COPPER RECOVERY FROM A
BRASS BRIGHT DIPPING SOLUTION
James C. Egide, Senior Process Chemist
William M. Robertson, Manager
Environmental Affairs
Modine Manufacturing Company
Racine, Wisconsin 53401
INTRODUCTION
Modine Manufacturing Company, at its Trenton, Missouri facility, builds a variety of sheet metal
radiators. On a monthly basis the plant processes approximately 225,000 pounds of brass in its production of radiators for the automotive aftermarket, agricultural, and medium/light duty trucking
industries.
In order to transform the incoming sheet and/or coil brass into the various radiator components,
numerous production operations are completed which result in the metal surfaces being both oxidized
and coated with an oily film. These surface contaminants must be removed prior to assembling the
manufactured parts into a completed radiator.
The cleaning process is outlined in Figure 1. Brass subassembly parts are loaded into stainless steel
baskets and then sequentially dipped into the process tanks illustrated. The hot alkali tank serves as a
degreasing step wherein all surface oils are completely removed. Following the degreasing operation,
the parts are thoroughly rinsed before proceeding to an oxidative acidic pickle composed of hydrogen
peroxide, sulfuric acid, and water. This bath is referred to as a "bright dip" and serves the purpose of
removing surface oxides. After oxide removal the parts are again thoroughly rinsed and subjected to
an antioxidant coating. This latter treatment protects against re-oxidation of the surface that would
otherwise occur between cleaning and subassembly operations.
The processing of brass (70% copper, 30% zinc) through the bright dip results in a significant
removal of heavy metal from the processed parts. This leads to a rapid buildup of metal ions in the
bright dip solution and results in precipitation of blue copper sulfate pentahydrate crystals. The rapid
saturation of the bright dip solution with heavy metals and subsequent drag-in into the following
rinses added a significant cost to the waste treatment operations as well as production slow downs due
to the necessity of crystal removal from the bright dip tank. Also, because these crystals were classified as a contaminated (zinc, lead, and other trace metals) acidic waste, there was an additional cost
penalty associated with packaging and disposal of this material. Finally, because liquid drag-in is
WARM
AhMENT
AODtC
AMBCMT
AMBIENT
AMMNT
MMBfTEO
ALKALI
WATER
WATER
BRIGHT
WATER
WATER
WATER
WATER
RtNSE
DECREASE
MNSE
MNSE
OR*
(MNSE
RINSE
RINSE
Figure 1. Bright dipping process.
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