Aliphatic acids adsorption

The MEMED technique has been used to study the hydrolysis of aliphatic acid chlorides in a water/l,2-dichloroethane (DCE) solvent system [3]. It was shown unambiguously that the reaction proceeds via an interfacial process and shows saturation kinetics as the concentration of acid chloride in the DCE increases the data were well fitted to a model based on a pre-equilibrium involving Langmuir adsorption at the interface. First-order rate constants for interfacial solvolysis of CH3(CH2) COCl were 300 150(n = 2), 200 100(n = 3) and 120 60 s-1( = 8). 

An increase in solubility tends to oppose the attraction of the adsorbate to carbon. Therefore, polar groups having a high affinity for water usually diminish adsorption from aqueous solutions the greater adsorption of the higher aliphatic acids and alcohols is attributed in part to their relatively lower solubility in an aqueous solution. 

The molecular size of the adsorbate is of great importance in adsorption, since the molecules must enter the micropores of a carbon particle in order for it to be adsorbed. Hassler (23) discovered that within the homologous series of aliphatic acids, aldehydes or alcohols, adsorption usually increases, as the molecule size becomes greater. Culp and Culp (13) explained that the forces of attraction between a carbon and a molecule are greater the closer the size of the molecule is to the size of the pores in the carboiL That is, adsorption is strongest when the pores are just large enoi to permit the molecules to enter. 

Hansen, R.S., Diffusion and the kinetics of adsorption of aliphatic acids and alcohols at the water-air interface, J. Colloid Set, 16, 549, 1961. 

The adsorption of aliphatic acids (valeric, caproic, enanthic, caprylic, pelar-gonic) from 1% solution from cyclohexanone on an alumino-silicate catalyst, silica gel (KSK-2), and AI2O3 has been studied under dynamic conditions by Narmetova, Khashimova, Narimova, and Ryabova. The lower molecular weight acids were preferentially adsorbed. Both physical and chemisorption... 

Blocking of reaction sites The interaction of adsorbed inhibitors with surface metal atoms may prevent these metal atoms from participating in either the anodic or cathodic reactions of corrosion. This simple blocking effect decreases the number of surface metal atoms at which these reactions can occur, and hence the rates of these reactions, in proportion to the extent of adsorption. The mechanisms of the reactions are not affected and the Tafel slopes of the polarisation curves remain unchanged. Behaviour of this type has been observed for iron in sulphuric acid solutions containing 2,6-dimethyl quinoline, /3-naphthoquinoline , or aliphatic sulphides . 

The Frumkin isotherm can be regarded as a general isotherm from which both the Temkin and Langmuir isotherms can be obtained as special cases. Szklarska-Smialowski and Wieczorek found that the adsorption of various aliphatic compounds (acids, alcohols and amines) on steel in H2SO4 conformed with the Frumkin isotherm. 

The pzc of a pc-Cd renewed by cutting was determined in dilute fluoride and sulfate solutions by capacitance measurements.645,646 The C, E curves exhibited distinct minima whose depth increased with increasing dilution of the solution (Table 15). This value is ca. 30 mV more negative than that for polished electrodes and reflects the more disturbed surface stmcture of a renewed electrode. Adsorption of aliphatic alcohols and acids has also been studied on these electrodes.645,646... 

Polymeric aliphatic carboxylates, the poly(alkenoic add)s, were very much more strongly adsorbed than the difunctional carboxylates (Ellis et al., 1990). Results showed that adsorption depended on the conformation of the polyanion. When extended, as in dilute solutions, a polyanion is adsorbed onto a relatively large number of sites and further adsorption is hindered. Thus, increases in acidity (and concentration) were found to result in greater adsorption because the polyanion adopted a more compact... 

Ng, K.L., Pauli, B., Haddad, P.R., and Tanaka, K., Retention modeling of electrostatic and adsorption effects of aliphatic and aromatic carboxylic acids in ion-exclusion chromatography, /. Chromatogr. A, 850, 17, 1999. 

Ulrich, H-J., W. Stumm, and B.Cosovic (1988), "Adsorption of Aliphatic Fatty Acids on Aquatic Interfaces. Comparison between 2 Model Surfaces The Mercury Electrode and 6-AI2O3 Colloids", Environ. Sd. Techn. 22, 37-41. 

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