Adsorption of p-nitrophenol

Normally PNP is adsorbed flatwise with an effective molecular area of 0.525 iun2. In some cases, on polar inorganic solids, it is adsorbed end-on with an effective area of 0.25 nm. The mode of adsorption is indicated by the type of isotherm generated, an S-type curve indicating end-on adsorption. 

The experimental procedure is similar to that used for dye adsorption [79], Since PNP does not adsorb on cellulose it can also be used for the measurement of speciflc surface of colorants in cellulose [80]. 

The use of PNP adsorption from aqueous solutions on to porous adsorbents such as silica gel or carbons has been queried by Sarrdle (cit 81] who states that competition of water molecules for the surface will yield erroneous resirlts. Giles agrees that complete coverage is not always obtained with certain acidic solids and recommends the use of other solvents. 

Padday [74] states that the accuracy of PNP is suspect since many isotherms show no clearly defined plateau. 

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Adsorption of p-Nitrophenol from Dilute Aqueous Solution 138... 

The forces responsible for a second or third layer to be adsorbed cannot be very strong. We may, therefore, not expect multimolecular adsorption to occur at moderately low relative pressures on flat and homogeneous surfaces. By means of absorption spectra a bimolecular adsorption of p-nitrophenol could be established on CaF2 or BaF2 layers (250). The absorption spectrum of the first layer was quite different from that of p-nitrophenol itself, the absorption spectrum of the second layer being practically the same as that of pure p-nitrophenol. The first layer is apparently sufficiently polarized by the salt surface, to enable a second layer to adsorb the second layer, however, cannot accumulate a third layer. It may not be entirely excluded, however, that there is no more place in the capillary space between the salt layers to accommodate a third layer of p-nitrophenol. 

On the other hand, the adsorption of p-nitrophenol is better for samples prepared in the presence of SDS. Indeed, for the same quantity of pCD, TbS2 is more efficient for p-NP adsorption than Tb2. 

Lynam, M. M. Kilduff, J. E. Weber, W. J. Adsorption of p-Nitrophenol from Dilute Aqueous Solution An Experiment in Physical Chemistry with an Environmental Approach, J. Chem. Educ. 1995, 72, 80-84. 

Giles, C.H. and Nakhwa, S.N. (1962). Adsorption XVI The measurement of specific surface areas of finely divided solids by solution adsorption. J. Appl. Chem., 12, 266-73. Lopez-Gonzalez, J., de, D., Valenzuela-Calahorro, C., et al. (1988). Adsorption of p-nitrophenol by active carbons prepared from obve wood. An. Quim., 84B, 47—51. Femandez-Cobnas, J., Denoyel, R., and Rouquerol, J. (1991). Characterization of activated charcoals by adsorption from solution. Stud. Surf. Sci. Catal., 62, 399—408. Somasundaran, P. and Fuerstenau, D.W. (1966). Mechanisms of alkyl sulfonate adsorption at the alumina-water interface. J. Phys. Chem., 70, 90-6. 

Dry sur ce was measured by nitrogen adsorption solvated surface was measured by adsorption of p-nitrophenol from aqueous solution. 

Zhou, Q., He, H., Frost, R. L., and Xi, Y. 2007. Adsorption of p-nitrophenol on mono-, bi-, and trialkyl surfactant-intercalated organoclays A comparative study. Journal of Physical Chemistry C 111 7487-7493. 

Moreno-Castilla investigated the adsorption behavior of mono-substituted phenols of different solubilities on activated carbons obtained from an original and demineralized bituminous coal. The adsorption capacity of the activated carbon was found to depend on the surface area and the porosity of the carbon, the solubility of the phenolic compound, and the hydrophobicity of the substituent. The relative affinity of the phenolic compound toward the carbon surface was related to the donor-acceptor complexes formed between the basic sites on the carbon surface and the organic ring of the phenol. The adsorption was also influenced by the pH of the solution. Marsh and Campbell observed that the adsorption of p. nitrophenol at low concentrations on polyfurfuryl alcohol and polyvinylidene chloride activated carbons was extremely sensitive to the microporous structure of these carbons and showed adsorption isotherms similar to those of nitrogen or carbon dioxide. The adsorption of p.nitrophenol was so strong at low clc values that the adsorption... 

Similar results were obtained by Goyal -" on the adsorption of p.nitrophenol from aqueous solutions on the same activated carbons as used by Bansal et al. ° ° ... 

Contrary to the effects of surface carboxyl and hydroxyl groups, the surface quinone (or carbonyl) groups acmally increased the adsorption of aromatics. Epstein et al. (1971) observed these effects with the adsorption of p-nitrophenol. Their explanation was that the carbonyl groups aid the adsorption of aromatics by involving the formation of an electron donor-acceptor complex of the aromatic ring with the surface carbonyl groups, as proposed earlier by Mattson et al. (1969). 

Huang, T.C., and Cho, L.T., Adsorption of p-nitrophenol on anion exchange resin at various temperatures. Can. 

Khalil, L.B., and Girgis, B.S., Adsorption of p-nitrophenol on activated carbon prepared from phosphoric acid-treated apricot stone shells, Adsorpt. Sci. Technol., 12(1). 79-92 (1995). 

Since these initial proposals (differing) by Coughlin and Ezra (1968) and Mattson et al. (1969), and after many papers have been published, significant clarification has not been forthcoming. The publication of Haydar et al. (2003) describes the adsorption of p-nitrophenol on an AC with different levels of oxidation, the authors providing experimental evidence for the ir-rr-dispersion interaction mechanism. 

Haydar S, Ferro-Garcia MA, Rivera-Utrilla J, Joly IP. Adsorption of p-nitrophenol on an activated carbon with different oxidations. Carbon 2003 41(3) 387-395. 

It was established that functionalized nanoporous CD polymers may adsorb some organic water pollutants to ppb levels. The synthesis of several insoluble monosubstituted CD polymers, i.e. nanosponges has been reported. These polymers have high abilities for adsorption of p-nitrophenol and pentachlorophenol from aqueous solutions. 

Since the chloroanilines are sufficiently retained (k >5) in a 10 % v/v methanol water eluent, and the Ibuprofen enantiomers are sufficiently retained in a 30 % v/v acetonitrile buffer eluent, these solvents were selected as carrier solvents for the displacement chromatographic separations. Also, these solvents were used to determine the adsorption isotherms of p-nitrophenol and 4-t-butylcyclohexanol on beta-cyclodextrin silica. The isotherms were determined from frontal chromatographic measurements as described in (56). The isotherms are shown in Figs. 7 and 8. Since both isotherms are downwardly convex, p-nitrophenol and 4-t-butylcyclohexanol might prove useful displacers for our test solutes, provided that they are more strongly adsorbed that the solutes. 

Adsorption isotherms of p-nitrophenol and the most retained isomers of chloroanilines. Conditions 15 cm x 4.6 mm ID column packed with beta-cyclodextrin-silica solvent 10 % v/v methanol water temperature 30 C. 

A preparation in two steps has been chosen hrst a new hybrid silica precursor P-CDAPS, containing P-CD groups and amine functions, has been prepared and characterized. Then, this precursor has been co-condensed with tetraethyl orthosilicate (TEOS) via a sol-gel process involving the use of surfactant. We chose the anionic surfactant sodium dodecylsulfate (SDS). The chemical and structural characterization combined with adsorption tests of p-nitrophenol and lead nitrate led to the evaluation of the accessibility and the effectiveness of the binding functions in these hybrid materials. 

A number of molecules have become favourites for study at liquid interfaces and there have been a number of investigations of the adsorption behaviour of p-nitrophenol... 

MNPHP is a well-known irreversible inhibitor of lipases that is highly specific for reaction with active-site serine residues. Thus, MNPHP was selected as the inhibitor to determine, by titration, the fraction of catalytic sites that are accessible and active. Since we are concerned with CALB activity in organic media, inhibition was studied in heptane. LC-MS was used to determine the release of p-nitrophenol (pNP) which corresponds with accessible active sites. To ensure that adsorption of pNP by resins was taken into consideration, pNP concentration was corrected as follows. A fixed quantity of enzyme-free resin was incubated overnight in acetonitrile with different concentrations of j NP. Standard curves of pNP adsorption by each resin as a function of pNP concentration were constructed from LC-MS measurements. MNPHP-inhibited immobilized enzymes were used for e-caprolactone ring-opening polymerizations in toluene (70 C). No conversion of monomer was observed in 30 minutes. Hence, MNPHP titration resulted in complete inhibition of CALB activity. 

As shown in Secs. IV.A and IV.B, however, some adsorption systems involving aromatic adsorbates are very much influenced by electrostatic interactions. Additional examples are cited and discussed elsewhere [37]. Clearly, a model is needed that takes both electrostatic and dispersion interactions into account. Such a model has been presented by Muller and coworkers [106-108]. My coworkers and I [136,137,145] used this model to illustrate the possibly dramatic effects of modifications of carbon surface chemistry on equilibrium uptake of p-nitrophenol. We also extended it further to evaluate the relative importance of electrostatic and dispersive interactions [138,145]. 

It was found that the adsorption efficiency of p-nitrophenol and trichloroethylene by obtained polymers was higher than that of activated carbon and of native [3-CD polymers. It should be pointed out that the above polymers maintain ca 96% of their sorption efficiency after 25 use/regeneration cycles, and the loss of their initial mass after repeated use is minimal. 

Fig. 7a, b. Kinetics of poly(p-nitrophenyl acrylate) chemical adsorption on aminopropyl-Aerosil at 25 °C in dimethylsulphoxide. Filled circles ester group content (pmol/g support), empty c/rc/ei p-nitrophenol release (pmol/g support), a — l%solution b — 5% solution [55]... 

Baarschers, W.H., Elvish, J., and Ryan, S.P. Adsorption of fenitrothion and 3-methyl-4-nitrophenol on soils and sediment, Bull. Environ. Contam. Toxicol, 30(5) 621-627, 1983. 

Haderlein, S.B. and Schwarzenbach, R.P. Adsorption of substituted nitrobenzenes and nitrophenols to mineral surfaces. 

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