Adsorption kinetics acids

The tendency to form organized monolayers improves with chain length. This is illustrated in a study of adsorption kinetics in alkanoic acid monolayers on alumina by Chen and Frank [36]. They find that the Langmuir kinetic equation, discussed in Section XVII-3, (see Problem XI-6)... 

Fig. XI-1. Adsorption kinetics for C g alkanoic acids adsorbing onto alumina for various solution concentrations from Ref. 36. Lines are the fit to Eq. XI-IS.

The same resin was used for the purification via downstream processing of carminic acid, the natural colorant extracted from cochineal. By a direct adsorption method, a crude extract was applied on the polymeric bed gel and the adsorption kinetics studied using elution with hydrochloric acid and ethanol. The desorbed pure carminic acid concentrated under vacuum yielded a final product that complied with Codex Alimentarius requirements and FAO/OMS norms. 

Vilan A, Ussyshkin R, Gartsman K, Cahen D, Naaman R, Shanzer A (1998) Real-time electronic monitoring of adsorption kinetics evidence for two-site adsorption mechanism of dicarboxylic acids on GaAs(100). J Phys Chem B 102(18) 3307-3309... 

The study of adsorption kinetics of a surfactant on the mineral surface can help to clarify the adsorption mechanism in a number of cases. In the literature we found few communications of this kind though the adsorption kinetics has an important role in flotation. Somasundaran et al.133,134 found that the adsorption of Na dodecylsulfonate on alumina and of K oleate on hematite at pH 8.0 is relatively fast (the adsorption equilibrium is reached within a few minutes) as expected for physical adsorption of minerals with PDI H+ and OH". However, the system K oleate-hematite exhibits a markedly different type of kinetics at pH 4.8 where the equilibrium is not reached even after several hours of adsorption. Similarly, the effect of temperature on adsorption density varies. The adsorption density of K oleate at pH 8 and 25 °C is greater than at 75 °C whereas the opposite is true at pH 4.8. Evidently the adsorption of oleic acid on hematite involves a mechanism that is different from that of oleate or acid soaps. 

Fig. 7A, B. Adsorption kinetics of digoxin on XAD-4 , XAD-7) B acidic exchange resins ( ...

The quantitative difference in adsorption behavior of linear polymers between alkaline and acidic conditions can be verified from surface plasmon resonance (SPR) results [111]. As seen in Fig. 6, the adsorption kinetics change along any profile of rapid saturation, gradual increase after rapid increase or gradual increase, depending on the type of linear polymers. The equilibrium of adsorption is reached faster for NaPGA and NaHA than for DNA. However, the film at equilibrium is thicker at acidic condition than at alkaline condition. The quantitative estimation of adsorption of DNA on dendrimer SAMs can be also carried out from the intensity increase of a UV-vis absorption band at 258.8 nm [110]. 

Similar results were obtained by Yeliseyeva ei al. (1973, 1975) when studying the sodium alkylsulfonate emulsifier adsorption kinetics during polymerization of butyl acrylate and its copolymerization with such water-soluble monomers (3 o) as methacrylic acid, JV-melhacrylamide, and JV-methylolmethacrylamide, In all cases the introduction of water-soluble comonomers resulted in a decrease of the effective rate and in the value of the emulsifier adsorption. The authors attributed this to the hydrq>hili-zation and increase of polarity of latex particle surfaces. 

Pendleton and coworkers [46] showed (Fig. 25.5) that the adsorption of dodecanoic acid on different activated carbons linearly decreased when the oxygen content of the carbonaceous adsorbent increased and that the adsorption was not related to the micropore volume of the adsorbent. They concluded that the surface chemistry more accurately predicted the adsorption of dodecanoic acid in aqueous phase compared with the surface area or micropore volume. In addition, carbon surface chemistry also had a significant influence on dodecanoic acid adsorption kinetics. Thus, the adsorption rate was reduced by the high surface oxygen content of the carbon adsorbent, whereas its pore volume made a smaller contribution [47],... 

SERS was discovered with pyridine. Other aromatic nitrogen- or oxygen-containing compounds, such as aromatic amines or phenols, also display strong enhancement due to SERS. The enhancement can also be seen with other electron-rich analytes such as carboxylic acids. Although SERS allows easy observation of Raman spectra from solutions with concentration in the micromolar (10 ) range, slow adsorption kinetics and competitive adsorption limit its application in analytical chemistry. 

Moreover, adsorption isotherms, or equations of state, represent the basis for the evaluation of adsorption kinetics and rheological properties of adsorption layers. Exact equilibrium values of surface or interfacial tensions are necessary to determine adsorption isotherms. For surfactants of low surface activity (for example, sodium octyl or decyl sulphate, hexanol or hexanoic acid) the adsorption reaches its equilibrium state in a time of the order of seconds to minutes. Higher surface activity results in greater times for establishing the equilibrium state of adsorption which sometimes cannot be realised by available experimental methods. To avoid long-time experiments, extrapolations were often carried out in order to get equilibrium values. Different extrapolation procedures as well as criteria of an equilibrium state of adsorption are discussed in the literature (cf Miller Lunkenheimer 1983). 

Fig. 8.15 Plots of the integrated intensity of the 1578-cm" band (at 1621 cm" in acidic solution) from PySH adsorbed on Au electrodes showing the adsorption kinetics of this molecule after injecting into the solutions measured under different conditions (solution pH and applied potential) (a) pH dependence at the fixed potential of...

Kasuya K-i, Inoue Y, Doi Y (1996) Adsorption kinetics of bacterial PHB depolymerase on the surface of polyhydroxyalkanoate films. Int J Biol Macrom 19 35 0 Kasuya K-i, Ohura T, Masuda K, Doi Y (1999) Substrate and binding specificities of bacterial polyhydroxybutyrate depolymerases. Int J Biol Macromol 24 329-336 Kato M, M. HJB, Kang CK, Fukui T, Doi Y (1996) Production of a novel copolyester of 3-hydroxybutyric acid and medium-chain-length 3-hydroxyalkanoic acids by Pseudomonas sp. 61-3 from sugars Appl Microbiol Biotechnol 45 363-370 Kaushik N, Kumar K, Kumar S, Kaushik N, Roy S (2007) Genetic variability ruid divergence studies in seed traits and oil content of Jatropha (Jatropha curcas L.) accessions. Biomass Bioenerg 31 497-502... 

A. Vilan etal., Real-Time Electronic Monitoring of Adsorption Kinetics Evidence for Two-site Adsorption Mechanism of Dicar-boxylic Acids on GaAs(lOO), J. Phys. Chem. B 1998, 102, 3307-3309. 

Figure 11.4 SEM images of PANI nanotube (a) and PANI/silica composite (b) pseudo-first (c), pseudo-second (d) order adsorption kinetics and Langmuir (e) and Freundlich (f) isotherms of PANI/sUica composite to acid green Reprinted from Ref [36] with permission from Springer (2012).

Analogous to eq. (7.47), eq. (7.52) assumes that the rate of desorption is negligible. A study of adsorption kinetics in case of alkanoic acid monolayers on alumina was carried out by Chen and Frank [39, 77]. They found that the Langmuir kinetic... 

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