrochloric acid and the time of contact of the solution with the sorbent in the batch mode. The equilibrium and kinetic characteristics of the sorption of platinum with the POLYORGS 17-n sorbent were determined, on the basis of these data the conditions for the dynamic preconcentration of platinum from a 1 M HCl solution were calculated. Conditions were selected for the group preconcentration of palladium, platinum, and gold in the dynamic mode and for their subsequent determination in the sorbent. It was demonstrated that rhodium can be preconcentrated with the POLYORGS 17-n sorbent in the dynamic mode in the presence of tin chloride.     

Synthesis and Sorption Properties of Filled Fibrous Sorbents with Immobilized Hetarylformazan Groups

New sorbents were prepared by immobilization of structurally different sulfur-containing hetarylformazans on nonwoven polyacrylonitrile fiber filled with AV-17 anion exchanger. Sorption of some heavy metals on these materials was studied as influenced by various factors. Sorbents for selective recovery of copper(II) in the presence of nickel(II), zinc(II), and cadmium(II) cations were found.     

Sorption of Cr(VI) on the Anion-Exchange Fibrous Material Based on Nitron

The kinetics and thermodynamics of Cr(VI) sorption under the static and dynamic conditions on the fibrous sorbent SMA-1 prepared by chemical modification of polyacrylonitrile were studied.     

Kinetics of Antibiotic Sorption by Monocarboxyl Cellulose

Kinetics of the sorption of lincomycin and gentamicin from aqueous solutions of their salts and bases, as well as a cephalosporin group antibiotic cephalexin having the zwitterionic nature, by monocarboxyl cellulose is studied. It is disclosed that the sorption of the studied antibiotics is characterized by a combined diffusion type of kinetics. Effective diffusion coefficients (D _eff) are determined, and it is shown that they correspond to the times (t _1/2) of half-equilibrium establishment and increase with passing from lincomycin to gentamicin and, further, to cephalexin. The D _eff and t _1/2 values are found to depend on solution pH and the degree of cellulose sorbent swelling.     

Kinetics of Sorption,Desorption, and Diffusion in Zeolites

Sorption and desorption in zeolites (molecular sieves) have to be considered as complex processes, involving simultaneous diffusion in zeolite crystals, mass transfer in the intercrystalline void of a pellet, and heat transfer between the zeolitic sorbent and its surroundings. The kinetics of sorption and desorption, respectively, of n-C₄H₁₀ in zeolite X and of CO₂ in zeolite A have been investigated: only the initial rates of uptake or release of the sorbet are controlled by mass transfer alone whereas ultimately they also depend on the rate of heat transfer from the sorbent to its surroundings or vice versa. Diffusivities of the sorbate in the zeolite crystals can be obtained from the kinetics of mass transfer, provided the resistance due to viscous or Knudsen flow between the crystals of the zeolitic sorbent can be eliminated. A sample consisting of a monolayer of single crystals had to be used for this purpose in the n-butane/zeolite X system; the intracrystalline diffusivity obtained in this way is not in conflict with data obtained by NMR spectroscopy. The intracrystalline diffusivities obtained in this way—taking into account the coupling of several processes during sorption — are higher than values reported in the literature.     

Selective Sorption of Fe(III) Ions from Ni(II)-Fe(III) Mixtures with Chemisorbents

Selective recovery of Fe(III) ions from two-component nitrate solutions of Fe(III) and Ni(II) with synthetic nickel phosphate, natural chalk, and natural tripoli were studied. The mechanism of selective action of chemisorbents was considered, and high efficiency of the materials considered was demonstrated.     

Sorption Kinetics and Intracrystalline Diffusion of Methanol in Ferrierite: An Example of Disguised Kinetics

Sorption kinetics of methanol in large crystals of ferrierite have been studied in detail by interference microscopy (IFM) and infra-red microscopy (IRM). The IFM measurements yield the transient concentration profiles, thus providing a direct measurement of both the surface resistance to mass transfer and the internal diffusion resistance. It is shown that, for this system, the uptake rate is controlled by the combined effects of surface resistance and diffusion through the 8-ring channels (in the y-direction). Transport through the 10-ring channels (in the z-direction) appears to be blocked by surface resistance. Although the overall uptake curves conform well to the “root t law” the diffusivity values derived from the uptake curves vary widely depending on the assumed direction of diffusion. Even if the correct direction of diffusion is assumed, the diffusivity values derived from the uptake curves are seriously in error as a result of the intrusion of surface resistance. The existence of transport resistances at the crystal surface is clearly apparent from the transient concentration profiles but is not obvious from the uptake curves.     

Complex Sorption Kinetics of Carbon Dioxide in NaX-Zeolite Crystals

Ad-/desorption-kinetic measurements were performed for carbon dioxide on a mono-disperse crystal sample of NaX-type zeolite (mean crystal diameter: 2R (100 ± 6) m) by a constant-volume–variable-pressure method in a differential concentration mode over ranges of temperature, (193–293) K, and pressure, (20–26,700) Pa. They revealed a complex sorption process in sorbate uptake and release during experiments of ad- and desorption, respectively, which is comprised of a slow, hitherto unknown rate mechanism superimposed on very fast intracrystalline diffusion of carbon dioxide. IR-spectroscopic data that evidence formation of chemisorption species in CO₂-NaX sorption systems may allow for a tentative interpretation of this finding. Circumstantial evidence for the correctness of this conclusion follows from sorption–kinetic experiments for carbon dioxide on BaKX-type zeolite crystals (mean crystal diameter: 2R (120 ± 6) m).     

自然水体中3种固相物质吸附有机氯农药的动力学特征

研究了自然水体中生物膜、 悬浮颗粒物和表层沉积物3种典型固相物质对有机氯农药的吸附动力学特征. 研究结果表明, 有机氯农药在3种固相物质上的吸附动力学过程可分为快吸附阶段和慢吸附阶段. 准二级动力学模型较好地描述了三者对有机氯农药的吸附动力学过程. 吸附平衡时, 3种固相物质对有机氯农药吸附量的大小与它们的有机质含量顺序一致, 即, 生物膜>悬浮颗粒物>表层沉积物; 而在吸附初期阶段, 有机质含量最低的表层沉积物对有机氯农药的吸附速率最快, 吸附量的波动变化幅度最大, 其次为悬浮颗粒物和生物膜.     

Enthalpy and Entropy Barriers Explain the Effects of Topology on the Kinetics of Zeolite‐Catalyzed Reactions

The methylation of ethene, propene, and trans‐2‐butene on zeolites H‐ZSM‐58 (DDR), H‐ZSM‐22 (TON), and H‐ZSM‐5 (MFI) is studied to elucidate the particular influence of topology on the kinetics of zeolite‐catalyzed reactions. H‐ZSM‐58 and H‐ZSM‐22 are found to display overall lower methylation rates compared to H‐ZSM‐5 and also different trends in methylation rates with increasing alkene size. These variations may be rationalized based on a decomposition of the free‐energy barriers into enthalpic and entropic contributions, which reveals that the lower methylation rates on H‐ZSM‐58 and H‐ZSM‐22 have virtually opposite reasons. On H‐ZSM‐58, the lower methylation rates are caused by higher enthalpy barriers, owing to inefficient stabilization of the reaction intermediates in the large cage‐like pores. On the other hand, on H‐ZSM‐22, the methylation rates mostly suffer from higher entropy barriers, because excessive entropy losses are incurred inside the narrow‐channel structure. These results show that the kinetics of crucial elementary steps hinge on the balance between proper stabilization of the reaction intermediates inside the zeolite pores and the resulting entropy losses. These fundamental insights into their inner workings are indispensable for ultimately selecting or designing better zeolite catalysts.     

Kinetics and Mechanism of Ion-Exchange Sorption of Organic Cations on the Surface of Liquid Ion-Selective Membranes

Kinetics of ion-exchange sorption of organic cations on the surface of ion-exchange membranes with low permittivity, which are the base of the majority of ion-selective electrodes, is studied and quantitatively described. It is disclosed that the rate of ion exchange is primarily governed by the lypophilicity of displacing ions, but the time of the establishment of equilibrium state is the diffusion-limited parameter. A mechanism of ion exchange of hydrophobic organic cations on the surface of selective membranes is proposed.     

Sorption Kinetics of Acid and Reactive Dyes on Wool Fiber in the Presence of Redox Systems

Low-temperature dyeing with Acid Bordeaux and Reactive Brilliant Red 5CX is studied.     

Effect of Cationic Form of a Fibrous Sulfonic Cation-Exchange Resin on Sorption of Tetramminepalladium(II) and Its Cross-Sectional Distribution

The effect of the nature of exchangeable cation (Na⁺, Mg^{2 +}, Ba^{2 +}, La^{3 +}) in FIBAN K-1 fibrous sulfonic cation-exchange resin on sorption of tetramminepalladium(II) and its cross-sectional distribution in fabrication of Pd catalysts is studied.     

Sorption Equilibria and Kinetics of Hydrocarbons onto Activated Carbon Samples Having Different Micropore Size Distributions

This paper deals with the prediction of adsorption equilibrium and kinetics of hydrocarbons onto activated carbon samples having different micropore size distribution (MPSD). The microporous structure of activated carbon is characterised by the distribution of slit-shaped micropores, which is assumed to be the sole source of surface heterogeneity. The interaction between adsorbate molecule and pore walls is described by the Lennard-Jones potential theory. Different adsorbates have access to different pore size range of activated carbon due to the size exclusion, a phenomenon could have a significant influence on both multicomponent equilibria and kinetics. Activated carbons with three different MPSDs are studied with ethane and propane as the two model adsorbates. The Heterogeneous Macropore Surface Diffusion model (HMSD) is employed to simulate adsorption kinetics. The simulation results show that the MPSD is an important factor affecting both the multicomponent equilibria and kinetics.     

Kinetics and Mechanism of the Sorption of Some Aromatic Amines onto Amberlite IRA-904 Anion-Exchange Resin

The kinetics of the sorption of aromatic amines such as o-aminophenol (o-AP), o-phenylenediamine (o-PDA), and p-phenylenediamine (p-PDA) onto Amberlite anion-exchange resin in chloride form was investigated in batch experiments spectrophotometrically at different temperatures. The sorption rate is zero order in all amines sorbed, increasing directly in the order: p-PDA相似文献