Extraction of Phenol from Wastewater

Consider the extraction of phenol from wastewater using toluene followed by the recovery of the toluene by using a caustic water solution. For this problem use the following data ... 

TABLE 15-9 Simulation Results for Extraction of Phenol from Wastewater Using MIBK (Example 4)... 

The Phenox process (254) removes phenol (qv) from the efduent from catalytic cracking in the petroleum industry. Extraction of phenols from ammoniacal coke-oven Hquor may show a small profit. Acetic acid can be recovered by extraction from dilute waste streams (255). Oils are recovered by extraction from oily wastewater from petroleum and petrochemical operations. Solvent extraction is employed commercially for the removal of valuable... 

A A multistage extraction column uses gas oil for the preliminary removal of phenol from wastewater. The flowrate of wastewater is 2.0 kg/s and its inlet mass fraction of phenol is 0.0358. The mass fraction of phenol in the wastewater exiting the column is 0.0168. Five kg/s of gas oil are used for extraction. The inlet mass fraction of phenol in gas oil is 0.0074. The equilibrium relation for the transfer of phenol from wastewater to gas oil is given by... 

One common application of liquid-liquid extraction is the removal and recovery of phenol and compounds of phenol from wastewaters. Although phenol can be removed by biological treatment, only limited levels can be treated biologically. Variations in phenol concentration are also a problem with biological treatment, since the biological processes take time to adjust to the variations. 

SFE and SFE/derivatization for the extraction of phenols from a coal gasification wastewater have been performed by first collecting the wastewater organics on "Empore" C-18 sorbent discs (8). The sorbent discs were first prepared by washing with methanol and water as per the manufacturer s instructions. A 100-mL sample of wastewater was acidified to a pH <2, 4 mL of methanol was added, and the waters were filtered through the sorbent discs. The discs were then placed in a 2.5 mL cell and extracted at 80°C and 500 atm using pure C02, C02 with 1.0 mL methanol modifier placed in the cell, or C02 with 1 mL of 0.1 M TMPA in methanol placed in the cell. (Extractions using methanol modifier and TMPA derivatization were each performed statically for 5 minutes followed by dynamic extraction for 10 minutes.) No attempt was made to dry the discs before SFE. 

Liquid extraction is utilized by a wide variety of industries. Applications include the recovery of aromatics, decaffeination of coffee, recovery of homogeneous catalysts, manufacture of penicillin, recovery of uranium and plutonium, lubricating oil extraction, phenol removal from aqueous wastewater, and extraction of acids from aqueous streams. New applications or refinements of solvent extraction processes continue to be developed. 

Phenolic compounds and especially their chlorinated derivatives are important water pollutants that are present in wastewater discharged from a variety of industrial sources. A fast method for direct determination of phenols in wastewater based on solid-phase extraction coupled online to a flow injection manifold has been developed. The phenol... 

The general proportions may be varied from one end of the tower to the other to accommodate changing liquid volumes and physical properties. These towers have been used in diameters ranging from a few inches for laboratory work up to 2.4 m (8 ft) in diameter by 12.2 m (40 ft) tall for purposes of deasphalting petroleum. Other commercial services include furfural extraction of lubricating oils, desulfurization of gasoline, phenol recoveiy from wastewaters, and many others. Columns up to 4.5 m in diameter and up to 50 m in height have been constructed. 

Wastewater Treating. Earlier we discussed the importance of bringing environmental experts into the project early. Wastew ater treating can be part of the battery limits process area in the case of phenol extraction from coal gasification gas liquor, but this is an e.xception. 

The previous chapters have demonstrated that liquid-liquid extraction is a mass transfer unit operation involving two liquid phases, the raffinate and the extract phase, which have very small mutual solubihty. Let us assume that the raffinate phase is wastewater from a coke plant polluted with phenol. To separate the phenol from the water, there must be close contact with the extract phase, toluene in this case. Water and toluene are not mutually soluble, but toluene is a better solvent for phenol and can extract it from water. Thus, toluene and phenol together are the extract phase. If the solvent reacts with the extracted substance during the extraction, the whole process is called reactive extraction. The reaction is usually used to alter the properties of inorganic cations and anions so they can be extracted from an aqueous solution into the nonpolar organic phase. The mechanisms for these reactions involve ion pah-formation, solvation of an ionic compound, or formation of covalent metal-extractant complexes (see Chapters 3 and 4). Often formation of these new species is a slow process and, in many cases, it is not possible to use columns for this type of extraction mixer-settlers are used instead (Chapter 8). 

Extraction is a process for separating components in solution by their distribution between two immiscible phases. Such a process can also be called liquid extraction or solvent extraction. The former term may be confusing because it also applies to extraction by solid solvents. Since extraction involves the transfer of mass from one phase into a second immiscible phase, the process can be carried out in many ways. The simplest example involves the transfer of one component from a binary mixture into a second immiscible phase — extraction of an impurity from wastewater into an organic phase. In some cases, a chemical reaction can be used to enhance the transfer, e.g., the use of an aqueous caustic solution to remove phenolics from a hydrocarbon stream. 

The developed biosensor based on graphite/capric acid modified with PPO from jack fruit crude extract was sensitive, of easy construction and reliable in determining total phenols in wastewater samples. The results of the proposed method agreed at the 95% confidence level with the results obtained using the standard method procedure. 

Verhoeven W, Sluyts D, Denecker G, van Osselaer T, Hinz J, Vaes J, van Herck W, de Vos S. Treatment of phenolic wastewaters from manufacture of polycarbonates, bisphenols or diphenyl carbonate by reactive extraction. DE 19510063, Bayer Antwerpen N.V., 1996. 

Shen, S., Z. Chang, and H. Liu. 2006. Three-liquid-phase extraction systems for separation of phenol and p-nitrophenol from wastewater. Sep. Purif. Technol. 49 217-222. 

Other plants such as potatoes, cauliflower, cherries, and soybeans and several fungi may also be used as sources of peroxidase enzymes. Soybeans, in particular, may represent a valuable source of peroxidase because the enzyme is found in the seed coat, which is a waste product from soybean-based industries [90]. In this case, it may be possible to use the solid waste from the soybean industry to treat the wastewaters of various chemical industries. In fact, the direct use of raw soybean hulls to accomplish the removal of phenol and 2-chlorophenol has been demonstrated [105]. However, it should be noted that this type of approach would result in an increase in the amount of solid residues that must be disposed following treatment. Peroxidases extracted from tomato and water hyacinth plants were also used to polymerize phenolic substrates [106], Actual plant roots were also used for in vivo experiments of pollutant removal. The peroxidases studied accomplished good removal of the test substrate guaiacol and the plant roots precipitated the phenolic pollutants at the roots surface. It was suggested that plant roots be used as natural immobilized enzyme systems to remove phenolic compounds from aquatic systems and soils. The direct use of plant material as an enzyme source represents a very interesting alternative to the use of purified enzymes due to its potentially lower cost. However, further studies are needed to confirm the feasibility of such a process. 

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