Sorption isotherm of cation

Chromatography on a cation-exchange resin has been studied as a means of separating the glycoalkaloids of Solarium laciniatum. Sorption isotherms of the solasodine glycosides a-solamargine, /3-solamargine, and solasonine were measured. ... 

Vente JA, Bosch H, de Haan AB, Bussmann PJT. Comparison of sorption isotherms of mono- and disaccharides relevant to oligosaccharide separations for Na, K, and Ca loaded cation exchange resins. 

FIGURE 4.12 Sorption isotherms of dodecylpiridinium cation in a soil in the presence of 0.01 M NaN, (10 mM Na+) and 0.01 M NaNj + 0.09 M NaCl (100 mM Na+). Linear plot (a) and double logarithmic plot (h). (Reprinted with permission from Brownawell, B.J. et al., 1990, Environmental Science Technology, 24, no. 8,1234-1241. Copyright 1990 American Chemical Society.)... 

The (I)-(III)-samples sorption ability investigation for cationic dyes microamounts has shown that for DG the maximum rate of extraction is within 70-90 % at pH 3. The isotherm of S-type proves the physical character of solution process and a seeming ionic exchange. Maximal rate of F extraction for all samples was 40-60 % at pH 8 due to electrostatic forces. The anionic dyes have more significant affinity to surface researching Al Oj-samples comparatively with cationic. The forms of obtained soi ption isotherms atpH have mixed character of H,F-type chemosorption mechanism of fonuation of a primary monolayer with the further bilayers formation due to H-bonds and hydrophobic interactions. The different values of pH p for sorbents and dyes confirm their multifunctional character and distinctions in the acid-base properties of adsoi ption centers. 

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%). 

Nevertheless, surfactant sorption isotherms on natural surfaces (sediments and biota) are generally non-linear, even at very low concentrations. Their behaviour may be explained by a Freundlich isotherm, which is adequate for anionic [3,8,14,20,30], cationic [7] and non-ionic surfactants [2,4,15,17] sorbed onto solids with heterogeneous surfaces. Recently, the virial-electrostatic isotherm has been proposed to explain anionic surfactant sorption this is of special interest since it can be interpreted on a mechanistic basis [20]. The virial equation is similar to a linear isotherm with an exponential factor, i.e. with a correction for the deviation caused by the heterogeneity of the surface or the energy of sorption. 

Fig. 6.10 shows idealized isotherms (at constant pH) for cation binding to an oxide surface. In the case of cation binding, onto a solid hydrous oxide, a metal hydroxide may precipitate and may form at the surface prior to their formation in bulk solution and thus contribute to the total apparent "sorption". The contribution of surface precipitation to the overall sorption increases as the sorbate/sorbent ratio is increased. At very high ratios, surface precipitation may become the dominant "apparent" sorption mechanism. Isotherms showing reversals as shown by e have been observed in studies of phosphate sorption by calcite (Freeman and Rowell, 1981). 

The amount of adsorbed chemical is controlled by both properties of the chemical and of the clay material. The clay saturating cation is a major factor affecting the adsorption of the organophosphorus pesticide. The adsorption isotherm of parathion from an aqueous solution onto montmorillonite saturated with various cations (Fig. 8.32), shows that the sorption sequence (Al > Na > Ca ) is not in agreement with any of the ionic series based on ionic properties. This shows that, in parathion-montmoriUonite interactions in aqueous suspension, such factors as clay dispersion, steric effects, and hydration shells are dominant in the sorption process. In general, organophosphorus adsorption on clays is described by the Freundhch equation, and the values for parathion sorption are 3 for Ca +-kaoUnite, 125 for Ca -montmorillonite, and 145 for Ca -attapulgite. 

Figure 11.9 Sorption isotherms for some charged organic compounds interacting with natural solids (a) quinolinium cation on a subsoil of /oc = 0.024 and cation exchange capacity of 84 mmol/kg (Zachara et al., 1986), ( >) anilinium cation on a surface soil with /oc = 0.013 and cation exchange capacity of 112 mmol/kg (Lee et al., 1997), and (c) sorption of 4-(2,4-dichloro-phe-noxy)-butyrate anion on a sediment with/oc = 0.015 and unknown anion exchange capacity (Jafvert, 1990).

The swelling of clays in water results from the extra hydration of the interlamellar cations (Fig. 77). This is the best known example of the important phenomenon of intercalation, which is simply the insertion of guest species into an accommodating host, usually, but not exclusively, a layered solid. The degree of swelling, however, is governed by the nature of the interlamellar cation and the sorption isotherm often exhibits steps, as so often occurs with clathrates. 

Figure 4 Comparison of sorption models. Several commonly used sorption models are compared with respect to the independent constants they require. These constants are vahd only under specific conditions, which must be specified in order to properly use them. In other words, the constants are conditional with respect to the experimental variables described in the third column of the figure. is the radionuclide distribution constant K and n are the Freundlich isotherm parameters and are surface complexation constants for protonation and deprotonation of surface sites K-, are surface complexation constants for sorption of cations and anions in the constant...

Water vapour sorption isotherms for a 10% crosslinked sulfonic acid cation exchanger and a 0.4% crosslinked reference resin are shown in Figure 5.2 together with a calculation of the swelling pressure. The anomalous relative positions of the curves at low values of relative humidity P/Pq may be explained in terms of van der Waals type intramolecular forces which weakly bind adjacent polymer chains in de-swollen exchangers of low crosslinking. 

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