An Improved Method for the Isolation of Phenols from Water

A rapid and sensitive method for the separation and isolation of phenols from waters is described. A column adsorption and desorption procedure is used prior to the analysis by colorimetry with aminoantipyrine. The determination of phenols in water may be accomplished by many different analytical methods. At mg/l levels and higher, ultraviolet absorption spectrophotometry is often used for analysis in waste and effluent waters1,2. Phenols are determined at ug/l by colorimetry using the aminoantipyrine method3. In this procedure the phenols are separated from non-volatile impurities by a distillation at pH 4. The aqueous phenolic solution is adjusted to the proper pH and reacted with 4-aminoantipyrine in the presence of potassium ferricyanide to produce a colored dye which is concentrated by extraction into chloroform. The absorbance of the chloroform solution is then measured. The distillation procedure for the separation of the phenols is quite time-consuming requiring a few hours for completion and suffers from volatile interferences such as anilines which can produce a color with aminoantipyrine at certain pH values. Sensitivity is limited as only a maximum volume of 500 ml of water can be conviently analyzed. In an effort to decrease the time of analysis and improve the sensitivity, the distillation process has been replaced by adsorption and desorption of the phenols on a macroreticular resin. Commercial solid adsorbents XAD-2 and XAD-4 (Rohm and Haas Company, Philadelphia, Pennsylvania) are hard, white, insoluble beads composed of divinylbenzene cross-linked polystyrene. They have extremely high surface areas; 300m2/g for XAD-2 and 784m2/g for XAD-44. Adsorption of the phenols from water occurs due to Van der Waal's forces between the polystyrene surface of the beads and the hydrophobic portion of the phenol. Desorption is possible by conversion of the phenol into its salt form by elution with base. The combination of a low binding energy of the phenol to the beads and rapid diffusion of the eluting solvent allows quantitative and rapid elution of the phenol.