Assessment of solvent extraction for the recovery of phenol from wastewater

Abstract

Water is precious and the pollution through organics such as phenol is more serious. Even though aqueous effluents from organic and petrochemical complexes contain a significant concentration of phenol, sometimes as high as 7000 mg/L, the effluent is subjected to secondary treatment to reduce the biological oxygen demand to acceptable levels thus losing value in the form of phenol. Several methods are available by which phenol can be removed from aqueous streams including adsorption, solvent extraction, ion exchange, electrocoagulation, photodecomposition, advanced oxidation, and biological treatment. Out of these, only the first three processes remove phenol as such while in all other cases phenol is either converted to some other form or is destroyed. Adsorption and ion exchange processes are not highly selective and the recovery of phenol as value is more challenging but on the other hand, solvent extraction is selective, and the extracted phenol can be easily recovered. In this context several solvents including methyl isobutyl ketone, ethyl acetate and benzene were studied at 303 K and atmospheric pressure. The purpose of the present investigation is to compare the efficiency of different solvents used for phenol extraction, based on percentage extraction and distribution coefficient. The percentage extraction of phenol using methyl isobutyl ketone was found to be the highest among the other solvents used. Similar results were also obtained using ethyl acetate as the solvent but show less percentage extraction and distribution coefficient as compared to methyl isobutyl ketone. It can be concluded that both methyl isobutyl ketone and ethyl acetate are good solvents for the extraction of phenol from wastewater.