Phenol adsorption equilibria

More recently, Kander and Paulaitis (16) have studied the adsorption of phenol onto activated carbon and measured its sorption equilibria from dense C02. These researchers found that temperature controlled the adsorption equilibria and that phenol uptake was negligibly effected by changes in the gas phase density. Such a result indicates that factors other then a solute s solubility in a dense gas play a key role in defining the adsorption equilibrium which accompany such processes. 

LI Zhong, LI Xiangbin, XI Hongxia, Effects of Ultrasound on Adsorption equilibrium of Phenol on Polymeric Resin, Chemical Engineering Journal > Vol.86 (2002) PP375-379. 

We have already described in Chapter V phenol photoconversion in slurry photocatalytic systems with adsoiption assumed at quasi-equilibrium. In many cases, however, photocatalytic reactors ai e operated under non-equilibrium conditions the pollutant concentrations in the solid phase and in the fluid phase are significantly fai away from the adsorption equilibrium values. As demanded by cai eful modeling, accounting for adsorption at non-equilibrium conditions is needed. 

Another adsorptive equilibrium model was also used in adsorption of phenol and BTEX in organoclay. This is the Dubinin-Raduskevich s model, represented by Equation 11 (Akgay, 2004, 2005). 

Vidic, R. D., M. T. Suidan, and R. C. Brenner. 1993. Oxidative coupling of phenols on activated carbon— Impact on adsorption equilibrium. Environmental Science Technology 27(10) 2079-2085. 

Only five carbons are included consistently in all investigations. In Table 3, t(50) is the half time of the phenol break-througli curve, t is the bed density and t(50)/ t, are the corrected for differences in density breakthrough half times. The breakthrough half times are taken as a measure for the adsorption equilibrium constants. 

Cost estimation and screening external MSAs To determine which external MSA should be used to remove this load, it is necessary to determine the supply and target compositions as well as unit cost data for each MSA. Towards this end, one ought to consider the various processes undergone by each MSA. For instance, activated carbon, S3, has an equilibrium relation (adsorption isotherm) for adsorbing phenol that is linear up to a lean-phase mass fraction of 0.11, after which activated carbon is quickly saturated and the adsorption isotherm levels off. Hence, JC3 is taken as 0.11. It is also necessary to check the thermodynamic feasibility of this composition. Equation (3.5a) can be used to calculate the corresponding... 

Irrespective of the sources of phenolic compounds in soil, adsorption and desorption from soil colloids will determine their solution-phase concentration. Both processes are described by the same mathematical models, but they are not necessarily completely reversible. Complete reversibility refers to singular adsorption-desorption, an equilibrium in which the adsorbate is fully desorbed, with release as easy as retention. In non-singular adsorption-desorption equilibria, the release of the adsorbate may involve a different mechanism requiring a higher activation energy, resulting in different reaction kinetics and desorption coefficients. This phenomenon is commonly observed with pesticides (41, 42). An acute need exists for experimental data on the adsorption, desorption, and equilibria for phenolic compounds to properly assess their environmental chemistry in soil. 

On the other hand, an attempt to accelerate the step of coordination of the substrate to the Cu catalyst was successful because it used the hydrophobic domain of the polymer ligand156 That was the oxidation catalyzed by polymer-Cu complexes in a dilute aqueous solution of phenol, which occurred slowly. The substrate was concentrated in the domain of the polymer catalyst and was effectively catalyzed by Cu in the domain. A relationship was found to exist between the equilibrium constant (Ka) for the adsorption of phenol on the polymer ligand and the catalytic activity (V) of the polymer-ligand-Cu complex for various polymer ligands K a = 0.21 1/mol and V = 1(T6 mol/1 min for QPVP, K a = 26 and V = 1(T4 for PVP, K a = 52 and V = 10-4 for the copolymer of styrene and 4-vinylpyridine (PSP) (styrene content 20%), and K a = 109 and V = 10-3 for PSP (styrene content 40%). The V value was proportional to the Ka value, and both Ka and V increased with the hydrophobicity of the polymer ligand. The oxidation rate catalyzed by the polymer-Cu complex in aqueous solutions depended on the adsorption capacity of the polymer domain. 

Adsorption equilibria for the systems phenol-p-toluene sulfonate, phenol-p-bromophenol and phenol-dodecyl benzene sulfonate are shown in Figures 5, 6 and 7. In these figures, the ratio of the observed equilibrium values and computed values from equation (14) are plotted against the equilibrium liquid phase concentration of the solute in the mixture. It is seen that most of the data points are well within a deviation of 20%. The results for these diverse solute systems indicate that equation (14) is suitable for correlating binary equilibrium data for use in multicomponent rate models. 

As seen from Table 2, phenol, j>-toluene sulfonate and 2 bromophenol have similar adsorption rate characteristics. The equilibrium data for these solutes indicate that phenol and p-toluene sulfonate have similar energies of adsorption (24), as indicated by the constant b in the component isotherm (qe Qbx,ce/ (1 + bLCe) -bromophenol and dodecyl benzene sulfonate are adsorbed more strongly than phenol (22). 

The experimental and predicted profiles for the adsorption rates of phenol and -bromophenol from an equimolar mixture of concentration 5 x 10-4 M are shown in Figure 12. The predicted profile for j>-bromophenol is in excellent agreement with the experimental data. However, for phenol there is some deviation after the Initial time period. The experimental adsorption rate for phenol appears to be faster than predicted for about 60 minutes after the first 15 minutes. Thereafter, the rate Is slightly slower than predicted. From an examination of the binary equilibrium data, this deviation may be attributed to the Inadequate correlation of the mixture equilibrium data in this region. The predicted and experimental total concentration profiles are shown In Figure 13. Initial concentrations of 2.5 x 10 4 M for phenol, and 5 x 10 4 M for j>-bromphenol were used in another rate study, the data from which are shown in Figures 13 and 14. The experimental and predicted curves are in fair agreement. 

Phenol and dodecyl benzene sulfonate are two solutes that have markedly different adsorption characteristics. The surface diffusion coefficient of phenol is about fourteen times greater than that for dodecyl benzene sulfonate. The equilibrium adsorption constants indicate that dodecyl benzene sulfonate has a much higher energy of adsorption than phenol (20,22). The adsorption rates from a mixture of these solutes can be predicted accurately, if (1) an adequate representation is obtained for the mixture equilibria, and (2) the diffusion rates in the solid and fluid phases are not affected by solute-solute interactions. 

The experimental and predicted profiles for adsorption from a mixture 5 x 10 H phenol and 5 x 10 H dodecyl benzene sulfonate are shown in Figure 15. The rate of adsorption of dodecyl benezene sulfonate is faster than predicted, and for phenol, the rate is slower than predicted. However, the shape of the predicted profiles for both solutes closely parallel the experimental curves. Similar trends may be noted in Figure 16 for the adsorption rates from a 10 4 H phenol and 10 4 H dodecyl benzene sulfonate mixture. The mixture equilibrium data for these solutes have been correlated satisfactorily. Thus, it would appear that solute-solute interactions are affecting the diffusional flux of each solute. Moreover, from Figure 17 for the total concentrations, it may be seen that the interaction effects are mutually compensating. The total concentration profiles for both... 

Experiments were performed in batch reactors at 21 1°C with a continuous stirring at 300 rpm and some ratio solid/solution fixed at 2.26 g.L for dry pulp and 0.3 g.L for activated carbon. A pre-hydration of 90 min of the pulp was necessary and the pH of the solution was stabilized at 5.5. Equilibrium times were deduced from the kinetics. The mixed metallic solutions had equimolar initial concentrations (8.10 mol.L ). The influence of benzaldehyde, benzoic acid and phenol on the fixation of Cu onto the pulp was conducted using 100 mg.L (expressed in TOC) of organic compounds. The adsorption on the mixture of sorbents of phenol and Cu ions was carried out with 50 mg.L of each components. 

Isotherms are normally developed to evaluate the capacity of the carbon for the adsorption of different contaminants. Data are obtained in batch tests, which determine the equilibrium relationship between the compound adsorbed on the carbon and that remaining in solution. The isotherms are used as screening tools to determine which carbon is suitable for a given application. Batch equilibrium tests are often complemented by dynamic column studies to determine system size requirements, contact time, and carbon usage rates [19]. Other parameters that are used to characterize activated carbons for water treatment include phenol number, an index of the ability to remove taste and odor, and molas.ses number, which correlates with the ability to adsorb higher molecular weight substances. However, these parameters still do not reflect performance in service, and they can only be considered as guidelines. 

TABLE 15 Equilibrium Adsorption and Desorption Results for Substituted Phenols on a Commercial Activated Carbon"... 

Table 5 shows the excellent adsorption characteristics of the home prepared carbons, in comparison with 3 of the 10 commercial carbons tested. The results obtained in the equilibrium adsorption study of phenol, pentachlorophenol, dodecylbenzenesulphonate, and p-toluenesulphonate were discussed in a previous paper [9 ]. Also this study showed a very good performance of the home produced carbons. Based on these results carbon J 23 and J 32 were selected for further research. 

The secondary effluent from a biological treatment plant is treated with the activated carbon adsorption process and allowed to arrive at eqnilibrinm. The equilibrium data in terms of phenol are given below. Determine the constants for the Langmuir and Freundlich isotherms. 

However, in general, solvent recovery is an important step in the overall solvent extraction process. Solvent recovery from the raffinate (i.e., water phase) may be accomplished by stripping, distillation, or adsorption. The extract, or solute-laden solvent stream, may also be processed to recover solvent via removal of the solute. The solute removal and solvent recovery step may include reverse solvent extraction, distillation, or some other process. For example, an extraction with caustic extracts phenol from light oil, which was used as the solvent in dephenolizing coke plant wastewaters (4). The caustic changes the affinity of the solute (phenol) for the solvent (light oil) in comparison to water as will be explained in the equilibrium conditions section. Distillation is more common if there are no azeotropes. 

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