Sorption quantitative

The capacity factors of SN-SiO, for metal ions were determined under a range of different conditions of pH, metal ions concentrations and time of interaction. Preconcentration of Cd ", Pb ", Zn " and CvS were used for their preliminary determination by flame atomic absorption spectroscopy. The optimum pH values for quantitative soi ption ai e 5.8, 6.2, 6.5, 7.0 for Pb, Cu, Cd and Zn, respectively. The sorption ability of SN-SiO, to metal ions decrease in line Pb>Cu> >Zn>Cd. The soi ption capacity of the sorbent is 2.7,7.19,11.12,28.49 mg-g Hor Cd, Zn, Pb, andCu, respectively. The sorbent distribution coefficient calculated from soi ption isotherms was 10 ml-g for studied cations. All these metal ions can be desorbed with 5 ml of O.lmole-k HCl (sorbent recovery average out 96-100%). 

Solution processes of complexes of Mo(VI), W(VI) and V(V) with BPR as well as these complexes in the presence of dodecylpyridiniy chloride from aqueous solutions on aminosilica gels surfaces have been considered. The presence of dodecylpyridiniy chloride increases significantly the sorption degree of metals and broadens pH range of their quantitative extraction. 

Doucette, W.J. (2003) Quantitative Structure-Activity Relationships for Predicting SoU-Sediment Sorption Coefficients for Organic Chemicals. Environmental Toxicology and Chemistry, 22(8), 1771-1788. 

The chief uses of chromatographic ad-sorption include (i) resolution of mixtures into their components (ii) purification of substances (including technical products from their contaminants) (iii) determination of the homogeneity of chemical substances (iv) comparison of substances suspected of being identical (v) concentration of materials from dilute solutions (e.g., from a natural source) (vi) quantitative separation of one or more constituents from a complex mixture and (vii) identi-l ig., 46, 3. anj control of technical products. 

The main characteristic features of HPTLC (use of fine particle layers for fast separations, sorbents with a wide range of sorption properties, high degree of automation for sample application, development and detection) are the exact opposite of conventional TLC. Expectations in terms of performance, ease of use and quantitative information from the two approaches to TLC are truly opposite [419], Modern TLC faces an uncertain future while conventional TLC is likely to survive as a general laboratory tool. 

A procedure for characterizing the rates of the volume change of gels has not been uniformly adopted. Often, the kinetics are simply presented as empirical sorption/desorption curves without quantitative analysis. In other cases, only the time required for a sample of given dimensions to reach a certain percentage of equilibrium is cited. One means of reducing sorption/desorption curves to empirical parameters is to fit the first 60% of the sorption curve to the empirical expression [119,141]... 

SSZ-35 the reactions would be influenced by the presence of very strong Lewis sites. Quantitative sorption of ammonia, pyridine and d3-acetonitrile in both zeolites showed that the real number of acidic groups was close to values, derived form the number of aluminum atoms (taken from AAS analysis) in the idealized unit cell. Obtained values are 1.1 H+/u.c. for SSZ-33 with idealized unit cell composition H2.9[Al2.9Si53.iOii2] (plus 1.3 Lewis sites per u.c.) and 0.3 H+/u.c. for SSZ-35 with ideal formula Ho.4[Alo.4Sii5 6032] (plus 0.05 Lewis sites per u.c.). 

Sabljic A (1989) Quantitative modeling of soil sorption for xenobiotic chemicals. Environ Health Persp 83 179-190... 

This assumption is implicitly present not only in the traditional theory of the free-radical copolymerization [41,43,44], but in its subsequent extensions based on more complicated models than the ideal one. The best known are two types of such models. To the first of them the models belong wherein the reactivity of the active center of a macroradical is controlled not only by the type of its ultimate unit but also by the types of penultimate [45] and even penpenultimate [46] monomeric units. The kinetic models of the second type describe systems in which the formation of complexes occurs between the components of a reaction system that results in the alteration of their reactivity [47-50]. Essentially, all the refinements of the theory of radical copolymerization connected with the models mentioned above are used to reduce exclusively to a more sophisticated account of the kinetics and mechanism of a macroradical propagation, leaving out of consideration accompanying physical factors. The most important among them is the phenomenon of preferential sorption of monomers to the active center of a growing polymer chain. A quantitative theory taking into consideration this physical factor was advanced in paper [51]. 

There is a continuing effort to extend the long-established concept of quantitative-structure-activity-relationships (QSARs) to quantitative-structure-property relationships (QSPRs) to compute all relevant environmental physical-chemical properties (such as aqueous solubility, vapor pressure, octanol-water partition coefficient, Henry s law constant, bioconcentration factor (BCF), sorption coefficient and environmental reaction rate constants from molecular structure). 

Thomsen M, Dobel S, Lassen P, Carlsen L, Mogensen BB, Hansen PE (2002) Reverse quantitative structure-activity relationship for modelling the sorption of esfenvalerate to dissolved organic matter. A multivariate approach. Chemosphere 49 1317-1325... 

The octanol-water partition coefficient, Kow, is the most widely used descriptor of hydrophobicity in quantitative structure activity relationships (QSAR), which are used to describe sorption to organic matter, soil, and sediments [15], bioaccumulation [104], and toxicity [105 107J. Octanol is an amphiphilic bulk solvent with a molar volume of 0.12 dm3 mol when saturated with water. In the octanol-water system, octanol contains 2.3 mol dm 3 of water (one molecule of water per four molecules of octanol) and water is saturated with 4.5 x 10-3 mol dm 3 octanol. Octanol is more suitable than any other solvent system (for) mimicking biological membranes and organic matter properties, because it contains an aliphatic alkyl chain for pure van der Waals interactions plus the alcohol group, which can act as a hydrogen donor and acceptor. 

Pollutants with high VP tend to concentrate more in the vapor phase as compared to soil or water. Therefore, VP is a key physicochemical property essential for the assessment of chemical distribution in the environment. This property is also used in the design of various chemical engineering processes [49]. Additionally, VP can be used for the estimation of other important physicochemical properties. For example, one can calculate Henry s law constant, soil sorption coefficient, and partition coefficient from VP and aqueous solubility. We were therefore interested to model this important physicochemical property using quantitative structure-property relationships (QSPRs) based on calculated molecular descriptors [27]. 

Some emphasis is given in the first two chapters to show that complex formation equilibria permit to predict quantitatively the extent of adsorption of H+, OH , of metal ions and ligands as a function of pH, solution variables and of surface characteristics. Although the surface chemistry of hydrous oxides is somewhat similar to that of reversible electrodes the charge development and sorption mechanism for oxides and other mineral surfaces are different. Charge development on hydrous oxides often results from coordinative interactions at the oxide surface. The surface coordinative model describes quantitatively how surface charge develops, and permits to incorporate the central features of the Electric Double Layer theory, above all the Gouy-Chapman diffuse double layer model. 

Generally, there is no simple and easy theoretical procedure which can provide exact or nearly precise quantitative predictions of what and how much will be adsorbed/desorbed by any solid phase over a period of time [9, 136-139]. Understanding sorption/desorption characteristics of any solid phase materials requires two main laboratory experimental techniques (a) batch equilibrium testing, and (b) continuous solid phase column-leaching testing. These involve... 

Sorption and desorption of contaminants into, onto, or from subsurface soils, bottom sediments, and suspended solids constitute a consideration in the characterization of the nature of both solid phases and contaminants. There is no simple and easy theoretical procedure that provides an exact quantitative prediction of what and how much of what will be sorbed/desorbed by a certain solid phase over a period of time, and to predict the sorption/desorption-time relationship and the fate of contaminants once they are released into the environment. 

Accordingly, sorption has received a tremendous amount of attention and any method or modeling technique which can reliably predict the sorption of a solute will be of great importance to scientists, environmental engineers, and decision makers (references herein and in Chaps. 2 and 3). The present chapter is an attempt to introduce an advanced modeling approach which combines the physical and chemical properties of pollutants, quantitative structure-activity, and structure-property relationships (i. e., QSARs and QSPRs, respectively), and the multicomponent joint toxic effect in order to predict the sorption/desorp-tion coefficients, and to determine the bioavailable fraction and the action of various organic pollutants at the aqueous-solid phase interface. 

The second modeling approach discussed in this section presents an overview of the fundamentals of quantitative structure-activity relationships (i.e., QSARs [102-130]) and quantitative structure-property relationships (i.e., QSPRs [131-139]). It will show how such an approach can be used in order to estimate and predict sorption/desorption coefficients of various organic pollutants in environmental systems. 

Hu, Q., Wang, X., and Brusseau, M.L. Quantitative structure-activity relationships for evaluating the influence of sorbate structure on sorption of organic compounds by soil, iujFiron. Toxicol. Chem., 14(7) 1133-1140, 1995. 

With particular reference to reverse osmosis systems involving cellulose acetate membranes and aqueous solutions, the membrane material has both polar and nonpolar character, and the solvent, of course, is polar. When these two components of the reverse osmosis system are kept constant, preferential sorption at the membrane-solution interface, and, in turn, solute separation in reverse osmosis, may be expected to be controlled by the chemical nature of the solute. If the latter can be expressed by appropriate quantitative physicochemical parameters representing polar-, steric-, nonpolar-, and/or ionic-character of the solutes, then one can expect unique correlations to exist between such parameters and reverse osmosis data on solute separations for each membrane. Experimental results confirm that such is indeed the case (18). 

Sorption. Kqp values have been looked upon as constant for neutral organic chemicals. Independent of soil type (73). The parameter Is valid for comparison of leaching potential of pesticides with widely varying water solubility however. It Is difficult to make quantitative comparisons among polar organics. For example, note the wide range In Kq, for oxamyl described In Table IV. This may be due In part to Interactions with soil mineral fractions which become Important when the soil organic matter content Is low (56,112). Also, use of water solubility... 

In order to apply this technique for quantitative characterization of counter-transport phenomena in zeolites it had to be checked first for the more simple case of single-component diffusion. As an example, benzene diffusion in H-ZSM-5 was chosen, because results for this case had been already reported by several authors. Their results, obtained from sorption kinetics as well as from NMR experiments, were in very good agreement and, thus, provided a reliable basis for comparison [13,14]. 

A fourth application is a convenient assessment of the removal of a transition metal by a supported chelator vs sorption on the substrate. It appears that the supported chelators were able to remove copper ion in a quantitative manner, but a goodly proportion (83%) was removed by sorption on silica gel. In contrast, a Linde molecular sieve (alone) with fairly defined pores removed about half of the copper ion through sorption. 

To achieve optimal sensitivity and selectivity, it was necessary to develop three totally separate methods, one for each compound. Initially, it was necessary to develop, optimize, and calibrate a procedure for quantitating each analyte. With these steps successfully completed, candidate collection media were screened in tests designed to find a material with three attributes (1) an acceptable sorption capacity for the appropriate... 

This example illustrates the qualitative nature of information that can be gleaned from macroscopic uptake studies. Consideration of adsorption isotherms alone cannot provide mechanistic information about sorption reactions because such isotherms can be fit equally well with a variety of surface complexation models assuming different reaction stoichiometries. More quantitative, molecular-scale information about such reactions is needed if we are to develop a fundamental understanding of molecular processes at environmental interfaces. Over the past 20 years in situ XAFS spectroscopy studies have provided quantitative information on the products of sorption reactions at metal oxide-aqueous solution interfaces (e.g., [39,40,129-138]. One... 

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