Extraction of 8‑Hydroxyquinoline by Tributylphosphate in Kerosene

Extractions of 8-hydroxyquinoline (8-HQ) by tributylphosphate (TBP) in kerosene, as well as pure TBP and kerosene, were carried out. The investigations involved the equilibrium pH (pHeq) of 3.0 to 11.5, initial 8-HQ concentrations of (0.5 to 5.0) mmol·L–1, and initial TBP concentrations of (0.05 to 1.0) mol·L–1. The distribution ratio (D) was found to be highly dependent on pHeq, and larger D values appeared at pHeq range of 6.3 to 8.4. The distribution constants (K D) for pure TBP and kerosene were calculated to be 236.6 and 26.98, respectively. The experimental K D for TBP/kerosene was expressed by K D,TBP, K D,kerosene, and the volume fractions of TBP or kerosene. The mix of TBP and kerosene was found to be a nonideal process. The deviation of K D from the ideal is proportional to the product of volume fractions of TBP and kerosene. The (1:1) TBP:8-HQ complex was verified by fitting experimental data, and the apparent extraction reaction equilibrium constant was calculated to be 64.58 L·mol–1. The results are of significant importance for the practical separation of 8-HQ from diluents.