KINETICS OF PHASE-TRANSFER OF 5-CHLORO-8- HYDROXYQUINOLINE BETWEEN TOLUENE AND AQUEOUS SULFURIC-ACID

In synergistic extraction of metals, the partition mechanism between o rganic and aqueous phases of the synergist used plays an important rol e. Many studies on measurement of the partition equilibrium have been carried out so far, but few studies on the phase-transfer rate have be en conducted. In this work, the phase-transfer rate of 5-chloro-8-hydr oxyquinoline (HA) between toluene and aqueous sulfuric acid was measur ed using a stirred transfer cell. The transfer rate varied inversely a s the first power of the hydrogen-ion concentration in a low pH range, and was proportional to the concentration of HA. Analysis of the expe rimental results taking into account the partition equilibrium at the interface between the organic and aqueous phases gives the mass transf er coefficients of HA in both the aqueous and organic films. The calcu lated results of the transfer rate using these values agree well with the experimental ones. The experimental results in the high pH range d eviate slightly from the calculated ones. This tendency is also explai ned qualitatively by considering the effect of pH on the solubility of HA in sulfuric acid aqueous solution.