Evaluation of tri-n-octylamine oxide as phenol extractant in a solvent impregnated resin

Tri-n-ocytlamine oxide (TOAO) is evaluated as alternative to the state-of-the-art phenol extractants tri-n-octylphosphine oxide (TOPO) and Cyanex 923. Liquid–liquid equilibrium experiments show that TOAO in 1,3-dimethylnaphthalene achieves higher phenol distribution coefficients in an extractant concentration range of 0.1–1.25 mol L−1 than respective TOPO/1,3-dimethylnaphthalene or Cyanex 923/1,3-dimethylnaphthalene solutions. In a solvent impregnated resin (SIR) application, the SIRs impregnated with TOAO/1,3-dimethylnaphthalene have a higher phenol capacity than the SIRs impregnated with Cyanex 923/1,3-dimethylnaphthalene. Regeneration of the SIRs with alkaline solution of pH 13 shows that both SIRs maintain a constant phenol capacity during at least seven cycles. Based on these observations TOAO can be considered as a better alternative to Cyanex 923.