Chemical analysis and sorption data

Chemical analysis and sorption data. Chemical analyses (ICP-AES) of highly crystalline and pure ZSM-20 materials give Si/Al ratios in the range of 3.7 (Table 2) to 4.7 (Table 1). Na/Al ratios of 0.7 are typical, as are (Na+TEA)/A1 ratios of about 1.1. Single point n-hexane sorption capacities at 40 torr and 23°C, after burn off of the TEA at 550°C in air for 3 hours, are invariably in the range of 18% to 20% wt.- values typical for high silica directly synthesized faujasite type product (24.) ... 

A successfid indexing of the powder diffraction pattern, which can often be done automatically, yields the unit cell dimensions and information on possible space groups. The chemical analysis and sorption data indicate the framework density, or number of tetrahedra per unit cell. The challenge is then to position these tetrahedra within the unit cell such that (1) they fully interconnect in a sensible manner and (2) the necessary analytical data are reproduced. These structural constraints are quantified in an energy expression and simulated annealing [33,34] is employed as the global optimization approach. 

Loukidou et al. (2005) fitted the data for the equilibrium sorption of Cd from aqueous solutions by Aeromonas caviae to the Langmuir and Freundlich isotherms. They also conducted, a detailed analysis of sorption rates to validate several kinetic models. A suitable kinetic equation was derived, assuming that biosorption is chemically controlled. The so-called pseudo second-order rate expression could satisfactorily describe the experimental data. The adsorption data of Zn on soil bacterium Pseudomonas putida were fit with the van Bemmelen-Freundlich model (Toner et al. 2005). 

Spectroscopic techniques (particularly infrared, x-ray photoelectron, and x-ray absorption spectroscopy) have been applied to fill the information gap about chemical speciation and interfacial reactions of As in model and natural materials. They have been used to determine the stmcture of x-ray amorphous particles involved in interfacial reactions, to identify the types of sorption reactions occurring in simplified model systems containing As and one or more phases, and to identify the valence and speciation of predominant As species present in natural, heterogeneous materials. This chapter summarizes much of the recent spectroscopic information on arsenic speciation in minerals and other solid phases that are analogous to phases present in aquifer sediments. These data are primarily derived from analysis of synthetic samples or natural model compounds. 

The authors review the theoretical analysis of the hydrodynamic stability of fluid interfaces under nonequilibrium conditions performed by themselves and their coworkers during the last ten years. They give the basic equations they use as well as the associate boundary conditions and the constraints considered. For a single interface (planar or spherical) these constraints are a Fickean diffusion of a surface-active solute on either side of the interface with a linear or an erfian profile of concentration, sorption processes at the interface, surface chemical reactions and electrical or electrochemical constraints for charged interfaces. General stability criteria are given for each case considered and the predictions obtained are compared with experimental data. The last section is devoted to the stability of thin liquid films (aqueous or lipidic films). 

Transport properties of films on a basis chitosan and medicinal substance are investigated. Sorption and diffusive properties of films are studied. Diffusion coefficients are calculated. Kinetic curves of release of the amikacin, having abnormal character is shown. The analysis of the obtained data showed that a reason for rejection of regularities of process of transport of medicinal substance from chitosan films from the classical fikovsky mechanism are stractural changes in a polymer matrix, including owing to its chemical modification at interaction with medicinal substance. 

Within routine studies of new chemical entities, the initial focus is to explicate a comprehensive description of the drug. The aim is to provide specific information on its physical aspects such as morphological form, polymorphism, crystal habit and solvate state. This information is combined with data from other techniques such as dynamic vapour sorption (DVS), particle size analysis, XRPD (x-ray powder diffraction), solid state NMR, IR spectrophotometry and Raman spectroscopy. 

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