Maximum sorption

Regarding submerged plants, sorption of Cu(II) by Myriophyllum spicatum L. (Eurasian water milfoil) has been shown to be fast and fits isotherm models such as Langmuir, Temkin, and Redlich-Peterson. The maximum sorption capacity (c/lll l j ) of copper onto M. spicatum L. was 10.80 mg/g, while the overall sorption process was best described by the pseudo-second-order equation.115 Likewise, Hydrilla verticillata has been described as an excellent biosorbent for Cd(II). In batch conditions, the qmsx calculated was 15.0 mg/g. Additionally, II. verticillata biomass was capable of decreasing Cd(II) concentration from 10 to a value below the detection limit of 0.02 mg/L in continuous flow studies (fixed-bed column). It was also found that the Zn ions affected Cd(II) biosorption.116... 

Hall et al. (2001) measured the biosorption of copper by P. syringae, fitting the experimental data to the Freundlich, Brunauer-Emmett-Teller (BET), and Langmuir equations. Meaningful maximum sorption capacities... 

The 95% confidence interval amounted to 1.3 log units, which corresponds to a scatter in the ATdoc values by a factor of 20. Burkhard (2000) argues that the uncertainty in Eq. 3.25 originates partly from inter-laboratory variation, and partly from differences in DOC quality. In view of the wide range of DOC sources included in Eq. 3.25, it does not seem likely that the uncertainties in any ATdoc encountered would be more than 1.3 log units. Hence, the worst-case estimate (maximum sorption of dissolved phase residues by DOC) can be described by... 

Table 11.2 Adsorption of Nonionic Nitroaromatic Compounds (NACs) to Aluminosilicate Clays (a) Surface Area Factors,/saf, for Different Clays Expressing Maximum Sorption Sites Relative to Kaolinite, and (b) KNAC EDA Values (L- mol 1 sites) Measured for Several NACs on K+-Kaolinite Allowing Estimates of KNACd Values Due to Electron Donor-Acceptor Interactions (Eq. 11-20) ...

The index m, representing the maximum sorption in the cavity, may he derived from considerations of the zeolitic cavity volume and molar volume of the sorhate, as m <. v/0. However Schirmer et al. (7 ) state that a maximum of 6 terms has been used in their work. 

Increasing the number of methyls in the arsenic species resulted in decreased sorption at low arsenic concentrations and an increase in the ability of the species to desorb (Lafferty and Loeppert, 2005, 2120). Like As(V), maximum sorption of MMA(V) and DMA(V) occurs under low pH conditions and decreases with increasing pH (Lafferty and Loeppert, 2005, 2120). 

As with other pesticides, organic matter appears to be the soil constituent most important for basic pesticide sorption. Weber et al. (1969) showed that maximum sorption of several s-triazines on organic matter occurred at pH levels close to the pKa values of the compounds. The molecular structure of the pesticide and the pH of the sorbent strongly affected the degree of sorption. The pH-dependent sorption and the relationship between pH and dissocation constant with pH suggests an ion exchange mechanism (Saltzman and Yaron, 1986). 

Explain the general relationship between water solubility of organics and maximum sorption. 

Macroreticular polystyrene-based resins with functional aminothiazole, imino-thiazole, or thiazoline groups exhibit a high selectivity for mercury(II). A thiazoline resin column has been used to concentrate mercury from sea water adjusted to pH 1 with hydrochloric acid. Maximum sorption capacity for mercury was found to be 2.8 mmole/g. The sorbed mercury is recovered quantitatively by eluting with 0.1 M HC1 containing 5 % thiourea 100). 

A nonlinear local isotherm model is clearly required for description of sorption reactions between the TCB and the shale isolate. A variety of conceptual and empirical models for representing nonlinear sorption equilibria, exists (2). The Langmuir model is one of the ideal limiting-condition-type models cited earlier. It is predicated on a uniform surface affinity for the solute and prescribes a nonlinear asymptotic approach to some maximum sorption capacity. 

Formation of the structure of co-precipitated adsorbents depends on many factors, among which the pH of precipitation of mixture components is one of the most important factors. It should be noted that porosity of the co-precipitated adsorbents is a function of the pH of initial and final precipitation of hydrogels in the case of hydrogels, the pH of initial and final co-precipitation is different, adsorbents formed have a maximum in the sorption capacity (Vs) - composition curve and, vice versa, when the pH of co-precipitated hydrogels coincides, adsorbents produced have the sorption capacity directly proportional to Vs of the components in mixture. It cannot be excluded that the phenomenon revealed is of a general nature and occurs in natural conditions with the appropriate combination of the pH of the medium and the presence of suitable salts. In the present work universality of the found relationship will be proved by numerous examples. This relationship is extremely useful in the synthesis of complex adsorbents with the predicted structural parameters. From the sorption capacities of individual components it is also possible to calculate the mixture composition corresponding to the maximum sorption capacity of porous materials produced. 

To conclude the section, it should be noted that the new approach to understanding the mechanism of the porous structure for co-precipitated hydrogels considered in [4,15,20] may be extremely useful for the purposeful selection of component compositions and their percentage in the solution to ensure a maximum sorption capacity of the porous material synthesized. 

Sarkar et al. (1999) showed that the presence of small concentrations of Pb and Ni decreased the sorption of Hg at pH values of maximum sorption of 38 and 31% on quartz and 14 and 11% on gibbsite, respectively. Recently, Violante et al. (2003) carried out experiments on the competitive sorption of Cu and Zn on a ferrihydrite. They demonstrated that Cu has a greater affinity for the surfaces of ferrihydrite and thus inhibits the sorption of Zn on common sites and is also able to remove Zn previously sorbed onto them. 

So far, mats of some polymers, such as poly(propylene) and poly(urethane), have been used for the sorption of spilled oil. Their maximum sorption capacity is about 10-30 g of heavy oil per 1 g of polymer [35]. However, they sorb water, as well as heavy oil, and show no special selectivity for heavy oils. Therefore, the effective sorption capacity of the polymer mats for heavy oils floating on water must be lower than the figures mentioned above. Some natural sorbents prepared from cotton fibers, milkweed flosses, and kenaf plants were reported to have rather high sorption capacity and certain potential for oil recovery and sorbent reusability [35—41]. The sorption capacity of macroporous carbon materials, exfoliated graphite, and carbonized fir fibers, is very high in comparison with these materials. Preferential sorption of oils is an advantage of carbon materials in addition to their high sorption capacity. 

Toyoda, M., Moriya, K., Aizawa, J., et al. (2000). Sorption and recovery of heavy oils by using exfoliated graphite. Part I maximum sorption capacity. Desalination, 128, 205-11. 

Finally, ionic compounds are more readily isolated by reversed phase, if the pH of the sample is adjusted such that the molecule is not ionic or a lesser frac-(ion is ionic. Typically, the pH of the sample should be lowered to two pH units below the pA for organic acids in order to protonate all of the carboxyl groups and to have the maximum sorption capacity (Thurman et al., 1978). If ionic compounds are still polar after pH adjustment, then it is typically necessary lo isolate them using an ion-exchange method. This topic was discussed thoroughly in Chapter 6. 

Maximum sorption of irradiated fibres is considerably lower which is probably caused either by polymer construction seal in the process of irradiation, similar to the seal at thermal treatment, or by structurization taking place at severe irradiation and being similar to structurization in other polymers, namely, polystyrene [311]. 

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