Kinetics of phenol removal from saline solutions by solvent extraction coupled with degradation in a two-phase partitioning bioreactor

A combined process of solvent extraction and two-phase biodegradation was proposed to remove phenol from saline solutions by Pseudomonas putida BCRC (Bioresource Collection Research Center) 14365 at 30 °C, where kerosene was selected as the organic solvent due to its biocompatible and non-biodegradability. The saline solutions contained 100 kg/m³ NaCl at pH 3.0 and the initial cell concentration in mineral salt medium was fixed at 25 g/m³. The effect of initial phenol level (320-3000 g/m³) in saline solutions on phenol removal and cell growth was experimentally studied. A simple model that combined steady mass-transfer equations and dynamic growth kinetics of suspended cells was further proposed to follow the whole process. For the convenience of kinetic modeling, the organic-aqueous interfaces remain quasi-quiescent during the process. Under the conditions studied, phenol could be completely removed from saline solutions and degraded in the aqueous cell medium within 90 h even though the initial phenol level was high up to 1850 g/m³. It was shown that the proposed model satisfactorily described the process as long as phenol level in the cell medium did not exceed the toxicity limit of suspended cells. This model also allowed us to estimate the optimal partition coefficient for a qualified organic solution.