OXIDATION OF ORGANIC COMPOUNDS IN CONCENTRATED
INDUSTRIAL WASTEWATER WITH OZONE AND
ULTRAVIOLET LIGHT
G. J. Macur, Staff Chemist
W. A. Alpaugh, Development Engineer
J. E. Sharkness, Senior Associate Engineer
Systems Products Division
IBM Corporation
Endicott, New York 13760
The additive copper plating process produces a chemical waste stream comprised of a
number of chemical species. This waste stream is currently processed to remove copper and
recover and recycle the EDTA complexer in a series of operations called Primary Recovery.
The resulting effluent from the Primary Recovery loop contains low levels of residual copper
and EDTA and large quantities of dissolved organic and inorganic salts. This material is
currently unacceptable for direct discharge to the existing plant waste treatment systems.
This paper describes a secondary treatment process (ozone in the presence of ultraviolet
light) to remove the objectionable chemical species from the additive effluent so that the
treated effluent can be discharged directly to the existing plant waste treatment facdity.
The ultraviolet light/ozone (UV/O3) process represents the best practical technology known
today for the treatment of the subject effluent.
Waste streams from two copper removal processes, chemical copper recovery and electrolytic copper recovery (deplating), were treated with the UV/O3 process. The copper
removal process is important because the residual metal ion species that remain after the
removal of the copper cause physical and chemical problems in the UV/O3 process for
the destruction of HCOOH and, more importantly, EDTA. The final concentration of
EDTA must be less than 5 mg/1 in order to discharge the waste solution through the plant
clarification system.
The chemical copper recovery process produces a solution which has a negligible iron
content and a copper concentration usually much less than one mg/1. The solution resulting
from copper removal by deplating, however, always contains dissolved iron and copper.
The iron comes into solution by corrosion of stainless steel anodes. Although the plating
solution is strongly basic (pH 9-11), iron goes into solution as a ferric-EDTA complex
because of the high EDTA concentration (ca. 40 g/1) and the strong complex formed by
the iron with EDTA. The copper remaining in the solution is also complexed with EDTA.
The copper concentration, after deplating, ranges from 10-20 mg/1. The iron concentration ranges from 5-20 mg/1. Lower copper concentrations can be achieved; however,
this reduction usually results in higher iron concentrations. Copper concentrations around
50 mg/1 have also occurred due to procedural errors by the operators. In any case, use of
the deplater always yields solutions containing significant amounts of iron and copper.
During the oxidation of deplated solutions using ultraviolet light and ozone, very fine
precipitates of Fe(OH)3 (reddish-brown) and CuO (black) are formed as EDTA and other
organics are destroyed. These exceedingly fine precipitates tend to form despite control
of solution pH in the range of 4-6. Onset of precipitation is indicated by an initial faint
cloudness. In some cases the particles did not actually settle until 12-24 hours after the
sample was removed for examination. It is very possible that both Fe(OH)3 and CuO, as
fine particles, can catalyze the decomposition of a significant portion of the ozone fed
into the reactor to oxygen before it can oxidize any of the organic substances in solution.
In addition, it is also possible that the very presence of ferric and cupric ionic species in
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