Phenol Extraction into a Perfluoroalkane Phase Containing Extractant Tributyl Phosphate Enhanced by Addition of Alkane

Abstract

The extraction behavior of phenol by extractant TBP (tributyl phosphate) into perfluoroalkane (Florinert®) was studied in the partition equilibrium of phenol. The intrinsic nano-scale solution structure of Florinert containing alkane and TBP was deduced from the results of the dynamic light scattering measurements. The solubility and extracting ability of TBP were found to be greatly enhanced by the presence of alkane dissolved in Florinert. Dynamic light scattering revealed that n-hexane dissolved in Florinert FC-72 formed nano-scale clusters. These nano-scale clusters were so small that the perfluoroalkane phase was optically transparent, however, they dominantly promoted the solbilization of extractant TBP in perfluoroalkane and increased the partition ratio of phenol in the perfluoroalkane phase. Since TBP molecules need to behave collectively to extract a phenol molecule, those nano-clusters of n-hexane molecules are considered to offer TBP molecules nano-scale spaces necessary for them to act in a grouped fashion. Extractant TBP molecules cannot work effectively for the extraction of phenol in the case where they are alone in perfluoroalkane. Extraction behavior of oil phases which are mainly comprised of perfluoroalkane is largely determined by the nanoscopic structures additives which dominantly contribute to the extraction. Therefore, the function of the additive (n-hexane) entirely differs from that in the case of conventional mixed-solvent systems from the viewpoint of their extraction mechanism.