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- <Br- <I-. This behavior is also observed using the ABEC resins where halo complexes of mercury will adsorb to the resin from (NH4)2SO4 solutions with retention following the same order. The onset of mercury extraction or adsorption is different for the three extractants, occurring at the lowest extractant concentration for I-, followed by Br-, and then Cl-. Fluoride does not extract mercury. Extraction or adsorption of mercury is improved at the lowest halide concentrations in the presence of sulfuric acid. The addition of sulfuric acid to (NH4)2SO4 solution results in ABEC retention of mercury even in the absence of halide extractant.