Instruments and Analytical Method. pH was measured using a pH211 acidometer (Hanna, Italy).
The concentrations of total chromium in the middle and bottom phases of the TLPS were analyzed
with an OPTIMA 7000DV inductively coupled plasma atomic emission spectrometer (Perkin-Elmer)
at a wavelength of 267.716 nm.
The Cr(VI) concentration in the presence of Cr(III) was determined by UV vis spectrophotometry
(Perkin-Elmer Lambda Bio40) at a wavelength of 540 nm based on the complex formation between
1,5-diphenylcarbazide and Cr(VI).
Each analytical value reported is the mean of three replicates.
The concentrations of Cr(III) and Cr(VI) in the top organic phase were calculated based on the analytical results for these ions in the middle and bottom phases of the TLPS.
Radiometrically determined distribution ratios are generally accurate to (5%; however, because of the complexity of this TLPS, a conservative accuracy of (10% is reported.
The extraction percentages (E) of the two metal ions in the top and middle phases were calculated according to the equation
where M denotes the metal ions, Cr(III) and Cr(VI), and i
represents the top (t) or middle (m) phase.
CM,i and Vi are the concentration of metal ion in the ith phase and the volume of the ith phase, respectively.
CM,0 is the initial concentration of the metal ion in the stock solution, and V0 is the volume of stock solution added to the system.
Fourier transform infrared (FTIR) spectra were acquired using a Bruker Vector 22 FTIR spectrometer with BaF pellets. Measurementswere taken in thewavenumber range from 400 to 4000 cm1.