Phenol distribution coefficient

For determination of phenol distribution coefficients the extraction proceeded for 15 minutes in order to reach equilibrium. The time required to reach equilibrium was determined by making five replicate injections of the headspace onto the SFC system. The first injection was after the extraction had proceeded for 15 minutes at 50°C and 100 atm. Following the equilibration time, four further injections at ten minute intervals were made, after which the pressure inside the extraction apparatus was increased and the system was again allowed to equilibrate (i.e. 15 minutes). The five replicate injection process was then repeated. The amount of phenol in each injection was then noted by referring to an external phenol standard calibration curve. As the total volume of the system was known, the amount of phenol in the SF could be calculated. The amount of phenol in the aqueous phase could then be calculated by mass balance. 

Figure 6. Phenol distribution coefficient as a function of temperature at constant density.

Hydroxyquinoline, having both a phenolic hydroxyl group and a basic nitrogen atom, is amphoteric in aqueous solution it is completely extracted from aqueous solution by chloroform at pH < 5 and pH > 9 the distribution coefficient of the neutral compound between chloroform and water is 720 at 18 °C. The usefulness of this sensitive reagent has been extended by the use of masking agents (cyanide, EDTA, citrate, tartrate, etc.) and by control of pH. 

The use of distribution coefficients for the QSAR treatment of ionizable compounds has been extended to consideration of ion-pair partitioning into biolipid phases. Two experimental methods for determining ion-pair partition coefficients are described. One is a single-phase titration in water-saturated octanol, in which case (for acids) log Pj = log P + pKa - pKa. The other is a two-phase titration (octanol/water) from which the ratio (P + 1)/(Pj + 1) can be calculated. An example outcome is that the uncoupling activity of phenols can be represented by an equation in log instead of log D and pKa. 

Log D accounts for where the "dose" is, so to speak. The distribution depends on the pKa as well as the pH of the medium. The advantage of using log D is that it incorporates these factors, so, for simple processes such as absorption, distribution coefficients "ej lain" the whole process. An example from our earlier work ( ) is the colonic absorption of acids ranging from phenols to strong carboxylic acids. The absorption rate is given by an equation involving only log D terms. 

The nature of soil-phenolic acid interaction adsorption-desorption. Adsorption of a solute from solution onto a solid matrix results in a higher solute concentration at the fluid-solid interface than in the solution. Huang and coworkers (27) observed a high sorption capacity of the mineral fraction of four latosols for phenolic acids. On the basis of their results, distribution coefficients,... 

Modeling and optimization of MBSE and MBSS of a multicomponent metallic solution in HF contactors is discussed in ref. [77]. A short-cut method for the design and simulation of two-phase HF contactors in MBSE and MBSS with the concentration-dependent overall mass-transfer and distribution coefficients taking into account also reaction kinetics was suggested by Kertesz and Schlosser [47]. Comparison of performance of the MBSE and MBSS circuit with pertraction through ELM in case of phenol removal presented Reis [78] and for copper removal Gameiro [79]. 

For example, the ratio of the n-octanol/watcr distribution coefficient of the nondissociated species to that of the ionic species is nearly 10,000 for 3-methyl-2-nitrophenol, but only about 1000 for pentachlorophenol because of the greater significance of the hydrophobicity of the ionized form of pentachlorophenol. The logarithm of the -octanol/water distribution coefficient of pentachlorophenol as the phenolate is about 2 (determined at pH 12, and 0.1 M KC1), which indicates significant distribution of the ionized form into the n-octanol phase [8,37], Extraction of such highly hydrophobic ionogenic organic compounds can result from mixed-mode mechanisms that incorporate both the hydrophobic and ionic character of the compound. 

There is some evidence that Np04(0H)2 can be extracted into organic solvents by phenol and pyrazolone ligands that replace hydroxide in the inner coordination sphere. For example, extraction by bis(2-hydroxy-5-octylbenzyl)amine or 2-hydroxy-5-tert-butylphenyl disulfide was confirmed by NMR. Optical absorption data indicated that Np reduction to Np does occur, but that Np is extracted more slowly and with smaller distribution coefficients than is 74375... 

Phenol, a common priority pollutant, was extracted from two environmental matrices, soil and water, using near critical and supercritical carbon dioxide. The primary objective of this study was to determine the distribution of the contaminant between the soil or water and the supercritical phase, and the effect of soil moisture and co-solvents on the distribution coefficients. Static equilibrium extractions were performed on dry and wetted soil contaminated with 1 wt.% phenol and on water containing 6.8 wt.% phenol. Supercritical carbon dioxide (with and without en-trainers) was chosen as the solvent for the study. An appropriate entrainer for dry soil extractions (methanol) ffiffered from that found for aqueous extractions (benzene). However, soil moisture was found to have a significant impact on the effectiveness of en-trainers for soil extractions of phenol. Entrainers appropriate for extracting wetted soil were found to be the same as those advantageous for aqueous extractions. Benzene was also extracted from dry and wetted soil to investigate the extractability of a hydrophobic compound. 

A detailed description of the experimental apparatus and procedure used for the aqueous study are given elsewhere (Roop and Akgerman, Ind. Eng. Chem. R., in review) Static equilibrium extractions were carried out in a high pressure equilibrium cell (300 mL Autoclave). After the vessel is initially charged with 150 mL of water containing 6.8 wt.% phenol and supercritical carbon dioxide (and a small amount of entrainer, if desired), the contents were mixed for one hour followed by a two hour period for phase separation. Samples from both the aqueous phase and the supercritical phase were taken for analysis and the distribution coefficient for phenol calculated. 

The distribution coefficients of phenol obtained for the aqueous system as a function of pressure and temperature using pure supercritical carbon dioxide are shown in Figure 2. The values increase proportionately with pressure for each isotherm, but decrease overall at higher temperatures. At 298 K, reproduction of the distribution coefficients yielded an average standard deviation of 1.5 %. At 323 K the data axe somewhat more scattered due to fluctuations in the temperature caused by control. Figure 3 shows the effect of various concentrations of benzene and methanol used as entrainers in supercritical carbon dioxide at 17.3 and 27.6 MPa at 298 K. Methanol, a commonly used entrainer in studies concerning solid organics, was found to have little effect on the distribution of phenol in the aqueous system. The presence of a small amount of benzene, however, did increase the distribution coefficient up to 50 % over those obtained with pure carbon dioxide. 

Figure 4 shows the results of the extraction of water (figure 4a) and dry and wetted soil (figure 4b and 4c, respectively) using pure carbon dioxide, carbon dioxide with 2 mol % benzene, and carbon dioxide with 2 mol % methanol at 15 MPa and 298 K. For the extraction of dry contaminated soil, the distribution coefficient of phenol between the soil and pure carbon dioxide was 0.35, as shown in Figure 4b. The presence of benzene increased the distribution coefficient almost 100 %, while the presence of methanol resulted in the removal of essentially all of the phenol from the soil (within experimental accuracy, K-values > 7 correspond to almost complete removal). For the extraction of wetted soil (10 wt.% water )with pure carbon dioxide the distribution coefficient of phenol was again 0.35. The effect of the entrainers on this system, however.

Phenol was successfully extracted from water using pure supercritical carbon dioxide at pressures up to 31 MPa for two isotherms 298 and 323 K. The distribution coefficient increased with increasing pressure, but decreased with increasing temperature. This is expected since increasing the temperature severely drops the carbon dioxide density and hence the solubility of the phenol in it. Increased volatility at the higher temperature is not sufficient to off-set the density effect, since phenol has a low vapor pressure. Benzene was foimd to be a suitable entrainer since its solubility in water is very small and it enhances the distribution of phenol into the supercritical phase. The presence of methanol was found to have no effect. Since methanol is polar and completely soluble in water, it favors the aqueous phase and therefore does not change the characteristics of the supercritical phase. Others have found that the distribution of short chain alcohols between water and supercritical carbon dioxide highly favors the aqueous phase (ifl). 

Two soil systems were considered contaminated dry and wetted soil. Pure supercritical carbon dioxide was able to remove phenol from both systems equally effectively. For the contaminated dry soil, both entrainers increased the distribution coefficient of phenol. However, methanol was by far the most effective. The presence of 2 mol % methanol (based on carbon dioxide) provided almost complete removal of the phenol from the soil. This is probably due to an increase in the polarity of the supercritical phase with the addition of methanol (li). The benzene/carbon dioxide mixture doubled the distribution coefficient, which can be attributed to structural similarities between the benzene and the phenol. 

In summary, phenol (a model toxic pollutant) was successfully extracted from both water and soil (dry and wetted) using supercritical carbon dioxide. It was found that entrainers greatly enhance the distribution coefficient of phenol for each system. However, the choice of a good entrainer is not independent of the contaminated matrix or, in the case of soil, its moisture content. Benzene was successfully extracted from both dry and wetted soil using pure carbon dioxide. Entrainers such as methanol could serve to decrease the distribution of such hydrophobic systems, indicating that further investigation in this area is warranted. 

Strzelbicki et al. [82] showed that chromium(VI) extraction rate decreases sharply after a pH value of 6.0. In case of phenol extraction, Wan et al. [11] observed that low values of pH favored extraction as the undissociated form of phenol which is the only form soluble in oil is predominant only at pH < 4.0. Liu and Zhang [83] showed that the extraction rate of Samarium (Sm ) in low pH range is inversely proportional to the H+ concentration. Sahoo and Dutta [45] noted that the solute distribution coefficient for cephalexin extraction increased with increase in pH up to a pH value of 9.5 beyond which the distribution coefficient appears to decrease marginally. Chakraborty et al. [76] found similar result for extraction of chromium (see Fig. 4.11). 

The result is three different patterns. Simple alkanes, represented by hexane in hexadecylpyri-dinium chloride, exhibit an activity coefficient that gradually decreases from about 5 to about 3.2 at the solubility limit, which for this system is rather low. For benzene we observe a different trend. The activity coefficient increases from abont 1.15 to abont 1.5, apparently going through a maximum at around 0.5. Compared with hexane the activity coefficient of benzene does not vary much with composition. The activity coefficients of pentanol and phenols are less than unity at low solute contents. Typically, the valnes are aronnd 0.1 at infinite dilntion, increasing gradually toward unity as the mole fraction increases. For pentanol, nnity is practically reached around the solubility limit. This is as required by the reciprocal relationship between the distribution coefficient and the activity coefficient. 

Figure 15.2-4 shows measured equilibrium data for extraction of phenol from an aqueous feed containing 5000 ppm phenol at 22.5°C into a solvent composed of 25% w/w TOPO in diisobuty] ketone (DIBK). Here the dnta are expressed as K , the concentration (mass or moles/volume) in the solvent divided by the concentration of phenol in the equilibrium aqueons phase. Predicted curves are drawn for a thenrerical model, in which fitted parameters are KF, the physical (or nareacted) distribution coefficient, and Kk, the equilibrium constant of a complexalion reaction with one-to-ons stoichiometry. The curves are drawn for... 

FIGURE 15.2-5 Equilibrium distribution coefficients vs. temperature for extraction of phenol and catechol from dilute aqueous solution into a solvent mixture of 25% w/w TOPO in DIBK. Stoichiometric ratio 2.5 mol TOPO/mol solme.M... 

Table 15.2-1 Equilibrium Distribution Coefficients for Extraction of Phenol and Higher Phenols from Water with Various Solvents...

Amine Organic acid Amine concentration at equilibrium (mol/kg) Phenol concentration at equilibrium (ppm) Distribution coefficient... 

CHU Churilina, E.V., Sukhanov, P.T., Korenman, Ya.I., Il in, A.N., Shatalov, G.V., and Bolotov, V.M., The distribution coefficients of phenol and substituted phenols in the attunonium sulfate-poly(A/-virtylpyrrolidone)-water system, Russ. J. Phys. Chem. A, 85, 568, 2011. 

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