Anionic and Cationic Exchange for
Recovery and Purification of Chrome
From Plating Process Waste Waters
M. K. YOUNG
Finishing Superintendent
Die Casting Division
Electric Auto-Lite Company
Woodstock, Illinois
In recent years ion exchange has found increasing application in the
metal finishing industry for purification and recovery of process solutions. The advance of ion exchange methods for such purpose has been
paced by the development of suitable ion exchange materials. A notable
example of this has been in the purification and recovery of chromic
acid used in chrome plating, anodizing and other finishing processes.
In earlier investigations it was found that chromic acid attacked
and destroyed ion exchange materials then available. Later, when sul-
phonated polystyrene cation exchange resins were introduced, Costa1
established their effectiveness in removing metallic impurities from solutions containing as much as 100 grams per liter of chromic acid. The
economic advantage of such purification by cation exchange was soon
proven on a commercial scale.2 Costly disposal of contaminated chrome
baths was no longer necessary and the hazard of stream pollution was
greatly reduced.
Of less economic advantage is the removal of chromate ion from
process rinse waters by anion exchange. Bueltman3 has described this
as a break-even proposition. To date the strongly basic quaternary amine
type exchange resins have shown best results for removal of chromate
ion from solutions containing 1000 parts per million  (ppm)  or less.
Apparently all exchange resins of this type do not possess equal
stability. Reents and Stromquist4 have recommended that chromic acid
solutions be neutralized with caustic to prevent resin attack. Paulson
and Saunders5 have not found this necessary.
With ion exchange materials now available for purification and
recovery, the elimination of chrome from waste effluent becomes largely
a matter of adapting equipment design to particular requirements. Such
has been the case at the Die Casting Division of the Electric Auto-Lite
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