Adsorption Of P-nitrophenol Research Articles

Infrared studies of aromatic compounds adsorbed on the surface of carbon films

IR spectroscopic studies were carried out on the bond character of benzene, phenol, and p-nitrophenol molecules adsorbed on the surface of carbons. Interaction between the carbon surface and the π-electron system of an adsorbed aromatic molecule leads to changes in the IR spectrum (the value of the absorption coefficient). Oxygen chemisorbed on a carbon surface appears to strongly influence adsorption of aromatic compounds, especially when the adsorptive properties of carbon are partly determined by its molecular-sieve properties. Also, IR studies were carried out to determine the effect of ion exchange H + → Na + on the mechanism of phenol and p-nitrophenol adsorption.

Adsorption of Phenol and p-Nitrophenol on Activated Carbon: Determination of Effective Diffusion Coefficients

Adsorption of phenol and p-nitrophenol in aqueous solution on granular activated carbon has been studied in a stirred-tank system. Equilibrium isotherms and concentration decay curves were obtained experimentally for each adsorbate in the finite batch adsorber, for three temperatures in the range 274-313 K. Effective internal diffusion coefficients, Di, of the two adsorbates were calculated by means of a mathematical model of diffusion-adsorption that takes into account ordinary liquid phase diffusion and surface diffusion mechanisms. Surface diffusion coefficients, DS, were also calculated and correlated with temperature and surface coverage. Isosteric heat of adsorption and activation energy for the adsorption of p-nitrophenol were calculated; values obtained are between those of characteristic physical and chemical adsorption.

A Study of the Physical State of some Water-Soluble Dyes in Cellulose by p-Nitrophenol Adsorption

The p-nitrophenol adsorption method has been used to measure the specific surface of two direct dyes and an acid wool dye in various forms of cellulose. The state of association is then determined. At weak shade depths a monolayer of dye is formed on the internal surface of the substrate, but as the shade is deepened multilayers appear to form, and event ually these break up into three-dimensional aggregates. Association occurs more readily in "never-dried" regenerated cettutose film than in normal film and is not influenced by drying. There is a correspondence between the state of association of C.I. Direct Blue 1 measured by the present method and heat of dyeing and specific gravity data of the same dye/film system, determined by Daruwalla and D'Silva.

Measurement of the Particle Size of a High-Lightfastness Direct Dye in Cellulose by p-Nitrophenol Adsorption

The p-nitrophenol adsorption method has been used to determine the specific surface, and hence the particle size and aggregation number, of a high-lightfastness direct dye (C.I. Direct Green 26) in regenerated cellulose film. The particle size found at high concentrations is of the same order as that found for other dyes of this type, in cellulose film, by Weissbein and Coven, using electron microscopy. The aggregation number rises rapidly with rise in dye concentration in the film to a maximum of the order of 106 at shade depths above about two percent pure dye on film weight.

Experimental verification of design methods for liquid phase fixed-bed adsorbers.

The validity of methods for designing fixed-bed adsorbers is experimentally examined. The breakthrough curves predicted by two design methods without the assumption of the constant pattern and three methods with the assumption are compared with those obtained from the experiments of the liquid phase fixed-bed adsorption of DBS and p-nitrophenol on an activated carbon (CAL). A diagram is presented for estimating minimum column lengths required to establish the constant pattern for the Freundlich isotherm. The validity of this diagram is also examined experimentally.

Study of the adsorption of p-nitrophenol on platinized platinum electrodes

Study of the adsorption of p-nitrophenol on platinized platinum electrodes

Study of the adsorption of p-nitrophenol on platinized platinum electrodes

The adsorption of p-nitrophenol was studied by tracer and electrochemical methods. It was found that there is no unambiguous relation between the extent of the adsorption and the rate of the hydrogenation reaction. At potentials more positive than 1200–1300 mV an increase in the adsorption may be observed. The amount adsorbed corresponds to several monolayers. The adsorbed species are bonded strongly to the surface. From these statements it was concluded that the phenomena observed above 1300 mV cannot be attributed to simple adsorption.

Electrochemical investigations of surface functional groups on isotropic pyrolytic carbon

Isotropie pyrolytic carbon (Pyrolite®) electrodes subjected to electrochemical oxidation at widely varying current densities develop a very distinctive, reproducible surface functionality. This surface functional group exhibits a peak reduction current in the region from 0 to–400 mV (vs. SCE) in 1 M H 2SO 4, and is easily quantitatively reduced. It can then be reoxidized, with a peak oxidation current occurring in the range from + 1300 to + 1700 mV (vs. SCE) in 1M H 2SO 4, to re-form the original surface group. The cycle can then be repeated ad infinitum, with quantitative reduction and oxidation every time. The oxidized and reduced forms of the surface functionality may correspond to quinone and hydroquinone groups. In view of the high dipole moment associated with quinone oxygen attached to large ring systems, a high electron density would be expected at the oxidized carbon surface. The specific adsorption of p-nitrophenol on carbon, thought to be an electron donor-acceptor complex, is shown to be strongly dependent on the state of surface oxidation. Coulometric studies indicate that the p-nitrophenol adsorption is favored on the oxidized surface.

The characterisation of microporous carbons by adsorption from liquid and vapour phases

Two series of activated carbons were prepared from pure polyfurfuryl alcohol and polyvinylidene chloride by gasification with carbon dioxide at 850°C. Micro-pore volumes in these carbons were estimated by adsorption of carbon dioxide (273K) using Dubinin theory, by adsorption of nonane (273K) and by adsorption of nitrogen (77K) on carbons with and without pre-adsorbed nonane. Reasonable agreements are found. Adsorption on these carbons is reported, from aqueous solution, of p-nitrophenol, malonic, benzoic and oxalic acids, and of iodine from carbon tetrachloride solution. Transitional pore filling occurs by these adsorbates (with exception of malonic acid). Adsorption of p-nitrophenol, particularly at low C/C s values of about 1 × 10 −3, is extremely sensitive to microporous structure. Its adsorption over larger ranges of C/C s resembles closely adsorption of carbon dioxide (195K) and at higher C/C s values of nitrogen (77K). Other adsorbates adsorb little at C/C s values of 1 × 10 −3. Adsorption of p-nitrophenol is probably the most informative of adsorbates in solution, and the experimental procedures are convenient. The usual problem of giving significance to surface area values, using the BET equation, is encountered giving some limitations to interpretations of isotherms of p-nitrophenol from aqueous solution.

The adsorption of p-nitrophenol on platinized platinum electrodes

The adsorption of p-nitrophenol on platinized platinum electrodes

The adsorption of p-nitrophenol on platinized platinum electrodes

The adsorption of p-nitrophenol on platinized platinum electrodes

Note on stability of p‐nitrophenol in aqueous solutions

AbstractIt has been shown that p‐nitrophenol (PNP) solution is stable only at pH ≥ 9 when PNP is in the completely ionised form. In benzene, PNP exists in a neutral molecular form. These considerations are important in the estimation of surface areas of solids by adsorption of PNP from solution.