title: Naphthol- and resorcinol-based azo dyes as metal ion complexants in aqueous biphasic systems.
abstract: Aqueous biphasic systems (ABS) are comprised of both a polymer-rich phase (e.g., polyethylene glycol, PEG) and a salt-rich phase [e.g., (NH4)2SO4] such that both phases are 80% water on a molar basis. ABS have demonstrated applications as environmentally-friendly methods to separate relatively hydrophobic anionic species, such as pertechnetate and mercury halide anionic complexes, from high ionic strength solutions although partitioning of hydrated metal ions, such as Fe3+ and actinides, to the PEG-rich phase is negligible without the addition of a metal ion complexant to the system. Four naphthol- or resorcinol-based dyes; 1-(2-pyridylazo)-2-naphthol (PAN), 1-(thiazolylazo)-2-naphthol (TAN), 4-(2-pyridylazo)-resorcinol (PAR) and 4-(2-thiazolylazo)-resorcinol (TAR), each incorporating a naphthol or resorcinol with an ortho azo functional group, have been studied as metal ion extractants in ABS as a function of pH. In the PEG-2000/ (NH4)2SO4 ABS, the distribution ratios of Fe3+, Co2+ and Ni2- were enhanced by several orders of magnitude at high pH in contrast to the behavior of Cs+, Cd2+ and Eu3+ whose partitioning behavior was largely unaffected by the presence of these extractants at any pH. The three extracted metal ions, Fe3+, Co2+ and Ni2+, could be stripped by contact with a fresh salt phase at low pH.
authors.affiliation: Department of Chemistry and Center for Green Manufacturing, The University of Alabama, Tuscaloosa 35487, USA.
authors.forename: A E
authors.initials: AE
authors.lastname: Visser
authors.forename: S T
authors.initials: ST
authors.lastname: Griffin
authors.forename: D H
authors.initials: DH
authors.lastname: Hartman
authors.forename: R D
authors.initials: RD
authors.lastname: Rogers
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008670:Metals / Q000737:chemistry*; D009284:Naphthols / Q000737:chemistry*; D012118:Resorcinols / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D008670:Metals; D009284:Naphthols; D012118:Resorcinols; D014867:Water; C031389:resorcinol