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Poly(ethylene glycol)-based aqueous biphasic systems (PEG-ABS) can be utilized to separate and recover metal ions in environmental and hydrometallurgical applications. A concurrent study was conducted comparing the partitioning of mercury between aqueous layers in an ABS [Me-PEG-5000/(NH4)2SO4] and partitioning of mercury from aqueous solutions to aqueous biphasic extraction chromatographic (ABEC-5000) resins. In ammonium sulfate solutions, mercury partitions to the salt-rich phase in ABS, but by using halide ion extractants, mercury will partition to the PEG-rich phase after formation of a chloro, bromo or iodo complex. The efficacy of the extractant increases in the order Cl-

Aqueous biphasic systems (ABS) are suitable for the separation of small organic molecules in industrial and environmental applications and thus, it is important to correlate partitioning behavior of model organic solutes with their structure in order to develop predictive models. The partitioning behavior of five, uncharged, substituted benzenes (benzene, toluene. chlorobenzene, 1,4-dichlorobenzene and 1,2,4-trichlorobenzene) were studied in ABS prepared from stock solutions of 40% (w/w) PEG-2000 and increasing concentrations of four water-structuring salts (K3PO4, K2CO3, (NH4)2SO4 and NaOH). For a given solute and a defined concentration of salt, the partition coefficients increase as the deltaGhyd value of the salt anion becomes more negative (e.g., Dbenzene increases in the order OH-

The purpose of these studies was to examine the axial evolution of the negative glow in a hollow cathode discharge. The time-average negative glow profiles along the central axis of a hollow cathode were recorded for 81 pulse widths over the range of 5-25 microseconds in increments of 0.25 microseconds at a constant interpulse delay of 206.4 microseconds. Subsequent numerical processing yielded the instantaneous negative glow profile. The negative glow was viewed through a mesh-covered slot along the length of the hollow cathode. The negative flow profiles were imaged using a vidicon video camera. A PC-based frame grabber digitized the video images and stored them for subsequent processing.