The electrically switched ion exchange (ESIX) process, being developed at P
acific Northwest National Laboratory, provides an alternative separation me
thod to selectively remove ions from process and waste streams. In the ESIX
process, in which an electroactive ion exchange him is deposited onto a hi
gh surface area elecrotrode, uptake and elution are controlled directly by
modulating the electrochemical potential of the film. This paper addresses
engineering issues necessary to fully develop ESIX for specific industrial
alkali cation separation challenges. The cycling and chemical stability and
alkali cation selectivity of nickel hexacyanoferrate (NiHCF) electroactive
films were investigated. The selectivity of NiHCF was determined using cyc
lic voltammetry and a quartz crystal microbalance to quantify ion uptake in
the film. Separation factors indicated a high selectivity for cesium and a
moderate selectivity for potassium in high sodium content solutions. A NiH
CF film with improved redox cycling and chemical stability in a simulated p
ulp mill process stream, a targeted application for ESIX, was also prepared
and tested. (C) 1999 Published by Elsevier Science B.V.