Regeneration and recycling of waste chromic acid-sulfuric acid etchants

Technical Report · Mon Jan 01 04:00:00 EST 1979

OSTI ID:5740634

Soboroff, D M; Troyer, J D; Cochran, A A

Etchants containing hexavalent chromium and sulfuric acid are used in a variety of surface-finishing operations. When the resultant spent solutions are discarded, substantial quantities of chromium are lost and pollution problems are created. To minimize the undesirable environmental effects while improving metal and minerals recycling technology, the Bureau of Mines is conducting research on a method for the economic inplant recycling of these waste etchants. Trivalent chromium, produced when the etchant reacts with a substrate, is oxidized in the anode chamber of a diaphragm cell; other metals, dissolved during the etching operation, are transferred to the catholyte. When waste brass etchants are treated in this manner, all of the trivalent chromium is oxidized and more than 40% of the copper and zinc is removed. Similar copper removal and chromium oxidation are achieved with waste printed circuit board etchants and rinse waters from plastic etching operations. The electrical energy needed to regenerate 1 kg sodium dichromate is less than 9 kwhr. Regenerated brass etchants evaluated by two companies equaled or exceeded the performance of fresh etchants.

• Research Organization: Bureau of Mines, Rolla, MO (USA). Rolla Metallurgy Research Center
• OSTI ID: 5740634
• Report Number(s): BM-RI-8377
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320305* -- Energy Conservation
Consumption
& Utilization-- Industrial & Agricultural Processes-- Industrial Waste Management
CHROMIUM
COPPER
ELEMENTS
ETCHING
INDUSTRY
LIQUID WASTES
MANAGEMENT
MATERIALS RECOVERY
METAL INDUSTRY
METALS
NICKEL
PROCESSING
RECOVERY
RECYCLING
SURFACE FINISHING
TRANSITION ELEMENTS
WASTE MANAGEMENT
WASTE PROCESSING
WASTES
ZINC