(265f) Equilibrium in the Reactive Extraction of Aqueous Phenol Using Tributyl Phospate in n-Hexane

Phenol is a hazardous chemical which usually contained in the wastewater from some industries, such as oil refineries, coal processing, and plastics. Phenol is dangerous substance to a microorganism although in low concentration in wastewater. According to the United State Environmental Protection Agency, the maximum concentration of phenol in wastewater is 1 ppm. This requirement is lower than the concentration of phenol in normal wastewater discharged from industries that is 100 to 1000 ppm. So phenol recovery from wastewater must be done to lower its concentration. Phenolic substances are very difficult to be destroyed by oxidation in the present of microorganism. Chemical oxidation of phenolic substance using ozone or combination between the ozone and UV irradiation is impossible to handle huge amount of wastewater due to the expensiveness of ozone production and also its low solubility in water. The prospective method to recover of phenol from wastewater is reactive extraction in which phenol makes a complex with the extractant.

This research investigated the equilibrium of the reactive extraction of phenol from water using tributyl phosphate (TBP) in n-hexane. An equilibrium model has been developed in this research and the laboratory experiments have been carried out. The parameters of the laboratory experiment are the initial concentration of phenol in water, initial concentration of TBP in n-hexane, and the extraction temperature.

The experimental results showed that the higher the TBP concentration in n-hexane, the higher the amount of phenol which can be extracted to the organic phase. The correlation between the distribution coefficients (K_C) with the ratio of TBP concentration (Co_TBP) to the initial TBP concentration (Cio_TBP) in n-hexane can be formulated by K_C=11.59-12.002Co_TBP/Cio_TBP with the error of 17.32%. The lower the extraction temperature, the higher the amount of phenol extracted to the organic phase. The correlation between the distribution coefficients with the temperature (T) can be approached by K_C=1505.45 (1/T)-4.06 with the error of 14.52%. The value of distribution coefficient of physical equilibrium (K_p) is lower with the increase of temperature meanwhile the value of the equilibrium coefficient of solvation reaction (K_R) is increase with increasing the temperature.

Keywords: Equilibrium, Reactive Extraction, Phenol, Tributyl Phosphate, n-Hexane.