Pilot scale application of the Membrane Aromatic Recovery System (MARS) for recovery of phenol from resin production condensates

This paper describes the application of the Membrane Aromatic Recovery System (MARS) to the recovery of phenol from wastewater streams arising from a phenolic resins production plant. These wastewater streams typically contain between 2 and 8 wt.% phenol, and their detoxification has a significant economical and environmental impact, since about 30% of the global phenol consumption is intended for phenolic resins synthesis (annual production of approximately 3 million metric tons resin). A MARS pilot plant unit operating in batch mode was installed at a United Kingdom resin manufacturing site, and average efficiencies of 94 and 84%, for the phenol extraction and the phenol recovery stages, respectively, were achieved. The final MARS product, an organic phase, composed of 77-80 wt.% phenol and 20-23 wt.% water, was recycled back to the original manufacturing process and successfully used as a reagent for resin production. The phenol content in the discharged wastewater stream was successfully reduced to 0.1-0.3 wt.%, sufficiently low to allow further detoxification by a destructive process, such as biotreatment or chemical oxidation. The influence of different parameters, such as stripping solution pH and neutralizing HCl solution concentration on the process performance was evaluated. Scale up effects on the mass transfer at the extraction stage were also analysed on the basis of the liquid film theory and the resistances in series approach.