Two-phase reactors applied to the removal of substituted phenols: comparison between liquid-liquid and liquid-solid systems

In this paper, a comparison is provided between liquid-liquid and liquid-solid partitioning systems applied to the removal of high concentrations of 4-nitrophenol. The target compound is a typical representative of substituted phenols found in many industrial effluents while the biomass was a mixed culture operating as a conventional Sequencing Batch Reactor and acclimatized to 4-nitrophenol as the sole carbon source. Both two-phase systems showed enhanced performance relative to the conventional single phase bioreactor and may be suitable for industrial application. The best results were obtained with the polymer Hytrel™ which is characterized by higher partition capability in comparison to the immiscible liquid solvent (2-undecanone) and to the polymer Tone™. A model of the two systems was formulated and applied to evaluate the relative magnitudes of the reaction, mass transfer and diffusion characteristic times. Kinetic parameters for the Haldane equation, diffusivity and mass transfer coefficients have been evaluated by data fitting of batch tests for liquid-liquid and liquid-solid two phase systems. Finally, preliminary results showed the feasibility of polymer regeneration to facilitate polymer reuse by an extended contact time with the biomass.