Separation Science and Technology, Vol.35, No.4, 623-629, 2000
Poly(ethylene) glycol as a selective biphasic transfer agent for the extraction of chromium(VI) from aqueous salt solutions
Poly(ethylene) glycol (PEG) has been used as a medium for the phase transfer recovery of chromium from aqueous salt solutions. Bubbling ammonia through an aqueous solution with the Cr(VI) in the upper PEG layer results in transfer of Cr(VI) to the lower layer. Similarly, passing carbon dioxide through the system in aqueous ammonia with Cr(VI) in the lower layer results in its transfer to the upper phase. Addition of ferrous sulfate leads to reduction of Cr(VI) to Cr(III) and essentially quantitative transfer of the chromium from the PEG to the salt layer. A combination of electrolysis and the Fe(II),(III) redox couple can be used to reduce Cr(VI) to Cr(III) because after oxidation of the added Fe(II) to Fe(III) by Cr(VI), the Fe(III) can be electrolytically reduced back to Fe(II). The Fe(II) needs to be present in only catalytic quantities.