Waste alkaline etchant was considered a hazardous waste because the material was corrosive to steel. The material is a hazardous waste even though it is recycled. Along with cupric chloride, which is also recycled, hazardous waste volumes increased from 20,000 gallons a year to greater than 100,000 gallons a year because of a regulatory change.
Around 1991 the Alkaline Etch team determined that the best alternative to the alkaline etchant to be the "Elo-chem" process. Basically, the environmental advantage of the "Elo-chem" process was that the etching chemistry changed form copper ammonium chloride to copper ammonium sulfate. Copper is plated directly from the "Elo-clean" etchant, and the ammonia released in the plating cell is recycled back into the etchant. This formed a closed loop process and eliminated the need for bulk chemistry and off-site hazardous recycle. (This also eliminated the need for two bulk chemistry tank systems and the potential for an environmental spill on-site.)
The quantity of ammonia used at the process was reduced by 90% and off-site hazardous waste shipments were reduced by nearly 200 tons per year.
Details of Reductions
Additional Information :
The cost of the process was equivalent to the process it replaced. No additional costs were incurred. The primary returns were in shifting of waste disposal costs to operating costs for the regeneration system. The success of the project has been measured by the reduction in usage of "Alkaline Etch" and a 25% improvement in the etch process quality and performance.