Extraction of phenol from aqueous solutions by means of supported liquid membrane (MLS) containing tri-n-octyl phosphine oxide (TOPO).

This paper deals with the liquid-liquid extraction and the facilitated transport through a supported liquid membrane (SLM) system of aqueous phenol using tri-n-octyl phosphine oxide (TOPO) dissolved in an appropriate organic solvent. Phenol has been quantitatively extracted from aqueous acidic solutions using TOPO dissolved in kerosene as organic phase. The effect of TOPO concentration dissolved in kerosene on the extraction efficiency reveals that TOPO combined with phenol in the ratio of 1:1. Using a flat-sheet SLM (FSSLM) system, more than 65% of the initial phenol content in the feed phase was extracted and stripped in a NaOH aqueous receiving phase. The important operational variables affecting the facilitated transport of phenol through the FSSLM system studied are concentration of TOPO, membrane viscosity, feed phase pH, initial phenol concentration, polymeric support type and membrane stability. Regardless of its comparatively low extraction efficiency of phenol, the SLM based on TOPO exhibits higher long-term stability as compared to tributyl phosphate (TBP). Elaborated SLM system retained its stability and initial performance during the 5 days long experiment contrary to the TBP-SLM system where a time dependent negative tendency (transport efficiency decline) was observed.