Phenols extraction from aqueous solutions

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. 

Phenols are about a million times more acidic than alcohols (Table 17.1). They are therefore soluble in dilute aqueous NaOH and can often be separated from a mixture simply by basic extraction into aqueous solution, followed by ceacidihcation. 

Table III also presents our data for the extraction of Group 4 phenols from aqueous solutions. The o-bromophenol was added as an internal standard when some initial recovery problems were noted for the 2,6-di-terf-butyl-4-methylphenol results for its extraction are also reported here. The three phenols show good recoveries in the traps and overall good mass recoveries. One experiment was conducted under liquid C02 extraction conditions (temperature = 30 °C and pressure = 1500 lb/in.2) in an attempt to compare the relative efficiencies of the two states of CO2 for phenol extraction. Unfortunately, the phenols showed evidence of substantial breakthrough from the trapping system. The experiment does, however, demonstrate that liquid CO2 is also a good extractant for phenols present in water at parts-per-billion concentration levels.

Extraction of phenol from aqueous solution using hollow fiber membrane contactor was first investigated in Ref. [100]. However, the membrane used was not completely microporous. Instead, it was a dialysis-type membrane. A commercial plant to separate phenol from hydrocarbon fraction using microporous membrane contactors was reported in Ref. [101]. Soda lye was used to react with the phenol transferred from the feed phase to create and maintain the driving force for separation. This industrial-scale application enabled the processing of hydrocarbon fraction to a full-value raw material for phenol and acetone synthesis. 

Cooney DO and Jin CL, Solvent extraction of phenol from aqueous solution in a hoUow fiber device. Chemical Engineering Communications 1985, 37, 173-191. 

The ARALEX process can also be used to extract detergents from aqueous solutions containing actinides for example, contaminated laundry solutions. Detergents from all three classes (anionics such as alkyl sulfates and alkyl benzene sulfonates cationics such as N-benzyl-N-alkyl dimethyl ammonium chloride and nonionics such as polyoxyethylenated alkyl phenols) are... 

Experiments were conducted to investigate the extraction of 2-chloro-phenol (2-CP) from aqueous solution by liquid membrane [49]. Depending on the pH of the aqueous solution, molecular 2-CP and its ionic form are known to exist in equihbrium according to the following equation ... 

Extraction of free fatty acids from naturally occurring glycerides removal of HCl from chlorinated organic compounds recovery of aliphatic acids HE and HCl from aqueous solutions nitration of phenol solvent extraction in mineral processing interfacial polycondensation and esterification manufacture of organo-phosphate pesticides. 

Catecholamines are particularly polar and difficult to extract from aqueous media. An acylating agent convenient to use directly in aqueous solution is methyl chloroformate [236], Cl-CO-OMe. Amino and phenolic hydroxyl groups are converted to carbamate (MeO-CO-NHR) and carbonate (MeO-CO-OAr) groups simultaneously, with aliphatic hydroxyl groups subsequently silylated. 

That phenolic alkaloids are soluble in aqueous solutions of fixed alkalies need not be stressed but it is important to note that some free bases (notably corydine and ochotensine) are extracted from such solutions by ether while others (bulboeapnine and hunnemanine) are not. A convenient method for recovery of these phenolic bases is to saturate their aqueous alkaline solutions with carbon dioxide or ammonium chloride. The latter reagent, however, is not invariably satisfactory (e.g., hunnemanine). 

Enhanced hydrophobicity of hypercrosslinked polystyrene, combined with additional 7r-interactions with aromatic moieties, explains the unusually strong retention of phenol and its derivatives from aqueous solutions. This makes it possible to pre-concentrate traces of phenols and chloro- and nitrophenols from water samples directly on the top of the analytical HPLC column (with MN-200 disintegrated to 15 im particles) [199] and then analyze the mixture on the same column with an aqueous-acetonitrile RP eluent. This approach increases the sensitivity of the determination because the whole amount of analytes initially present in the sample appears in the column and arrives at the detector, contrary to the situation with the off-line solid phase extraction (SPE) pre-concentration approach. 

Hexagonally ordered silica, SBA-15, were also fabricated with PANI to prepare PANI/hexagonally ordered silica nanocomposite, which was used to extract polycyclic aromatic hydrocarbons from aqueous solutions, including naphthalenes, biphenyl, acenaphthene, anthracene, pyrene, and so on [37]. The same nanocomposite exhibited selective adsorption toward 2,4-dini-trophenol in aqueous solution in the presence of phenol with the adsorption capacity of 55.0 mg/g [38]. Chemical oxidation of aniline on hexagonal mesoporous silica (HMS) was carried out to generate PANI/HMS nanocomposite for Ni(II) elimination from aqueous solutions [39]. This process was spontaneous and endothermic and can be applied to Freimdlich isotherm and a pseudo-second-order kinetic. The removal efficiency was 99.87% for 50 mg/L Ni(II) solution, and the maximum sorption capacity can reach 253.17 mg/g at 300 mg/L Ni(II) solution. 2,6-Dichlorophenol can be selective removed from aquatic environment by PANI/silica gel composite [40]. A spontaneous and endothermic process was also observed with a Langmuir isotherm. 

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